Disadvantages of holes in aircleaner cover

[octanemaestro]

My car came with 5-6 holes 2" holes drilled in the air cleaner cover. I think people do this to increase horsepower. Are there any practical reasons (not talking about originality or authenticity, but rather specific mechanical reasons) that I should replace this cover with a non-holy one?

[GH85Carrera]

All it really does is make it louder. Porsche did a very good job on the air intake.

[octanemaestro]

That's a very, very significant disadvantage. Because I am in a remote part of Brazil I don't have easy access to used parts. I did bring Dynamat material with me though last time I was in the U.S. I will cover those holes ASAP. I should write a different thread about this (I think that's the right forum protocol online, not sure), but considering that I have an inappropriately loud exhaust and speaker hole in my rear shelf with no speakers in them and various parts of my AC missing, other than covering the speaker holes and installing Pelicans firewall sound absorber the best I can without removing the engine, is there anything anyone else can recommend to quiet down the cabin noise? I could, for example, cover everything wall surface in the engine compartment with Dynamat. Is that effective? I don't want the sound to just bounce around inside, but as far as I understand acoustics (which isn't much) you would want to absorb sound or deflect it. Dynamat deflects sound I think. It's like a metal sheet basically with a thin layer or tar-like rubber adhesive substance.

[JohnJL]

What year is your car? Porsche itself offered a "motorsound package" option on some 993s which was just a couple extra holes in the intake filter cover. What is your car?

[octanemaestro]

This is an '80 Euro SC.

[darrin]

don't think the holes in the airbox are going to have a material effect on the issue you're having.

I'd start by finding/installing a stock muffler and go from there -- do you know if you still have the stock factory headers (easy to check -- does the exhaust gas enter your muffler from the left side of the car, or from both the right and left sides? if the former, you still have stock headers, if the latter, you're running SSI (or early 911) headers -- believe that the ssi/early 911 headers > dual inlet muffler setup is inherently louder than the single inlet muffler setup that came stock with the SC. Either way, aftermarket exhausts can be a LOT louder than stock (and frequently don't add power in the process) -- if you're fighting noise, start with a quiet muffler and go from there

[octanemaestro]

Originally Posted by darrin

don't think the holes in the airbox are going to have a material effect on the issue you're having.

I'd start by finding/installing a stock muffler and go from there -- do you know if you still have the stock factory headers (easy to check -- does the exhaust gas enter your muffler from the left side of the car, or from both the right and left sides? if the former, you still have stock headers, if the latter, you're running SSI (or early 911) headers -- believe that the ssi/early 911 headers > dual inlet muffler setup is inherently louder than the single inlet muffler setup that came stock with the SC. Either way, aftermarket exhausts can be a LOT louder than stock (and frequently don't add power in the process) -- if you're fighting noise, start with a quiet muffler and go from there

In a way, like with a motorcycle, the loudness can actually increase the safety factor. 911's -- especially RoWs (Euros) with their lower ride height -- are uncommonly low and regular cars and especially pickup trucks and regular truck can look right over you and not notice you, especially in parking lots it's vulnerable and a silent 911 is just asking someone to crash into you. Same goes for the U.S., I think. It's a tiny European car also, let's not forget. You feel like a pipsqueak next to a Ford F150 pickup. So the noise can let them know you're there. There are thousands and thousands of overly loud scooters with ridiculous "performance" non-muffler mufflers and straight pipes and overly loud Harleys and Harley clones and rice rockets around (by the way come to think of it, talk about not adding horsepower by adding ridiculous exhausts, I can't see an aftermarket horribly loud high pitch exhaust helping a 49cc scooter). Anyway especially because of all that I am not too concerned about any noise pollution I may be causing society as long as I don't have to endure any of my own noise pollution inside the car. I also can't easily bring a stock muffler to Brazil. Every time I bring something oversize it costs me $200 in baggage charges, and it may be too large anyway, not to mention finding someone to install it.

[boyt911sc]

Originally Posted by octanemaestro

This is an '80 Euro SC.

Octane,

How far are you from Rio De Janeiro? I will be visiting Brazil end of winter. Love to help fellow 911 enthusiasts. PM me for your CIS needs.

Tony

[octanemaestro]

Originally Posted by boyt911sc

Octane,

How far are you from Rio De Janeiro? I will be visiting Brazil end of winter. Love to help fellow 911 enthusiasts. PM me for your CIS needs.

Tony

Hi Tony, thousands of kilometers from Rio unfortunately. But Rio is a great place, I'm sure you'll enjoy it.

[ClickClickBoom]

Originally Posted by GH85Carrera

All it really does is make it louder. Porsche did a very good job on the air intake.

Ask Steve Wong and his dyno work, don't confuse DOT noise regulations with performance, like life, everything has its trade-offs.

[Fly911]

One of my race buddies told me that drilling holes in his 3.0L CIS air cleaner lid, gave him 5Hp more on the dyno. The sound increase is not significant, but you will get more of the wonderful flat six howl on wide open throttle. Enjoy!!!

[DRACO A5OG]

OP, consider a stock or dansk sport muffler.

BTW, which muffler do you have on her now?

Disadvantage, yes, louder at WOT

Performance no loss but some gain per my observations on a couple of 3.2s on the dyno. 3.0, never tested or seen results.

[gomezoneill]

And if it rains, plenty of water on the air filter element.

[T77911S]

absorb sound.
you could get some rubber mat about an inch thick. cut it just a little bigger than the hole, then glue it over the hole, as a temp fix,.

short of welding another piece back in the hole, you could use the same rubber matt, cut it to the size of the hole and place it in the hole, then install a complete engine bay shielding mat.

[tcar]

Originally Posted by T77911S

short of welding another piece back in the hole, .

SC has a plastic filter cover...

[Geronimo '74]

Originally Posted by gomezoneill

And if it rains, plenty of water on the air filter element.

Yeah, dunno 'bout that...
I live in a pretty rainy country, and this issue you speak of, has never been an issue for me, not even remotely.
I think that, when it is raining so friggin' much that a cut-up air filter lid (mine's almost completely cut away) is going to result in rain going through the filter, we would all be boarding Noa's ark, instead of going for a cruise in an aircooled 911....
Maybe if you're driving backwards into pond, but otherwise this really is a non-issue.