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Aerodynamics


Whitelightning

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I see what you mean

 

Side on,

 

A _____/____ design would keep the bottom flat and guide air upto the starved radiator, thus reducing the cooling losses of having an FMIC, and further helping to box the FMIC.

 

And you could extend the lip of the undertray out an inch for added hi/lo pressure benefits.

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Quite honestly I think it's down to, frontal area - which an undertray wouldn't impact on - styling - negligable impact - and height above the ground for manouvering (multi stories etc) but I hope Digsy or Tony can confirm.

 

Also, the flip up for the rad wouldn't have to be the full width of the rad. As long as the undertray finished at the stock height and location can't see the removal of the hot air being impacted and that's the only real concern here.

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Guest Terry S

Ah that car has exactly what I was thinking of, but I *think a bog stock 360 doesnt have that Lip you show there Tony. What is the purpose of the raised centre section if the lip is not present

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It's the raised lower edge between the intakes...the Stillen and the old veilside raise up in the middle of the nose.

 

Is this going to serve any purpose other than, asthetics, reduced frontal area?

 

http://www.linney.org/images/bluesup1new.jpg

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Guest Terry S

Thanks Ian

 

Tony thinking of building an undertray

 

The plan being to direct the air scooped by that centre section through the radiator to aid cooling

2550-V-1.jpg

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Ahhh OK.

 

I'm not sure what Ferrari were intending with a raised center. TBH it's the exact opposite of what I would want to do. The centre is the part you could potentially get to work hardest. (ie be lowest to the ground) :shrug:

 

As far as putting an undertray on, as I said before you're into completely unchatered territory in terms of effects. However that said, I guess if you created a duct there, it would be as if it were replacing the stock lip (Obviously with the addition of a duct!) So maybe there wouldn't be any major side effects.

 

Ducts are a REAL PITA when it comes to flows. Especially if they area going up to a massive blockage like a radiator or brake discs (or in fact most things that get hot and you want to cool them - typical!) It really depends upon how thorough you want to go really. You could create a quick "bodge" and splash some water with food dye all around it and then go for a raz up the road and back and see whats working and whats not, or you could throw a few pressure sensors around the duct, or if you're real flash you could go and buy some pitots and install them to get an idea of whats happening throughout the duct cross section(Very expensive though!) Once you've got an indication of what works and what doesn't, you can then start on the more refined finished example.

 

The main problem isn't so much on getting the air into the duct (although obiously avoid *any* sharp corners as the airflow will stall - if you can't avoid them, blend them in and smooth them through with body filler) The real problem with ducting is getting the air out once it's done it's job. Ideally a real low pressure area behind the part your cooling would be what you need, (Again a job for the pressure sensors!) Bonnet vents and the like should help that out.

 

The other question is of course, would the creation of a duct create any drag? Unforunately this is a real difficult one to answer without some reasonably complicated testing. (Torque sensors on the driveshafts to calculate load, known RPM's, and some pitot tubes attached to pressure sensors to calculate vehicle speed relative to airflow would just about do it) Other than that the other option is some top speed testing and see how fast she goes.

 

The final question (which maybe should be the first question!) is does whatever you're intending to cool, actually need cooling? MY rad temps (alhough my car is no-where near as modified as many on here) remain nicely btween 80-90 degs, even on heavy blasts. Are you seeing temperature spikes a lot higher than that? Just thinking there maybe more cost effective ways (although no-where near as flash) of reducing high temps. You could probably tell me more about that than I could tell you mate.

 

So basically, yeah, if done rightly I can't see too many flaws with it, but then I thought the bodywork I'd been drawing for the last two months was going to be good :cry: :thumbdown Oh well back to the drawing board.....

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Guest Terry S

Maxx thanks for the link

 

Tony, great input mate. The water temps on this car havent been too bad so far, where as the last car with a Bigger FMIC would suffer on a hot day with sustained blasts. The FMIC obviously gives the stock Radiator a harder time than usual and I was thinking this would help alleviate it, but I do not believe it is necessary for road use, purely track.

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  • 2 weeks later...
Sure I read somewhere that removing the stock rear spoiler actually ups the drag coefficient +0.01, since it acts to reduce turbulence over the rear of the car. Don't know if it's true.

 

:looney:

it is true

 

n/a supra is .31

supra turbo is .32 due to wider tyres/frontal area

supra turbo with rear wing is .33

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HMMM either I'm going mad or I'm not reading the sites I've visited corectly But most of them put the Supra Turbo with spoiler at 0.33 and without at 0.34 and some of them even list it as 0.32 with and 0.33 without ..Either way they are all making it less efficient without spoiler ... :confused:

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John, last two numbers mixed up. It is 0.32 with spoiler, 0.33 without.

The rear spoiler could only worsen the Cd dude...

(that's why you can get a few mph extra without it ;) )

 

Maybe you're thinking of lift or something...

 

http://www.max-boost.co.uk/stuff/Supra_Cd.gif

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The rear spoiler could only worsen the Cd dude...

 

In this instance yes, but not necessarily true all the time.

Quite often we add parts that look like they're going to add drag, to our cars but end up reducing it. (They usually get added for other reasons - we don't intentionally design draggy cars..... On current form I've opened myself up for a slating there maybe :cry: )

 

The chimneys (The exits on the sidepods that let air out once it's passed through the radiators, the bits with Honda written on them) reduced drag. So much so that it was better to run them on the car but tapped over than it was to remove them when the abient dropped.

 

image

 

But essentially if it creates downforce, IT WILL create drag, However if it creates drag it doesn't necessarily create downforce.

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