Allen

Don't you think that's a bit..."stiff". Of all the replys to this thread, yours is by far the most offensive. I'm not a newbie...so I can tell from experience, that nobody here means any harm...it's just a bit a friendly "jabbing" amoung cars guys. So I welcome you to the site and hope you stick around long enough to see what a great group of people are here...

TheOtherEric

It's all in good fun, noob. You'll get used to it.

luv2ride

Take it easy buddy. 99.99% of these people are non "*****" or (NP) and have all sorts of great information. Although we are all considered P-car *********. 993 owner = (DH). lol enjoy rl and welcome.

ignomini

To get back on topic. Drilling the airbox lid reduces power. The computer may re-learn its way back where you started (long term trim), but Porsche called it a "motor sound kit" because they knew the truth. Here is the dyno comparison we ran down at Jackson Racing.

Thaddeus

Well, that's info I can use, ignomini! Thanks. I guess my butt dyno is fooled by soundwaves....

Stock airbox lid stays on then.

Hm... what can I monkey with next?....

TheOtherEric

Very interesting, thanks for posting. I must admit that I don't fully believe it, though. Very very odd that the cup race cars would use a mod that reduces power. And logically it just doesn't make any sense that slightly reducing the intake restriction would HURT power. Perhaps your results show that the drilled airbox doesn't help, but it seems illogical that it would hurt power.

InTheAir

Well, I'll definitely give up 1.7 hp for the sound.

Thaddeus

Unless sucking in more heated air does something negative. Maybe an open airbox lid helps on real cool days and hinders when it's hot?

Red rooster

Thaddeus,
Intake air temperature is a big factor in the bhp equation. Chances are the sound box will give a little more in winter and a little less in summer !!
Maybe a bi-metalic strip actuator is needed just like 60s carburettor motors had on the air intake snorkel !!!!!!
Now thats a project !!

All the best

Geoff

Steve Weiner-Rennsport Systems

Geoff is right; air temps play a BIG role and its virtually impossible to replicate real-world airflow when the car is parked on a chassis dyno,.....

Like many things, there is more to this than meets the eye,...

TheOtherEric

I agree with Geoff too, that intake air temp plays a big role, especially on a dyno. But let's not say that intake air temps go up when driving at speed due to the open/drilled airbox. I think that idea been pretty much put to rest. Idling temps will go up, sure, but air temps at speed won't.

Edward

Indeed. IIRC, another here (I won't mention his name but he can step out if he likes) did temp readings WITHIN the engine bay while driving at the track. While I can't recall the specifics, the gist of it was that at normal speeds (as low as 50mph IIRC), the area in the engine bay surrounding the intake has little-no appreciable temp difference compared with just out of the engine bay. The reasonable conclusion to be drawn is that the engine fan and the air pressure flowing down the tail in that region creates plenty of cool intake air ("cool" that is, in comparison to actual ambient temps). So "sucking in hot engine air" with a more open intake really is not a valid argument.

Edward

Jean

I am with TheOtherEric, or this Eric on this one. Even if there was any difference you would not be able to feel it even if you are an experienced racer having driven the same car for the last 20 years. The sound factor is crucial in butt dyno assessments, and in my opinion, this is where you might have been misled.

This is not the first dyno chart that I see showing losses with drilled airboxes or less restrictive mufflers etc.. the reason for it is not obvious nor anyone can give you an accurate explanation other than a guesstimate...

Just keep the one you prefer the sound of, and don't worry about performance. If you are REALLY wanting to get tto the bottom of it, grab one of those GPS based dataloggers and do back to back tests. I can bet you will see two identical and overlapping curves.

TomF

To throw another wrench in the works.... maybe the dyno results above are symptomatic of the combination of the B&B mufflers and the motorsound airbox. Remember, Porsche is famous for engineering the complete package, where each component complements each other. Just my .02...

Thaddeus

I found a compromise. The stock air box cover has a 'snorkle' thing that runs inside the cover, that blocks part of the filter after the air flows into the chamber. I found this snorkle assembly unsnaps from the cover, leaving a larger opening for air to enter, and removing the obstruction to the filter. I think I have about 30% more opening for the air to enter, and the entire filter can now do its work. The engine is still quieter than when using the Fabspeed cover. Cheap mod, indeed: no cost whatsoever, and no permanent modification. I can put it back in under a minute. Perfect!