Poll: Who has ever hit the rev limiter?

[tf95ZR1]

Question as above in title. I remember awhile back someone was shocked at hitting the rev limiter. Even with a Harlan shift light (highly recommend it), I hit the limiter more than I'd like to admit. Think it does any harm if you back off or shift right away? Happy Holidays, stay safe and healthy.
Ted Feder
95 ZR1 #106 Blk/Blk
So. Calif. 80 degrees and sunny

I would have reversed the poll, ie who has never hit the limiter, but this is easier.

[Kevin]

I hit it once or twice but I manage to glance down and keep the top of the tach in my sight as I am driving it hard. If i was racing I'll bet you I would hit it alot more.

[cuisinartvette]

Northridge, youre a local!:thumbsup:

I've hit 7400 once, but sont believe I've bumped a limiter before.

[BBBAD94ZR1]

I Dont Think That Would Be A Smart Decision.[-x

Ray

[tomtom72]

Okay another dumb rookie Q! How do you know when you hit the limiter? Does it sound like the F1 cars, like you have a miss in the motor? I'm fairly sure I've never even been close due to the fact that I watch for the "shift" light & if I see it & haven't shifted already, I make sure I get to it pronto.

Lately I've been practicing & I find in my stock Z that it seems to "feel" like it has a sweet spot just before 7 g's on the tach. So I've been shifting between 6.5 & 7 as it seems stronger there than if I go to the shift light. Isn't the peak somewhere before 7 g's?

Oh, I voted "no" on the poll.:o
:cheers:
Tom

[Aurora40]

Lately I've been practicing & I find in my stock Z that it seems to "feel" like it has a sweet spot just before 7 g's on the tach. So I've been shifting between 6.5 & 7 as it seems stronger there than if I go to the shift light. Isn't the peak somewhere before 7 g's?
I hit it once and it feels like something is wrong with the car, it's sort of jerky on the limiter.

As to shifting, I would think if the curve doesn't drop off precipitously, which it doesn't, that you'd want to stay in it past the peak. When you shift, it will drop you back down the power band, so the later you shift, the less far down it will move you (i.e. shifting at 6500 may put you at 4000 in the next gear, where shifting at 7200 may put you at 4350 or something). So the goal for maximum acceleration would be to stay under the fat part of the power curve as much as possible. If it's fatter in the 6500-7200 rpm range than the 4000-4300 range, you'd want to stay in it. Those are guess numbers and it may be it's better to shift early, but the way the car pulls I kind of doubt it.

[Kevin]

I Dont Think That Would Be A Smart Decision.[-x

Ray

hitting it once or twice isn't a big deal. The only time it may cause a problem is if you keep running the car against the red line for an extended period of time

[Nick]

I've hit it twice, on the dyno. Fuel cuts off and the engine misses badly. Its not hard to notice :mrgreen:

[bobbyhi]

Doesn't sound like something I want to try. I usually shift around 6900 and it seems that is the power limit.

[RICHARD TILL]

i didnt know that there was a rev limiter. i assumed the limiter was bang-clang-clang-pow, ..."oh sheet".... never wound it up past 65 anyway. too many miles on this ole gal.

[tf95ZR1]

"Never wound up past 65" ? I hope you mean in first gear!
:sign10:

[RICHARD TILL]

nope, just thru 4th. 138 is fast as i`ve ever had it. never brought it out of the hole either. just roll-offs. afraid of breaking something. i`m the second owner. had i been the first and with warranty, "oh boy". people like me are the reason that GM quit the 5 years/50,000 mile warranty in about 1971.

[Kevin]

i didnt know that there was a rev limiter. i assumed the limiter was bang-clang-clang-pow, ..."oh sheet".... never wound it up past 65 anyway. too many miles on this ole gal.
Oh I did not just read this....

[tomtom72]

I don't know Kevin, I'm with Rich on this one. I've never seen a shift light in anything except 1st & 2nd gears. The "hole shot" thing I agree with him on too...too many bad things that can break, I mean IRS suspension systems were not made for drag racing, right???

If I'm wrong about this please share the light. I just think back to when I had my C3 and all the work rebuilding the rear gear & the PIA it was to change out u-joints. I looked at the whole set up and thought..."don't be launching this car too much or you'll be back under here in no time swapping broken parts!". I know that the peices under the Z are way bigger than what my C3 was using but they are or look like they are mostly made from aluminium???

Straight up, I'm not trying to be a smart a$$. But launching an IRS like ya got a ford 9" with a detroit locker center, well you get where my Q is coming from, right?? Heck the Eaton in my C3 was okay, but not as good for launching as the detroit locker in my Mach 1, and that I know for sure. What am I not gett'in??

Tom

[Kevin]

Tom,
I don't really launch the car all that often either but when I do I leave at 2.5k and just hammer the **** out of her. I look at it this way, I have street tires on the car and if anything is going to break on the car, they will go first. But I hit 7000 in third quite regularly

[tomtom72]

Hi Kevin & gingle bells! Thanks for the tip, 2.5 seems to be the # everyone uses. Yea you are right about the tires..I forget that they are not gonna hook up to cause a failure in the IRS. I guess I'm too conservative in my thinking. Chicken me I am.

Let me ask, a combination of speed of coming up with the clutch pedel and going down on the gas, right? Object is to not bogg it and keep a reasonable degree of traction, so it's a balancing act between the two. I'm thinking care is a must or the clutch disc will over heat?? I've just recently started to try a little of that in brisk accleration from traffic lights. I was doing what the owner's manual said about " you can come off the clutch slowly and your corvette will move along without giving it gas except on steep grades". I know it must seem funny to all the other Z owners but it's been 20 yrs inbetween vettes. Coming from 150 or less hp for the past 20 yrs makes you forget what a real motor can do for you, let alone the TQ an LT5 has. To me it is a marvel the smooth power it has!

Thank you for your insight!:thumbsup:

Tom

[Kevin]

Tom,
What I do is I hold the RPMs at 2.5 and bring the clutch back toward me as fast as I can without sidesteping it and I mash the go peddle as hard as I can

[tomtom72]

Oh! & Duh! Thanks for the "how to" on the technique, Kevin! That sounds reasonable, and not very abusive to the drive train. It's been along time for me between vettes, and a car that has some hp for that matter.

Hey, I have had my ZR-1 for a whole year now! Yea!
Man, these cars can cure a bad day!:thumbsup:

Tom

[Aurora40]

I was doing the ~5,000 rpm launch described on CF at Englishtown. That seemed to work well. The idea was to hold ~5,000 rpm and launch the car with the clutch. I was probably seeing more likt 4-4.5k, but you just let the clutch out as the tires can handle it and off you go. Of course my 2.2 and greater 60' times might not lend credibility to this, but with 10 year old GS-C's putting it down, I thought it worked ok. Seemed to work better than lower rpm launches that either broke it way loose or bogged down (which seems worse for the clutch).

Tom, so your shift light actually comes on? Mine doesn't seem to and I thought later GM ECM calibrations didn't turn it on anymore. But maybe I just have a bulb burned out...

[cuisinartvette]

Still a Z noob here, but it seems with a Dana44 and spicer Ujoints there shouldn't be any breakage issues.

[Kevin]

I was doing the ~5,000 rpm launch described on CF at Englishtown. That seemed to work well. The idea was to hold ~5,000 rpm and launch the car with the clutch. I was probably seeing more likt 4-4.5k, but you just let the clutch out as the tires can handle it and off you go. Of course my 2.2 and greater 60' times might not lend credibility to this, but with 10 year old GS-C's putting it down, I thought it worked ok. Seemed to work better than lower rpm launches that either broke it way loose or bogged down (which seems worse for the clutch).

Tom, so your shift light actually comes on? Mine doesn't seem to and I thought later GM ECM calibrations didn't turn it on anymore. But maybe I just have a bulb burned out...

This techinque will work quite well....I just don't like having to replace the clutch all the time.

I know with my aftermarket chip I lost the upshift light which made me sad I'd like to find a way to get it put back in.

[tomtom72]

Thanks guys, Kevin, Bob & CAV!

Humm, I never thought about a chip turning off the shift light Bob. The chip I bought is just the replacement update for the OEM 1990 chip. Yes the shift light does work. I guess your bulb could be out? Maybe you have an aftermarket chip? Also thank you for sharing what you did at Englishtown. I hear ya about the GSC's, mine were old & hard & I replaced them with D3's.

I guess I worry too much about the IRS, too many parts & no place to work. The stuff sure looks nice though! I hate to say this but I'm still partial to the detroit locker in my Mach1, that would do the trick in the launch department!

Once the clutch is engaged & the speedo says something I have no quams about lett'in her rip, it's fun! I guess I'll never be a drag racer!:mrgreen:

Thanks for sharing Guys!:thumbsup:

Tom

[ZR-1 Mack]

At Carlisle last Summer on the road course I watched a C5 Z06 hit it every time he was on the course. My friends ZR-1 had lower times, won his class and never hit the rev limiter once.

