|
|
|
|
|
|
BMW Garage | BMW Meets | Register | Search | Today's Posts | Mark Forums Read |
|
BMW 3-Series (E90 E92) Forum
>
Manual launching xdrive
|
|
06-01-2015, 07:05 AM | #1 |
Captain
82
Rep 604
Posts |
Manual launching xdrive
Hey guys, so I've had my 6mt 335 for almost a year now, most of it was winter weather, got FBO, and ready to take her to the strip to see what kind of times she puts down. Launching is my problem, it always seems to be a sensitive balance between the throttle and clutch, to an extent it should be, but if I rev too high or dump the clutch too quick, the rpms just fly around.
This is with all traction control off, how does it still come to be that the clutch is engaged but its still free-revving, I do see the traction light blink while its happening, and I need to let go of the throttle to let it engage and recover from that. Almost feels as though a slipping clutch, but never does any of this happen while I'm already in gear, its just the engagement part of it. This is my first awd/xdrive car so I am learning something everyday, but I'm looking to get some feedback on how you guys launch aggressively, I only seem to get it right half the time, the other half of my launches either bog, or free rev. Maybe I need a new clutch, maybe I need more launching practise, how do you guys launch? Thanks!
__________________
///FBO+METH 6MT N55///
|
06-01-2015, 07:15 AM | #2 |
First Lieutenant
74
Rep 315
Posts
Drives: 2008 Deep Green 335xi 6MT
Join Date: Sep 2014
Location: Falling Waters, WV
|
Have you done the CDV delete? It delays engagement and you might be putting too much throttle while it's still engaging. Once it's spinning against the flywheel, it's harder for it to lock. I've experienced this a few times in autocross before I deleted my CDV.
What would happen to me, rev high, dump clutch, rpms would stay high with foot off clutch, eventually it would lock up with a jerk. Poor clutch. There's really no way to launch repeatably with the CDV still there.
__________________
|
Appreciate
0
|
06-01-2015, 07:24 AM | #3 |
Lieutenant
57
Rep 439
Posts |
Yea you need to delete your cdv. But also your stock flywheel pressure plate combo is the weak leak if you can't get the car to launch. Depending on how good you are with driving stick on this car you need to find that grip point and not just drop the clutch. You can rev the car to about 3k while simultaneously depressing the clutch a little past its grip point and you will feel the car jerk forward. Then smoothly, disengage the clutch all the way while applying 75-90% throttle. Then once the car goes to about 10mph, hammer the throttle and shift as you would.
Once your clutch starts going, which with fbo on a awd will be quick. Get either the 335is clutch with pressure plate combo from ECS or anywhere or go with an aftermarket.
__________________
LMB , M-Sport, JB4 Stg. 2, AR catless res. dp, ETS cp
|
Appreciate
0
|
06-01-2015, 08:00 AM | #4 |
Lieutenant
179
Rep 427
Posts |
not an expert on launching technique but +1 for CDV delete. It makes a big difference. Clutch engagement is immediate after this simple mod. I've done mine at RMP motors (since you're in TO). They just punch out the contents of the stock one and put it back. No parts required.
|
Appreciate
0
|
06-01-2015, 06:26 PM | #5 |
Captain
82
Rep 604
Posts |
Thanks or the reply guys, yea I do have the CDV delete, I just want a more aggressive bite on the engagement, I know it would stress other components some more. Trixdout thats the method I use when I am trying to launch it, basically the "fine balance" I mentioned in the first post, I'll definitely be practising more. I've only ever owned manual cars, my buddy with a FBO auto xi slingshots that thing, but he also brake boosts etc.
I'm going to keep practising, was just trying to get an idea of everyone's methods. The first sign of clutch slip and I'll be upgrading! Thanks for the feedback. |
Appreciate
0
|
06-02-2015, 08:28 AM | #6 | |
First Lieutenant
74
Rep 315
Posts
Drives: 2008 Deep Green 335xi 6MT
Join Date: Sep 2014
Location: Falling Waters, WV
|
Quote:
Manuals on the other hand can't provide full torque (effectively) until the clutch is fully engaged. The only way for you to get quicker launches is to be more aggressive with the throttle, which in turn will reduce your clutch engagement time. FYI the torque multiplication for the automatic only lasts until the wheel speed is roughly the same as the translated engine rpm https://en.wikipedia.org/wiki/Torque...ational_phases (See Acceleration) Here's a good picture showing the actual ratios over differential impeller/turbine rpm Remember: F = m * a a = F/m T = F * r F = T/r therefore a = (T/r)/m F = force a = acceleration m = mass T = torque r = moment arm or radius r in this situation is wheel radius
__________________
Last edited by cmg5461; 06-02-2015 at 08:35 AM.. |
|
Appreciate
0
|
Bookmarks |
Thread Tools | Search this Thread |
|
|