View Full Version : Boost Controller Jerkiness?

06-04-2007, 09:17 AM
I recently bypassed my N75 with a MBC. I noticed a pretty decent gain in power throughout the RPM band (does this mean the N75 was shot?)- it drove almost like a completely different car.

Anyways, I noticed that letting off the gas resulted in the car shaking like crazy, any ideas what would cause that? I'm still not sure what's wrong with my N75- it allows me to boost to about 15 or 16 PSI on my PC16 setup, which doesn't seem quite right. I'm going to try running the MBC inline with the N75 tonight to see if that makes anything better.

I also noticed that if I let off the gas slowly, my bypass valve wouldn't make just a single sound, it was more like "Pss Pss Pss Pss" instead of "Psss". Maybe I just bought a cheap boost controller...

06-04-2007, 09:31 AM
its normal for the car to be jerky when you use an MBC and the pss pss pss is also normal as its your DV fluttering because it cant react fast enough since the MBC works like an on/off switch with the boost. oh and on my PC-16 file im spiking 28psi and holding 17-18psi up to redline

06-04-2007, 09:45 AM
holy crap! 28psi! I was going to run a MBC only to prevent boost spikes.

06-04-2007, 09:31 PM
alright, I put the N75 back inline with teh MBC and it runs exactly the same. I don't think this is normal... it literally bucks back and forth when I let off the gas!

06-05-2007, 11:14 AM
mine does the same either way. i was told it was normal.

06-05-2007, 11:34 AM
mine bucks too, but not really that much in 4th or 5th.

06-05-2007, 01:29 PM
mine dosent buck...

06-05-2007, 01:38 PM
hmm. I have 100,552 miles and it's on the original mounts and snub...

06-05-2007, 02:24 PM
holy crap... 28psi... not sure my boost gauge goes that high... but holding at 17 to redline... OMG... mine drops down to 12-14 psi after 5500 rpm... mostly in 1st, 2nd, and less drastic in 3'rd - 5th...

yeah, it's basically an on off switch with my MBC... 16-17psi is normal for my c valve w/no mbc... we all need to get 28rs's....

(side note: I get all my boost/power around 3k rpm... i don't feel more power after 5k - but the mph keeps climbing - is this normal?

06-27-2007, 05:21 PM
I am running just a mbc, and should i plug up the hole in the intake that the n75 leaves behind? could that be a boost leak?

06-27-2007, 05:33 PM
I am running just a mbc, and should i plug up the hole in the intake that the n75 leaves behind? could that be a boost leak?

you need to leave the N75 valve in the intake and plugged in

06-27-2007, 05:46 PM
Thanks...that would be like having a boost leak right?
Does it matter what model n75 i have plugged up? Meaning C, H, or J?
Do i need a hose clamp on the n75 going into the intake?
thanks again!

06-27-2007, 09:41 PM

06-28-2007, 08:55 AM
no it doesnt matter which type of N75 you have plugged in since you arent using it. You may be expirencing low boost if you had the N75 unplugged since it throws the car in limp mode. and yes you need to keep it clamped as well