I have a completely stock 03 Auto Vert. I Took it to the track wednesday just to see what it (and me) would do. I have never raced before as is reflected in the R/T's.

My first run:
R/T 1.080
60' 2.052
1/8 8.699
1/4 13.383
MPH 101.95

I was pleased and optimistically confident I could get into the (at least upper) 12's with a little better R/T and better brake-tourque launch technique.

Now the problem. Each consecutive run got worse and worse. I tried everything. The car came out of the hole great, the shift to second was perfect, but then at around 5,500-5,5800 RPM it started cutting out and missing real bad, delaying the shift to third. This was with the car left in "D" to shift automatically.

I tried T/C ON, T/C OFF, Competitive Mode, Auto Shift, Manual Shift...Nothing helped. It just CRAPPED OUT before the shift to third! I know the car could have done considerably better if not for this performance loss.

My car has never done this before and I tromped on it several times on the way home from the track and it wound-out and shifted fine.

One thing I did notice was my "TEMP" was up around 220 degrees. I called TNT Motorsports and they said that wouldn't cause the problem as these engines are designed to run at those temps.

It just really ticked me off to have my car run so crappy (popping and missing) ONLY at the track!

Can anyone explain what happened? My thoughts are either problem with the Rev-Limiter, Fuel Starvation, or detonation from the heat. I can only suspect tourque-Braking the start may have put a larger demand for fuel and made the problem show up???

It was a cool SE Texas night. Temps were in the low mid 70's (best run) dropping to mid 60's during the evening.

Ed Holler
Lake Conroe, TX.


[Modified by Mellow Yellow, 8:08 AM 4/4/2003]


[Modified by Mellow Yellow, 8:09 AM 4/4/2003]

 

I have had weird things like that happen to my car "only at the track" too. Bogging, cutting out and S-like that. Of course on the way home or the next day the car runs fine... :rolleyes:

vetterdstr :cheers:

 

Congrats on your first visit to the track. I can tell your trap speed is not indicative of your et's for a Vette. I have a 2000 Formula(A4 3.23) and it was doing the same thing first time out, a buddy who works at a turner shop hooked it up to the LS-1 edit and found that I was bouncing off the rev limiter. I know you mentioned that it happens at 5500 to 5800 rpms or so...trust me, those gauges are not always right. Nevertheless, he raised the rev limiter to 6500 and adjusted the shift points/line pressure via LS-1 edit and it went from 13.3's @104 to 13.00 @ 106.6 on GS-C's. Yes, a Formula with only the above trans mods and a air lid. My 99 hardtop rpm gauge is also a little wacky...oh, she ran 12.60's on run craps. Now, as far as quicker ET's... my friend do not look at your R/T, look at your 60ft. Get it down to about 1.80's, fix the trans issue via a LS-1 edit, HPPIII or Predator and you will be in the 12's all day long. :yesnod:


[Modified by Myhardtop, 10:59 AM 4/4/2003]


[Modified by Myhardtop, 11:02 AM 4/4/2003]

 

A faster R/T won’t change your ET because ET is measured from when your front wheels clear the stage beam to when you break the finish line beam. Nevertheless, I have found that over the years the better my R/T the better I seem to launch and shift the car, which results in a better ET.

As far as your launch goes, I think that brake stalling your car hurts you in two ways. First, brake stall is usually a hundred RPM or two lower than flash stall. Hitting the gas off idle or flash stall is higher because of the added inertia from the spinning motor whereas in brake stall that inertia effect has dissipated. Also, it heats up your A4 that may contribute to it slipping and making slow shifts.

In order to make the 4L60E automatic survive the torque the LS1 delivers GM has programmed the PCM with Torque Management to limit the engine torque delivered to the A4. In addition all 4L60E’s use relatively soft shifts, which can be hard on the clutches but minimize the strain on the other components like the planetary gears and the input shaft drum that tend to fail under really firm shifts. Bottom line is your A4 is marginal for normal driving and unsuitable for drag racing in stock form.

The symptoms you describe are typical of an A4 that is slipping when shifting into 3rd gear. Boosting the line pressure should eliminate the problem albeit at the expense of reliability. How much it will affect reliability is anybody’s guess but it will put more strain on the components. However, if you drag race the car you should do it in order to keep the clutches from slipping and destroying themselves.

Needless to say anything you do to the motor that significantly increases the power can be detrimental to the A4. Removing Torque Management will make your car faster and can be done with LS1 edit or by using the power programming packaged with the Predator programmer but will also put strain on the A4.

I am not saying this to scare you out of drag racing your car or modifying it for more power but I think you need to know that the A4 is a marvel of bean counter engineering and a very weak link in your drivetrain. It may very well be possible that by boosting the line pressure and even adding some HP that the A4 will serve you well and cause no problems even if you continue to drag race for as long as you own the car; as they say your mileage may vary. Down the road if the A4 does give up, you can always go with a FLP Level 4, which has proven itself to be a bulletproof transmission.

 

:iagree: My car did the same thing before I had Steve Cole tune it. He said it was bouncing of the rev limiter. I though it was a detonation problem.