My car is a turbo cruiser with some drag strip abuse. I'm not interested in some crazy shifter or trans brake. I built my own 4L80E controller a long time ago with many thousands of mile under it's belt and a bunch of drag outings. For the past few years, I haven't been able to foot brake and hold any boost on the starting line. This last trip I tried out the Sloppy Brake at the track. I can hold any boost now.

Before the launch, the shift solenoids are set to 3rd. On the launch, they switch to 1st and the car takes off.

 

Wow, crickets.

My 60 foot improved from 1.7 to 1.5 with the sloppy brake. I raised launch boost for another run, but I spun all first gear, so too much boost for the track condition.

I ran 4 tests in my driveway to log response time of various variations. All tests were done at 2200 RPM. I logged the duration between the launch button release and when the tires started spinning. My driveway was wet and full of leaves, so each test spun the tires. All tests with shifter in 3 ("D"), footbrake is released the instant launch button is released. Trans is dual feed, 2 and 3 accumulator delete, shift feed holes enlarged.
1) No sloppy brake, in 1st gear, just ignition cut 2 step.

The first test was the only ignition cut test, all other tests were my computer maintaining 2200 RPM with throttle plate while my foot is mashed to the floor.
2) Sloppy brake in 2nd gear, launch switches to 1st.
3) Sloppy brake in 3nd gear, launch switches to 1st.
4) Sloppy brake in 4nd gear, launch switches to 1st.

 

Were you wanting a response?
Crickets were because there wasn't really a question

You can do this without any fancy controller. This works with the factory pcm if you just have a single ground switch/button...and turn off a couple codes in the pcm

ground B solenoid to command 3rd with the button, let off button, default back to 1st

it's a cheap trick...better than nothing...but still not anywhere near as consistent or effective as actual transbrake

 

Agreed, very simple to do, no special controllers needed. That's the beauty of it, and boy, does it make a difference and improve the ability to launch hard without the cost and down sides of a transbrake.

Agreed, not as good as a transbrake. I thought I saw in some other sloppy posts that they felt it was mushy, for lack of a better term. I did not see that in my experience. Launches were firm and hard. As for consistancy, it seemed pretty consistent, I don't understand how that would change from run to run. Transbrake definitely reacts faster as the hydraulics are usually optimized for speed of activation.


So I thought I'd post some real words test results rather than seat of the pants comments.
1) No sloppy brake, in 1st gear, just ignition cut 2 step. Logs showed this took .093 seconds.
2) Sloppy brake in 2nd gear, launch switches to 1st. This took .391 seconds.
3) Sloppy brake in 3nd gear, launch switches to 1st. This took .393 seconds.
4) Sloppy brake in 4nd gear, launch switches to 1st. This took .341 seconds

So all the sloppy brake launches started between .248 to .300 seconds later than just an ignition cut. I don't have a transbrake in there so I can't compare to a transbrake launch, but let's assume it would start earlier than any of the sloppy brake ones.

I sometimes bracket race and other times I like to see how fast a run down the quarter mile. I'm probably going to stick with the ignition cut for bracket racing, and use the sloppy brake for trying to get a best time.

 

The "Sloppy Brake" was developed at my shop around the same time as the D1 transbrake. One of my friends at the time, who's car we used for testing the D1, had the idea that using the same method as the D1 of activation would put the trans in 3rd and kill the gear multiplication, taking some load off the brakes, allowing more stall and boost building.
It works for that.
It's not really a transbrake, but a gear change.

A bleed hole in the drum, heavier direct clutch return springs, and some work on the separator plate would make it downshift back to 1st quicker, for better reaction times and less wear on transmission.

 

One of the downsides to the sloppy deal is that it still relies on footbrake
So you have to time your foot just as much as your finger on the button etc

 

Yes, most people do it that way.
I have a brake pressure sensor that triggers the two step and sloppy brake. No finger on the button required and repeatable.
There are other methods, some better than others.
The sloppy could be triggered by a switch on the brake pedal, should be repeatable.
A finger button could trigger sloppy and line lock, also repeatable.

Needless to say safety measures need to be taken with transbrake as well as sloppy brake to insure it can't be engaged accidentally in normal driving.

 

I happened upon the sloppy brake pretty early on in my turbo LS endeavors. I wasnt able to manage much better than 1.60 ish ....and I had friends who were foot braking into the 1.20's so I gave up pretty quick. neat idea though. Nice to see you measuring consistency!

 

Engaging a "sloppy brake" in normal driving would simply result in a shift to 3rd gear. Not much danger there.

 

I was holding my mouth shut, but o well...

I have SOOOOOOOO MANY ISSUES WITH THE SAFETY OF THE SLOPPY BRAKE...
Especially in JUNK-YARD Units that have "RUN-A-WAY LINE PRESSURE"!