[Aurora40]

Humm, I never thought about a chip turning off the shift light Bob. The chip I bought is just the replacement update for the OEM 1990 chip. Yes the shift light does work. I guess your bulb could be out? Maybe you have an aftermarket chip?
As far as I know it's the stock chip. But the owner before me did buy the updated GM prom to fix the idle thing. I have the original in the GM box the replacement came in. I've never seen the light on, so I suspect it must be burned out. I guess I'll have to fix that sometime...

[Kevin]

At Carlisle last Summer on the road course I watched a C5 Z06 hit it every time he was on the course. My friends ZR-1 had lower times, won his class and never hit the rev limiter once.

that tends to happen with a 7,000 rpm redline :dancing

[Aurora40]

For anyone wondering what it sounds like, here's me hitting the rev limiter in 1st gear. Not intentionally...

Hitting limiter (http://aurora40.dyndns.org/Hometown/corvettezr11990/clips/limiter.mpg) ~1.5MB

[tomtom72]

Okay I know now that I have never let the rpms get to the limiter...I must be early enough at shifting in 1st & 2nd to stay off of the limiter...I guess if you use the shift light there must be a few hundred rpm cushion or I would have hit it for sure...the motor sounds so sudective up top I get mesmerized by the sound & almost forget the shift light!:o

Man that thing sounds sweet, Bob!!!:thumbsup:

[Aurora40]

Well then here's me not hitting the limiter. :) Oh, apparently the shift light was taken out of later programs. Though, you bought the latest PROM for 1990, right? And yours still works? I guess I'll have to pull the dash and change my bulb...

Not hitting limiter (http://aurora40.dyndns.org/Hometown/corvettezr11990/clips/0to110.mpg) ~3MB

[tomtom72]

Okay I had to think about this. I bought the GM updated Prom, code ABYK, from P & G Chevy. I had the 1990 OEM PROM. I looked after reading the TSB over at the Reg site & my symptoms matched so I put it down on my list. I know the shift light worked before I swapped PROM's and I know that after I did my plenum stuff I put in the GM/ABYK coded PROM and the shift light still works.

btw, Bob it sure does sound nice...sweet music you're car's making! You must be:D

:thumbsup:
Tom

[Bell Curve]

How much damage will hitting the rev limited do over a long period of time

[Kevin]

Do you mean running it against the limiter or just smacking it a lot?

[blackjack]

i did,coupla times
it is my understanding that an engine should be shifted at peak horsepower,and if the gearing is well chosen,the engine will fall back
to its peak torque...thats what we aim for,at the drags,with our sportster
JMO...
blackjack
91/1735

[blackjack]

by the way...i think till`s rev limiter is the funniest
blackjack

[Mika73]

I also had broken valve spring and broken cam last summer..

:censored: :thumbsdo:

[RedRiderZR1]

Hit it once on a missed downshift (DOH). Hate it when that happens. Thank god for limiters.

[ZR1 MK]

I it mine at the track because of clutch slippage at 125 mph. I saw my shift light, but by the time it registered, it was to late. I like modern technology.

[Patton]

I hit it hard once in my 89 IROC on a missed shift, I was 18 and still learning but thinking I was an F1 driver at the same time. I was going through a tight corner at high speed, needless to say I was *** end first coming close to eating the curb, with a red face and wearing a humble grin. :o

But I havent hit the limiter on the Z, Even though I have gone 182 on the freeway in her. That'll pucker your *** like no other. Things go by very very quickly and that rock hard suspension starts to feel more like a 77 cadillac.

I shift when I can feel the power band tapering off, why stay in that gear when the next one will give you more power? Unless I go from 3rd to 2nd, I dont plan on bang'in the limit.

And shift light?? huh? Who? Where? Are they on 94's?

[Patton]

Oh and Richard,... dude... I cry for your Z!
She wants to get out and run again!!! Let her stretch those legs!! Hell it will probably brake for driving to SLOW!!! And when it brakes,.... Fix it.

[LuxZ]

Hello
I am a new member on the forum, and this is my first post

Well looks like I am the only one who goes often to the rev limiter... the cars straight to the limiter from 1st till fourth gear, but I have not yet been to the disruptor in the 5th gear.
The engine runs marvelously well, it is 65000+ miles. I will just continue driving it hard, and should the engine explod, then I will buy a new one!

[tf95ZR1]

Gotta love the attitude.
But the limiter is probably there for a reason,
and the best time to shift is before 7200+ RPM!
Somethings gonna give.........

[Patton]

Unless your torque and Hp band has changed extensively from stock, you are needlessly damaging your engine by hitting it ESPECIALLY ON EVERY GEAR SHIFT! If your engine is stock, than you aren’t even getting the benefit of better track times, you are going SLOWER.
You know now that I think of it, even if your engine IS modded hitting the limiter cuts fuel and sputters the engine, taking seconds off of your end time. My advice would be to shift earlier than the limiter, there just is absolutely no benefit, while creating a healthy chance for a potentially catastrophic failure..... Why?? :icon_scra

But I must admit, I like your attitude much better than those who keep garage queens... Unless you are just filthy rich and have a collection of course.... But I would still drive the nuts out of a different one each day.

Oh ya and limiter in 5th gear, I couldnt bang it and I was on a very very very long straight part of I-5 in central CA. just had it WOT for some time, got up to about 182 or so, its scary to look away from the road for more than a nano second. And it took an eternity (probably just 15 seconds or so) to climb even one MPH. So Im not sure you can really hit that sucker with a stock motor. I wonder what the top speed of 5th gear is mathmatically (i.e. in a drag less setting). Anybody?

[Aurora40]

Oh ya and limiter in 5th gear, I couldnt bang it and I was on a very very very long straight part of I-5 in central CA. just had it WOT for some time, got up to about 182 or so, its scary to look away from the road for more than a nano second. And it took an eternity (probably just 15 seconds or so) to climb even one MPH. So Im not sure you can really hit that sucker with a stock motor. I wonder what the top speed of 5th gear is mathmatically (i.e. in a drag less setting). Anybody?
Around 205mph.

[Patton]

But of course even before you hit 205mph and the limiter, your alternator will be generating the needed 1.21 gigawatts and then who knows where you'll end up,... or when you'll end up.

[zvetteman]

Yep hit while drag racing. Running GSC's and spinning the tires in third gear. If it would hook up I would probably break something!

[WB9MCW]

never hit mine yet but i think my chip has it at 7400 now..I shift at 7000 and it gets to abt 7200 buy the time im done! Works for me! Im am at the point now I can tell the rpm by ear. I was going to get a light but my ear can now tell me when to shift. Took a while on the lt5 compaired to other engines to get a tuned ear for the rpms cause she pulls so hard for so long but afer a couple of years now and some practice I have a handle on it!!! I dump the clutch at 3k for launch and it spins the tires just a bit all the way through first, squaks into second and chirps into third....gotta luv my new chip and alum. flywheel and race clutch, b4 the best was a chirp into second only!!! Now she snorts they way we like it! I dont dump it too often (only to show off to friends mostly) since we all know abt the weak link of the u joints!!! and if u dont have driveshaft loops installed well.... i do have to say the gear rattle is quite noisy and it took a while to get used to it(actually u never really do) and it is a bit funny when people first hear it(they think ur tranny is broken) but once u hammer it they soon figure that it must be ok and healthy!!! lol

[gbrtng]

TOMTOM72:

With a stock chip in my 91 the shift light will light in any gear except
sixth if you hold speed for a while. Cruising 70 mph in 5th for a few
minutes at constant throttle it comes on. Change throttle position
and it goes out. GM nanny wants to remind you not to waste gas
and upshift.

I never watch the light when I'm hammering it so I don't know
whether it goes on at the rev limit - too many other things to
pay attention to !

[tomtom72]

TOMTOM72:

With a stock chip in my 91 the shift light will light in any gear except
sixth if you hold speed for a while. Cruising 70 mph in 5th for a few
minutes at constant throttle it comes on. Change throttle position
and it goes out. GM nanny wants to remind you not to waste gas
and upshift.

I never watch the light when I'm hammering it so I don't know
whether it goes on at the rev limit - too many other things to
pay attention to !

Now I just learned why I get such bad gas milage! I'm not paying attention to the General's advice about how to drive my Z! No chit, I didn't ever notice it telling me how to save gas! Oh well no one ever said I was the sharpest knife in the rack!

One thing though.........my secondaries should be really clean! I guess ya can't have everything, hugh?:mrgreen:
:cheers:
Tom

[HADI-ZR1]

my shift light is OFF :D

[GrayZ]

my shift light is OFF :D

not the only light off at your house :mrgreen:

[4DSZR1]

not the only light off at your house :mrgreen:



:sign10: :sign10:

[WB9MCW]

HADI HAS THE RED LIGHT ON AT HIZ HOUSE THOUGH!

