Aerodynamics Question

[aston@ultrasw.c]

I know that to answer this question properly I will need a CFD workstation and someone who knows how to use it. However, I am hoping that someone with sufficient experience can apply general principles and get me 80% of the way there.

The project is to install an oil cooler in the front fender of a 928, with a surprisingly good duct

I will have more questions later but lets start with the inlet: should it poke out into the airflow (lower) or be flush to the contour of the front bumper (upper)?



In both cases the back of the light housing will be cut open to approx 11 x 4.” The turn signal will be relocated to the inboard end of the housing.

Here's a quick look at the back end




Thanks in advance for any help or advice you can provide.

[Arizona_928]

Should be plenty... the mk4 tdi puts the intercooler in that location but lower.

As for location... That will destroy the oil radiator with tire/road debris.
Put it in a box/cover, or remote it to under the trunk w/fan.... That one will be the easiest option.
What's your engine? Dry sump conversion?

[island911]

You will find the highest pressure in front of the front wheel.

Not only do you have dynamic pressure there (from fwd motion) but also from the top of the tire bringing air fwd and down. ... and then all that air gets pinched off between the tire and the road.

IOW, a vent going upwards from under the nose....

[aston@ultrasw.c]

Thanks.

The duct will fully enclose the cooler.

The current idea is to capture high pressure air from the front and exit via the upper surface of the fender in a low pressure area. Approximately from the top of the tire, then forward 12." Outlet is a 12" x 9" APR extractor vent.

My first thought was make use of existing holes before cutting additional ones.

A lower inlet is a good idea, especially if it capitalizes on air caught by the splitter.

Like this (only had a pic of the 911 handy)

[3rd_gear_Ted]

Airflow out the back of the cooler is just as important as the front.

[aston@ultrasw.c]

Lets say we have a square sheetmetal duct 12" x 12"

If the corners had a radius Vs square would airflow improve?

Say r of 0.5" or 1" or 1.5"

Or is the gain negligible such that the extra difficulty in fabrication is not worth the effort?

[aston@ultrasw.c]

Originally Posted by Arizona_928

Should be plenty... the mk4 tdi puts the intercooler in that location but lower.

As for location... That will destroy the oil radiator with tire/road debris.
Put it in a box/cover, or remote it to under the trunk w/fan.... That one will be the easiest option.
What's your engine? Dry sump conversion?

Hey Arizona_928

I am embarking on an LS project down in Tucson.

Maybe I could buy you a beer?

[Arizona_928]

Originally Posted by aston@ultrasw.c

Hey Arizona_928

I am embarking on an LS project down in Tucson.

Maybe I could buy you a beer?

That's awesome. If you need some issues ran through another set of eyes, or general Q's. I probably won't make it down to the Dity T until it cools off though!

[island911]

Originally Posted by aston@ultrasw.c

Lets say we have a square sheetmetal duct 12" x 12"

If the corners had a radius Vs square would airflow improve?

Say r of 0.5" or 1" or 1.5"

Or is the gain negligible such that the extra difficulty in fabrication is not worth the effort?

The cooler is likely the biggest flow hit (restriction). The corner radii are not likely going to affect the flow much.

[Shifter]

Take a look at the oil cooler design on the 944 S2 and 968 cars. They have the oil cooler mounted under the bumper on the passenger side. I bet Porsche spent a bunch of money on the air flow characteristics that might save you some time.

[john70t]

A scoop to create ram-air might help or hurt at higher speeds, and there is probably a swirl-vacuum in the wheel well for pulling air out(I don't understand the dynamics there), but also consider a couple separate layers of screening in the airflow for stone chips and other road detriments.

[Arizona_928]

Originally Posted by Shifter

Take a look at the oil cooler design on the 944 S2 and 968 cars. They have the oil cooler mounted under the bumper on the passenger side. I bet Porsche spent a bunch of money on the air flow characteristics that might save you some time.

The 951 oil cooler is giant brick. The S4 928 trans cooler is a long cooler. I Should have a spare of both that I can snap a pick of.