Drilling holes in CIS cover for HP+

Posted this question a year ago and still no difinitive answer.

Heard you can drill holes in the CIS air cleaner cover will give extra HP+, also heard some racers trim away all the plastic around the cover just leaving enough to hold air cleaner in place.

Anyone have ideas of validity of these claims?

I think we've heard definitively (from Bruce Anderson) that these modifications will result in NO performance improvements whatsoever. The CIS air system is already fully adequate. It is the EXHAUST system that is choked somewhat. Upgrading to the SSI heat exchangers does result in more horsepower, but that is one of only about two things you can do to a 3.0L to improve performance without rebuilding the engine. Webers are the other thing.

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'83 SC

Once, just once, when I was at the track, on a nice dry and warm day, I removed my entire air box cover, and allowed the straps to hold the air filter in place (crossed them).

We timed the car around the track both with and without the cover, and there was absolutely no difference in the time. Admittedly, this was not a "scientific" experiment, but I think I have to concur with Bruce, there is no difference in the power that the SC engine with CIS can generate with more air. If you will remember, the CIS has a sensor plate, which upon moving, opens a valve to let in more gas, thus the two are intertwined. More air automatically yields more gas, and thus you accelerate. In carburators, there is usually an additional accelerator pump, which when you mash on the trottle, actually pumps more gas in through the venturis, thus giving you more instananeous throttle response. CSI does not do this. More like a locomotive - slower but inexorable.

Thus, we concluded that the risk of going off track into huge dust clouds not worth the risk for no HP gains (sorry for the double negative, but you catch my drift), no pun intended!.....Andras

Bruce Anderson uses a dyno to assess the impacts of various changes on horsepower and torque.

I'd like to drive something with Webers and experience this throttle response thing. But the danger is that I would probably be unable to sleep until I got Webers for my car!

Your car is really beautiful, Andras, by the way.

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'83 SC

Ubermensch:

I blush at your praise!

This weekend I put all the "heavy" stuff back into the car (like rear seat backs, carpeting, etc.) in anticipation of this weekend at the Cleveland GP. We will be guests at the Team Rahal compound, and Paule and I will be driving the SC up there, and we need the backs of the rear seats for our luggage. And the bra and tires with Endurance on them, well, it just gleams. When I dropped Aurelia off to play basketball with her girl friends,it was fun to drive up and get the stares.

Anyway, upon getting it all back together again, my previous analogy of being inside a Hershy's Kiss is still so apt!!!! I wish I had a scanner at home, so I could post it, especially that one photo I have right in the middle of the Corkscrew at Laguna Seca (the Kiss being trailed by a red M&M-looking 911.) Such fun! Too Much fun!!!!....Andras

Thanks for the replies,
I also tried removing my cover and securing the air filter on with straps a while back the car seemed a little more responsive to me but It could have been the added noise factor from the intake making it seem so, it definately made some nice sounds though with it removed

Food for thought...Bruce Anderson, in the June 2000 issue of Excellence, mentions Porsche itself boring holes in the airboxes of the Supercup cars. He tested 3.6 liter cars with the same modification, and saw them gain 6-8 hp or so. Hey, if it's good enough for the factory.....

Clay:

I have also read that claim by Bruce, but I believe I read a further clarification that this works only on cars later than CIS, namely DME. I still stand by my response that added air will not improve the HP ratings of a 3.0 CSI.

Jim:

I also noticed a louder induction noise, but I do think that's all you'll get, just more sturm und drang, kein kraft.......Andras