TILL ROCKSANNE MOVED IN AND TURNED IT OFF!!! LOL

[jonszr1]

AW i guess poor hopalong is going to be getting the gas for a while. But he seems to be a good sport. Also was nice enough to give us a great sounding video. how do you speed shift with that cast . horefully no holes in the fire wall:mrgreen:

[DDSLT5]

This thread has been very interesting.

The stock rev limiter is set to 7072 rpm. It is set there to preserve the life of the water pump, alternator and steering pump. The engine's redline is 8000 rpm. Above that rpm you risk valve float, although a few members have run their motors above 8000 rpms without issue.

Will it hurt to hit the rev limiter? No. Will it hurt to hit the rev limiter many times? No. Will it damage the engine to run it on the limiter all day? Well - that can't be good for the cam chains or the cams themselves, but the rest of the engine won't give a damn.

Moral of the story - don't worry about touching the rev limiter from time to time. Mine is set to 7400 rpm with a 4.125 inch stroke, which is the same piston speed as running a stock motor above 8000 rpm. I also have larger pulleys on the water pump and alternator to slow them down, use less power and extend their life as I wring it up to 7400 rpm on a regular basis.

As for shift lights - set them 200 rpm below where you have the limiter - shift just after you see the light, and you'll never hit the limiter.:thumbsup:

The stock shift light is too difficult to see to be useful. It was calibrated for peak power on the stock calibration when at WOT, and for fuel economy at part throttle. It was pretty cool.

[WB9MCW]

good info---nice to see ya postin here doc---hope u are happy in yankee land now---

[cward]

This thread has been very interesting.

The stock rev limiter is set to 7072 rpm. It is set there to preserve the life of the water pump, alternator and steering pump. The engine's redline is 8000 rpm. Above that rpm you risk valve float, although a few members have run their motors above 8000 rpms without issue.

Will it hurt to hit the rev limiter? No. Will it hurt to hit the rev limiter many times? No. Will it damage the engine to run it on the limiter all day? Well - that can't be good for the cam chains or the cams themselves, but the rest of the engine won't give a damn.

Moral of the story - don't worry about touching the rev limiter from time to time. Mine is set to 7400 rpm with a 4.125 inch stroke, which is the same piston speed as running a stock motor above 8000 rpm. I also have larger pulleys on the water pump and alternator to slow them down, use less power and extend their life as I wring it up to 7400 rpm on a regular basis.

As for shift lights - set them 200 rpm below where you have the limiter - shift just after you see the light, and you'll never hit the limiter.:thumbsup:

The stock shift light is too difficult to see to be useful. It was calibrated for peak power on the stock calibration when at WOT, and for fuel economy at part throttle. It was pretty cool.

I have been following this thread with a large smile. :-) My rev limiter was set to either 7600 or 7800, I can't remember which. I have banged off of it so many times, I couldn't even begin to guess how many times. I agree with what Dwight says. No damage. That is what it was designed to do. To stop you from damaging the engine. I will say also that I ran my Z very hard and it was used to the treatment I gave it. Even at 105K miles on the engine, it still ran pretty good. Would I recommend that for every LT5, probably not if you don't do it all the time. Do I think it will hurt it, probably not. My engine has done things that most will never see. I have had it 180 mph in 5th with 4.10 gears and held it there for several seconds (BBORR 2001 heading to finish line). I am not sure but seem to remember that it was at about 7400 - 7500 rpm at the finish line. And I had the "pedal to the metal (fiberglass)". With modified engines, going above 7000 makes sense when racing or playing. With a stock Z, there seems to be no good reason to rev much over 7000 as it runs out of air. My car was slightly modified and on the dyno was still producing good hp at 7400. Just thought I would comment. I am sure there are many Z owners who hate what I did to my Z. However, I feel like when racing in ORR, I was doing what the car was designed to do. It is a great ORR car. With just a few thousand dollars worth of mods, it was able to beat a lot of very expensive cars. And give its owner (me) memories to last a lifetime.

[40th#381]

Curtis:

I always enjoyed it when I heard of something else No 364 had done or was about to do. Always was courious what would have happend next if 364 wasen't wrecked.


Jan

[cward]

Curtis:

I always enjoyed it when I heard of something else No 364 had done or was about to do. Always was courious what would have happend next if 364 wasen't wrecked.


Jan

Hi Jan,
There were two things that I wanted to do with #364: 200 mph and 10 sec 1/4 mile. I did one and will always believe that I would have done the other on Sat. at BG when #364 was wrecked. Now had I accomplished both goals, I probably would have raised the bar but will never know. 11.08@129 will just have to suffice.

Curtis

[jonszr1]

wow that a great et and mph . what mods did you have to get there? what did you do to the suspension to get it to hook up? love to learn from ya. thanx:mrgreen:

[cward]

wow that a great et and mph . what mods did you have to get there? what did you do to the suspension to get it to hook up? love to learn from ya. thanx:mrgreen:

#364 had only a few mods, all bolt on. RWHP was 392. I had the normal stuff done: inj housings, plenuum, headers and 3 1/2 inch SS open exhaust with X pipe. For most of the time I ran 4.10 gears except when ORR then 3.45. For drag racing, I sprayed a little. Best 60' was 1.59. I used 10" ET Streets when spraying and they hooked pretty good. I set front shocks to full soft and rears to 3/4 hard. My FX3 system was disconnected and I set all shocks by hand. Fronts are easy. Rears more fun.

[A26B]

It's north of 7500, I know that!

[RHanselman]

It's north of 7500, I know that!

Corey set mine at 7500 because I was still making good power up top. I bounced it several times today during the autocross on Nellis AFB. I had a blast and all the attendees really liked the way the LT5 was singing!

[tf95ZR1]

Corey set mine at 7500 because I was still making good power up top. I bounced it several times today during the autocross on Nellis AFB. I had a blast and all the attendees really liked the way the LT5 was singing!


Vice President, ZR1 Net Registry
90 ZR1 Black Grey Remote Mount Twin Turbo
91 ZR1 Black Black 400 RWHP 13.7K miles




Hey Ron!
Which car did you drive today?
How did it do? Huh, Huh, Huh?

[Kevin]

26 of you really need to go out and drive your cars

[cadillac531]

I hit mine, briefly, on a burn out. No big deal, just let off the gas.:mrgreen:

[rogerzr1]

Tom, so your shift light actually comes on? Mine doesn't seem to and I thought later GM ECM calibrations didn't turn it on anymore. But maybe I just have a bulb burned out...[/quote]

I have only had my car since last August, but I have never seen a shift light on my car either. I don't know that I want to see it.:wink:

[95ZR1#418]

I've never hit the rev limiter. When I dynoed my car I had the operator rev it because I didn't want to do it, he never hit it either-for the reason it wouldn't show more HP or TQ by doing so. I agreed & will probably do it myself next dyno...:cool:

[Kevin]

I've never hit the rev limiter. When I dynoed my car I had the operator rev it because I didn't want to do it, he never hit it either-for the reason it wouldn't show more HP or TQ by doing so. I agreed & will probably do it myself next dyno...:cool:

just find your favorite stretch of road and get on it

[USAFPILOT]

I'm not sure if my limiter is enabled...that or the tach is off a little. But I can get way over 7K and near 8K without any limiter. I have stock gears and can hit 84MPH easy in 2nd. Is that normal?

[rhipsher]

But I havent hit the limiter on the Z, Even though I have gone 182 on the freeway in her. That'll pucker your *** like no other. Things go by very very quickly and that rock hard suspension starts to feel more like a 77 cadillac.
Poly bushings will take care of that I guarantee it. :cheers:
http://i301.photobucket.com/albums/nn63/keeno1970/image8-2.jpg
http://i301.photobucket.com/albums/nn63/keeno1970/image7-1.jpg

If your a DIY guy you'll need a 12 ton press and be prepared for a big job. But it will feel rock solid at any speed and have very little body roll around corners.

[sammy]

ah the old tiger shark, but the women in the pic are too pretty compared to the actual ones

[Paul Workman]

Just following along here...

Seems to be a lot of pushrod SBC experience being projected onto a DOHC platform; a platform that was tested by alternating it from max rpm to max torque continuously for over a week before being torn down for inspection. It was deemed ready to go again!

I believe it was in the book "Heart of the Beast" where it was mentioned that the motor was good to about 8000 rpm, and above that oiling was the problem and lubrication-related failures of varous kinds, e.g., cams seizing, chains breaking ensued, as I recall. (However, Fastlane was running his LT5 to the mid 9000s in the quarter, but I never saw anything written about what all mods were done to that motor to address the rpm issue - if any.)

The (approx) 7200 factory limiter setting was chosen as a practical limit because 1) the power curve had peaked around 6400 (stock motor) and was tailing off past practical use, but 2) the main concern was the periphery components - alternator, PS pump, etc. (The AC compressor is shut off by the ECM above 4xxx rpm)

Serious performance is in the offing after porting and especially porting with cams, and cutting it off at 7200 is apparently premature for most properly modded LT5 motors (or certainly the case with the "FBI" modded motors at least).

