Help, only dynoing 300RWHP

[EvanZR1]

Ok, as I posted in NachoZR1's post over on CF, we were at the dyno last night, and my car only did 300RWHP. Car has (supposedly, need to find receipts from previous owner) a Corey Henderson chip, and top end porting from him. Also has 4.10 gears, but that shouldn't affect dyno readings. I was going to check the secondaries by turning the power key to normal, but apparently with Corey's chip it is full power all the time. The car runs really well, and pulls strong all the way to the top. If I hadn't seen the dyno on it, I'd say it was putting down a little more than my LT4 Firehawk (330RWHP).

So my thoughts for what might be wrong are:
collapsing intake duct
failing/clogged cats
secondaries not opening

Any other ideas?

Here's the dyno:
http://www.lt1.net/images/zr1/ZR-1_dyno_122210.JPG

[Pete]

I had gotten 270 rwhp with secondaries off.

I would first fix your intake duct.

I would take secondaries completely out and be done with them.

Pete

[EvanZR1]

Yeah, I'm thinking about just removing the secondaries completely. Corey has already offered to update my top end porting for free, so I think I'm just going to have him pull the secondary system completely and burn a new chip while he's doing that. He thinks I'm probably down about 80HP from where it should be, which would be great. Now I just have to figure out when I can get the car down to him for a couple of weeks.

[Pete]

Yeah, I'm thinking about just removing the secondaries completely. Corey has already offered to update my top end porting for free, so I think I'm just going to have him pull the secondary system completely and burn a new chip while he's doing that. He thinks I'm probably down about 80HP from where it should be, which would be great. Now I just have to figure out when I can get the car down to him for a couple of weeks.


"Do It" "Do It"

Better find the time and way to get it to Coreys as fast as you can,heck walk back home if you have to :)

Corey is probably spot on about the HP loss.
If you think the car feels fast now wait till after he's done with it.

Pete

[Locobob]

Here is a dyno of a 91 before and after porting, no headers. If you compare this to your dyno you will note that yours is down on power over the whole rpm range - not just at the top. So whatever issue you are having is effecting the whole curve, probably not a collapsing air duct as that usually just shows up at the higher rpms.

http://www.pnwzr1.net/Robert/Misc%20Pics/Be-Afportingresz.jpg

[Pete]

Here is a dyno of a 91 before and after porting, no headers. If you compare this to your dyno you will note that yours is down on power over the whole rpm range - not just at the top. So whatever issue you are having is effecting the whole curve, probably not a collapsing air duct as that usually just shows up at the higher rpms.

http://www.pnwzr1.net/Robert/Misc%20Pics/Be-Afportingresz.jpg


Peaks at 5600 :icon_scra
Some details please.

Pete

[Locobob]

Peaks at 5600 :icon_scra
Some details please.

Pete

My first porting job so the runners were a bit more conservative than what I do now but it's mainly the lack of headers causing the early hp peak. Might also be breaking up a bit at the top cause of lack of tuning - you can see some "seismic" activity starting at around 5600rpm. Car was a pretty stock 350cid with Power Effects exhaust.

Back to the comparison: You can see on my graph the car is making 200hp around 3300rpm vs your 165ish - that says a lot about the nature of your issue - look at Nacho's dyno and you'll see the same trend = Your problem is across the board. Secondary issue.... good possibility.

[EvanZR1]

Yeah, I was comparing Carlos' (NachoZR1) graph to mine last night, and noticed I was down over the entire rev range.

[Kevin]

is the duct collapsing?

[EvanZR1]

Not sure, the dyno was an above ground unit, so I wasn't able to get up next to the car while they were doing the run.

[Kevin]

do you have a reinforced duct, if no, then it is collapsing

[Corvette95]

A pre-93 stock LT5 with mild porting and a chip isnt going to produce 380 rwhp. You are only about 20 to 30 hp off, the dyno could be a little out of calibration.

