I recently decided to invest in my r53 and try to make some power. I went to RMW and met with jan to have him install a 15% reduction pulley from alta and a 2% crank. I had done a decat header, MF exhaust, and Madness mini CAI. I figured I'd try to do all bolt-ons and see what numbers I can make. So after I got my car back from Jan I noticed something different, my car was getting another kick in power at when in full throttle around 4k-5k rpm. I decided to buy a autometer boost gauge to monitor my supercharger and the supercharger makes decent boost, roughly 15-17psi with everything however my car doesn't just work up to 15, it works up to about 8-12psi, then at around 4-5k rpm it jumps to roughly 15,16psi and builds continuously till about 17psi. it doesn't fall back again, it becomes very stable. I just have no idea what is going on. It's been happening ever since I got my car back and only the injectors(to 550cc), tensioner, and pulleys were changed. I never used to experience this problem prior to this change. It is a boost problem. I don't build steadily you can feel it just pull when it does it's jump to 15,16 psi.



here is a video of whats happening:

 

It sounds like either your BPV is sticking -or- your belt is slipping.
First thing I'd try is zip tiring the BPV closed, then you'll know for sure about it.

 

Yep....what others have said. Check your belt and check your bpv.

After listening to the video again...I noticed that the pitch (rpm) of the supercharger didn't seem to change at the end when the boost jumped from 10psi right up to 15psi. That would lead me to think that you have a problem with the BPV...not the belt. The springs in the BPV's can break, and the valve will just flutter around....doing erratic stuff.

When the car is idling and you are showing vacuum on the gauge...is it consistent? That would rule out a problem with the gauge and/or tubing going to it.

 

The gauge is stable when I turn the car on and let it idle.
yeah I noticed the sound doesn't change much in the video as well. I zip tied the bpv shut but tomorrow I might take it off to check it, or i might upgrade it anyway. I ordered a better belt should be here tomorrow, i will update once I change them

 

BPV is my guess.

https://www.northamericanmotoring.co...-shut-r53.html

 

do you have a picture where you zip tied the bpv?

 

i don't but I ordered a detroit tuned bpv, and I replaced the belt doesn't seem to be the belt slipping the problem is still happening so if the bpv fixed the issue I will update the thread!

 

just ordered a DT bpv last week, got lots of recommendations, hoping it does the fix. We'll see this upcoming friday.

 

Little update: Changed BPV and Belt, I noticed my intercooler horn was leaking massive amounts of oil through the gasket which was completely blow. I cleaned and copper sprayed it. My old BPV was easy to see light through so it definitely wasn't shut or near it. it had about a quarter inch or more gap of light coming through which wasn't good. I am now making around 16PSI without it spiking around however only if I cruise into it. I believe the blown gasket is still an issue as more oil is draining out of it. I am going to replace the gasket this weekend along with some other things. Will update when I am done