Here is my $.02. What RPM are you currently crossing the finish line? I would say you are looking to cross at 6000 rmp. Bolt-ons will change the results (gears, tire diameter, converter, headers, shift points, etc).


In my 95 Formula convert, stock, auto, 2.73 gears, 26" diameter drag radials. I bumped the 1-2 shift point up to 50mph and moved the rev limiter to 6200rmp. I was able to cross the finish line in 2nd gear at 6000rpm. I was able to duplicate this in a 95 Formula hardtop.

I have another formula , 383lt1, turbo 400 auto, 27" diameter tires. I have changed gears and tires to get the finish line rpm desired. Nothing like spending $$$ to have gears installed only to have the work redone the following week. I made the mistake of changing gears and tire diameter at the same time. Duah, make only 1 change at a time.

1" change of tire diameter = one jump in gear ratios
26" diameter tires and 3.73 gears = 27" diameter tires and 4.11 gears

I would do the boltons first then see where you at rmp wise. Then make addjustments via tire diameter and gears.

 

My first (ever) three passes last night: The shift light came on in third right before the trap. I had enough tach left to roll thru. Stock gearing, obviously. So about 6500rpm.

 

I tried that once, the car nosed over when it hit the rev limiter about 30ft before the finish line

 

Get it to hit the rev limiter around 100 ft out and you'll be damn near perfect!

 

Mine hits the limiter about 300 feet out in 3rd gear (M6). So, I pull 4th gear and add about 6mph to my trap speed instead. It's worth a few tenths on my ET.

My goal is to put in a set of 3.73 gears and then add enough power to max out 4th (~125mph).

 

^ What would 4.11's trap? I really want gears.. been wanting a set of 3.90's.. Good median between 4.11's and 3.73's...

 

You want to be on the limiter in 4th gear with an M6, 3rd gear with an A3/A4. I would absolutely pull 4th gear at the 1000 ft mark if I were at my shift point. However, that simply means that you are grossly under-geared for the 1/4 mile.

 

Assuming a 6500rpm rev limiter, 1.00:1 trans ratio, 275/40R17 tires, and everything working right (no traction issues and plenty of clutch grip), your maximums are:

3.23 - 153 mph
3.42 - 145 mph
3.73 - 133 mph
3.90 - 127 mph
4.10 - 121 mph
4.30 - 115 mph
4.56 - 108 mph

Yeah, that's because it's (mostly) stock. I'm just working with what I have until I can afford to do something about it.

 

Would the six speed guys get your own thread please. I started this asking about mod stock engs with AUTOMATICS !

 

Re-read post #15.

 

I believe Warren Johnson once said, "red-line + 5% at the stripe!" Therefore, you should work backwards from that goal (trap RPM), selecting your gears and slick height that will place you there (your red-line + 5%).

With my LTX Camaro I’m turning 7K+ at the stripe with 127 MPH.

WD

 

4.86 gears with a TH400 trans and 32" tall tires. I shift at 6500 rpms but I go through the traps just below 7300 rpms.

 

Your car is an example of the Warren Johnson trap RPM theory. But with a few extra trap RPM beyond +5%. Specifically, you're at +11%

WD

 

Tricky bracket racers there. Her crew chief may have instructed her to short shift in order to slow the ET down a bit. Gives a high MPH to ET ratio for a top end advantage.

 

I never really understood the whole +X% thing until I started driving my own car. I used to sit in the stands up at the top end and wonder why the shift light was on in most cars while going through the traps. The first time I ran my car I thought I broke something because my shift light was on and I had no more gears left... DUH!!!