91 ZR-1 Dyno Results

[YESZREE]

The last few days I was in Kissimmee,Fl attending the NCRS regional and spent a little time on the Breatless Performance Dyno.

My car was not dyno tested prior to my changes so I am starting now with this baseline.

My adders are a Magnaflow X-pipe with Magnaflow race series mirror finish mufflers, Breathless Vortex cold air induction, and a DRM chip.

The results were 370 RWHP and 385 ft. lbs. of torque.

The power band was most effective @ 5500 rpm. after that it began to fall. Here are some of the numbers:

363 rwhp@ 5600 rpm and 363 ft. lbs.

332 rwhp@5700 rpm and 360 ft. lbs.

323 rwhp @5800 rpm and 357 ft. lbs.

As you can see the longer you stay the weaker it got.
I don't know if this is how it is supposed to be but my crew chief from my Top Gas race team said that we are going to look at the Z this week . He thought it was running out of fuel. He said it was breaking up at the high rpm's.

If anyone has had this experiance I would appreciate your help.

I talked to BIZ on the phone and he told me he had similar numbers with the exception that he has long tube headers w/o cats. I still have the stock components except for the changes I mentioned.

I guess when I raced xsmph (julio) in his ZO6 I stayed too long because I was running all gears to 7200 rpm.

So there you go Julio, next time I'm shifting @ 5600 rpm!!!!!!

 

[Demps]

Great numbers. I'd check my air duct for collapsing at higher rpms. It's a very common thing with earlier ZR-1s. The power will continue to the 390ish range I'd bet when you get it straightened out. That's a lot of torque.

 

[90 Corvette ZR-1]

you are either leaning out on the top end or your air duct is colapsing. Id check the air duct first, and you may need a retune on the chip.


Great #'s though that is one stong king

 

[DDSLT5]

you are either leaning out on the top end or your air duct is colapsing. Id check the air duct first, and you may need a retune on the chip.


Great #'s though that is one stong king

Yep - sounds about right - your power should climb (with the stock exhaust/cats) to right about 6000 rpm, then hold relatively steady until 6400 rpm, then gradually trail off to the numbers you reported - mind you - at 7200 rpm. This trailing off is solved by the addition of headers - just check out BiZ's dyno graphs - very telling indeed!! Sounds like the duct is collapsing badly - mine was collapsing half way, and when I installed the Coplon duct, I gained 5 rwhp, and comparable torque.

 

[xsmph]

No Need to shift at 5600 rpms. Something is killing that top end. No wonder I pulled you a little in fourth gear ( my weakest gear).
It could be a collapsing duct or some sort of fuel problem. the 7000 rpm shift point is good, but you should be making still 350 rwhp at that point.
Let me know when we can hook up again.. I'm in desperate need of seen some ZR-1 Tail lights!!
Julio

 

[rkreigh]

verify that the car is holding fuel pressure and put a wide band A/F check on the next dyno. the marc coplon air duct is very cheap solution to the air duct (or you can just use stiff wire).

the car should be making peak power up around 6600 and stay pretty flat.

lots of possibilities of what could be limiting power, secondaries not opening all the way, injectors, weak fuel pump. lets find out why this lt5 is wheezing.

cya.

 

[BERTZR1]

Hey Yeszree,are those the only mods you have on your car?
If so, I think those Dyno #'s are A bit high.
May be you can share with us your best ET and MPH.



thanks

 

[Jeffvette]

Hey Yeszree,are those the only mods you have on your car?
If so, I think those Dyno #'s are A bit high.
May be you can share with us your best ET and MPH.



thanks

I have to agree, sounds like the car has either headers or P&P on the top end with some tuning done as well.

My car hit 339 on the dyno with a catback and then 354 with a P&P and 391 with the the P&P and headers.

 

[YESZREE]

No Need to shift at 5600 rpms. Something is killing that top end. No wonder I pulled you a little in fourth gear ( my weakest gear).
It could be a collapsing duct or some sort of fuel problem. the 7000 rpm shift point is good, but you should be making still 350 rwhp at that point.
Let me know when we can hook up again.. I'm in desperate need of seen some ZR-1 Tail lights!!
Julio

Mucho things were wrong my friend. I took the ZR to the shop yesterday for a look see and we removed the intake and found many vac leaks and a bad check valve. We replaced all of the old stock lines with silicone lines and replaced the check valve. Mark C. is ending my air duct, I should get it Monday!

Whew! I was worried about that 4th gear surprize of yours, I thought you sprayed me a little!

