Turbo noise

[maggot]

Right, in my 87 944 turbo often when i accelerate hard (sometimes on less harsh acceleration) all i can hear is a massive gush of air escaping from somewhere and when this happens i lose a lot of power. the turbo meter doesn't indicate any problem. I've been told that it could be something to do with my air filter? as i don't have a standard one, it looks like a standard cone just sitting infront of the engine sucking in all that piping hot air. (obviously will be replacing soon) any ideas what could be wrong, also any suggestion for a new induction kit?? thanks

[AaronM]

Check the hoses going to the intercooler and to the throttle plate, those are the most common. Somewhere in your system a hose is coming loose under boost.

Are you getting 18-20 inches of vacuum at warm idle? If not, you probably have a persistant vacuum leak that will need to be taken care of.

[Lawrence Coppari]

My cone filter is right behind the driver's headlight. About 7 years ago I got to wondering about how hot the air was that it was being taken in. I rigged up a thermocouple right at the cone. As long as the car is moving at about 20 mph or more, the intake temperature is within a couple of degrees of ambient. At highway speeds, it was ambient. When the car is stopped, the temperature rises sharply but falls like a stone to near ambient as soon as the car gets going.

If your air intake is right behind the intercooler, that would not be good.

[Lawrence Coppari]

Also check the blow off valve to see if it is letting off pressure. I doubt the air filter is the problem. It's a hose or the blow off valve. There are a number of small vacuum/positive pressure lines in the system. If they are leaking (at the y's), your blow off valve will not remain shut. Blow off valve also has a diaphragm in it. Check to see if diaphram is torn. Nipple on top should be a dead end. If it does not hold + pressure, diaphragm is torn. Positive boost pressure holds blow off valve closed in addition to spring force.

[maggot]

thanks for the replies, will be looking into it. my cone filter is right behind the intercooler and i cant see anyway of having it in anyother place as there is such little room in the engine. anybody got any pics of there engine bay/induction system?

[Lawrence Coppari]

Picture of AF behind headlight.

[nize]

+2 on checking the BOV

[nine50one]

to me an audible rush of air that doesnt result in any measured boost loss but kills power deffinately screams BOV..

I may be wrong - but wouldn't a simple way to see wether or not it's a broken BOV be to simply to disconnect it at one end or the other?

if there's no change in symptoms that would indicate that the BOV has gone bad.. otherwise you'll have to look elsewhere for a pipe that has blown loose

(any comments on whether or not that's a good idea are more than welcome - i havent had a problem with the vavle yet myself so i haven't tested that.. but it seems like that would be an easy method of diagnosis )

[nize]

the easiest (and more accurate) way to check the bov is to connect the top nipple to a hand pump and see what pressure it opens at.

[JustinL]

It's even easier to just suck on the nipple and see if you can pull air through it.

[nize]

i've seen bov's fail even when you can't suck air through using your mouth.