STLPCA

The trumpet is a vacuum hose to cool the clutch housing. It has been suggested by Bruce Anderson & Joel Reiser (PCA Tech Committee 993 guru) that an open box or too many drilled holes may reduce suction to the hose & therefore reduce cooling.

As to HP gains, Porsche has never claimed any increase. I can't imagine why they wouldn't have captured those free extra horses for all the 993s when they've spent tons on R&D for less. My factory MS 993 feels no stronger than non MS cars I've driven, although it sounds quicker. I'd be very interested in seeing dyno tests. As recently as last year Joel answered when asked online if the MS package added power:
Would there be any noticeable differences in starting or power, no not really. Mostly sound. You may feel like the car is going faster, and that's OK too.

BTW, the holes increase intake noise, not exhaust sound. The full factory MS package (M159) included the drilled box, different exhaust tips & less restrictive mufflers.

Bogwan

Well, while this is a simple modification with very good acoustical results, do not let the beautiful new music coming from your engine compartment distract you the first time out. This was my situation last night (11:30), as one of the local policia took note of the same music, and decided to investigate. Nice guy, had someone else pulled over in a 7-11, so didn't have the r-gun out, and didn't know how fast I was going, so he let me off with a,'Nice car, please toe the line.' Just thought I'd share.

Great Mod thou.

Bruce SEA 993

One thing that we all forgot to point out: the '96s and newer will have a "step function" in the sound when the VarioRam opens up. Under WOT it can be a very new sound when you drill the airbox.

Is the sound linear in the '95s? I do know the sound increase will be noticable in the non varioram cars but the varioram opening is a hoot in the '96+ cars at 5000 RPM.

Bogwan

Everything seems preatty normal for me until 4000, then it starts to growl , and just seems to get better as you pour it on. I heard a rumor that the varioram was found in some very, very, late production 95's? how can I tell, VIN#, or anything in the engine bay give it away?

Bruce SEA 993

Look at the top of the engine...all kinds of big aluminum intake mainfold piping. Some cars say VarioRam, others don't. You will hear the thing kick in at 5000 RPM with the airbox drilled.

Bob Rouleau

Dan96C2 - the answer aas to why Porsche did not provide better airflow on the intake of the 993 is on my follow up post. It had to do with meeting Swiss noise level restrictions. The 993 had a hard time meeting them. That's why the induction system was compromised. I'm too lazy to go though back issues of Pano but the HP gain from the airbox mod was published there in a summary of the Tech Tactics meeting. lastly Joel is not always right. he thinks the yellow pads on a GT3 are Pagid RS-19's when nothing could be farther from the truth. Nobody is right all the time. Perhaps Bruce A will chime in, I know he is on the List.

Rgds,

96C4S

Thanks Steve.

Feehliks

@Bogwhan

That is presumably the resonnator flap opening at around 5000 rpm on the non Vario-Rams. With the drilled box the accoustic effects of this are amplified.

Some claim a few hp might actually be lost because the engine sucks in warmer air from behind. I doubt this effect is noticeable.

@BobRouleau

If the 993's standard box is a Swiss speciality, why didn't Porsche just provide a Swiss version? With those few clips it wouldn't be a big deal to have something special for Swiss regulations while saving all other's from this restriction.

Felix

STLPCA

Bob
I know he's not, nor for that matter is Bruce Anderson. However, my point was that his quote from last year is from the published PCA Tech section. One would think he would be aware if his fellow Tech Committee member, Bruce, had contrary dyno data. Further, I also recall Bruce giving a similar answer in either Pano or the PCA Tech section to the same question.

I have factory MS & believe I've read every 993 MS mention in Pano, although maybe I missed the one you recall. Although I'd like some validation that I've got more ponies, I just don't remember anyone citing a comparative dyno w/& w/o the MS box.

Indeed, it doesn't make sense to me. Nothing indicates the 993 intake is constricted by the size of the air inlet & that the engine is suffocating. If it were, it would have been quite simple & cheap for Porsche to open it up w/o any increased sound issues. If the engine is taking in all it needs, how could adding holes help?