How to build boost at the line?

DAVE

Specialist
Feb 19, 2017
73
22
0
Dallas, TX
Ride
135i
So, being a pretty versed drag racer I have one question for you guys because I'm in a quandary. On an auto with JB4, MHD and xHP how in the heck do you build boost at the line? In my experience, once I go past 2k rpm power breaking it the engine cuts and I loose all boost. I've got good mph but my 60' is so slow...
 

Deltalima0

New Member
Sep 16, 2017
3
3
0
Ride
2011 335is
So, being a pretty versed drag racer I have one question for you guys because I'm in a quandary. On an auto with JB4, MHD and xHP how in the heck do you build boost at the line? In my experience, once I go past 2k rpm power breaking it the engine cuts and I loose all boost. I've got good mph but my 60' is so slow...

Try brake boosting at the line let off brake and then back to standing on it again and see if it will build boost without cutting power.

My last car did the same thing it would kill power at the line but if i let off the brake then back in to it quickly it would hold and build. i cut a lot of 1.6 and 1.7 60s by doing the above, somehow it worked for my car it may do the same for you.

By doing the above I was able to do a record at the time and still the best time for the N54 non upgraded transmission.

510.721130.9207.000103.3401.6642007Dorsey JamesE90 6AT Super RB (Link)
[TBODY] [/TBODY]
 
Last edited:

Sshec152

Corporal
Nov 3, 2016
213
118
0
Aston pa
I think its due to the dme seeing the throttle and brake being pressed and causing throttle closures. If theres not a way to tune around this you could hook up line lock to the rear so you’re able to load up the engine without getting throttle closures/boost loss. Or a transbrake
 

Kenjermen

900 HP Club (N54)
Nov 6, 2016
259
78
35
N las vegas NV
Unfortently we can not run a transbrske on these transmissions due to them being internal electric valve bodies. A line lock kit would help. Mine is setup up for the front but I use it to keep the car pushing itself through the light.
From a tuning standpoint you must trick the dme to drop intake temp to drop timing and not build power but boost instead, this can be done and AD-E is your answer for that
 

Rcboosted2007

Lieutenant
Jan 28, 2018
902
89
0
Parts unknown
Ride
07 335i
I always have what seems like a 50/50 chance at brake boosting also. Ill get brake/ acc codes.
2F8F and 2EF4 map thermostat.even when it does push throuthe brakes the car bogs down after a solid launch as if dme tries to adjust. Has anyone tried line lock on the rear
 

Rcboosted2007

Lieutenant
Jan 28, 2018
902
89
0
Parts unknown
Ride
07 335i
Try brake boosting at the line let off brake and then back to standing on it again and see if it will build boost without cutting power.

My last car did the same thing it would kill power at the line but if i let off the brake then back in to it quickly it would hold and build. i cut a lot of 1.6 and 1.7 60s by doing the above, somehow it worked for my car it may do the same for you.

By doing the above I was able to do a record at the time and still the best time for the N54 non upgraded transmission.

510.721130.9207.000103.3401.6642007Dorsey JamesE90 6AT Super RB (Link)
[TBODY] [/TBODY]
Did you launch in first gear. Also how much boost where you able to build at the line.im running a 30psi tune with mmp stage 3
 

Deltalima0

New Member
Sep 16, 2017
3
3
0
Ride
2011 335is
Did you launch in first gear. Also how much boost where you able to build at the line.im running a 30psi tune with mmp stage 3

I did best with 1st gear launches as for how much boost i built i never really payed much attention to it, it was a feel thing building boost and not moving.