Chris Ng

Need some suggestions..

During my car's winter hibernation, I installed a HKS FMIC, profec B boost controller (spec 1), ported my wastegate (Hybrid turbo, S5 exhast side)..
I had set the profec's high boost setting to 15 psi and everything was good.. 1st gear I would see about 10 psi, 12.5 psi in 2nd, and 15 psi in 3rd-4th gear... the boost was consistant and could hold quite well.. I was happy...

I took the car out to the track the other night to make a few runs... That's when strange things started occuring... I could not make more than 12 psi of boost... I checked for boost leaks, but all my piping and clamps looked good.. I even turned the profec settings up, but still could not get beyond 12 psi of boost... I called it a night...

On my drive home, I did a 3rd gear WOT run... to my amazement, I hit 15 psi boost! .. 4th gear netted 15 psi as well... I slowed down, went into 2nd gear, and did a hard run shifting to 3rd gear and running it up... I could not get beyond 12 psi doing this... what the heck is going on? what could be causing this?

So long as I start a wot run in 3rd or 4th gear, I can easily make my 15 psi boost.. but if I make a hard run starting in 1st or or 2nd, I will peak at 12 psi right through 4th gear...

I double checked my pipeing, and everything seemed well, I reinstalled my Manual bosot controller to see if the profec could be acting up, but I was experiencing the same issue with the manual boost controller..

I would love to ehar any theories you guys might have as to what is causing this situation.. I'm kind of clueless at this point!...

Thanks,
Chris

Chris Ng

Ignore this post.. I belive I found the problem...

sonnguyenrx7

what was happen?please let me know casue i have the same prolem
Sonny

Chris Ng

Actually, the cause of the problem turned out to be a large boost leak.. Since I'm running a standalone engine management system which is utilizing a MAP sensor, The boost leak didn't effect the way my car ran or idled... I basically just capped off both ends of my intercooler pipeing, attached a hose to a nipple on the ic pipeing and pressureized the piping and intercooler..
My HKS front mount IC has 2 mounting points on it.. one on top of the IC and one on the bottom.. I have the IC mounted just using the top mounting point.. Unknown to me, but the threaded hole on the bottom of the IC was actually threaded right into the endtank! .. So all this time, I had been venting boost pressure out of a hole roughly the size of a dime...

When I start to boost in 3rd or 4th gear at a lower rpm, there is enough load on the motor to be able to create my 15 psi boost.. however when shifting hard from second into third, there is less load to create the boost and my boost dropped off...

After plugging up the hole with a bolt and making sure there were no other pressure leaks, I found that I was making full boost by 3200 rpm rather than 4000 rpm, and no longer had the problem of having lower boost during hard shifts....

so for the last 3 months that I've had the intercooler installed, and making 15 psi boost on the street, I was venting alot of that pressure out and causing the turbo to overspin to make that kind of boost.. hopefully It will hold up and not pre-maturely fail on me..

sonnguyenrx7

thanks for the infor
Sonny