Van

I agree with this. A cone air filter is only an improvement if it is in a seal box that gets fresh air from outside the engine compartment. On my car, I have the air duct in the front bumper next to a fog light (which is now a brake duct).

Amber Gramps

Guess what....I went back and found a second one.

The 911 fan pulls so much outside air into the engine compartment that the need for "cold air intake" does not exist. Heat isn't an issue.

rsabeebe

except that the whole AFM/cone filter assy. is out with one loosen hose clamp. that stock airbox was so damn annoying, i got rid of it from that standpoint alone. plus, the way i look at it, it's pre-intercooler anyway. who knows, the turbo under the intake could have a greater effect on air temps than an open filter in the engine bay.

mel_t_vin

Of course the turbine heats ambient air under the hood. And, by using an open, under-hood, filter in a 951, you're electing to ingest warmer air from square one...at the compressor inlet.

I suspect you haven't given much consideration to the implications of the laws of thermodynamics on ambient air and their affect on resulting IAT. If the filter box was as restrictive as some people think, do you really think Porsche would designed the system as-is?

rsabeebe

i did actually consider Wiedemann-Franz Law on heat transfer before installing the open element, but decided i would be replacing and upgrading too many items in the engine bay to worry about the potential losses in power due to intake temps vs. simply undoing 1 hose clamp each time - as stated earlier. when i do replace the AFM with a MAF unit, i plan to use the Ideal Gas Law to determine the optimum structure dimensions of my custom airbox and will be using the stock air intake hole in the fender.

mel_t_vin

Sorry if my previous comment may have come across a bit gruff.

No argument regarding component accessibility with a cone filter. And, as you reiterated, being in the process of making a few modifications, that would easily trump any [minor] power losses due to resulting higher IAT.

It also sounds like you've given your custom air box more than a bit of consideration. If you fabricate your MAF/intake to pull air from the stock fender location, I suspect you'll observe a noticeable performance improvement.

Please keep us posted with your project.

Dash01

Fluid mechanics basically dictate as straight runs as possible, no or as few restrictions as possible, no transitions (or as gentle, faired transitions as possible) from one cross-section to another. A short, straight run of circular cross section from a cold air source would be best. The abrupt change from round to square of this unit, with no fairing and sharp edges, is, frankly, very poor. The stock round-to-square unit has at least some ramp transition.

It might not matter much at low rpm, but at full throttle, those abrupt shape changes and sharp edges surely make this thing much worse than stock.

One cheap way to find out would be, say, a 100 gallon tank of water suspended so it could drain out the bottom through each such shape. Measure how long it takes to drain each tested shape under gravity pressure. I'd wager this shape is much worse than the stock, and stock isn't that good.