Low on power?

[1990 quasar blue]

I was reading through some threads and seeing some numbers of cars with similar mods. LocoBob's old 91 making 374rwhp, another guy making 386. I have ported plenum and injector housings by G.V.D., Flowmaster exhaust, HAT PROM, open lid, and a Coplon duct. The best the car has done is 355 rwhp and that was about a full point lean. I had it fattened up a little and now it's down to 350. Could this be a cam timing issue? The car seems to run good and pull hard but, the numbers just don't seem to be there. Any thoughts?

TIA,
Mike

[Z Factor]

Originally Posted by 1990 quasar blue

I was reading through some threads and seeing some numbers of cars with similar mods. LocoBob's old 91 making 374rwhp, another guy making 386. I have ported plenum and injector housings by G.V.D., Flowmaster exhaust, HAT PROM, open lid, and a Coplon duct. The best the car has done is 355 rwhp and that was about a full point lean. I had it fattened up a little and now it's down to 350. Could this be a cam timing issue? The car seems to run good and pull hard but, the numbers just don't seem to be there. Any thoughts?

TIA,
Mike

Mike,

Assuming their numbers are accurate, don't most of the cars you are referring to have headers, no cats, an x-pipe, and a 3' exhaust like the B&B tri-flow? Almost everyone trying to hit the magic 400rwhp without cubes or the juice goes that exhaust route along with top end porting.

[WB9MCW]

1990 quasar blue my gud buddy zr1pete does p&p and exhaust mods to ZR-1's in the chicago area and i am sure u could benifit from e dicussinos with him. he is a zr-1 fanatic 4 sure and a great guy. he will get u too the 400 mark,, he told me anytime i want to let him do his majic to my Z he could get me there!!! here is his email and ill let him know of this post. he is a member of zr1net/reg and assists me at corvette mech. as one of the mech's i consult to solve ?'s we get there from zr-1 owners!!!

[Locobob]

Could be a lot of things: Production power level variation, Different dyno, Test conditions, something amiss in the motor - dirty air filter, plugged cat, etc etc. Incidently my old Z made 355rwhp with Power Effects exhaust and a DRM chip. Power climbed to 374rwhp after porting the intake. To contrast Jeffvette made 340rwhp with Corsa exhaust, about 355rwhp with intake porting and about 390rwhp after adding headers to the mix. Every car is different and a lot of factors can affect dyno numbers. I wouldn't stress over it too much.

[1990 quasar blue]

Thanks for the replies.

ZFactor, I don't think they had headers, or at least LocoBob didn't. As far as 3" exhaust, I don't think it makes a huge difference with stock cubes.

WB9MCW, I'm familiar with Pete from the other forum, and he is very knowledgeable. As it stands I have everything but the headers. Maybe this winter.

LocoBob, The car was a little weak from the start. Only 320/320 but, that was stock right down to the eight year old plugs. I'm not worried, it still does pretty well for a fifteen year old car. I just keep wanting a little more.

[Z Factor]

Originally Posted by 1990 quasar blue

ZFactor, I don't think they had headers, or at least LocoBob didn't. As far as 3" exhaust, I don't think it makes a huge difference with stock cubes.

I just keep wanting a little more.

To get up to the levels you mentioned it would be tough to do without headers and a good exhaust. The 3" exhaust with x-pipe does not make a huge difference over other non restrictive aftermarket systems, but it does help. With our cars, every little bit helps considering that major power increases equate to major $$$ beyond simple bolt on's.

Like Locobob said "every car is different and a lot of factors can affect dyno numbers".

As to your desire for a "little more", we know where you are coming from. My best advice would to talk to a respected tuner like Aaron or Mark. They are both generous with their time and advice.

[rkreigh]

350 is actually not bad. dynos vary a HUGE amount depending on which one, correction factors, ect. the "dynojet" is pretty much the standard.

the real question is how does it run MPH at the track as it's a bit easier to gauge performance than dyno queen numbers.

I've seen some cars that dyno 340 post up some pretty impressive MPH.

alot of the "porting" isn't very agressive and as you already pointed out, you started at 320 which really isn't far off.

plus or minus 10 hp is pretty minor considering the various correction factors and dyno readings.

don't get too hung up on numbers, go flog it and see what she'll do.

[Aurora40]

My numbers aren't any better. This is on a Superflow dyno at Tony's Corvette Shop in MD. My car with ported plenum/IH's (and new injectors, tune up, etc) made like 327hp. After swapping mufflers and resonator (described in this month's HOTB newsletter) it made 350hp. The car has not been tuned though, it has a Haibeck chip he shipped me along with my ported top end.

My hope is it's the dyno that reads low, that's what the dyno operator mentioned as well when compared to a Dynojet. But whatever, it makes what it makes. The best 1/4 time on a summer NJ day was 12.7@114 with my meager driving skills.

[1990 quasar blue]

Thanks Ron, I'd forgotten all about this one. I've since sent the intake and injector housings out to Jeff for PC. While there, Lococbob did a little more port work. I've yet to go back to the Dyno but, the car does feel a little better. The car has been to the track once and they cut it back to 1/8 mile due to wind. It consistently ran over 89 mph with a best of 89.43. That being said, I've had people tell me that the only reason it trapped that high was 2.1 - 2.6 60' times. Everyone there was complaining about traction as it was pretty cold.

[1990 quasar blue]

Aurora, I think we both need headers and a Fidanza. Or at least a real time dyno tune.