I went to the track last night (only heads up, no clocks). Anyways, I have to shift into 4th gear which I guess is normal for having 4.10 gears but I bounce off the rev limiter just before crossing the 1/4 mi. marker. Is this normal? I do have the PCM tuned by Madz28 and he set my limiter at 6000rpm. I want to hear some input from other guys with the same set up as mine and hear what they think.
Thanks.


Mike

 

4th gear at like 5500ish is when i crossed the line with mine...it's right

 

Run taller tires or make the engine rev higher.

What kind of MPH do you trap?

 

I was running normal street tires with 25lbs of pressure on each side. I guess I never noticed it before but I also havent ran my car at the track in awhile. Last night, they didnt have times but I was watching my speedometer each time it was anywhere between 96-99mph. We are at 4500 ft elevation. As for the rev higher when taking off, I was dropping the clutch at 2500rpm each time and feathering it to not get as much wheel spin.


Mike

 

Sounds like to me the rev limiter should just be moved up to 6200 or 6400.
With those 'shorter' tires, less than 26", hitting the limiter at 6k is common.

Buddy was running a 4.10/Th350 set up with BFG DRs and was hitting the limiter in the 1/4, we put on the ET Streets and no more problems, my 26x11.5x15 are nearly and inch (or more) taller and they should grow a slight amount on the top end.

 

I'm running 4.10's w/ my A4, and in 3rd gear (1:1 ratio, same as your 4th gear) I don't hit the rev limiter and I'm crossing the traps around ~106 - 107 usually ... mind you, my rev limiter isn't set at 6000 rpm, but still, you should be able to run faster than ~99 mph I'd think?

Check out the handy-dandy gear calculator and see where you're at ... it looks like you should be good 'til ~109 mph, at 6000 rpm, even with 25" tires?

 

your right, but I think the low trap speeds has alot to do with the high elevation Im at. Im going to borrow some taller drag radials and see if that helps. If not, back to the drawing board...


Mike

 

Power and elevation may be related, but speed is speed ... if you're running ~96 mph, especially with a standard where there shouldn't be the amount of slip an automatic is prone to, then you should be able to do direct calculations back through the tires, gears, tranny and to the motor, which should not be running higher than ~5200 - 5300 RPM?! Maybe you should double check your tire height, and confirm that your rev limiter is really set to 6000 RPM.

 

With a stock sized tire you should be able to go 112 mph in 4th gear with 4.10's. You either have a big miss up top or your limiter is at 5200 rpms.

 

I appreciate all of your input. I finally figured out the problem. After the car gets warm or hot at the track the fuel pump starts acting up. So when I thought I was hitting the rev limiter, it was actually the fuel pump cutting out. So I will have to replace it with an aftermarket one.


Mike

 

Bummer. At least you figured it out though. That makes more sense.