27 replies to this topic

[Aerodynamic]

Regarding our cars downforce and how to creat a downforce balance. As I have understood it the Speedster have a downforce of 19 kilos in 100mph(?) in the front and 4 kilos up force in the rear. to increase downforce in rear you can add wings and or diffusers. And my question is does anyone have any figures of what you can expect to gain with a nown diffuser as for example TAT or any other unknown is also ok? BR, Per

[techieboy]

VX220.org.uk + diffusers or wings ≠ real data on downforce (or reduced lift)

[Aerodynamic]

Opps, can somone mov this to
Tuning & Modifications

Techiboy, I am not sure what you mean?!

[rob999]

I'm afraid you'll have to settle for people saying 'I can really feel the difference' ....

[Boombang]

Nobody knows what increase in downforce, some do report they can feel an increase. I can't think of a reasonably priced way of measuring it either.

[Aerodynamic]

Well, it should need to be too cimplicate to actually measure or? 2 springs and measure some ride heigh on a airfield

[slindborg]

Two or four linear pots and a data logger with gps for speed..... See the ride height change with speed. Cheap with a basic logger.

[ciderbooze]

Two or four linear pots and a data logger with gps for speed..... See the ride height change with speed.

Cheap with a basic logger.

Would that work? Given the uneven surface of the road?

You would need a wind tunnel like thorney used surely

[pete-r]

Mine made zip all difference. But it looks SOOOO cool

[slindborg]

Two or four linear pots and a data logger with gps for speed..... See the ride height change with speed.

Cheap with a basic logger.

Would that work? Given the uneven surface of the road?

You would need a wind tunnel like thorney used surely

It would give a damn good clue, just find a decent bit of Tarmac to do the testing on and you can see what speed the ride height drops.

[siztenboots]

would a manometer be good enough

[FLD]

would a man-o-meter be good enough

As long as Joe wasn't using it. It would read 0 in that case

[fezzasus]

I'm sure they'll add a couple of kg of downforce...

[rob999]

would a man-o-meter be good enough

As long as Joe wasn't using it. It would read 0 in that case

[VIX]

I can't image the Tats having any aerodynamic effect at all, particularly the short ones.

[elwill]

I can't image the Tats having any aerodynamic effect at all, particularly the short ones.

Yeah can't see TAT funding a wind tunnel session any time soon.

[fezzasus]

Here are some figures for you: OEM diffuser - 1.6 kg of downforce tat diffuser - 3.2 kg of downforce

[Nev]

If you genuinely want downforce on your car then you should forget diffusers and install a wing high up IMO. Even my big wing doesn't seem to have much effect until over 110 leptons (though it is set on it's minimum rake angle).

[Crabash]

Diffusers are actually one of the most efficient ways to gain downforce when done properly. Unfortunately they add to the front downforce not the rear, or the front of the venturi if you want to be accurate. Also the closer to the ground the car is the better they function. I belive Simon McBeath has a basic guide for deciding wiether or not you should use a wing, something like if the top speed at the fastest circuit you drive on is less than 120mph then it will actually increase lap times. (that figure may not be accurate and it is obviously not that simple). In theory it would be possible to measure the difference with and without aero addons if you had a very flat road where you can do 100 plus and a fixed camera capable of taking a "fast" enough exposure, triggered by a light beam or such like. Or if you have a data logger you can buy a device (linear pot) which attaches to the body and susspension arm, as slindborg suggests. Both ways require a test track as the speeds need to be quite high to see much. Just had another thought, we have been using lasers to sense objects and measure distances at work recently, They are are much cheaper these days, so much so we now use them just to let the PLC know something is there, not even measuring. They can be accurate down to 0.1mm, can have smoothing applied at sensor and give a 4-20mA output.

Edited by Crabash, 30 June 2012 - 09:18 AM.

[Nev]

Diffusers are actually one of the most efficient ways to gain downforce when done properly.

Yep, but I only know 2 VXes that run 4 to 6 CM clearance for it to operate, hence ground effect aero mods will have very limited effect on 10 cm road cars or even lowered track car of. However, a wing will work regardless of ride height, hence it is more reliable way of making downforce on the rear.

BTW, if you don't want to spend money on a wishbone strut to measure downforce, you can do the 'poor mans' option of putting a tie wrap around the suspension strut, then drive the car upto speed X on a very flat road taking care not to accelerate hard (to stop any rocking motion). Then get out of the car and see how far up the tie wrap has moved (due to downforce). Yud need to repeat this multiple times and eliminate statistical variance to get a half accurate reading as its a very crude way of doing it.

Edited by Nev, 30 June 2012 - 09:15 AM.