Cases in point:

Y'all have seen Pete's video (http://www.youtube.com/watch?v=SFNFOhGGlR4)where he hits 129.x mph in 3rd gear. (The video done at Great Lakes Dragway showing a couple burnouts and 3 runs) Considering 120 mph is achieved at 7200 in third gear for stock tire sizes, Pete would have to set his limiter north of 7700 rpm to hit 129 mph.

Then there's the 10.x second big inch LT5s running way north of 7200+++ at WOT

After porting my LT5, it was still pulling hard when the danged limiter would cut me off; I hit the limiter many times. I, as well as Dom and others had to bump the limiters to at least 7600 to accomodate (in my case) a 7200 shift point, AND allow some headroom as I hit the 7200 rpm mark way short of the finish line.

Something else...

Some have questioned if their rev limiter was working at all because they had observed the tach sweeping up to or past 8000 without hitting a limiter. I can tell you that before I recalibrated my tach the needle would sweep off the end of the scale before hitting 7200 rpm! It is apparently quite common for these tachs to go out of calibration over time - mine was reading 20% high, in fact (resulting in running off the scale before hitting 7200 actual rpm).

So, I suspect there are some that have been cutting their LT5s waay short of their potential because of a combo of unwarranted concern for reving too the stock limiter setting, and because they're looking at a tach that may be reading significantly higher than the actual rpm. That is too bad, because it is robbing them of the biggest gift the DOHC LT5 has to offer...RPM!;) (I observed this very phenomenon when I let a friend of mine drive my Z while I rode shotgun. He was short-shifting it at about 5800 rpm! I asked him why he wasn't riding it out, and his response was he was going by the sound and what he knew from "regular" V8s. So, I wonder how many Z drivers there are out there that are instinctively shifting their Zs according to patterns long etched into their minds by experience with pushrod putters!?[-X AND, here (http://www.youtube.com/watch?v=PzPPEK9Qf3M) is a classic comparison between a pushrod LS1 and a stock LT5. Notice what happens to the gap every time the C5 driver has to shift. You'll get a really good view of the beauty of the LT5's reving)

Fuel cut-off is the method used by the limiter. The result of hitting the limiter is the engine will pop and sputter until the rpm is reduced. I don't know why anyone would attempt to hold the rpm against the limiter intentionally - that can't be a good idea (on so many levels). But, bumping into the limiter occasionally is apparently not going to hurt anything: after all, the limit of the stock motor itself is somewhere more like 8000 rpm. (excluding belt-driven accessories - I'd be more concerned about that Chinese-made replacement alternator than anything.:neutral:)

A shift light, e.g, the Raptor that can be hidden behind the vent grill, would be "thee" way to know when to shift without bumping the limiter - AND the lights are much more accurate than the tach, due to the tach's inertia lagging (especially in lower gears).

Uz guys afraid of going above 6500 rpm either have lace on your panties, or have "pushrod characteristics" embedded in your brains, I recon! :p Let that LT5 stretch it's legs and show ya what she'll really do!:dancing


P.

[sammy]

where can one get the raptor shift light .?????and how does it get wired to the car ???

[rhipsher]

I've never seen a shift light in mine and have reved as high as 8k. But at 8k I do notice the drop in torque. The engine revs faster than my tac needle can keep up with in first gear. I don't make hitting 8k a habit either. 2500rpm drag strip launches may be fine with the dual mass flywheel but not with a Fidanza. If you launch at 2500 with the Fidanza you'll drop like a rock and bog for a second before the rpm's come back up. I've launched mine with the Fidanza at 4500rpm's with Mickey Thompson s. Thats the sweet spot for me. Having a stroked LT5 with a Fidanza may not cause you to bog off the line because of the massive torque and hp they produce.

[WB9MCW]

On the Dunlop street tires I do a 3500 rpm clutch dump.

Having a nice ceramic stage II from CC helps a lot as well on the launch plus my secret tuner chip all have worked well to give extra spunk to the Z.

I really do like the Fidanza a lot.

I shift at 7K on the needle and have only hit the rev limiter once - so I know it works!!

[bdw18_123]

I hit the rev limiter once, I was in 4th gear. Put the hammer down and didn't let up until the needle was right at 7K and that is when the engine hit the fuel cutoff limiter. I don't remember exactly what my speed was I think it was a bit north of 140MPH.

So I think my tach is actually fairly accurate still, being that the limiter is set at 7200, that would mean it was reading only 200 RPM low at that point.

Nearly every time I drive my Z, I do at least one short run through the gears to at least 6K to make sure the secondaries stays clean and working. :mrgreen: And every time it amazes me how it just keeps pulling and pulling! Not to mention the awesomeness of the scream of the LT5 at those higher rpms. Love it!! :-D

[Kevin]

top of 4th is probably closer to north of 160

[A26B]

where can one get the raptor shift light .?????and how does it get wired to the car ???

http://raptorperformance.com/products/Shift_light.htm

http://i190.photobucket.com/albums/z224/A26B/TachConnection.jpg

http://i190.photobucket.com/albums/z224/A26B/GaugePod.jpg

[Paul Workman]

(I thought I posted this earlier, but now can't find it here. Anywayz..)

Thanks Jerry for the detailed info re the A pillar mount.

The shift light is ever so much more accurate than the analog tach, and when drag racing, ya don't have to be looking directly at it to see it in your peripheral vision - and keep ya from bouncing off not only the rev limiter, but the guard walls too!

I really like the clean cockpit look, so the hidden approach apeals to me. Your mileage may vary. AND, the popular AC vent installation looks like this...

(Note: there are acutally six (or so) leds and on start-up the light says "hello" by turning them on and off in a circular pattern for a second or so. The camera only caught a couple, but when the time comes, all come on, and even in daylight you will not miss it. In fact, I have mine intentionally aimed toward my right eye. As you can see, ya miss it!)http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/Raptorlight.jpg

The Raptor is only 3/4" in diameter, and can easily be inserted through a hole drilled in the plastic. Plastic tape is wrapped around the barrel of the lite to generate the desired fit.

Referring to the FSM, the C100 connector is where the white tack wire can be intercepted. You'll have to remove the hush panel to see the connector, located about 2" from your big (left) toe (while driving).

To fische the wires down there, after disconnecting the negative terminal of the battery...very important...you can use a coat hanger wire to snake down to where you can grab it, and tape the Rapor wires to the other end, you can them pull the wiring down to the footwell area and splice them.

[tomtom72]

:o the only time I hit the limiter on a consistent basis is in 2nd gear. I usually watch the tach like a hawk with my left eye in 1st as I find by not watching closely it is too easy to hit the limiter in 1st. If I shift by "ear & feel" of the motor in 2nd I will always hit the limiter, but then my only other vette was a C3 LT-1 car. So seeing 6 to 7 k rpms on a tach is "normal" for me! Even my DD, Cobalt Sport 2.4 DOHC/4V has a 6.5 k rpm limit on the tach! :redface:



JMHO, but 1st gear ratio is too big ( isn't it like a 2.63 gear? ) for the power available and the stock rear gear ratio. If I had money to waste I would like to see the Z's box with a 2.20 1st gear like the M22's used? That set up in my 72 LT-1, an M22 box with a 3.55 rear gear & 15" wheels, yielded 10 mph per 1k rpm in 1st gear. So 0 to 60 mph was done in 1st without even being close to the factory red line of 6800 rpms. To a road work person, having a "useable" 1st gear is a God send! Those pesky hairpin turns & all ya know.:mrgreen:

:cheers:
Tom

[mlotruglio]

I have never hit the limiter in mine but Im almost 100% sure I have cams in it, the higher you run it up the harder it pulls all the way to 8k. My close uncle has a 90 Z and his " dies" at 6700-6800 ish

[mlotruglio]

As a matter of fact she is going on the dyno tomarrow after work so we will see what happens

[rhipsher]

I have never hit the limiter in mine but Im almost 100% sure I have cams in it, the higher you run it up the harder it pulls all the way to 8k. My close uncle has a 90 Z and his " dies" at 6700-6800 ish Same here. Mine pulls beyond 7k. I've driven many others Z's that don't run as good as mine. I always thought that there was just something wrong with theirs. Maybe its the other way around. Maybe somethings been done to give it more pep besides what I've done to it. I guess I'll never know. Not knowing doesn't hurt my feelings one bit. Lol!

[Paul Workman]

I have never hit the limiter in mine but Im almost 100% sure I have cams in it, the higher you run it up the harder it pulls all the way to 8k. My close uncle has a 90 Z and his " dies" at 6700-6800 ish

8k? Yeah, maybe. It would take cams and some porting and exhaust, etc to pull to 8k. With 315x35x17s at 7200 rpm in third, 3.45 rear gear will get you to 120 ish mph. If you're north of 132 mph + in 3rd gear, I would agree you're rubbing shoulders with 8k. Otherwise, I suspect the tach is off a bit.

