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From digest.v7.n525 Sat Nov 1 19:34:19 1997
From: "Carl Buckland" <>
Date: Sat, 1 Nov 1997 15:10:41 +0000
Subject: M3 Air Induction

Scott McC, a very fine driver and driver instructor from CA, writes:

> Hello Carl -
> Nice to see you at Laguna last weekend.... too bad about the trailer
> "Owie"...

I am glad to finally have the first dent out of the way. From here on, it will be easier. The dent will be fixed next week, but I like having it for awhile; it is like a war wound. It actually happened at a gas station, in reverse, at about 2 mph, but the stories about how it happened grow each day (see previous post, Re: hyperbole)

> I spoke to (snip) He was
> just great and very helpful... even to the point of saying that the larger
> Throttle Body wasn't as necessary (in order of priority) and that the stock
> exhaust is OK. (Shaun doesn't like LOUD exhausts..)

I say DO IT ALL. If you open up one part of the air induction chain, why leave another part of it constricted? Same goes for exhaust. The Supersprint is NOT loud. Freer flowing, and a soft mellow sound. Even My car, with headers, Dr. Gas, and the SS muffler, is "relatively" quiet.


ram air duct from front grill (more on that below) Euro box (gutted)
Euro HFM
Steve Brown adaptor (BMP sells them. They are the best) big bore throttle body
Custom Conforti chip to account for all that added air Larger injectors, especially if you run at sea level

the keys to the initial air induction are:

  1. cold, outside air 2)under preassure

The open cone filters bring in hot engine bay air (VERY bad) and even if they are shielded from the engine bay, the air intake is passive, coming from behind the headlight. I have seen some very sophisticated heat shields, that virtually block out all hot engine bay heat (Trigger's is really trick), but they still miss the FORCED, OUTSIDE air component.

I think that the air intake needs to be SEALED. The little toy of an intake unit, called the Motorsport Ram Air Intake , is the right idea, but doesn't work. Instead of a skinny little tube coming off the brake duct, I say feed the airbox with a sealed hose from a front grill duct.

I use a gutted Euro airbox. To the front, I attatched a 3 1/2 (?) inch flexible hose. The hose goes down behind the headlight (remove and relocate the horn), thru an easily moved plastic plate to the grill behind the (removed) front license plate. Secure the hose with plastic ties. This is all done at the same time that you install your absolutely essential brake ducts, and involves removing the front bumper (which is very easy). The air intake hose can also be put in place of the left side fog lamp, but this involves removing the light, which I didn't want to do (it is also illegal in SCCA to remove the light. There is also discussion as to whether relocating the horn is legal).

The Euro air box needs to be replaced with a more streamlined air box. I look for someone (Milos? Peter?) to eventually do this in carbon fiber (the weight is insignificant, but the CF looks really trick). Until someone makes a better box to which I can attatch my outside air intake hose, I will stick with the Euro airbox. (A stock airbox won't work, for the outlet is not large enough for Euro HFM.)

I am told that there should be a 3 to 5" tube between the airbox and the Euro HFM, to stabilize the airflow. With the Euro airbox, there is not enough room to add this tube. I have attatched the HFM directly to the airbox, wich is not optimal.

Carl From digest.v7.n528 Sun Nov 2 19:45:14 1997
From: "Carl Buckland" <>
Date: Sun, 2 Nov 1997 13:43:44 +0000
Subject: What could be Simpler than a Box?

. Thanks Carl, I've been wondering about the advantages of Euro airbox vs. Cone filter. I'd appreciate hearing the arguments from the coneheads. Would carls development of a custom airbox utilize the cone filter enclosed in a sealed unit?

Yes. that is it. Simple. A cone or cylinder filter, enclosed in a large (the larger the better. the GTS-3 M3's have boxes as large as a suitcase) box. Air coming into the front from a sealed hose that goes to the front grill.

The concept is easy, but no one to date has made the box. That may change very shortly. Stay tuned.

I've envisioned making a plastic
extension of the air pickup that covers the cone filter and seals around it's big end.

No, if I understand you correctly. The air intake must be *to the chamber,* not directly to the filter. Putting an airtight intake into the end of the filter will force all the air thru the relatively small END of the filter. The chamber must *surround* the filter, which will take in air from all around it, not just from the end. Another way would be to draw the air thru a plate filter, such as the OE shaped K&N, but in a much smoother air box than the OE or Euro. I am not a filter expert, or even a scientist, for that matter, but I think that the larger the filtering surface the better.

That is my thinking, now pick it apart, and someone who IS a scientist figure out a proper box for us air=power proponents.


My opinions are a product of what I read and what I think. My own internal filters sometimes wear rose tinted glasses.

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