Hey all,

During my diagnosis of my underboosting issue I was curious if my stock BPV was leaking. I was at work and we have hand sanitizers everywhere (I work in a hospital) and I went to go change one and it broke... what came out? A spring. Hmm, looked just like my BPV spring. That gave me an idea.

I opened my BPV to find that the spring has about 8 coils. So did the hand sanitizer spring! Same diameter and everything. I put the 2 springs together so I have double the spring pressure on my stock BPV. I reassembled it and popped it back on my car and went for a spin.

This, in combination with the K04R I recently installed, gives me some wicked blow off sounds. It sounds like a BOV only not as loud. I'm digging it. Just thought I'd share my findings. I'm sure this has been done before but I did a search for "BPV mod - BPV spring- BPV..." about 7 different searches and wow there's too many results to look through!

A silly little video here for any1 that wants to hear it. Yes I said BOV in the video, it sounded like one heh so I fumbled my words BPV Spring Mod, Cobalt SS 2010 That was with the windows closed too.

 

The spring inside is there to set the vacuum at which it opens. So more pressure on the BPV only makes it open later

 

I've heard of people saying that boost can be lost if the BPV valve spring is weak, hence the mod. I used to be able to boost to say 10 PSI, release gas a bit and loose all boost but still have .2 PSI or something register on the RPD and get an ~1.5 second long 'sssssssss' bpv release. It was very sensitive.

With the higher boost of the K04r, the fact that the compressor isn't surging, BPV is functioning properly and makes a louder sound, I'm satisfied

 

its probably not opening and what your hearing is the turbo surging.

 

If u dont mind me asking, what is your position at the hospital? They generally don't like people messing around with their equipment. Lol

 

The moment I come off the gas, BPV is opening and I go into vacuum without an issue. I still have my vacuum tank hooked up, I changed the check valve as well so it's working just fine to pull the BPV in. Just thought it was neat that changing spring pressure changed the noise significantly.

 

Haha, I'm a desktop field tech, it was just a hand sanitizer dispenser. I put a new one in, dropped the old one and the plastic broke and out popped a spring. No tampering

 

^^ This

Installing a stiffer spring does more harm than good imo. If you're losing boost pressure, and doing this somehow resolved that issue, this is only acting as a band aid for something else going on here.

 

I wasn't loosing boost pressure due to the BPV leaking, but in my experiment to confirm that wasn't the case I doubled the spring and confirmed it wasn't leaking.

The diaphragm is oscillating causing the noise. Compressor flutter maybe, compressor surge is a whole other beast. Sounds great and the vacuum is strong enough to overcome the spring(s).

When I release the gas even a little, all boost is lost so I'm not too concerned. Any one care to provide info on turbo flutter and how it can be bad? Mine is not fluttering like when you google "turbo flutter"

 

I would just get a forge. My new k&n sounds much better then all the videos I've seen of the puppy dog being kicked with the stock bpv haha

 

The flutter is caused by the pressurized air which is bouncing in a wave pulse back and forth between the compressor and the closed throttle plate... First flutter is the 1st release, 2nd, quieter flutter is the pulse that hit the throttle plate and bounced backwards, 3rd a bit quieter... I count 4 on mine. Some said on sites elsewhere it was the valve ocillating, eh I don't know about that.

So 3 pulses of compressed air that should have never existed have nowhere else to escape but backwards through the compressor. While that's the turbo's job to compress air, no need to have it surge unnecessarily. I guess this is still considered surging, though it's not surging during boost which is much more damaging! Yikes. Taking that 2nd spring out and retiring the boy racer mentailty. Thanks all for your input.

 

Looks like u solved ur own question. Well done.

 

I was thinking its probably no good. Nice research op

 

https://www.cobaltss.net/forums/08-1...riment-166386/

Thats a good thread to read on the topic. it's comparing the stock spring to the upgraded dejon spring. I have the dejon spring, but never put it in. I'll be lucky if I can find it at this point

 

Wow, that is an excellent write up as well. Here I am thinking a tighter spring means holding more boost, lolz... I'm so glad I blew up my stock turbo. Doing my own turbo swap and bench testing solenoids, reading up on how the entire turbo system works, checking downpipes for clogs and boost leak testing pipes... this has been an incredibly awesome learning experience.

I went back to stock spring and car feels the same, haven't noticed anything really, I'm just happy to know it won't surge. Perhaps I can do this BPV mod?