dime1622

from the FAQ at clark's garage about the cycling valve:

"The cycling valve is controlled by the KLR Unit (Knock Regulator Unit). The KLR receives signals both directly and from the DME Control Unit to determine how the cycling valve should be controlled. The chips in the KLR have a boost limit which comes preset from the factory. When the actual boost reaches the computers preset limit, the KLR sends a signal to the cycling valve to close which allows exhaust pressure to open the wastegate. If the cycling valve fails, loses power, or a problem occurs in the KLR unit, the cycling valve will fail fully closed. In this mode boost is limited to approximately 1.2 bar. This is essentially the boost at which the force of the exhaust pressure will overcome the wastegate diaphragm spring pressure. "

i get a really loud "whoosh" noise when i hit 1.2 bar, it does it about 98% of the time i get on the boost. it sounds like someone has put their mouth up to one of the intercooler pipes and is going "kchhhhhhhhh" in it (if you can understand that :P anyway, could the wastegate be bad? i looked at all my IC piping and rubber connections but they all look ok, and all i know is that the noise comes from in the front of the car, cant tell what side or anything. id like to be able to hear it with it parked and someone hitting the gas but there isnt enough load on the engine to get above about .9 or .95 bar, so the only way i could really search for it would be to put it on a dyno or something, just some way to be able to build that much pressure. could a busted wastegate make this noise?

also, with my autothority chips, is it ok to get rid of the cycling valve? would i need a boost controller?

thanks in advance!

PorscheDoc

yes and yes

diskzero

Did you try to vacuum test your blow off valve? It is located on the driver side, right behind the headlight assembly. The diaphragm often fails and many owners replace the valve with a more reliable part.

http://www.smartcart.com/Paragon/cgi...tem_num=EBDV18

is one possible replacement.

Gene

dime1622

i actually did have to replace the recirc valve, the rubber piston was shot. i now have a forge, but im still gettin the noise

and does yes and yes refer to the autothority and boost controller question, or is that pertinent to the wastegate question?

Mike Murcia

Are you running with an open element airfilter like a K&N? If so, the sound you are hearing could just be the excess boost bleeding to the turbine between shifts. With a K&N, it's much easier to hear these sounds.

PorscheDoc

Oh sorry, the cycling valve and MBC

dime1622

no, stock airbox. it really sounds like air whooshing thru metal

sayporsha

I've heard this sound on 3 different 951's (mine included). Each car had a boost leak in or around the rubber hose going from the turbo to the boost pipe. I'll bet you find it there.

sayporsha

I almost forgot: better check the hose from the cycling valve to the wastegate. If it's cracked or broken it can't control the wastegate.

dime1622

the vacuum hose? i think my vacuum hoses are messed up so im replacing them all (ok, i KNOW theyre messed up, but not exactly where)

sayporsha

Get under the car and find the wastegate. Follow the rubber hose from there up to the cycling valve. The nipple on the cycling valve is plastic and might be broken. Mine was, but someone stuck it back on with silicone.
If that hose leaks your wastegate won't get a boost signal and your turbo will overboost. That probably burst your boost hose (coming out of the turbo) or made it slip off of the boost pipe. My boost hose split on the underside - you couldn't see it. I really had to grope around to find the leak.

dime1622

rock on, thanks for the help. time to go digging!