Ed

 

[YESZREE]

Hey Yeszree,are those the only mods you have on your car?
If so, I think those Dyno #'s are A bit high.
May be you can share with us your best ET and MPH.



thanks

Those are the only mods. The dyno was The Breathless dyno that shows up at most big Corvette events. The intake air temp was in the high 60's.I don't know about the validity of the dyno or for that fact anyone's dyno. But it's better than guessing.

I deal in the engineering community and I question most every statistic I ever hear. I am very aware that with a few program changes or tweeks of a screwdriver you can create any result you wish with electronic diagnostic equipment which is exactly what a dyno is. How long ago was it certified? And by what standard was it calibrated to? Who knows. Next time I see those guys, which will be in Gonzales, La next month at the NCRS regional meet I will ask them for some documentation.

I'll let you know what they say.

 

[xsmph]

Mucho things were wrong my friend. I took the ZR to the shop yesterday for a look see and we removed the intake and found many vac leaks and a bad check valve. We replaced all of the old stock lines with silicone lines and replaced the check valve. Mark C. is ending my air duct, I should get it Monday!

Whew! I was worried about that 4th gear surprize of yours, I thought you sprayed me a little!

Ed

Ed, no spray.. I wanted you to win.. remeber Zr-1 Team!
I'll be going to Bradenton on the 9 as an expectator. My friend is taking his 01 GTS. If you go , we can hook up on I-75 and Rematch!
Julio

 

[YESZREE]

Ed, no spray.. I wanted you to win.. remeber Zr-1 Team!
I'll be going to Bradenton on the 9 as an expectator. My friend is taking his 01 GTS. If you go , we can hook up on I-75 and Rematch!
Julio

I'm there!!!!!

 

[xsmph]

call me at 786-208-2957.. we got a new weapon on our team just in case you kick my a$$

 

[YESZREE]

Hey Yeszree,are those the only mods you have on your car?
If so, I think those Dyno #'s are A bit high.
May be you can share with us your best ET and MPH.



thanks

I have not run the car in the 1/4 mile, but I have had it to 182 mph. and still pulling.

All I can say is it must be a freak. I've heard of the guys at Stillwater playing around with some of the engines while they were in production. I had the intake off this week and removed ALL of those pitifull excuses for vaccuum lines and replaced them with high grade silicone lines of various sizes from NAPA. I see no sense in paying excess amounts of money for these vaccuum systems when the supplies are avaliable from a local source.

Anyway, while the intake was off I looked into the port walls and there were very visible spiral swirls cut into the walls all the way down to the secondaries. Is this stock or a sample of machinists spare time? Maybe someone can answer.

I am going to put the car back on the dyno as soon as I get the new Mark C. air duct in the mail.

I don't think I will run this car at the track as I am preparing my Super Gas car for the upcoming Poweraide Drag Racing season. This is taking alot of my spare time and racing funds.

 

[Jeffvette]

Anyway, while the intake was off I looked into the port walls and there were very visible spiral swirls cut into the walls all the way down to the secondaries. Is this stock or a sample of machinists spare time? Maybe someone can answer.

I'd say they've been touched, as well as the injector housings. You need to get a caliper and measue the port diameter.

 

[YESZREE]

I'd say they've been touched, as well as the injector housings. You need to get a caliper and measue the port diameter.

Any idea what they should be?

 

[locobob]

Ports should be about 1.300 in. - 1.310 in. at the plenum / injector housing gasket surface. The ports should be very rough inside - if they are smooth then they have been worked over. You may also see some very basic port matching between the parts, this was done at the factory.

 

[xsmph]

His is a 91, I never heard of this been done on a 91. The machining he might be referring to is the one found on all motors right on the secondary intake port. It goes from the head surface to where the secondary plates are located.

 

[luvmy92]

I think Breathless's Dyno runs a little high. I had my car dynoed at Vinci's, which uses a Dynojet 248E I believe, and my numbers were 351/351 at the rear wheel. About 1 month later, I dynoed it on Breathless's Mustang Dyno at the Eckler's event, and it was 366/378.

I'm not sure what's going on there but I am inclined to believe the numbers from the Dynojet are more accurate. Regardless, that seems like a strong running ZR-1 you have there. BTW, I was at the Kissimmee show. It would have been nice if I could have hooked up with some of you guys...

Mike

 

[xsmph]

YESZREE, Give me un update... was your loss of power do to the collapsing air duct? Did you get the Coplon one already?
I'm filling up my bottle just in case you come back TOO Srong...