Thread: ssqv causing compressor surge

Ok. Stupid question of the month:

Will restrictive exhaust cause surge?

No. A good BOV knows no exhaust restriction. Remember, BOV's are dependent on boost and vacuum sources alone, and not exhaust gasses. Wastegates are directly affected by exhaust gasses.

^^^

This is why I asked that.

Im pretty much running the stock exhaust. I have a 3" down pipe, then stock everything until my magnaflow 2.5" muffler. I plan on doing 3" soon, just saving up for it, was just wondering if maybe that could be some of my surging problem.

Creep or spike, yes. Surge? No.

do you know if you are getting any creep or spike? where do you have your vacuum line connected to and is it a dedicated vac line for the bov alone?

It is not common at all to have an exhaust cause surging problems especially on smaller turbos but it is possible that with a large turbo, a free flowing exhaust could make you cross over the surge line during throttle openings of 60-100%. This isn't something 99% of people have to worry about though, and won't cause the type of surge we're all talking about here in this thread.

Im not gettting any creep or spike, just a really nice gradual boost. I have the vacuum coming off the top of the manifold on its own source, it shares nothing. Funny thing is, my first bov was terrible, I switched it out and it got significantly better, so I bought the recirc fitting, after I recirculated it, the surge came back as bad as before, so I unhooked the recirc hose and left it venting into the atmosphere, cause it gets a lot better then, its still there slightly, but not near as bad.

cliff, i never had surge before or never noticed. i believe im getting it now under high boost. the car will lurch during transistions of on and off the gas. this is surge correct ?

i am running a hks ssqv love the sound but i dont want to damage my turbo. synapse sounds very similiar just not as loud. either way i think synapse is the way to go. do you really believe ill get gains from just changing the bov off ?

stratton.

Strat, compressor surge doesn't cause lurching. You can only really hear it.
It sounds like a chuffing, or flutter, or sometimes pigeons in a wood chipper. It's the pressurized air and shock wave rebounding off the throttle body and running back into the compressor blades. The videos in this thread have great examples of the sound. You can't feel it though. The engine doesn't behave oddly.

Sometimes the surge happens for a very short time immediately before the BOV opens and you can only hear one or two "chuffs" (one is very hard to discern). That's not great, but not terrible either.

And to answer your second question, Rich:

Yes, I do believe (and there are many tests that have been done on different dyno's and cars) that you will see gains just from switching the BOV. Synapse really is the way to go.