TwinCharged RX7

iTrader: (14)

This is not really directly related to an rx7, and I know most of us do not use superchargers on the rotary engines. But I was working on a friends car (Vortech supercharged G35) and the bypass valve is insanely loud and annoying. And because its a bypass valve, it vents almost all of the time (except when boosting).

I was thinking about just reciruclating it to the intake side of the supercharger (just after the air filter but before the compressor) on the intake pipe between the air filter and the inlet to the supercharger.

I don't understand how this could cause compressor surge, but my friend called vortech just to make sure it was ok and they said not to do it because it causes compressor surge.

I've read the BOV write up on here regarding the actual need for one, and it looks like even if there is compressor surge it doesn't matter all that much. But on a supercharger I think compressor surge may be a slightly bigger deal as the supercharger is directly linked to all of the pulley's on the engine via the belt.

So I understand not wanting surge on a supercharger, but how could recirculating the bypass valve really cause surge if it is going inbetween the airfilter and supercharger? If the pressure was really that great, wouldn't the air just end up going out through the air filter (reverse of the normal flow of air)?

arghx

iTrader: (3)

maybe the Vortech guy didn't understand what your friend was saying? this is a centrifugal blower, it's just like a turbo except it's driven by a belt...

StavFC

Its fine, most setups run as you describe, and that would never, ever, cause surge, in fact if it at all pressurised or minimised vac on the pre-s/c side it would help prevent it..

Warning though, I recently drove a 500bhp S2000 with it as you describe, and even though it recirculated it at least 2 feet after the air filter, you could still here the constant wooshing of the BOV very loudly on the over-run.

So basically, it doesnt silence the noise that much!

Evil Aviator

If the volume of bypass air is too great, then the supercharger will not be able to ingest it. The general rule of thumb is not to recirculate anything over 12psi boost. Since Vortech said not to do it, then it's probably not a good idea.

Maybe your friend could vent the bypass valve to a small muffler from a motorcycle or lawn mower?

arghx

iTrader: (3)

Why don't you get a 50/50 blowoff that recirculates and vents? those are pretty quiet. They're used on a lot of cars that have a factory MAF sensor, like STi's .

http://www.customcarscentral.com/txs...gt-05-up-.html

you'd have to get the flange figured out. i think it would work...

StavFC

Why would the supercharger injest it if you recirc it back to the inlet pipe? I cant see how it would? Surely any air it didnt need would just come out the air filter?
Air takes the path of least restriction and you are simply bypassing the air back in to the inlet pipe rather than forcing the compressor to have it.

Evil Aviator

So would the "path of least restriction" be the ambient pressure end with the air filter restriction or the suction end with the supercharger gulping up air?

Yes, some of the air would end up backtracking through the filter once the supercharger inlet is overwhelmed.

I just found an online article, but it pretty much says what I already posted:
http://www.superchargersonline.com/content.asp?ID=14

TwinCharged RX7

iTrader: (14)

Awesome, thanks for all the good info. I'll check with him and see what he wants to do. If it was me I'd do the recirc, but he's a little more cautious than I am when doing something to the car.

I'll post up the results of whatever we end up doing.

Thanks again.