[EvanZR1]

Considering that a stock 92 dynoed 345RWHP just before me, I think their is something wrong. Considering stock is 375, I'd expect about 310-320RWHP for a stock car, and then at least an extra 30HP from the chip and porting. Corey Henderson has offered a free update on the porting, and can fix the issue while he's got the top end off (obviously not free for the work other than porting, but still too good to pass up). I think I'll probably just have him pull the secondaries completely if that's what the problem is. Will probably be mid January or even February before I have time to get it down to him though. :(

[Corvette95]

a stock 92 will not dyno 345 , what mods did it have. Porting and a chip is being optimistic looking for 345, especially with no exhaust work, at least none was mentioned. Porting and chip with no outlet will do little with everything else stock
345 rwhp from 375 crank hp is less than 8% total output loss.

[EvanZR1]

Yeah, we're kind of wondering what's up with NachoZR1's car. From all appearances, it's a stock car with just an open air lid and Dynomax mufflers.

[mgbrv8]

Mmmmm 4.10s? What gear did you pull in??

[Paul Workman]

a stock 92 will not dyno 345 , what mods did it have. Porting and a chip is being optimistic looking for 345, especially with no exhaust work, at least none was mentioned. Porting and chip with no outlet will do little with everything else stock
345 rwhp from 375 crank hp is less than 8% total output loss.

I'm just making "conversation" here (over a cup a 'nog' :)) - not casting dispersions, but you seem pretty emphatic about a stock 90-92 not making 345 RWHP. You may be right...maybe. I believe he (Nacho said) the raw hp was 346.5 hp but we see that after correction for air temp, etc, the strongest pull was 342.5, and averaged approx 340.

(posted on CF as well)...

Ok so here go some more updates. When the first run was complete, the technician yelled out "346.5" and I became awash with excitement! He mentioned that these were raw numbers and the printout would contain the SAE corrected figures. The printout shows the following:

Run 1 - 342.49 hp and 316.80 tq
Run 2 - 340.23 hp and 318.81 tq
Run 3 - 337.57 hp and 321.27 tq

Give or take a couple hp for conditions and dyno calibration AND whatever "standard" is being applied to make corrections, 340 has been recorded on several similarly equipped 90-92s. But, my point is cam timing can make substantially more than a 5 hp variation at the rear wheels - as Dominic just learned (from Pete's inspection of his 92 motor):jawdrop: - So, again, not impugning your experience, I don't think I'd be quick to make a flat statement that a stocker wouldn't make 345 ish rwhp. I'm just sayin.

Nacho's car aside, as for Evan's ZR-1 making 300 IN SPITE of having some top end porting, he's short a lot more than 20-30 hp. There are many examples of 370 + for other cars; LOCOBOB recently posted one; Evan is missing 70 - 80 hp somewhere. And, by bolting on headers and a free flowing exhaust, he could be up against 390-400, according to examples by others...mods being mods, of course.

Bottom line...I'd just like to see the expression on Evan's face when he whacks the throttle after a 70+ hp boost!:dancing

Merry Christmas / happy holidays...(lifting my 'nog' to you and all the 'Brotherhood of the Beast").

P.

[EvanZR1]

Mmmmm 4.10s? What gear did you pull in??
4th.

[Locobob]

I'm just making "conversation" here (over a cup a 'nog' :)) - not casting dispersions, but you seem pretty emphatic about a stock 90-92 not making 345 RWHP. You may be right...maybe. I believe he (Nacho said) the raw hp was 346.5 hp but we see that after correction for air temp, etc, the strongest pull was 342.5, and averaged approx 340.



Give or take a couple hp for conditions and dyno calibration AND whatever "standard" is being applied to make corrections, 340 has been recorded on several similarly equipped 90-92s. But, my point is cam timing can make substantially more than a 5 hp variation at the rear wheels - as Dominic just learned (from Pete's inspection of his 92 motor):jawdrop: - So, again, not impugning your experience, I don't think I'd be quick to make a flat statement that a stocker wouldn't make 345 ish rwhp. I'm just sayin.

Nacho's car aside, as for Evan's ZR-1 making 300 IN SPITE of having some top end porting, he's short a lot more than 20-30 hp. There are many examples of 370 + for other cars; LOCOBOB recently posted one; Evan is missing 70 - 80 hp somewhere. And, by bolting on headers and a free flowing exhaust, he could be up against 390-400, according to examples by others...mods being mods, of course.

