B.Kish

I am looking to purchase a 964 that has been modified with an MAF. So far the car seems to pull more strongly than other similar cars without the MAF and have a deeper, throatier intake noise.

However, there seems to be a whistle/chirp at very partial throttle, as there is increased load on the engine. As the load decreses the whistle/chirp dies away.

Is this normal for an MAF, is there a vacuum leak (my guess) or was a small, innocent, bird accidently sucked into the intake?

Thanks a million.

slant911

I had one of these on my last P-car (1986) and it did the same thing. Made a small sound at about 1/8 throttle that sounded like a whistling or air leak. I was told that it was normal as everything is much more opened up (less restrictive). I never had any problems with it over the year I had the car with it installed. Don't know if it's the same thing you are describing, but, it sure sounds similar. I just used to turn the stereo up louder so I didn't have to hear it

richard glickel.

I noticed this too when I had my 3.2. I have the same filter set up on the 3.6L engine and have yet to hear that little whistle. Could be that I can no longer detect the whistle over the sound of the roar!

Richard
'87 Carrera 3.6L

MikeF

I have an MAF on my 964 (1994) and you are right, the sound above 3500 rpms is intoxicating...can't get enough. Mine does not whistle but I understand that it is quite common and not indicative of problems.

Or...it could be a bird.

phil@tech9

Guys,

The whistle that you hear is the air passing over the throttle butterfly. With the MAF sensor tube in place the engine has the ability at part throttle to 'suck-in' more air, this is the sound that you hear !

As the throttle is opened further the intake opening is made larger, thus the air can travel on its course with less restriction.

Jeff Curtis

Phil is right on that one...two of my friends that have that setup experience the same "whistle"...I think it's cool!

I had an SC that did the same thing...oops...that was due to a supercharger though!

J richard

B.

I've got the whistle as well. For the longest time I was asking folks with the same setup the exact same questions with mixed responses. Some cars seem to have it others don't. The short intake path with the autothority setup has no acoustical attenuation. Under high vacume/part throttle conditions I get a high pitched squeal not unlike a vacume leak. It's air around the throttle plate. Why some cars have it and others don't is unclear. What's also apparent is some people can't hear what is very obvious to me, real frustrating when you are trying to diagnose the cause. I've learned to live with it, I dosen't bother me now that I know everything is OK. Do however get the original parts from the PO and watch out for those small birds, they plug up the air filter...

Regards