I knew my tach was reading high (common problem) but not 20% high! Marc mentioned it and I confirmed with my scanner too - yep - 20%. The tach would run off the scale and then some before the limiter would engage!

So, screw the tach. I did calibrate it, and now it tracks pretty well. But, the shift light is soooo much better for best/consistent shift performance and avoiding testing the limiter, methinks;)

P.

[Z51JEFF]

Not me,most this cars seen from me is a touch under 6 grand,if I break it cant afford to fix it.

[Paul Workman]

Not me,most this cars seen from me is a touch under 6 grand,if I break it cant afford to fix it.

Under 6K???

Dat LT5 ain't no LT1! Let da big dog loose! :dancing Dave Mclellan says the LT5 loves to rev to 7k "...and it will thank you for it!"

:cheers:

P.

[WB9MCW]

Under 6K???

Dat LT5 ain't no LT1! Let da big dog loose! :dancing Dave Mclellan says the LT5 loves to rev to 7k "...and it will thank you for it!"

:cheers:

P.

HAVE TO AGREE

Ain't nuthin better than to let the 32 DOHC's and 16 FI's do their thing and that is to REV and to REV HIGH very HIGH!!!

She was designed and born to run just like a

"Cheetah" achieves by far the fastest land speed of any living animal—between 112 and 120 km/h (70 and 75 mph) in short bursts covering distances up to 500 m (1,600 ft), and has the ability to accelerate from 0 to over 100 km/h (62 mph) in three seconds.

http://i126.photobucket.com/albums/p110/HAMMERHATE/Cheetah.jpg

[Paul Workman]

HAVE TO AGREE

Ain't nuthin better than to let the 32 DOHC's and 16 FI's do their thing and that is to REV and to REV HIGH very HIGH!!!

She was designed and born to run just like a

"Cheetah" achieves by far the fastest land speed of any living animal—between 112 and 120 km/h (70 and 75 mph) in short bursts covering distances up to 500 m (1,600 ft), and has the ability to accelerate from 0 to over 100 km/h (62 mph) in three seconds.

http://i126.photobucket.com/albums/p110/HAMMERHATE/Cheetah.jpg

Saw where prey animals will freeze to avoid being noticed by a Cheatah preditor they can't out run.

Saw something similar a while ago when a "C4" linend up against some prey C5/6s. The prey animals in the stands were chatting it up and loudly scoffing. They didn't realize it was Pete's predator Z about to prey on the one of theirs...

The next time that Z came to the line, the prey animals in the stands went quiet! LOL!

P.

[Jagdpanzer]

http://www.cheetahcars.com/images/logo.gif

[Blue Flame Restorations]

Yep. I bought this car to have fun. I don't plan on hitting again but hey, **** happens. I didn't mean to hit it the first time.

Geoff Jeal told me that during the LT5 Calibration Certification, the LT5 was run for a continous period with an RPM cycle of 5500 to 7100 and back again. Not one component failed and not one fastener came loose. This was the certification. Seem like the duration was 200 hrs?

[John Boothby]

Yup. Hit it by accident. Hit the throttle in second and spun the tires. Surprise, hit the limiter! Thought I blew the motor! Then I realized it was the limiter. Nice insurance!

[mgg]

The question should be who has not hit their rev limiter. If the answer is they have not they should be forced to release their car to a car ( ZR-1) enthusiast and buy a Prius. That is the most ridiculous question I have ever read. I really hope there is no one that would take pride in admitting that. If they do they probably live an alternative lifestyle.

[efnfast]

Well, I'm pleased to say, I don't think the po, nor myself run this car bouncing off the rev limiter. I've seen the ricers run their cars that way and they all smoke. I would rather throw my money at improvements, not repairs.

[boostedmaxPSI]

I have an L98 and an LT1 in addition to the "Black Momba" and I rarely hit the rev limiter on those cars. I typically shift based on the power curve and after owning and driving these cars for years you just learn where the shift points are. However, that is not the case with my Black Momba.

I've hit the rev limiter more times in that car then I have combined in the other two. Some of this is based on me still getting use to the car but damn, this car pulls all the way to the set limit.

[BigJohn]

I have an L98 and an LT1 in addition to the "Black Momba" and I rarely hit the rev limiter on those cars. I typically shift based on the power curve and after owning and driving these cars for years you just learn where the shift points are. However, that is not the case with my Black Momba.

I've hit the rev limiter more times in that car then I have combined in the other two. Some of this is based on me still getting use to the car but damn, this car pulls all the way to the set limit.

WHAT!!
You sold the 92???

:(

[boostedmaxPSI]

WHAT!!
You sold the 92???

:(

The CR1 went to the new owner on Monday. Two down and one more to go. You need a twin turbo for your collection. Come get it. :cheers:

[Paul Workman]

The question should be who has not hit their rev limiter. If the answer is they have not they should be forced to release their car to a car ( ZR-1) enthusiast and buy a Prius. That is the most ridiculous question I have ever read. I really hope there is no one that would take pride in admitting that. If they do they probably live an alternative lifestyle.

...and know what a "NO-NO" is (and use one!) - definitely are WAXERS!:sign10:

[efnfast]

The CR1 went to the new owner on Monday. Two down and one more to go. You need a twin turbo for your collection. Come get it. :cheers:

Hey Big John, I'll drive ya' out there to pick it up.

[Bob Eyres]

The question should be who has not hit their rev limiter. If the answer is they have not they should be forced to release their car to a car ( ZR-1) enthusiast and buy a Prius. That is the most ridiculous question I have ever read. I really hope there is no one that would take pride in admitting that. If they do they probably live an alternative lifestyle.

My sentiments exactly :thumbsup:

I am shocked...:confused:...SHOCKED at seeing the poll results.
Almost HALF of the respondents confess to never treading the furthest regions of the LT5's rev capacity. :redface:
What a disappointment. You 'oughta be ashamed :thumbsdo:
Well, just keep changing that oil kids, keep it nice, polish that paint, and put some more shiny juice on them tires. 'Cause some day a real ZR-1 enthusiast might own that car. :p

(If the above comments offend thee, I am deeply sorry and wish to blame it on the three cups of coffee I've ingested so far today :cheers:)

[batchman]

OK, I'll confess. I've never hit the limiter but not for lack of trying - it's for not knowing where it is! Anyone know what a typical DRM chip sets the limiter at?

I'd have to dig to find the dyno sheet from early in our ZR-1 adventure but I seem to recall power peaking maybe middle 6k's or so and I don't think we went to the limiter on those three runs.

I have to make the 1-2 shift by where I am on the course, not by rpm. And although it sometimes feels like it I never quite reach the top of 2nd gear (I need to go to the 3.54 rear, most I can do within class rules). For this car, the street is just for transport between events - and soon that will be by trailer.

Cheers,
- Jeff

[We Gone]

Never...LOL

CatBack Flomasters - YouTube (http://www.youtube.com/watch?v=7gsYgGZN1fY&feature=em-upload_owner)

[8cam]

Where's the option for "Not yet?"

[Hog]

People are very afraid of damaging an engine, GM set that limiter way below the point of rev related damage.

I remember the poster of a ZR-1 on my buddies wall, fuel shutoff=7200rpm. Such a magical number esp. for a stock GM engine with 80's technology.

[Paul Workman]

With the "500" package installed, it was still pulling hard when I would hit the 7200 limiter. In fact, I'd hit the limiter in 3rd gear just short of the 1/4 mile finish line. Marc reset it to 7600, and once in the "water box" at the track, I tickled 7600 briefly.

Now I depend on a shift light, which does NOT lag. I played with the trigger point until I found that spot where my 1/4 mile passes were optimized; 7100, if memory serves. (By the time I react, I'm at 7200-7300ish in 1st, around 72xx in second and the light comes on in 3rd very close to the finish line - on a good day.)

In the book "HEART OF THE BEAST" the certification was to cycle between max rpm every so many minutes (hours) and max torque. This they did for 200 hours; OR 8.33 DAYS! The test crew reported back to Dave McLellan after measuring it for wear, and told him it was good to go for another round. I don't think you're gonna hurt it if you bump the limiter, and certainly not for a run at 7000 rpm.

If the motor is stock, then (as I recall) 6800 shift may be about right. But, after the full porting, headers, free flowing exhaust and cam phasing, 7200 is too little - least here in FBI land.:dancing

[Blue Flame Restorations]

I hit it today. At around 50 degree cool air, that Turq car is absolutely brutal with the B&B exhaust and 4:10 gears. Can't wait to do a stroker!

[WARP TEN]

I hit it today. At around 50 degree cool air, that Turq car is absolutely brutal with the B&B exhaust and 4:10 gears. Can't wait to do a stroker!

