bumblezc

So what does it sound like excactly. Between shifts it make a funny noise. Sound like it's coming out of the open exhaust not blow of valve. Anybody know how to describe it?

turbo z24 guy

its like a fluttering noise when you let off the gas and the throttle closes... the sound can be heard through your intake filter. watch your bov and see if it opens when you hear the noise. if it doesnt open, then its compressor surge.

willahlborn

Sorry to jack this thread, but this is related.

Okay this may sound like gibberish to all you Honda-heads but my friend has a '01 Subaru Impreza 2.5RS, with a '04 STi block, t3/t4 turbo, 550 rc injectors, Link engine management, etc. and ever since upgrading his block, has had terrible knocking if he goes over 4psi. The Link engine management system is basically like your zdyne or Hondata, except it can control more paramaters and is very popular among Impreza tuners. He has tried more fuel, less timing, and still has this problem. So he had a shop install a big *** fmic (yes he didn't have one before) and now he can go past 15 psi no problem, but has horrible compressor surge. He can't figure it out... anyone know what might cause this? BTW I left out the fact that he has a tial external wastegate, with an 8psi spring, manual boost controller, and a blitz type s bov. Thanks!

warren83

the link is a lot better then the zdyne ...but thats of topic .........the compresure surge is all in how you have the type 2 bov hooked up my friend with a turbo miata had the same issues with it ....hooked it up right the way the manaul said to and he got really bad surge ....after reading the forums for his miata he found out a different way to hook uo the 2 vacume lines for the bov something about using a t fitting and 2 different intake sorces....but really important because it probally different for the subie anyway have your friend try difernt vacume sorces or look for some subie owner with the same set up ..

bumblezo -------this is probally going ot get a lot of feed back but the best way i can think of is to hold you fingers together and run a aircompress blow gun acrost then kind of fast ....that will make the same sound only slower then the compressor surge

willahlborn

would the solution be to modify that bov somehow that it stays open longer, or opens wider, or just to get a different bov?

atLdohc

well keep in mind some cars (ie. grand national) didnt even come with a bov. so it will take a little while to wear out your turbo. but at 20-30 bucks, why not get a bov for a longer lasting turbo?

baldur

Saab 900 turbo didn't come with a dump valve either. I think OEMs put dump valves mainly to silence the cars.
You don't need a dump valve unless you're at 30psi boost with a big turbo.