Air Box Info......

Melv · Oct 10, 2004

Jst talking with a Porsche pal in the States. He's been involved with the factory and last week had a meeting with Roland Kussmaul, Porsche's Chief Racing Engineer. He was responsible for the weight loss programme on the Cup Car's in 1990.

Two relevant 964 items came out of this:

-Kussmauls personal Porsche is a 964....

-Air box holes...waste of time. Cut out the whole box to within 30mm of the edge -it's worth 5bhp.

Remember -you heard it here first!!

Do I hear the rush of feet to the 964's acompanied by manic hacking of air boxes??

I'll give it a try for Donington....

Have fun!

Mel

Guest · Oct 10, 2004

Kussmauls personal Porsche is a 964

Did he say which model? Or do you suppose that with his contacts it is now a complete mixture of all sorts of bits and pieces from Weissach?

bones · Oct 10, 2004

This is why a modified Porsche is 'the' Porsche . Design by evolution. - quickly hides!

ClubSport 911 · Oct 10, 2004

Well, ain't this interesting.

I have on record, an e-mail from RUF.

They claim:-

4 or 5 25mm holes in the bottom of the airbox. To many = lose torque. Too few = waste of time.

Is there any credibility with RUF and the RS 964 ?
Any comments ?

Melv · Oct 11, 2004

ORIGINAL: ClubSport 911

4 or 5 25mm holes in the bottom of the airbox.

Interesting! Somebody showed me precisely this at JZ's on Saturday.

Mel

SimonExtreme · Oct 11, 2004

Surely this all depends on what else you do optimise the extra air available. Can you get the extra fuel into the engine as well? Do RUF take out other restrictions in the induction which means that the engine is getting enough air anyway while the other mod is good if nothing else is done? You cannot take one modification in isolation without understanding how it compliments or detracts from what else is done.

Yoda · Oct 11, 2004

I had completely removed my airbox and secured the filter on by alterior means (far too compex to explain here). Did some back to back runs last night and couldn't notice any immediate difference except that the induction noise with the airbox off is superb [

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Trying to find a spare airbox cover to cut away, failing that have found a couple of places that sell a bracket to hold the air filter on via standard clips but they are charging £150ish!!

Any one have any other ideas?

Dave Wilkinson · Oct 11, 2004

I think somebody else mentioned in a earlier post that the Fabspeed airbox is designed exactly this way. I believe it's a carbon fibre box designed to fit the standard intake but with a fully open back. Design 911 sell it here in the UK (at £125 + VAT) and you can see a picture on their web site (www.design911.co.uk). Their part no is ID96408012301A. No affiliation BTW - just pointing it out.

Regards

Dave

Laurence Gibbs · Oct 11, 2004

Mel should'nt your cup car already have this mod? I have heard from ninemeister i think, that if just the air box is done you can actually lose power! I think Colin has done some comparisons on the pro's and cons of all the options.
When my car was dyno'd at JZ's last year it was 257hp and had just the airbox mod, I put the lost 3 horses down to the airbox mod. If exhaust mods are done in conjunction with the free'r breathing airbox it does have a positive effect though.

Melv · Oct 11, 2004

The Cup Car airbox looks a like a battenburg cake with two square holes diagonally opposed, one in front of the intake trumpet immediately beind the filter.

I noticed that the intake trumpet has a mesh over it, so took the filter off at Donington a couple of years ago.....the noise was painful and power semed to be down....

Mel

Yoda · Oct 12, 2004

I will soon have a spare airbox cover, before I take a saw/drill to it what should it be - drill holes or cut the lot away?

I'm not expecting more power, would be sad if I lost some though [:'(]

Regards

ClubSport 911 · Oct 12, 2004

Frankly, I would start with the RUF recommendation. Yu can always drill more holes if required, but "undrilling" takes more time.

In any instance its only going to make a big difference on WOT.

Steve

Yoda · Oct 12, 2004

RSR · Oct 12, 2004

Yoda if you remember cutting it all away is exactly what I explained to you at the Ace Cafe a couple of weeks ago. As someone else said it depends what else you do with it, however I find it hard to believe you lose power by allowing the engine to take as much air as it wants with as few restrictions as possible.

One of my cars was recently dynod at 312 bhp and this is a picture of its air filter setup. Obviously power comes from a few other goodies as well.

Laurence Gibbs · Oct 12, 2004

The reason you lose power is because of what sort of air is being drawn in. The basic air filter cover has an extended trunk that pokes out into nice cool air from the air inlet from the engine lid. A drilled airbox can draw air from the considerably hotter air around the engine bay. The cooler the intake charge the greater the power and vice versa. This is why some aftermarket filters can actually decrease power rather than do as they claim. Several people have done independant tests on various filter mods and options and have found the above to be true. The air box mod on it's own should be best described as a way of increasing intake noise rather than a performance mod on it's own. Think of it this way, you can make a funnel as wide as you like at the top but you can only get more out if you widen the hole at the bottom. So more air in and no increase in exhaust flow means very little worthwhile change.

RSR · Oct 12, 2004

Totally understand on the first point Laurence. However is the standard setup (picture attached) really getting that much colder air than say the setup I previously posted? The rear wing should be flooding the top of the engine bay compartment with cool fresh air.

I guess if someone has tested it then you can't argue with that.

On the second point its not as simple as that. In the example you give you dont need to widen the bottom of a funnel to get more air out just because you have widened the top of the funnel. If you force or suck air through a funnel that decreases in diameter then the air velocity increases as it passes the length of the funnel. So the amount of air that goes in the wide end is the same amount of air that comes out the small end, except it is travelling faster. Indeed this is something that engine designers may specifically design in to increase air velocity into the engine.

Guest · Oct 12, 2004

Hey, the Venturi effect.

And, the constriction, as well as speeding up the flow, also reduces the pressure at the narrow bit, so potentially sucking in more air.

Guest · Oct 12, 2004

....tears rolling down my face! crying out loud!

Guest · Oct 12, 2004

...now that's flash...one with a modded filter and one with a standard airbox....and for my next shot......Paul, you do have the perfect job mate, you really do![

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Yoda · Oct 12, 2004

Jimbers - I'll have what ever you have been on. Perhaps this air cover business will seem more straight forward.

RSR - the saw it is, I'll just stick with the great noise as I can hear that for myself.

Thanks all for the info.