Temps dropped to about 40 degrees here this morning. I didn't hit the rev limiter but I did hit the tire limiter--Couldn't get any traction in either first or second gears. Even third was a bit iffy. Still fun though until the first snow flies. --Bob

[Kevin]

TOMTOM72:

With a stock chip in my 91 the shift light will light in any gear except
sixth if you hold speed for a while. Cruising 70 mph in 5th for a few
minutes at constant throttle it comes on. Change throttle position
and it goes out. GM nanny wants to remind you not to waste gas
and upshift.

I never watch the light when I'm hammering it so I don't know
whether it goes on at the rev limit - too many other things to
pay attention to !

just saw this old post,
90 is the one only that has the shift light for performance, the rest have it for fuel economy

[cadillac531]

just saw this old post,
90 is the one only that has the shift light for performance, the rest have it for fuel economy

I just saw this....

Not true, my 91 lights up for performance, and mine is all stock. I don't remember the actual rpm it lights up, but some where around 6400 I think.

[Kevin]

I just saw this....

Not true, my 91 lights up for performance, and mine is all stock. I don't remember the actual rpm it lights up, but some where around 6400 I think.

i'm trying to recall my conversation with marc but i'm too many beers in to do so accurately, I thought he said it was 90 only. oh well I've been wrong before

[Schrade]

I hit it once in an '02 1-Ton Express Van that I bought new.

Kicks in @ 100mph. Felt scary too - heavy torqueing 5.7 has inertial forces at 100 that shouldn't change like that.

I had 265's on the corners, instead of 245's, so it was about 107 - 108 :p

Lickety-Split Courier & Delivery!

https://lh5.googleusercontent.com/wPlTTpyLy6CfjgaovhuFbN7wbpECCsh-PFbV9cuxZLY=w813-h426-p-no

I had it subsidiary of my primary C&D............

[Paul Workman]

I just saw this....

Not true, my 91 lights up for performance, and mine is all stock. I don't remember the actual rpm it lights up, but some where around 6400 I think.

Around 6400 ya think? Hmmmm....

Pete and I were discussing the topic of where to shift for performance (on a stock ZR-1) with Jim (Jingles) Inglals (sp?). (Jim was the Corvette engineer that established - among other things - the drag strip numbers for the then new ZR-1) As I recall he recommended POWER shifting the Z at around 6300-6400 rpm (no throttle let-up between gears).

I think Pete and I agreed that neither of us is going to do any POWER SHIFTING as long as its on our dime if something breaks![-X But, to your comment regarding the UPSHIFT light coming on at 6400 for performance(?)...makes me wonder if it isn't more than just a "koinkeedink"

But, here's the thing: If Jim power shifts at around 6400, according to the tach, the actual rpm might well be at least a few hundred rpm higher than 6400, especially in the lower gears.

Just muddying the waters a bit...:cheers:

[edram454]

the question was,, can it damage your car?? well just yesterday I met up with a nice guy in my neighborhood with a 1991 z, he seems like a very handy person with lots of equipment in his garage, welders, press etc.. he had just powder coated and ported his top end and his cam covers.... but on the side of his garage on a crate stood a wrapped up lt5. he just bought that engine used because he over-reved his engine and damaged it. he turned it on and it make some bad noises internally. he thought it was maybe damaged lifters so he replaced some of them. he decided to replace the whole engine so he bought a long block. he was driving around while his tach was not working and over-reved it and lost his motor. I know when I have hit the limiter on my c5 it just drops cylinders and stumbles. maybe the lt5 will do the same but again we are doing many more rpms than a c5 would be doing so the damage is more iminent. I would say not a good idea bumping that limiter too many times. by the way, this friends zr1 had 130k miles on it and still was running as strong as a bull.

ed ramos #3028

[cadillac531]

Around 6400 ya think? Hmmmm....

Pete and I were discussing the topic of where to shift for performance (on a stock ZR-1) with Jim (Jingles) Inglals (sp?). (Jim was the Corvette engineer that established - among other things - the drag strip numbers for the then new ZR-1) As I recall he recommended POWER shifting the Z at around 6300-6400 rpm (no throttle let-up between gears).

I think Pete and I agreed that neither of us is going to do any POWER SHIFTING as long as its on our dime if something breaks![-X But, to your comment regarding the UPSHIFT light coming on at 6400 for performance(?)...makes me wonder if it isn't more than just a "koinkeedink"

But, here's the thing: If Jim power shifts at around 6400, according to the tach, the actual rpm might well be at least a few hundred rpm higher than 6400, especially in the lower gears.

Just muddying the waters a bit...:cheers:

Yeah, you may be right on that. I don't watch the tach very closely anymore except for the hole shot, where I bring it to 4000 off the line.

I just grab the next gear when the shift light pops, and in my peripheral, it looks like the needle is around that 6400 mark. The car is dead on consistent shifting with the light, though.

To the power shifting comment:

I power shifted it once on the street, and without a prepped surface, it blows the tires off on the 1-2 shift. That shifter has such a long throw though, that you really have to train that clutch leg to stay in long enough to complete the shift. I haven't, nor am I interested, in power shifting that 3-4 shift.

No worries on the muddy water...it makes things interesting. :cheers:

[cadillac531]

the question was,, can it damage your car?? well just yesterday I met up with a nice guy in my neighborhood with a 1991 z, he seems like a very handy person with lots of equipment in his garage, welders, press etc.. he had just powder coated and ported his top end and his cam covers.... but on the side of his garage on a crate stood a wrapped up lt5. he just bought that engine used because he over-reved his engine and damaged it. he turned it on and it make some bad noises internally. he thought it was maybe damaged lifters so he replaced some of them. he decided to replace the whole engine so he bought a long block. he was driving around while his tach was not working and over-reved it and lost his motor. I know when I have hit the limiter on my c5 it just drops cylinders and stumbles. maybe the lt5 will do the same but again we are doing many more rpms than a c5 would be doing so the damage is more iminent. I would say not a good idea bumping that limiter too many times. by the way, this friends zr1 had 130k miles on it and still was running as strong as a bull.

ed ramos #3028

Yeah, on a traditional pushrod motor, hitting the limiter can cause valve float. When that happens, the valves could contact the piston **BANG**.

In our LT5's, the movable valve train weight should be less, since there's no pushrod, so I would think the force would need to be much higher to get the valves to float. That sudden stop in accelerating RPM's still creates forces within the engine that attempt a valve float.

That's why aftermarket rev limiters try to soften that stop, like MSD's soft touch rev limit.

[WydGlydJim]

I've bumped it a time or two.......best I can tell the Lingenfelter is set at 8200.
:eek:

[tf95ZR1]

just saw this old post,
90 is the one only that has the shift light for performance, the rest have it for fuel economy


Not true, my 91 lights up for performance, and mine is all stock. I don't remember the actual rpm it lights up, but some where around 6400 I think.

Does anybody with a MY 1994/1995 have a OEM "Shift Light"? I have an aftermarket,
but never noticed or saw one that would have come with the car.

[WARP TEN]

the question was,, can it damage your car?? well just yesterday I met up with a nice guy in my neighborhood with a 1991 z, he seems like a very handy person with lots of equipment in his garage, welders, press etc.. he had just powder coated and ported his top end and his cam covers.... but on the side of his garage on a crate stood a wrapped up lt5. he just bought that engine used because he over-reved his engine and damaged it. he turned it on and it make some bad noises internally. he thought it was maybe damaged lifters so he replaced some of them. he decided to replace the whole engine so he bought a long block. he was driving around while his tach was not working and over-reved it and lost his motor. I know when I have hit the limiter on my c5 it just drops cylinders and stumbles. maybe the lt5 will do the same but again we are doing many more rpms than a c5 would be doing so the damage is more iminent. I would say not a good idea bumping that limiter too many times. by the way, this friends zr1 had 130k miles on it and still was running as strong as a bull. ed ramos #3028

Hi Ed--
We have a good FBI friend named Al who ran into a little problem at last year's half mile races. Here is a video of what happened to his motor due to a little over revving: http://www.youtube.com/watch?v=bgQiABT05tM --Bob

[Paul Workman]

the question was,, can it damage your car?? well just yesterday I met up with a nice guy in my neighborhood with a 1991 z, he seems like a very handy person with lots of equipment in his garage, welders, press etc.. he had just powder coated and ported his top end and his cam covers.... but on the side of his garage on a crate stood a wrapped up lt5. he just bought that engine used because he over-reved his engine and damaged it. he turned it on and it make some bad noises internally. he thought it was maybe damaged lifters so he replaced some of them. he decided to replace the whole engine so he bought a long block. he was driving around while his tach was not working and over-reved it and lost his motor. I know when I have hit the limiter on my c5 it just drops cylinders and stumbles. maybe the lt5 will do the same but again we are doing many more rpms than a c5 would be doing so the damage is more iminent. I would say not a good idea bumping that limiter too many times. by the way, this friends zr1 had 130k miles on it and still was running as strong as a bull.

ed ramos #3028

The limiter is there to prevent over-reving the motor, and in and of itself isn't going to cause any catastrophic issues. After completing the "FBI 500+" package, including the Fidanza FW and before installing a shift light (on my 90) I often bumped the limiter. It is nothing more severe than miss firing/sputtering or missing (read: pretty soft, but no drivetrain shock).

