So, any ideas why the car traps 114mph, but only goes 12.10s on a 1.65 60ft. with a dead hook? Full weight car with the mods in my sig. The car runs good and really pulls strong the last half, it gains almost 26 mph.

 

1-2 shift too early??

What are the rest of your numbers?

What is your race weight?

 

No idea what the weight is. It's a fully optioned car, minus the front sway bar and spare for the track. But I'm sure the KBDD subframe and the Spohn TA make up for that.

The car shifts at 6400 for the 1-2 shift and 6300 for the 2-3. Motor peaks at 6k and maybe loses 15 hp by 6400. I believe the shift points are right on.

Here is my best pass, and the other ones are right there also.
60'.........1.653
330........4.965
1/8........7.723
MPH.......88.86
1000......10.111
1/4........12.128
MPH.......114.47
I thought switching to the Yank 3600 would help some compared to the Vig.2800, but it didn't, although it was about 15 degrees hotter that day. I still cross the line at 5500 to 5600 rpm. But I'm leaving some room for the Nitrous install. Any ideas, most say this car should be in the high 11s.

 

Sounds right to me.

 

Some how you're losing et in the second 1/8. 7.72 x 1.55 = 11.97 and 7.72 x 1.53 = 11.81
You should be somewhere in that range. The real head shaker is that you're pulling the mph but not the et. The only thing that comes to mind is that 3rd gear is slipping then grabbing or the converter is just a tiny bit too loose and is loosing some et at the beginning of 3rd.

 

Have you tried logging any runs? I would guess you are slipping or lagging on a shift too.

Any bog on the runs? Also don't short change the weather. If it was hotter, the car will run slower and do all sorts of things it wouldn't on a cooler day.

 

It is the stock 30k mile trans. Maybe it is slipping a little and I just don't feel it? Thanks for running the #s. I had forgotten about that formula.

tireburnin, I don't have any way to log runs. That stuff is over my head. No bogs, nice shift points as far as I can tell. I guess I'll go back when the temps are in the 50s, and I am working on pulling a 100#s out of the car. I really would like to get it to run 11.90s before I spray it.

 

If you get this figured out be sure to post up because I think I have the same prob.

My slip from last weekend

1.67 60'
7.75 1/8
87mph
12.21 1/4
110.7mph

 

You don't have the same problem. Your MPH is falling off as well as your ET. Wrong rear gears/tires? Bad fuel pump? Bad ignition?

 

I'm running 4.11's with 26" tire. I'm leaning towards the stall being the problem. What amount of slip rpm is normal with a stall converter? Mines around 500 all the time even above stall speed.

 

converter slip is considered good if it's under 10%

 

List your drivetrain setup so we can better understand it.

But first things to check for are:
Trans fluid color, smell and shiney stuff in it

Next would be shift points relative to RPM - figure out what your tach says relative to your various break downs in the 1/4 mile. When my transmission came apart, the biggest indicator was an RPM too high for my given trap speed at various points down the track.

The amount of slip depends on the type of stall (lockup?th350? etc) and the brand. Some are tighter than others. Usually under 15% for an unlocked converter or less.

 

Trans has 6000 miles on it just swapped from T56. Fluid is not burnt at all. Transgo stage 2 shift kit, upgraded clutch pack etc. 4L60E with a Vig converter supposed to be 3400 but only flashes to around 3k on the launch from 1500 footbrake. Shifts are set at 6100 and comlete by 6400 rpm. My rpm at the line is 6400 at 110mph which is about 600rpm slippage. If it helps to understand how the cars runs

6spd________________Auto
1.77 60'_____________1.67
7.90 1/8th___________7.75
91mph_______________87
12.14_______________12.21
115mph_____________110.7

 

It's coming out of the hole just fine. But one key piece of info you left out is whether or not you lock up the converter? If that is locked at 80-90mph then you have a big issue. If that is unlocked then it isn't too bad.

If you are crossing at 6400 rpm locked/or with a manual you should be going around 120mph. Your crossing at 110 which would be around 5850 rpm with a manual/locked. That's 10-11% slip. Not real bad one way, very bad the other.

This site has a good calculator:
http://www.f-body.org/gears/

 

Thats unlocked do most guys lock it around 90mph?