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The mkiv Supra Owners Club

Rear Downforce- Tech Opinions


Thor

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Originally posted by Terry S

I mailed SPA Aerofoils yesterday Chris. I'll let you know if the respond.

 

Also Chris, whilst on the subject, what about lift. What would your opinions on lift in these cars at high speed, say 200+ MPH

 

Nearly all cars with a teardrop shaped roof line will generate lift, usually over the rear hatch area the most. Quite how MUCH lift I couldn't say, but quite a lot would be my gut feeling. The Skoda Special Saloon i used to race would lift its rear wheels off the ground under the main entrance bridge at Oulton and hit the rev limiter. The previous owner had it take off and go into the trees there when a rudimentary wing failed. I bought it cheap, terrified myself, nailed on a serious wing and a proper front splitter and won 2 championships with it.... That had a similar roof line to a MKIV, in many ways.

 

200 MPH is serious speed though, and aerodynamics are a major influence at that heady velocity.

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Guest Terry S

I was refering to all the BS before about the MKIV flipping at 196 mph. I think we could see some serious speeds this year & I worry about the front end more than the rear.

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Originally posted by Terry S

I was refering to all the BS before about the MKIV flipping at 196 mph. I think we could see some serious speeds this year & I worry about the front end more than the rear.

 

 

A properly made splitter to reduce air packing under the front, and the presence of all the factory undertrays will be enough I would think.

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I think that starting from a road car platform, you'd need a pretty monstrous wing on the back before you seriously unbalanced the downforce f/r.

 

I reead about the aero work on the Maclaren F1 (the road car) and Gordon Murray did lots of work to ensure that the centre of pressure (COP) didn't change when the car ptiched up/down under braking and acceleration. How important is that?

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Movement of centre of pressure is a problem on single seaters and things like my Zeus, and something which active suspension addressed before being banned. I think the McLaren actually creates meaningful and substantial downforce, for sure it spent a lot of time in various wind tunnels.

 

For something like the MKIV though it wouldn't be much of a problem.

 

As for the other question re downforce balance I would not suggest adding a wing without a front splitter too. The rear wing would have to be big, in clean air, and efficient thouh to ad so much rear downforce as to seriously imbalance the car. A front splitter wouldn't really create any front downforce, it would be too high and without recourse to a lot of testing wouldn't be that efficient, but it SHOULD help kill most front end LIFT.

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All you top speed merchants out there should also bear in mind that wing down-force is created at the expense of drag. In the turbo days of F1, the term "barn-door" was often used to describe the drag of a high down-force rear wing. When lifting off at high speed and not touching the brakes, a deceleration well in excess of 1G was experienced in these cars.

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Originally posted by John Packham

All you top speed merchants out there should also bear in mind that wing down-force is created at the expense of drag. In the turbo days of F1, the term "barn-door" was often used to describe the drag of a high down-force rear wing. When lifting off at high speed and not touching the brakes, a deceleration well in excess of 1G was experienced in these cars.

 

Yep, the 2 F3000's i have driven had the same retardation at about 150 just by lifting off as hitting the brakes hard at 70 in a family saloon. Lifting off AND hitting the brakes hard in an F3000 takes a lot of getting your head around... :eek:

 

Needless to say I'd opted for a LOT of wing angle, the added drag reducing the top speed was not a priority in my mind at the time, rather more important was nailing the beast to the track as hard as possible :D

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But all the Max Power brigade swear by those big (ricer) wings and lowering their cars...

 

:D

 

Seriously, this is a facinating subject for a technophobe like myself, I wouldnt have a clue as to whats going on with thw aerodynamics of my car, I get scared opening the bonnet!!!

 

Learning something new everyday on this forum, maybe reading the bbs should be on the national curriculum!!!!!!

 

:)

 

Pat

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Originally posted by Chris Wilson

Sorry, no. Aluminium skinned aluminium cored honeycomb is good to make them from though. Very light and very stiff, relatively easy to work with as you can glue it easily.

 

Hi Chris, we've just got an early 90's Le Mans type car in at work and the front lip (about 10mm off the ground) is made of what appears to be 5mm plywood!!! It's a bit difficult to see all the way underneath, but where I can see it from the side's it all seems like wood. I though odd at first, but is wood better if it hits any debris etc or do you think it's been added now the cars retired - it does look 'in tune' with the car though.

 

Wheels look good, Bridgestone 350x40x19's that also look road legal!!! Need to roll my arches a little I think :)

 

The rear wing probably works as well :innocent:

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Originally posted by Steve Cargill

Hi Chris, we've just got an early 90's Le Mans type car in at work and the front lip (about 10mm off the ground) is made of what appears to be 5mm plywood!!! It's a bit difficult to see all the way underneath, but where I can see it from the side's it all seems like wood. I though odd at first, but is wood better if it hits any debris etc or do you think it's been added now the cars retired - it does look 'in tune' with the car though.

 

A lot of race cars use a high resin content marine plywood known as jabroc as skid blocks. It is also used to make the infamous 'planks' on some F1 and F3000 cars

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Originally posted by Alex Holdroyd

This is the ONLY other wing which looks promising but might not be.

 

http://www.junauto.co.jp/products/aero-parts/jza80/rear-spoiler.html?en

 

This is the rear wing from the JUN 200mile Supra. Which lets face it was a very good track weapon...till they turned it into some lame Land Speed Record car :p :D

 

Just buy a used race car wing here in the Uk and have some nice mounts fabricared. I just love the JUN sales talk in the ad:

 

*Leave installation to the professional shop with trust because it has danger such as falling off at the time of running.

*Weight and a size are the value of a standard.It may differ from the thing.

 

:eek:

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*Leave installation to the professional shop with trust because it has danger such as falling off at the time of running.
You can't beat the Japanese when it comes to marginal translation.

 

This reminds me of the old (1980s) IT quote from Japan about floppy-disks (remember them) "Do not descend the power button in fear of removing your datas. Instead escape disk with finger after it has rested properly" - Your answers on a postcard!

 

What ever that plywood composite is, it's everywhere where flat bottoms are required.

 

Now I am departing from Supras - Technical:D

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