Mike Murcia

Routing the "bypass" air closer to the compressor wheel would help the charge air to do it's designed job - to keep the turbo spooled up between shifts, and heep that charge air from escaping out the cone air filter. If it's blowing directly onto the compressor, the bypass valve is more effective than just venting somewhere in the j-pipe. In between shifts, the throttle plate is closed, so the compressor will not be sucking much. As a result, it starts to lose rpms.

westcoastprshe

So you're assuming that the charge air being vented back in has enough velocity to actually help spin the compressor... which is kinda ridiculous.

How is the charge air design to keep the turbo spooled up? The CBV helps it stay spooled up by releaving any pressure, preventing a shockwave and stall, letting it spin freely, it doesn't actually pressurize the intake side of the turbo. The compressor is sucking... giving it a tiny tiny little breath from the CBV isn't going to affect it at all.

JustinL

I had always imagined that venting to the atmosphere was so you don't pump hot charge air into the turbo again.... and for the sound.

alpenweissisnice

Seems there are two schools of thought here...My understanding of our cars in stock form was that dump back into the intake stream for a purpose, but I am hearing from others that this really shoudn't make a difference...

Anybody have a copy of Corky Bell's "Maximum Boost" lying around as a reference tool?

Ahmet

Corky Bell's Maximum Boost doesn't say much on the subject other than the fact that some sort of a pressure relieving device is necessary to protect the compressor and throttle plate (as well as other parts) from surge/very high pressures. I prefer recurcilating, and do think that the bypass valves can keep compressor speed up, as they can be moving a descent amount of air (at very high velocity and pressure mind you).

Here's an auction for the intercooler pipes and godzilla bov if anybody's interested in upgrading both their blow off valve and pipes at the same time. Note that this adjustible valve can be used either as a diverter valve, or as a blow off valve.

http://cgi.ebay.com/ebaymotors/ws/eB...ESSE%3AIT&rd=1
Ahmet

Mike Murcia

Reading a little further into it, I've discovered that by passing the charge air over the compressor, it actually slows the compressor wheel instead of keeping it spooled. SO I guess that's why some vent to the atmosphere...in addition to the sound that emits. I just assumed that by looking at some other automaker's newer designs of the bypass valve position (routing charge air to the compressor) that this was a good setup. The real question is how much of a difference is there in your a/f ratio if you vent to the atmosphere or recirculate if you're using a cone air filter? It's already been stated that a MAP system will not be affected, but what about a MAF?

Ahmet

"Reading a little further into it, I've discovered that by passing the charge air over the compressor, it actually slows the compressor wheel instead of keeping it spooled."

Could you explain how you came up with that conclusion?

A MAF system will run rich anytime the BOV vents into the atmosphere as the engine computer will have fuel injected in a quantity that responds to what the MAF is reading (but the engine will be ingesting much less than this).
Ahmet

Mike Murcia

Read here: http://wwwrsphysse.anu.edu.au/~amh11..._off_valve.htm

At te end, it even states:

Whether you decide to vent/wooosh to atmosphere with a BOV, or quietly back to the turbo compressor with a CBV depends on your injection system. Magazine test results over the years have shown little performance difference between the two, other than an interesting aural sound. The reason for fitting one is to reduce strain on the compressor turbine wheel, the intercooler, hoses and fittings.

So it can be concluded that as long as your valve is not malfunctioning in any way, there are no real performance gains in spending a lot on a BOV/CBV.

Ahmet

I don't see how from that you conclude a diverter valve slows down the compressor more than a BOV.
Ahmet