Before I had my rev limiter bumped to 7600 and a shift light installed, I'd hit it quite often - Here is an example of how soft the limiter is:

This is Pete's Green Monster. Notice the little misfire on his second burnout at about 1:05.

http://www.youtube.com/watch?v=SFNFOhGGlR4

Nothing to worry about...BTDT many times, w/o issues - NO crashes of gears or anything like that. Very soft.

P.

[edram454]

I understand it is to prevent over-reving of the motor but there are only so many times a motor is going to let you bust its gut until it busts yours. they are definitely great engines and durable but they are not indestructible. My friends lt5 had 130k miles until it blew up. he bought the car with 120k miles. those are miles that could have been done a 1/4 mile at a time. I understand bumping the limiter during a grudge match or something. i dont understand just bumping it every time you go for a drive.

I dont like to be hard on my equipment and that is why I have never had catastrophic failures even in race engines. I use it and get what I need out of it at the time and leave it. I wont just beat on it for kicks. everybody has different driving habits and of course if the owner wants to rev it every time then its ok. I just think engines that are thrashed continually will one day bite you in the rump. that guys zr1 in the video is a monster. 11.30 at 129 mph and no power adder. Great car and great power.

ed ramos #3028

[5ABI VT]

Bumped it about 10x last week when I took it out. have to get a feel for where it is on the tach because they aren't exactly accurate. Pretty much figured it out now. I have no fear with this motor at all. if it blows up oh well stroker time :-D

[Paul Workman]

Bumped it about 10x last week when I took it out. have to get a feel for where it is on the tach because they aren't exactly accurate. Pretty much figured it out now. I have no fear with this motor at all. if it blows up oh well stroker time :-D

Tach calibration is a relatively easy DIY fix for anyone familiar with basic electricity; just soldering in a resistor in place of the deteriorated, printed one.

I believe Dynomite (our club's Archive guru) has the procedure captured in his archive. Check there first. Or, I have a copy of the article I wrote on it...somewhere around here if you need me to dig it up for ya!:dancing

http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/cut4and10-2.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/tech%20files/cut4and10-2.jpg.html)

Course too, with any analog meter (tach in this case) there is a certain % of lag which increases with changing (rpm) rate; naturally there's more in first gear especially. SO...a shift light is recommended. And, in the archives too is procedures for installing one. (I installed a Raptor light which is small enough to be hidden behind one of the vent grills. All seven LEDs wink on and off in sequence when the ignition is first turned on - as a test mode.)

http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/Raptorlight.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/tech%20files/Raptorlight.jpg.html)

In the book, "Heart of the Beast" there was a problem discovered when a single chain was used. But, the cure was the double chain that the LT5s have now. In the book, it describes how Lotus engineers tested the motor by alternating the engine between peak torque and 7000 rpm for a little more than a week w/o issues. So, I don't think occasionally hitting the limiter at approx 7200 is "pushing it" at all, long as it hasn't been run out of oil or the like. It ain't no pushrod motor!:cheers:

[WydGlydJim]

I've ran right through 7000 RPM, and the car was still pulling strong with no drop off, then right through 8000 RPM accidentally, and I've bumped the rev limiter a couple of times when I wasn't paying strict attention....best I can tell, it is set at 8200 RPM on my car. After that, I called Lingenfelter, and they thought is would be fine to 7800 RPM normally.

:jawdrop::jawdrop:

[Hog]

I thought the chains became the limiting factor over 8000rpm as they will break due to the small diameter of the sprockets, which were designed small to fit the LT5 into the C4.(in the end the cam sprockets could have been a tad larger it was found)

The secondary chain lets go, and then due to the LT5 being an interference engine, valves start smacking pistons and carnage ensues.

Hitting the rev limiter induces no ill effects. The engine simply defuels allowing revs to decrease slightly, then refueling once again. Floating the valves (where the lifter actually loses contact with the camshaft lobe) would be difficult with stock parts that are working correctly.

[5ABI VT]

SO what im looking at is... theres 55 people so far who don't even know how fast their z is yet ? =D>

[5ABI VT]

In my opinion hitting the rev limiter is ok but of course repeatedly doing that does in my opinion stress the chain as the sprockets are slowing and accelerating the chain back and forth. Also not all engines have a rev limiter because the engine will not spin that high and explode. More so due to the fact that they are cammed for lower rpm and efficiency and mileage so the powerband is pretty much over so they just set the limiter where it needs to be. There are a lot of motors that can safely rev a LOT higher than a factory limiter like some of the jap cars (2jz etc) with no ill effects. They just crank the boost and up the rpm on a stock motor and away they go.

[5ABI VT]

Bumped it about 10x last week when I took it out. have to get a feel for where it is on the tach because they aren't exactly accurate. Pretty much figured it out now. I have no fear with this motor at all. if it blows up oh well stroker time :-D

And just for the record I hit it twice because I needed to know where it was after all the mods lol. :-D

[Paul Workman]

I've ran right through 7000 RPM, and the car was still pulling strong with no drop off, then right through 8000 RPM accidentally, and I've bumped the rev limiter a couple of times when I wasn't paying strict attention....best I can tell, it is set at 8200 RPM on my car. After that, I called Lingenfelter, and they thought is would be fine to 7800 RPM normally.

:jawdrop::jawdrop:

The question of tach calibration...comes to mind. (Mine would read "off the map" at the limiter due to calibrations error.)

[32valvesftw]

I agree with all in that hitting the rev limiter once or twice is not a big deal, but I think bouncing off the limiter as I see of the 4 cylinders do on launch make me cringe. Good think we have our friend Torque so we don't have do that.

[8cam]

I agree with all in that hitting the rev limiter once or twice is not a big deal, but I think bouncing off the limiter as I see of the 4 cylinders do on launch make me cringe. Good think we have our friend Torque so we don't have do that.

Are you sure you're driving the right car? :D

I have redlined mine many times and plan on hitting it a few times today - autocross this afternoon! Sure these engines make torque, but they live for revs. I agree a redline launch is totally unnecessary and probably not ideal, but get it on a road course and really work that last thousand rpm. It's awesome.

[32valvesftw]

Are you sure you're driving the right car? :D

I have redlined mine many times and plan on hitting it a few times today - autocross this afternoon! Sure these engines make torque, but they live for revs. I agree a redline launch is totally unnecessary and probably not ideal, but get it on a road course and really work that last thousand rpm. It's awesome.

Yes Im driving the right car thanks very much.

[Hib Halverson]

When I owned Barney, I hit the rev limiter once in a while, mostly in first or second because I didn't properly anticipate the delay in the tach. What I wouldn't have given for an HUD back then.



As I ran my car on the chassis dyno enough to know where the engine made power and what the best shift points were, I almost never would tag the limiter intentionally. The Street Skinner engine in Barney which used stock manifolds and cats made right at 500-hp but it peaked at 6500 or so and was "all done" by 6800 and that's where I usually shifted such that after the shift I ended up down around peak torque.


With my current ZR1, Bad-Assed Bee, I'm always hitting the limiter in first and second if I'm manually shifting. Left in drive, the darn thing always shifts just before the limiter.



Innovation and Technology rears its ugly head.

[DRM500RUBYZR-1]

I treasure my car.
I baby the car.
I LOVE my ZR-1!

That said; If you are not, on occasion,bumping into the rev-limiter, then either let someone else drive it if you really cannot bring yourself to do it and witness that the sky will not fall.
OR
Play a little more aggressively with it each time until you do.

Few things in life are as much FUN as DRIVING a C-4 ZR-1.
Any car revs to 5,000.
6,000 still quite a few.
7,000 not many

Aim for 7,500 by holding off until you see the needle pass through 7,000.
At the rate age is slowing me down, I may have to soon start the shift at 6,000 to hit 7,500
When young, I left on the last yellow light.
Today I could almost start one second after the stage light glows.
Ahhhh, the golden years!!!!!!!!!!!!!!!!!

ENJOY IT WHILE YOU CAN!
Go for 7,500!!!
:cheers:
Marty

[richarde]

ZR-1 tachometers are notoriously inaccurate due to the IC within the instrument panel cracking and changing resistance due to age, heat and vibration. Batee.com sell a 90-96 Tach Fix 8000rpm kit for remedying this problem. In order to verify the accuracy of the tach, plug in a Tech 1 or ALDLDroid or similar.

[Zman]

ZR-1 tachometers are notoriously inaccurate due to the IC within the instrument panel cracking and changing resistance due to age, heat and vibration. Batee.com sell a 90-96 Tach Fix 8000rpm kit for remedying this problem. In order to verify the accuracy of the tach, plug in a Tech 1 or ALDLDroid or similar.

