I've got the cover off because I just installed the MO30 suspension and Bilsteins. Already got RSRs on--love them. Is it worth it to drill the airbox cover too, as many others have? If you've done it, did you use the (very) small pattern of dots inside the cover (perhaps 3/16") or did you drill bigger holes? What size? Anybody find a negative to said drilling....or find it not worth the trouble? Thanks for the color.

Chris

 

No do it, its just a factory motorsound air box. You're not going to hurt anything. Drill away.

 

Pro: slightly less air restriction.
Con: slightly higher intake air temp (maybe)

I've run an open airbox and I don't notice much difference in sound...

 

Aha! Thanks Eric, Yes! That's what my dim brain is recalling! Someone (Robin Sun?) told me he took the drilled cover off because he measured air intake temp and it was hotter with the drilled cover. However, if memory serves Robin's got a Turbo-style spoiler. Mine is a stock-appearing C2.

If there is very little difference in sound (once you've already modded the mufflers) perhaps it is not worth it to drill the cover?

More thoughts please.

 

I purchased an OEM Motorsound Airbox Cover (I'm just ~that~ **** ). I like the deeper sound when the varioram kicks in, but I'm not sure I hear much difference at idle. I have both the Motorsound cover and the stock and I mean to compare the two some day--we'll see.

 

There is a sound difference, very nice addition. Since the factory did it, no harm can come from duplicating the mod. Panorama ran an article years back which showed a 5-7Hp gain as a result of the holes. The air intake was restricted to meet tough noise regs in Switzerland and the air flow was suboptimal. Drill 7 one inch holes in a nice pattern on the side of the air box facing the element.

regards,

 

That over a 2% gain , incredible gain for less than $100! Hard to believe, buit if you say so and have seen the documentation; I have not

I listened to Robin Sun, and because I have a RS rear spoiler, I added a 993TT snorkel and the engine sucks the cool air (Cooler than the ambient air in the engine compartment) in through the grill right into the snorkel, into the airbox. Robin suggests that this way, cooler air gets into the motor/engine this way. I like that. Robin documented the improvement...maybe on P-Car.com

Personally, in my humble opinion, I think all you get nbout of the drilled air box is added noise, noise I don't need. I am in the stealth mode. But I do have the MS airbox in the garage...it could go on in a moments notice.

 

I believe that the Porsche's motor sound air box had many tiny little holes instead of several big ones for a reason, it creates better sound and without letting hot air into the intake. On cars without tail the defelector on the inside of the motorized tail directs cold air directly to the air box opening which is as effective as the wing with added snorkel.

So I would faithfully reproduce the tiny holes like the Porsche motor sound air box if I was drill the air box out instead of just several big holes.

 

Martin - the holes in the airbox trick was published in a Pano as part of a report on the spring Tech Tactics session. The data on the 993 airbox was reported by none other than Bruce Anderson who is noted Porsche expert.

Robin - I can't see much difference between seven one in holes and what seems to be more than a hundred quarter inch holes, except for more labor.

Best,

 

Bob,

My thinking behind that is the smaller holes restricts air flow, which will prevent hot air from far inside of the engine being sucked in. But the open holes does allow "noise" for good effect.

 

Uh oh - sounds like someone needs to run with and without modded airbox on the upcoming Dyno run. I got flamed for refuting Bruce A / Pano in the past. Lets see if we can do it again!!!

 

I never Dynoed the motor sound box cover compare to the standard box cover however I did do a Dyno with a cone intake filter compared to the factory box and there were no difference in horse power increase.

I really doubt the motor sound air box adds any horse power, if it did then Porsche could have easily market it as some sort of "S" option and would be able to charge a premium for the option.

 

I dyno'ed the car after I drilled my box and saw a solid 15HP bump in the midrange. I also noticed that really cute girls were checking out my car; when before I was getting no play.. this mod is amazing...



Coleman

 

I have drilled all the small holes. I thought it was mandatory?

 

My box is currently taped up..... with duct tape.

Just a thought, the clutch ventillation tube is also attached to the air box. I noticed that my air filter always gets quit dirty near the area of the clutch ventillation snorkel, by opening bigger holes it may cause a drop in vacuum pressure needed to draw the clutch dust out...... anyways, all just theory....

It may not even matter at all, as I don't believe the older 911s have the stupid clutch ventillation tube.