[ThatRWD]

I've got a JB4 on my 07 335i 41k AT and I've noticed sometimes when I floor it the boost gauge climbs up to max boost other times I get a kick and it flys to max boost.

I figured it's got something to do with the transmission downshifting that delivers that kick but that doesn't explain the difference in how boost is delivered, when it's climbing it's quite slow and I feel power increasing as it goes up and the shift that happens at max rpm feels slower than when it does when all the power kicks at you.

JB4 is my only mod, 93 shell v-power gas only and running map 2.

[Tiago@VRSF]

Sounds like it could be downshifting.

[ihc95]

LOL what your feeling is the transmission kick down. Since the revs spike up quick, the car is going to go to max boost quick. When the tranny doesn't downshift, the build up of boost is much more gradual since the revs are climbing much slower..

[ThatRWD]

What about all the torque being available down low at 2000RPM? Why do I feel the climb? Also when it does the kickdown and then goes into the next gear because it is still floored how come the next gear still has all that power instead of building it up like it does otherwise.

I know what your saying but it doesn't explain what I'm experiencing.

[Tiago@VRSF]

You can put it in 5th gear at 30 miles and hour and you'll be under 2k RPM, that doesn't mean your car will feel fast

[ThatRWD]

Alright, I'll have to do some more testing and figure out the details, just a suspicion at this point thought maybe it was an issue with the car like vanos solenoids messing up timing there for boost not being applied the same way everytime since I have gotten vanos codes.

How do you like the M4 compared to the V8 in terms of just driving pleasure?

[Tiago@VRSF]

It's not in yet but the powerband is much broader from the test drive, totally different animal and completely improved from the no torque feeling of the E92's V8.