Just installed my chip and K&N Filter...

[Rick Lee]

Saturday I set out to add a few horsies to my P-car. Getting the computer out was not a lot of fun, but I managed it. It was apparent that the PO had opened the box up before, as the aluminum tabs on the bottom had been bent and scratched -- no biggie. But it made me wonder whether I was removing a good (unknown) chip to install an inferior (Vertex) chip. I'll have to check out the number on the old chip to see if someone here can identify it for me.

Then I removed the air box and installed my K&N air filter. That was the easiest thing I've ever done to my 911. I was immediately pleased with the amount of space the K&N freed up in my engine room. The new accessibility alone is worth what I paid for the filter.

So then came the test drive. Luckily it was warm and sunny on Saturday, so it did not take long to get to operating temp. For those of you familiar with Fairfax Co., I used Chapel Rd. in Clifton as my test track. I did not notice any significant increase in pull. What I did notice was a sort of turbo-like hiss coming from the back. Above 4000 rpm the engine sounded a bit throatier. Maybe it's just too hard to notice a less than 10% increase in HP. But I will say the car ran a little smoother. Engine speed at idle stayed more regular at the red lights and seemed more constant when speeding up or slowing down. Not too sure what all this means, and dyno-ing it won't make it feel any different to me. Maybe it's time to try a cat by-pass next. All in all, I'm pleased with the increased accessibility to the engine, a better sound and somewhat smoother ride.

[Kurt B]

Glad it worked. Yes, the hiss is something you'll hear from now on. That is, until you swap out your muffler and get a cat-pipe.
You won't notice something as dramatic as a change in how it feels. That's why it's best to get an accelerometer and do some before and after test runs.

[juanbenae]

this hiss noise, on my 78 sc with chain tensioners upgraded iI have experienced a hissing/whirling noise at or above approximatly 3500 - 4000 rpm. what could cause this?