Cold air intake

Has anyone designed/played with, or currently use an after market cold air intake directing air from a either a whale tail, or another kind of spoiler? I didn't get anything from a search.

[Jack Olsen]

There is no good reason to do it.

The 911 engine fan moves so much air, so quickly, that the intake manifolds stay very cool when the engine is running at speed.

[Bill Verburg]

Jack is correct, the best you can do is have the intake snorkle right under the grill.

It's interesting that none pf the air cooled cars ever came w/ cold air intake but the water cooled GT3 does(no fan to move air through the grill)

So there is no benefit to have the cold air directed into the fuel intake? Isn't there some (although not much) benefit? All the 'hot rod' magazines seem to think it's a big deal, you know "more horsepower" bla, bla. . .

[Rot 911]

Originally posted by long board
So there is no benefit to have the cold air directed into the fuel intake? Isn't there some (although not much) benefit? All the 'hot rod' magazines seem to think it's a big deal, you know "more horsepower" bla, bla. . .

That is because they are dealing with a watercooled engine in a hot engine compartment. The 911 fan pulls so much air in that the engine compartment, while the engine is running, stays quite cool.

[bigrubberjeep]

Then why did the Turbo "S" model have those air scoops on the fenders? I figured those were cold air intakes. Was it for brakes?

[RickM]

Originally posted by bigrubberjeep
Was it for brakes?

Yup, as well as on the 930S

That seems to make sense. I deduce then that 'ram air' does not actually condence the air (thereby causing more air), but only cools it?

[304065]

No, ram air does increase the air pressure. In a naturally aspirated airplane you will actually get a rise in manifold pressure as cruise speed increases.

Actually, as airspeed gets higher, the compression of the air actually INCREASES the air temperature, but we're talking 200+ Knots here.

In a Porsche, the trouble is that you don't get any meaningful increase until the speed is VERY high, and even then, you have offsetting drag from the intake, friction in the inlet duct, and weight.

Front-running club racers don't use ram air inlets and they try EVERYTHING to go faster.

[bigrubberjeep]

Originally posted by RickM
Yup, as well as on the 930S

So these are for brakes?

[911ctS]

I read somewhere that for every 10 degress you cool off the intake air you get a 2% power increase.

...but as others stated above, for an air cooled porsche you would have to chill the air below ambient temps and thats tough.

[bigrubberjeep]

Originally posted by 911ctS
I read somewhere that for every 10 degress you cool off the intake air you get a 2% power increase.

...but as others stated above, for an air cooled porsche you would have to chill the air below ambient temps and thats tough.

Oh.....well 2% of almost nothing is almost nothing.

I'm better off going on a diet to cut weight down in the car........wait who am I kidding, how much is the air chiller cost?

[Wil Ferch]

I too also believed ( still do) of the high volume of air brought in by the cooling fan to make a specific cold-air induction system redundant..

...but.....

Look here for real test data that is intriguing... and runs a bit counter to this.

Experimental data for Cold air intake

---Wil

[bigrubberjeep]

Can anyone confirm where the air goes from these scoops on the fenders?



I would think that because they are so high, the air go's in to the intake and not the brakes. Usualy brake vents are lower on the fender

[tbitz]

A while back ago I did some experiments to see just how hot the intake air gets. When you see the data, you won't believe it!

The data clearly shows the intake air gets much hotter than ambient, contrary to what people think with respect to the fan moving alot of air through the engine bay.

If your interested in the data read this thread I posted a few years ago. I was just starting my CIS to EFI stuff back then.

Intake air temperatures

I also show how to make a cold air intake for a couple of dollars in five minutes.

Cheers,

[tbitz]

Woops, just noticed my thread was posted above by Wil.

[Bill Verburg]

Originally posted by Bill Verburg
Jack is correct, the best you can do is have the intake snorkle right under the grill.

It's interesting that none pf the air cooled cars ever came w/ cold air intake but the water cooled GT3 does(no fan to move air through the grill)

What tbitz did was position the air intake directly under the grill, if you want to call that a cold air intake fine. That is what I was referring to in the qoute

here is mine


A tail will enhance the air pressure at the grill

[diy83sc]

I took a small RoundUp container, trimmed the top so that it slides over the snorkel, cut a rectangular opening on one side facing the grill, and poked several small holes at the low end for rain. I can't measure it, but according tbitz, it's cooler coming form out than in.

[Paul Thomas]

There was a car in Excellence a few years ago that had a somewhat unique intake, presumably for the cold-air/ram-air effect. Y'all must remember it, i think it was built by Fabcar? Speed Yellow, with purple flames up the front?

Anyway, they used a roof scoop that fed into a lexan or plexi air box that was sealed to the back window so all of the intake air was fresh from the outside. The car made like 600hp.

I think if you could funnel cool-er outside air directly into the intake it would be a plus, but not something that would be cost effective on a street car or modest race car

[Bill Verburg]

Gt1s used a roof scoop such as you describe, as did Mike Bavaro on one iteration of his very successful PCA club racing car

GT1