jason74

I see a lot of info/ disagreement on HP results with CAI. My question is how does it affect fuel mileage. I ask because my old 2004 RSX type S, after installing K&N CAI, my highway gas mileage went from 31 mpg to 33 mpg, unexpectedly. Does anyone have reports that parallel this with a 997? I'm picking mine up my first in 10 days. I'll be using for my 90 mile daily commute, so, it would add up...

yvesvidal

Jason,

typically, cold and slightly humid air helps tremendously the combustion and increase the compression ratio, the cooling of the engine internals and thus decreases the consumption.

It is well known that driving at dusk, always makes your engine much happier than running at noon time, in full sun and heat.

Porsche installed a fuel coolant device (when you use the A/C) in order to inject very cold fuel that vaporizes and is richer than warm or hot fuel.

When I installed a K&N filter on my old BMW E30 M3 and R1100S motorcycle, I immediately felt the difference and could hit 34 MPG on the M3 (50 MPG on the bike) because the engine breathes better (measured on Highway).

I am not sure these comments answer your questions, but colder helps in many ways....

Yves

JW911

Ah but in the case of the 997, the debate is around the fact that the factory design is already a cold air intake. It draws outside air from the rear spoiler. So what does the aftermarket intake provide?

Some I've seen actually draw warm air from within the engine compartment. Go figure...??

Mike in CA

Exactly.

Edgy01

++ The aftermarket "CAI" is actually going to draw air from the engine compartment instead of via the snorkel arrangement that Porsche has designed into these engines. I would then expect to see your mileage drop instead of go up with a change to aftermarket.

Macster

Leave your new 997's intake alone. It is very efficient, removes alot more dirt than any aftermarket filter, is easier to renew when it gets dirty, and comes with the car.

If you still want to go the CAI route, before you do so, get a tool to monitor intake air temp for a while under various ambient temp conditions and then if you do go ahead and put on a CAI check to see how this has affected the intake temperature.

And be prepared for dirty MAFs, and increased engine wear due to the filter passing more particulate matter through its filter element.

Sincerely,

Macster.

jason74

This all makes sense. I was so impressed with the CAI on the rsx, that I assumed I'd put one on the 911, until I started looking at all of the posts...

From my understanding of OEM intakes is that they are largely designed for sound control which makes them less efficient but quieter. I really like intake sounds at WOT. Just as addictive as exhaust sound, IMO. Engine longevity is going to be a key priority for me as I'll be droning along 294 in Chicago at 72 mph for 45 minutes each direction...

Skibum

If it's noise you are after, then get the Fabspeed kit.
Blocking off the Heimholtz will do the trick.