Car doesn't pull strong right before the limiter
 

Recently I installed Pacesetter LT's, ORY, and an SLP 2OTL catback. The car has a lid, ported TB and is stock otherwise. I had wait4me do the mail order tune and took the car to the track.

I noticed a few hundred rpm before the shift light (set to 6000) in 2nd and 3rd the car just doesn't pull like it should. It doesn't stop pulling, the pull just slows and is noticable. My times with stock manifolds and y-pipe through a Corsa was 13.20s @ 107, with the LT's and ORY and this issue the car went 12.85@109. I was expecting better MPH and I think it is due to this issue.

I'm thinking two things, timing being pulled or valve float since it only happens right before 6000 rpm.

Any ideas?

*UPDATE*

I changed my fuel filter, air filter and through a can of sea foam in the car. Pulls hard right to the limiter now. I cut the fuel filter open and it was pretty bad. The air filter wasn't too bad but I replaced it anyway, and for the sea foam, not sure if that had an effect.


Doug D

I don't think I've heard of stock motors having any problems with valve float at 6,000rpm. A mail order tune will get you close and it sounds like he did a good job. You picked up ~3 tenths and 2mph from headers and a slightly better flowing catback. There might be 5hp lurking in your tune...but I'd say you're about where you should be.

Yes, the horsepower peak is around 5500 rpms. My dyno graph (with headers but before cam) starts slowly curving down after 5500. After the cam, it's still increasing at 6500.

Interesting, what should I set my light at 5800?

Doug D

I'd still shift at 6100~6200 w/ a stock cam. It's puts you in a better position for the next gear as the optimal shift point is not at peak hp.

Would I really beable to feel the car pull less due to the power naturally dropping off?

Doug D

yes..

my friends ls1 does the same thing, lid/cutout. right before the rev limiter it stops pulling and it feels your just waiting for 6k to come to shift.

I have a few friends who have had luck shifting at like 5700... RPMs dont alway equal hp... Try it, you're likely to pick up a little time then waiting til the motor dies off.

That's exactly how it feels. I figured these motors liked to breath, guess not.

Doug D

This motor has the same concept as all engines. The more air coming in the better. Just like a big air compressor....cause that is really all it is.

Oh I understand completely, I just thought the LS1 heads breathed all the way to 6000. I'm going to lower my shift point to 5800 and see if that helps.

Doug D

I would bet on your car leaning out up top. I have the same mods and mine was leaning out to 13.8-14.0, I tuned it and now it pulls much stronger to the limiter at 6300. :)

the 98 models have differnent head and cam... they have the worst flowing head out of all the ls1 f body years.. and dont have a ls6 manifold...

Just for reference.. i have a 2001 SS camaro. With a slp lid,free ram air, smooth bellows, nad a loudmouth exhaust, and a UMI adjustable T/A and SFC's. My best ET so far is 13.15@109.2 mph on a 2.15 60'. on a M6 stock clutch (whats left of it) and street tires. 35k miles on the clock

Well I scanned the car with an OTC scanner I use and it doesn't seem to have any knock. My scanner wont show knock, but will show total advance and I saw 26 degrees all the way up to red line in 3rd and 4th.

I'm going to dyno the car in a few weeks with a wideband and see if it's leaning out.

Doug D

*UPDATE*

I changed my fuel filter, air filter and through a can of sea foam in the car. Pulls hard right to the limiter. I cut the fuel filter open and it was pretty bad. The air filter wasn't too bad but I replaced it anyway, and for the sea foam, not sure if that had an effect.

Doug D

hello, maybe i missed it but do you have an auto trans or manual. my auto starts losing a little power over 5500 rpm. i believe do to the torque management system that can be deleted. if yours is manual i'd guess somethings wrong with the tune. goodluck

5750 on my tach is where I notice mine slowly nosing over or "leveling off".