I just hit the Rev Limiter for the first time yesterday. I hit it on a car that had the Tach corrected recently after being told it was reading high. I had the same reading corrected on another car. My guess would be that most Tachs read high. I see 7000-7500 occasionally and have only hit the limiter (once). Hitting the limiter for the first time took all the fun out of it, immediately! If the factory rev limiter is set at 7070 RPMS +/- and I can bump 7500 on a stock 90 without hitting the limiter then I must be reading high on that car also. Just my observations on the matter.

[Paul Workman]

After I finished calibrating the tach and doing my "510" porting (& Marc Haibeck tuning), I'd hit the rev limiter in 3rd gear about 100 yards BEFORE crossing the 1/4 mile trap. Marc Haibeck had to bump my limiter to 7500 to solve the "problem". I don't hit the rev limiter very often now tho. (I'm good for 121 mph in the traps now, in 3rd gear.

You can see from the 3.45 gear chart where the (7100 rpm) rev limiter would be a hindrance when trap speed of 121 in 3rd gear was in play... Oh! And if you haven't tried the "510" package, you don't know what your missing!!!

Edit: Update: Nearly 1/3 of Z owners have never "let the BEAST out of the cave"! Shame on you! [-X

[mcich7781]

Hit the limiter on the back straight at the Corvette Museum Motorsports Track. Then I had to slam on the binders to turn. It was glorious!

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[EvanZR1]

If you've never hit the rev limiter, you're not driving it hard enough! :wink:
Having said that, once I put a Raptor shift light in mine, I never hit the rev limiter anymore and I run my car to the shift light every time I drive it. My rev limiter is 7400, and my shift light is set at 7300. The shift light is in the AC vent pointed right at my eye and as soon as it lights, it's an instant reaction to shift (don't actively think about it, it's muscle memory and subconscious reaction). I've spend a LOT of money on this car, and the shift light was the best mod I did to it.

[BigJohn]

If you've never hit the rev limiter, you're not driving it hard enough! :wink:
Having said that, once I put a Raptor shift light in mine, I never hit the rev limiter anymore and I run my car to the shift light every time I drive it. My rev limiter is 7400, and my shift light is set at 7300. The shift light is in the AC vent pointed right at my eye and as soon as it lights, it's an instant reaction to shift (don't actively think about it, it's muscle memory and subconscious reaction). I've spend a LOT of money on this car, and the shift light was the best mod I did to it.

Why, the power drops off before you hit the limiter.

[rush91]

What is the rev limit on a Z? Honestly, I've never noticed on a hard run. I know I've hit it because the engine is saying that's all I got, time to shift.....But never been looking at the tach at time of shift to see exactly.

[EvanZR1]

Why, the power drops off before you hit the limiter.
Guess I should have clarified, I'm running a 391 with stage 2 cams. The power does NOT drop off. :)

[BigJohn]

Guess I should have clarified, I'm running a 391 with stage 2 cams. The power does NOT drop off. :)

Cool is it a stroked engine?

[Mikey]

Haven't hit it nor do I know what it is set at.

Only purchased the car a few weeks ago. 368ci Corey Henderson built 1991 Z. 4.10 gears. I did 3 pulls in second gear and the tach needle swept just above 8000 each time at which point I decided I better shift. Don't know if it is accurate but sure sounds like it's well north of 7000 anyway.

[EvanZR1]

Technically not stroked. It's one of Pete's 391 cubic inch closed deck blocks (larger bores) with stock crank. Add to that Pete's port work of everything and his aggressive stage 2 cams (plus of course long tubes, no cats and Corsa exhaust). Makes peak power at 6500rpm and holds it all the way to redline. Build thread here. (http://zr1.net/forum/showthread.php?t=29133)

[EvanZR1]

Haven't hit it nor do I know what it is set at.

Only purchased the car a few weeks ago. 368ci Corey Henderson built 1991 Z. 4.10 gears. I did 3 pulls in second gear and the tach needle swept just above 8000 each time at which point I decided I better shift. Don't know if it is accurate but sure sounds like it's well north of 7000 anyway.

You need to get your gauge cluster redone by Batee. When I bought mine, it was the same way. I could bury the tach past 8K and never hit the rev limiter. I used gps speed (Google Maps or Waze) on my phone to compare to tach one day and calculated it was at least 2K off. Having the shift light makes it even easier though as I can keep my eyes on the road and not have to watch the tach.

[Mikey]

You need to get your gauge cluster redone by Batee. When I bought mine, it was the same way. I could bury the tach past 8K and never hit the rev limiter. I used gps speed (Google Maps or Waze) on my phone to compare to tach one day and calculated it was at least 2K off. Having the shift light makes it even easier though as I can keep my eyes on the road and not have to watch the tach.

Thanks for the tip. Will verify rpm vs speed first. Also,planning to install a shift light.

Was your tach off a consistent percentage throughout the range or was it only skewed at the top?

[EvanZR1]

Was your tach off a consistent percentage throughout the range or was it only skewed at the top?
It's been several years, but I think it was skewed more at the top end (pretty sure I would have remembered it being off by 1K or more at idle).

[Paul Workman]

Haven't hit it nor do I know what it is set at.

Only purchased the car a few weeks ago. 368ci Corey Henderson built 1991 Z. 4.10 gears. I did 3 pulls in second gear and the tach needle swept just above 8000 each time at which point I decided I better shift. Don't know if it is accurate but sure sounds like it's well north of 7000 anyway.

Welcome to the BROTHERHOOD OF THE BEAST!

Here is a chart you might use to see if your tach is tracking correctly...assuming your speedo is corrected for the 410 gear!

And...(IIRC) there is a way to determine the RPM from the DIC (digital information center - the display in the dash). As I seem to recall, (someone please chime in here!) a number can be retrieved and a multiplier is used to ascertain the actual RPM. OR, if you have a scanner, of course you can read and compare the analog tach to the digital reading.

P.

[Mikey]

I checked the tach gauge vs the readout on the HVAC control. Hold up and down fan speed buttons simultaneously until 00 appears then tap up until 06. Tap the fan button. This gives you rpm/25. It won't read all the way to 7000 but I was able to verify my tach gauge reads about 15% high throughout the entire range. So 8000 is really only about 7000. Will have to get it calibrated.

[MuRCieLaGo]

I don't feel like reading the whole thread, but I'm wondering... I feel like I drive the car really hard... But I don't recall hitting the rev limiter! What happens when you hit it, RPM decreases a little bit by itself, then increases back up?

My 1993 had a steady rev limiter, RPM doesn't decrease when I hit it...

[Paul Workman]

I checked the tach gauge vs the readout on the HVAC control. Hold up and down fan speed buttons simultaneously until 00 appears then tap up until 06. Tap the fan button. This gives you rpm/25. It won't read all the way to 7000 but I was able to verify my tach gauge reads about 15% high throughout the entire range. So 8000 is really only about 7000. Will have to get it calibrated.

BATEE can either do the work for you, OR they can sell you the resistor circuit board replacing the old one, OR you can build you own precision voltage divider and install it yourself. (Personally, I built my own voltage divider, but that was before BATEE (https://batee.com/) was known to me, and the fact they now sell the "chip" for DIY'ers like me!)

[Bob Eyres]

The power doesnt drop off in a stock LT5 before redline.
Unless you go past the power peak, you will be way below it after your shift.


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[Paul Workman]

Well, in a stock motor, one starving for air, BTW, POWER does dip before the 7100 red line. In fact sources including "Mr. Jingles" (one of the (former?) test drivers for GM said he power shifts the ZR-1s @ 6200.

But, your right after the shift puts you right on top of the torque curve and behind the power peak as it is ramping up again.

Porting the LT5 - even (as I am) running stock cams, really turns the BEAST loose, and then the LT5 is just on the crest of the power curve (on a 5.7L motor). Add regrinding of the cams and some judicious phasing and you'll need to reset the cutoff to 7500 or 7600 or more to appreciate what the motor will deliver.

But, you don't have to take my word for it...ask Pete Polatsidis who ran his 5.7L LT5 to the low 11s on a regular basis before dropping in Kevin Costelos' 441 LT5 (that Pete also built).

Pictured are some more or less typical (inertia) dyno graphs showing the before (stock) and after (ported) results. Note the stock engine was cut off at ~ 6300 rpm, but the HP is just seen to be ebbing even then. And, the ported LT5 (before and after) shows the HP is at its crest at the 7000 rpm mark after porting; a significant improvement!

[Subfixer]

After my 415 build, I found the limiter pretty quickly. Mark did not change the upper limit.
This thing revs so fast, I wasn't ready.

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[tiegsd]

Can't say I ever have, try to shift before 6K or so when I'm trying to blow the carbon out. Near stock power is just fine for my driving profile & level of driving skill.