[ablangc]

Ok this may be a stupid question but I have used the search function and googled it numerous times before posting. This is my first automatic and i currently have a 335i Steptronic and read up about brake boosting to improve 0-60 and 1320 times. Ok i know I step on the brake and gas pedal (rev to 1500-2000 rpm's) to build up the the boost but my main question is if it wreaks havoc on the torque converter? If so, why? If not, please explain. Thanks for any info provided on this matter!

[Chrisb1231]

im not too sure but i would assume it isnt good for the car, so i wouldnt do it too often

[ablangc]

I can understand its not that bad when you are already rolling because i can see it burning through your brakes but from a complete stop, i think it is a different story. Hopefully somebody can answer this.

[dxb335d]

Ive done over 130 1/4mile runs in my car, Brake Boosting of course. + a load of other standing starts at a magazine event last year..
Im guestimating over 150 runs.

I launch hard now too.. So far so good.

Idea is not to load the Torque Converter up for too long.

[The HACK]

Here are some basics you need to understand about how the torque converter and transmission work wrt "brake" torque for launch.

Torque converter is basically two sets of finned fans spinning opposite each other in a high-viscosity liquid filled chamber. As one fan spins, it forces the liquid (ATF) to spin up therefore transferring that motion to the 2nd set of fans. This is the most basic explanation of how a torque converter works. It converts the torque from the engine into heat while the transmission remain static.

Where that comes into problem when standing on the brakes, is all that energy the engine is making has to transfer or convert into heat, period. There's no where else for all the torque and horsepower to go except get converted into heat by the torque converter. Heat is the ultimate enemy of any lubricant, for every 20 degrees above 210 degrees Fahrenheit it basically HALVES the life and the effectiveness of the lubricant. As the lubricant (ATF) heats up pas a certain point it starts to break down. Since the typical BMW automatic transmission is SEALED and not serviced at a regular interval, the broken down fluid from each brake stand has no where to go except to stay in the system and gunk-up the various passages of the internals of an automatic transmission.

I don't know how many of you have seen the internal workings of a BMW automatic transmission, do a "google" search for "valve body" and see how complicated the internal fluid passages are. It's a series of mazes and valves and passages that controls when one actuator moves one gear and disengages another. The passages are TINY. The valves are TINY. Once gunked up enough to stop flowing, various components break down rapidly in an automatic transmission. Not the most pretty sight, especially given the "lifetime" fill nature of BMW autos.

If you're still reading past all that mumble-jumble, here's the ramifications to brake torquing for launch. Is it bad for your torque converter and automatic transmission? Yes. Will it destroy your torque converter and automatic transmission to do it once in a while? Not likely. Should I do it when I stop-light race or at the drag strip? Not that I condone street racing, and I think people who need to prove they're faster on the street has something small they're compensating for, but if you want to beat the guy next to you at the drag strip or achieve a respectable time, you absolutely need to brake torque...However, just be aware that every time you do it, you're not doing your fluid any favors since all that energy generated by the engine is converted directly into heat that destroys your ATF, same ATF that's shared between the torque converter and transmission. I wouldn't brake torque regularly unless I can change my automatic transmission fluid on a regular basis.

[ablangc]

Great! Just the answer i was looking for. Thank you for typing that all out. I did read it completely and will research a few more things but that answered my question. Again, thanks for all your inputs. Now I also have to find out when the next open 1320 runs are in Southern California.