Last night.. i was trying to launch my 5AT by Brake torquing....with VDC off..... for some reason... it felt like VDC was still on.. even after i had it turned off..usually i could chirp my tires before taking off... it felt like i actually slowed down... and the RPM dropped all the way back down before the car actually started moving.... Does anybody know why this could have happened?

 

Brake torque launching takes a bit of practice - no doubt. When you release the brakes a sudden load (the wheels/tires) are placed onto the engine and will cause a drop in rpms. If you drop below the stall speed (2600 rpms), you will not have an instant launch as the engine will not be directly coupled to the driveshaft (rather the torque converter must spin past 2600 rpms again).

I have had the best success by doing a "mild" brake torque launch. I hold the brakes lightly. Then at launch time, I stomp on the gas, and release the brake about a half second later as I feel the car move (that's the driveshaft turning the wheels despite the brakes being "lightly" applied).

 

What if it doesnt let u ... rev upto 2600 rpm?..... it wasn't letting me ..with VDC off.... i'll try "mild" brake torque launch... thanks for your reply

 

sry.. but what's brake torque launching?

 

I think its when you hold down the brake a lil and step on the gas and let go of the brake

 

what's that suppose to do?

 

It helps you launch better... off the line ...

 

You're loading the torque converter which actually multiplies the torque and makes the car launch much harder. Without doing this technique, the 5AT will pull higher 2.3 60 foots. In my car, that's the difference between running a 14.7 or a 14.3.

 

Strange, I always got faster time on my auto Maxima when I just went from the brake to the gas. When I loaded the TQ converter it took off slower.

But of course it was a different car.

 

our cars computer decreases throttle by 30% when the brake is depressed. Its a safty feature.
To get full power you'll need a brake bypass switch! They're available from a couple of members on this site or my350z.com

 

Wow. Nice info

 

jeff,
noticed your sig:

...how do you like the autoenginuity odbII sacnner?
...how does it work with our nissan computer?
...how much did it cost you?
i'm looking into getting some type of scanner

not to highjack this thread but, pm me when you get a chance

 

I have the vortech on my car with 370whp and 300 torque.
I took my car to the track for the first time.
I had no idea what I was doing.

No burnout...I just rolled up to the light...turned green (had the vdc off and left it in drive) and I just slammed on the gas. I did the quarter in 13.9. I think that if I can figure out how to launch my car...I should be low low 13s.

I just gotta try this technique. I only got to do one run cuz some mustang blew its motor all over the place so it took like 1.5 hours to clean up.

Next time I go ... I gotta try this.

It was like 80 degrees by the way.

 

^u shud have done better... let us know what times u pull of when u hit the track next

 

I've done all the brake mods (yanking fuses, disconnecting the yaw sensor, etc) that do the same thing as the brake bypass switch. There's absolutely no differences in the way the car launches. It still feels like something is holding it back until 3000-3500rpms comes around.