3.6L Intake Question
 

Ok, I'm fabbing one of my famous sewer pipe intake for Jack Olsen's 3.6L. I have one on my car, and in a desperate search for those 1.5 seconds, Jack's decided he needs one too.

Because Jack's car has that girly-man accessory caled "Air Conditioning." he's going to have to trim the lead tube to fit his car. Fair 'nuff.

What I'm curious about is how different lengths would affect performance. Is shorter better? Is longer better? How would one figure this stuff out other than a Day At The Dyno?

Here's a pic of the device, version 3. A K&N filter goes over the end, unlike version 1 which used a smaller-diameter filter which fit flush with the tube and needed a funky coupler setup. I also chamfer the inner radius of the filter side, and chamfer the outer radius where it goes into the coupler, so there is no gap inside the coupler. The next time you're at the h/w store, put a fitting and piece of straight pipe together, and you'll see what I mean.

I'm no physisis (I can't even spell it), but I would think that longer would = greater velocity. But I'm just shooting in the dark.

To steal a phrase from Jack O, I'm glad I'm not the only who can claim Home Depot as a source of Porsche parts.:D

Thom,

Did you dyno test this contraption? Why not just cut up the air box cover like the factory did and install the K&N or factory filter for the five horsepower they claim its worth?

Tinker

I have dyno'd this baby, although not Version 3, and not against a stock airbox. This setup made ~2hp more over the Zucs setup with the cone filter attached directly to the AFM.

Allegedly, there's not sufficient room in my engine compartment for the stock airbox, but I've been shown otherwise. The other advantage of a setup like this is you have more room in the engine compartment.

Thom, Some relavent reading,

Intake/exhaust tuning

That's a cool page, lots of math, but I can't figure out how to make the calculator work!

Tuning the intake tract is important because of the physics involved with airflow into a pulsing valve and resonances. Thus intakes are "tuned" to deliver airflow at multiples of certain important frequencies. It's a fluid dymamics problem.

Here, you cannot apply this experience because it does not apply, the device is far to "upstream" to have this impact. As long as it does not cause flow restriction the length is immaterial.

Can it do any harm? My main reason for putting one in is that with a swapped engine, there's no room for the stock airbox (Bill Verburg's experience to the contrary). Having the Zuc-Z and K&N contraption back there has one drawback, in that it is unsupported; you can easily move the assembly up and down, which makes me uneasy. Thom's device allows you to use the airbox mounting bolt to hold things still.

He also saw an improvement on the dyno with it, although it was probably within the machine's margin of error.

My guess is that there would be no harm at all as long as the device does not impose a flow restriction, and it does not appear to. As a convenience item it seems like a great idea. All I'm saying is that I think it's a waste of time to tune it's length to affect the torque output. Of course this is my guess - the dyno rules.

Kicking myself here...a year, perhaps two, ago...HOT ROD ran an excellent piece on intake air velocity...the length/dia of the passage, displacement of engine...where to expect max torque and horsepower, the figures of those...all based on math formulas they published. DAMN I WISH I'D KEPT THAT ISSUE. I have the impression that the formulas are out there, and boxer, V-8 dosen't matter much. The physics of uncompressed air moving through tubes would remain pretty much the same. So, maybe a search of HOT ROD website???? They got pretty deep into wave pulse technology with this piece...

I think the only factor on the length will end up being the clearance for the AC compressor.

But if I get the car on a dyno, and it's do-able, I'll try with the old filter and the new, to see if there's a difference.

The factory air box fitted fine in mine. I don't think it is because it is a 72 either.

Tinker

Tinker, how about some more pictures of that car of yours, and some details (suspension, brakes, other mods)? It looks like a pretty great setup.

Jack,

You have already seen my beater. We met briefly out at the Streets late last year. I was running a POC slalom. The 3.6`s are a fun torquey motors in those early car, but mine is coming out soon. I am rounding up the parts to put my old small displacement mechanical motor back in. I want to run a group in the POC and I can not do it with the current set up (3.6). I am betting my times are going to improve with the smaller motor (less weight and the power band is more suited racing 6,000 - 7,800).

Tinker;)

2 good points about the "sewerpipe" are

1. at WOT the pipe does become an integral part of the intake tract and can contribute to the ram effect of a long column of moving air at high speed
2. the inlet is closer to the cooler air moving toward the fan rather than the more stagnant and thus hotter air at the rear of the engine compartment

3. - At WOT it makes a really cool howl!

Jack should have it in his hot little (and popular hands) any minute now...

Got it today. A whole new way to 'lay some pipe' in the 911. ;)

(Sewer pipe, that is.)