Does Adjusting the bpv have anything to do with exhaust

[skrappyyy]

I recently purchased a FORGE BPV from a fellow member and was wondering how the different spring/shim combos have an effect on exhaust flow, which would result in more or less backfire.

If it's holding the boost more consistently, wouldn't the result be an increase in backfire since it's going to run a bit richer due to the constant stream of boost going through the turbo?

Just wondering what the thoughts were on those who know more about turbos, since this is like my first turbo car, and I'm trying to figure out why with only a test pipe and cat back exhaust, my car is backfiring so much.

 

[iheartmyhatchie]

I recently purchased a FORGE BPV from a fellow member and was wondering how the different spring/shim combos have an effect on exhaust flow, which would result in more or less backfire.

If it's holding the boost more consistently, wouldn't the result be an increase in backfire since it's going to run a bit richer due to the constant stream of boost going through the turbo?

Just wondering what the thoughts were on those who know more about turbos, since this is like my first turbo car, and I'm trying to figure out why with only a test pipe and cat back exhaust, my car is backfiring so much.

Depends on what mods you're running. You shouldn't have any backfiring issues since the Forge Valve runs full recirculation. If you're at stock boost, try using the blue spring with no shims, and see if that holds fine.

 

[skrappyyy]

Well it was backfiring with even the stock bypass valve, I'm just running an intake, test pipe, and cat back exhaust.

 

[iheartmyhatchie]

Our cars run rich from the factory, and without that 2nd cat you're going to have some backfiring due to the unburnt fuel in the exhaust.

 

[skrappyyy]

Oh okay, I was playing around with the different springs and I know that using certain springs though reduces the amount of backfire, any thoughts on this?

 

[iheartmyhatchie]

What I know about the springs and shims is... If the spring/shim combo is too soft you may have stalling issues, and boost leaks... If the spring/combo is too hard, you'll get flutter. The fact that the valve holds boost better shouldn't have an impact on backfires since the Forge bpv dumps the air back into intake keeping the AFR's consistent. One of my friends ran the Forge valve before, and after he installed a test pipe on the blue spring. He didn't have backfires until he installed the testpipe.

Sorry for the novel!!!

 

[skrappyyy]

No problems, I appreciate all the feedback.

 

[skrappyyy]

What I know about the springs and shims is... If the spring/shim combo is too soft you may have stalling issues, and boost leaks... If the spring/combo is too hard, you'll get flutter. The fact that the valve holds boost better shouldn't have an impact on backfires since the Forge bpv dumps the air back into intake keeping the AFR's consistent. One of my friends ran the Forge valve before, and after he installed a test pipe on the blue spring. He didn't have backfires until he installed the testpipe.

Sorry for the novel!!!

How do I know what fluttering sounds like?

 

[iheartmyhatchie]

Here is a video of what flutter or compressor surge sounds like... This is on an sr20 motor, but you get the idea

http://www.youtube.com/watch?v=LZUbo_mNDZM

 

[Mid_Life_Crisis]

If it's holding the boost more consistently, wouldn't the result be an increase in backfire since it's going to run a bit richer due to the constant stream of boost going through the turbo?

This sounds backward to me. Boost is air pressure, not fuel pressure. A certain amount of metered air is expected to reach the cylinder, and the appropriate amount of fuel is injected into the cylinder. If the boosted air is not dumped back through the BPV to the beginning of the cycle, then the expected amount of air is delivered to match up with the injected fuel and life is good. If the boosted air is dumped through the BPV back to the beginning of the cycle, then for a few revs you would have a very rich condition because less than the expected amount of air is delivered, but the same amount of fuel is still injected. The system eventually catches up and the mix is even again, but I suspect that venting too quickly would lead to backfiring from excess fuel rather than the other way around.
I could easily be wrong and, if so, I expect someone will explain why.