Bottom line...I'd just like to see the expression on Evan's face when he whacks the throttle after a 70+ hp boost!:dancing

Merry Christmas / happy holidays...(lifting my 'nog' to you and all the 'Brotherhood of the Beast").

P.

I agree with Paul, 345rwhp while on the higher side is not unheard of for a close to stock ZR-1. My old 91 made 351rwhp with just a Power Effects cat back and a DRM chip which increased to 371rwhp after I ported the intake - dyno graph is posted on page one of this thread. A car with port work coming in at 300rwhp says to me there is something not quite right. Headers and exhaust do wonders for making the most of top end porting but to say that porting alone won't make a difference is erroneous.

[sammy]

Evan ask corey to show you my dyno sheet of my blk 90 after he ported and tuned it, it also had jeal headers a flowmaster 21/2 cat back exhaust and a fidanza flywheel . the results were 409.9 rwhp and 373.66 tq. id say something is off somewhere . but when you take it to corey he will find and fix the problem . he also does a very nice tune on our cars . i drive 1550 mile one way to have him tune my cars

[rhipsher]

Here is a dyno of a 91 before and after porting, no headers. If you compare this to your dyno you will note that yours is down on power over the whole rpm range - not just at the top. So whatever issue you are having is effecting the whole curve, probably not a collapsing air duct as that usually just shows up at the higher rpms.

http://www.pnwzr1.net/Robert/Misc%20Pics/Be-Afportingresz.jpgHum! interesting to see the difference between Locobobs dyno results and my dyno results with top end porting an my totally stock exhaust. Bobs increase shows up at about 4200rpm,s. And the increase in my dyno shows up right from the beginning all the way up. Interesting to see how different they are. I'm not sure which results are more typical. I guess it all comes down to porting technique.
http://i301.photobucket.com/albums/nn63/keeno1970/P1010024.jpg

[Hog]

Hum! interesting to see the difference between Locobobs dyno results and my dyno results with top end porting an my totally stock exhaust. Bobs increase shows up at about 4200rpm,s. And the increase in my dyno shows up right from the beginning all the way up. Interesting to see how different they are. I'm not sure which results are more typical. I guess it all comes down to porting technique.
http://i301.photobucket.com/albums/nn63/keeno1970/P1010024.jpg
was there any ECM tuning done to your combo at all, or is it simply the porting alone that is accounting for the difference?
I see that your PE mode A/F ratio is quite different between youir pulls, it would be interesting to see Locobobs A/F ratios as well.

peace
Hog

[rhipsher]

HOG there was no tuning done at all. That was simply the result of the top end porting alone. Corey simply laid down the before porting run done 4 years earlier over the after porting run so I could see the improvement over the before porting run. Im still running stock cats and exhaust which doesn't compliment the top end port at all. Once I get the proper headers x pipe and a more free flowing exhaust system with a fantastic Corey tune I'll be curious to see what kind of numbers it will produce then. But even with stock exhaust, top end porting makes a difference either way
But back to the reason your car is only producing 300. It could be so many different things. If you haven't already, pull the codes. They will help isolate the area to focus on. Wether its a fuel problem or secondaies not working properly. O2 sensors or cats failing. Start there first.

[rhipsher]

On my AF Corey said I was running lean. I expected to be running rich if anything.

[Locobob]

HOG there was no tuning done at all. That was simply the result of the top end porting alone. Corey simply laid down the before porting run done 4 years earlier over the after porting run so I could see the improvement over the before porting run. Im still running stock cats and exhaust which doesn't compliment the top end port at all. Once I get the proper headers x pipe and a more free flowing exhaust system with a fantastic Corey tune I'll be curious to see what kind of numbers it will produce then. But even with stock exhaust, top end porting makes a difference either way

I'm thinking the different A/F ratio's have a lot to do with the lower rpm gains, I've never seen intake porting pick up much below 4K. Porting should lean things out a bit although your A/F curve seems extreme. Hmmm 4yrs apart.... ethanol maybe?