Aerodynamics for Cooling Systems of Turbo Car

[wildman10]

Without wishing to stray further from the thread's aim, I want to point out to casual readers that air racers have far more done to them than just pitching weight and reducing form drag in order to optimize them for their very particular environment of fast low level turns. I'm particularly interested by the changes to counter the compressibility effects from going at close to 500 mph.

Also, I think we should be careful not to believe what is good for them is good for aircraft in general. For example, shortening the wing span will reduce stability and increase drag over most of the flight envelope.

Where P51 air racers are perhaps relevant is their use of water sprayed onto the radiator face. For example, Dago Red has a 45 gallon tank and generates significant thrust from the steam accelerated out of the exhaust ducting. Furthermore, their water/methanol mix engine induction injection systems are particularly relevant to the Wankel/rotary-engined car I'm working on as these engines are particularly susceptible to detonation.

Interestingly, its use in air racing has brought the P51 full-circle back to its origins, where the first versions (P51A) were generally used only at low level because their engines ran out of steam very quickly with height.

[freebeard]

Without wishing to stray further from the thread's aim, I want to point out to casual readers...

Your are OP, you can always go back and edit the title.

So where are these intercoolers located relative to the wheelwells. anyway?

[wildman10]

The oil coolers are ahead of the front wheels, as in your Porsche image, as shown in the atttached images. The slots in the fender splash guard have a lower area than the ideal for maximum cooling and people who open them up report improved cooling; the increased drag this creates is unknown and, as expected, the coolers get far more dirt sprayed on them.

The transmission oil cooler I'm looking to fit is a new item. Automatic transmission RX8s have their transmission oil cooler in front of the bottom of the radiator; I want to avoid this if possible as I'm looking at twice the power (400-450 bhp vs 189/212 bhp) with the same radiator area.

My intercooler will be ducted through the bonnet. 1/3 to 1/2 of the rad cooling air will be ducted through the bonnet, with the remainder free to vent either over the turbo & exhaust manifolds then out of a bonnet vent or over the engine then out under the car.

[jamesqf]

Originally Posted by wildman10

The weight saving of having no guns is irrelevant because all the P51 racers had them removed too.

Err... Then I misunderstood what you wrote. I understood you to say that replacing the guns with wing-mounted radiators made the planes faster (disregarding any other mods), implying that added thrust from stock radiators wasn't that much of a benefit. Of course doing the wing clipping and all that other stuff too makes A-B-A comparisons impossible...

[aerohead]

Get a copy of the book,Race Car Engineering & Mechanics,by Paul Van Valkenburgh from Amazon.
He'll show you how to create a means to measure the pressure profile around the Mazda,which you'll need to establish your options for extractor sites.
You'll be flying blind without this data.

[wildman10]

Thanks. I have, though, already measured static pressures at all the relevant exit points (bonnet, fender/wing upper surface, and at the vents behind the fenders/wings that are primarily for styling). My write-up contains more information and the attached images show some results at the bonnet/hood centreline and an RX8 with the carbon bonnet/hood that I inherited with my car (the main vent is as far forward as the car structure allows and the rear side vents are at the rear of the engine bay).

I cannot get any meaningful pressures inside the wheel well with my simple tube and Magnahelic gauge system as the turbulent air makes the readings fluctuate wildly.

[aerohead]

Originally Posted by wildman10

Thanks. I have, though, already measured static pressures at all the relevant exit points (bonnet, fender/wing upper surface, and at the vents behind the fenders/wings that are primarily for styling). My write-up contains more information and the attached images show some results at the bonnet/hood centreline and an RX8 with the carbon bonnet/hood that I inherited with my car (the main vent is as far forward as the car structure allows and the rear side vents are at the rear of the engine bay).

I cannot get any meaningful pressures inside the wheel well with my simple tube and Magnahelic gauge system as the turbulent air makes the readings fluctuate wildly.

Is it possible that a flow restriction, inline to the Mag would act as a damper,to average out a mean pressure inside the wells? It would certainly be helpful to know what was happening there.
With stagnation pressure ahead of all the heat exchangers we know that that the air will exit your discharge ducting,but sizing and orientation to the outer flow would be critical for optimization.
Kamm just dumped all the engine bay air at the base of the cowl

Morelli spent a fortune in wind tunnel time perfecting the extractors for the 1978 CNR concept.(the air exited at the identical velocity and direction as the boundary flow)

[wildman10]

I use a screw-in restrictor in each line to damp out oscillations. I normally have to open up the restrictor when changing speeds, allowing the pressures to change quickly, then damp out the oscillations by screwing the restrictor in until the balance between reaction and damping seems optimal. However, in doing this on my first wheel well location I got different final readings every time I tried to repeat them until I gave up.