Launch tips for a tuned 135i?

[BMW135pls]

Got a JB4 in my 135i and it's noticeably harder to launch now than before the tune. Use of brake pedal in the launch is noticeably more useless following the tune since the car seems very content to just sit there and burn rubber even on map 1, which is cool for show, but reduces launch proficiency for us nerdz who like to race for times.

Just wondering what the technique is, since on one hand you have the throttle down launch which is limited by the 750-1500rpm turbo lag, or the brake boosted launch which is limited by tire traction.

Share your favorite launch techniques!

[BMWX1-35i]

Not sure the JB4 can do this or not (I have the Cobb which can) but you could adjust the throttle so it does not come in so strong on the low end. Cobb I know has two, stock (which get the boost in soon and strong) or linear (even boost level across the RPM band) which should be much better for what your looking for. If you do allot of drag racing, you can get the the technique down with what you have over seat time.

[BMW135pls]

Originally Posted by 135droptop

Not sure the JB4 can do this or not (I have the Cobb which can) but you could adjust the throttle so it does not come in so strong on the low end. Cobb I know has two, stock (which get the boost in soon and strong) or linear (even boost level across the RPM band) which should be much better for what your looking for. If you do allot of drag racing, you can get the the technique down with what you have over seat time.

Yeah with the JB4 you can adjust the boost levels for the bottom 2 gears. So with a 3 and up level of 13psi, I would likely set gear 1 for 9psi, and gear 2 for 11psi, and gears 3 and up would get 13psi. At least that makes sort of a bit of sense...

[Silenus]

I've only launched my car 2 or 3 times, but I have over 10 years experience drag racing cars. I just rev it to about 3000 RPMS, and very quickly slip the clutch. I modulate the throttle as needed. This is a JB4 car with Michelin PS.

[BMW135pls]

Originally Posted by Silenus

I've only launched my car 2 or 3 times, but I have over 10 years experience drag racing cars. I just rev it to about 3000 RPMS, and very quickly slip the clutch. I modulate the throttle as needed. This is a JB4 car with Michelin PS.

Ahh, I've got the 6AT version, so I don't get the luxury of clutch action.

Since the JB4 tune I'm mostly finding that gear 1 is mostly just useful for spinning the tires in a showy manner, 2nd has plenty of torque for everyday driving and I'm fairly certain it'll launch better too. Any 6AT guys launching in 2nd with the brake? Could I damage anything if I just don't use gear 1 at all? Like ever? I basically don't need it, lol.

[edisapimp]

You can have the best technique but without good tires you'll never get what you want or what the car is really capable of. This isn't a "Technique" (and I don't have one for you because I am MT), but I would recommend drag radials or ET Streets.

[mike@x-ph.com]

With JB4 you can set up the max boost for 1st and 2nd gear.
Start with 10 psi and adjust it based on what the car can handle.
Of course with better tires you will be able to achieve higher psi even on 1st and second gear.

[Diver]

Try letting up on the brake just after you start to mash the accelerator to the floor.

[RX-BMW]

I have COBB Stage 2+ 6AT. Here's what worked best for me. Shift into M2 hold brakes down then rev to 2100rpm. At the same time, let off the brakes and hit the gas to 100% WOT *WITHOUT* flooring it--you dont want it to downshift to 1st gear. Once you're at 6200rpm or so in 2nd you can shift to 3rd and floor it all the way down.

That's how I got the best 1/4 mile time bud.

[BMW135pls]

Originally Posted by mike@x-ph.com

With JB4 you can set up the max boost for 1st and 2nd gear.
Start with 10 psi and adjust it based on what the car can handle.
Of course with better tires you will be able to achieve higher psi even on 1st and second gear.

Yeah, I haven't tried that feature yet, I'll def have to play with that soon as winter is coming... is it realistic to run 0psi of boost in 1st during winter? Maybe 4-6 for 2nd? Better to bypass the JB4 or leave it on and tune the boost levels? I read something in the BMW manual that said when using snow tires it may be a better idea to bypass the traction control system rather to leave it on?

Originally Posted by Diver

Try letting up on the brake just after you start to mash the accelerator to the floor.

I've tried revving to 1500 and then releasing brake/slam gas to the click point, but without clicking it, and the car just happily sat absolutely still, wheels spinning and sliding sideways.... in 2nd gear!

Originally Posted by RX-BMW

I have COBB Stage 2+ 6AT. Here's what worked best for me. Shift into M2 hold brakes down then rev to 2100rpm. At the same time, let off the brakes and hit the gas to 100% WOT *WITHOUT* flooring it--you dont want it to downshift to 1st gear. Once you're at 6200rpm or so in 2nd you can shift to 3rd and floor it all the way down.

That's how I got the best 1/4 mile time bud.

I had a feeling it would be something like that, as I've experimented with that actually. Thanks!




I think it's definitely time to take everyone's advice and get the tires changed out.

Interesting note on the tires, I was looking at the tires from the outside and the tread looked workable at least until it comes time for snow tires, but when my friend and I were installing my catback the other day I saw the inside of the tread and it was absolutely bald. Which also led to me noticing something else. The wheels, at least the drive wheels, look to have been cambered out. Nothing extreme, but it's firmly noticeable in the wear pattern. I think it's neat that somebody already did that to the car, but it also means that I'm going to be eating through tires faster I think. Anyone have any input as to keep/revert the cambering? Tweak it to be more than stock but not as much as it is now? Will the cambering ruin my snow tires? Am I wrong that it was tuned and the 135i with M sport pack just comes with a fairly strong negative camber?

[mike@x-ph.com]

Originally Posted by BMW135pls

Yeah, I haven't tried that feature yet, I'll def have to play with that soon as winter is coming... is it realistic to run 0psi of boost in 1st during winter? Maybe 4-6 for 2nd? Better to bypass the JB4 or leave it on and tune the boost levels? I read something in the BMW manual that said when using snow tires it may be a better idea to bypass the traction control system rather to leave it on?

Setting the feature to 0 psi will disable it and the Jb4 will target the regular boost target (depending on the map you have on)
As for disabling traction control, i would not recommend disabling it entirely on a tuned car during the winter. A better idea would be to to press the DTC button once and engage Dynamic traction control