Board logo

Downforce
mk_xe - 10/4/09 at 11:04 PM

Do any of the kit manufacturers claim any level of downforce for their cars.

I know lift can be problem cuased by the cycle wings at the fromt at high speeds 100+. Has anyone tried flat undertrays and rear difusers on a seven type

mookaloid - 10/4/09 at 11:18 PM

Seen a few caterhams and westfields with front splitters, side skirts, flat undersides and diffusers on the hill climbs. It wouldn't suprise me if they did some good.

Cheers

Mark

craig1410 - 10/4/09 at 11:36 PM

quote:
Originally posted by mk_xe
Do any of the kit manufacturers claim any level of downforce for their cars.

I know lift can be problem cuased by the cycle wings at the fromt at high speeds 100+. Has anyone tried flat undertrays and rear difusers on a seven type


I wonder if having vent slats in the trailing edge of the cycle wings would help. I've often wondered why the Seven has such a high drag coefficient and have also wondered if a diffuser could be fashioned into the naturally upward sloping rear end.

Craig.

Guinness - 11/4/09 at 07:42 AM

I have a rear diffuser fitted to my MK.

I never really noticed any effect on the road, but at Bruntingthorpe (which is a speed circuit) the front end was getting very light at 100 mph plus.

So I guess it must be working?

Theoretically I always considered the open space below the rear panel must act as an air brake?

Mike

catman - 11/4/09 at 07:50 AM

any pics?

Ed

speedyxjs - 11/4/09 at 08:08 AM

Im going to fit mine with a flat floor and some kind of diffuser although i dont think il have much of a problem with lift due to the weight of the thing

ETA - It will also have a full body front end to help with aerodynamics ala E-type

[Edited on 11-4-09 by speedyxjs]

SPYDER - 11/4/09 at 09:41 AM

We are kitting our Phoenix trackday car with a front splitter, engine undertray and rear diffuser. We will make it all ourselves, the splitter being made from composite.
Cost will be minimal, downforce probably likewise. But every little helps.

Aren't the weird shaped cycle wings on the Caterham CSR supposed to cancel out lift?
I've seen similar copies for sale.
Geoff

Badger_McLetcher - 11/4/09 at 11:03 AM

The problem is that 7's tend to have the aerodynamics of a small house brick. Unfortunately even bricks create lift if you get them going quick enough
If you've got a smooth underside just make sure the back is higher than the front (diffuser should help that). If it's not smooth the best idea is to stop airflow getting under with an airdam/splitter arrangement.
Ideally the underside of the car should form the upper half of a venturi to get the old ground effect going

Daimo_45 - 11/4/09 at 01:34 PM

Buy an Elsie diffuser


mr henderson - 11/4/09 at 02:31 PM

I think any improvment to the aerodynamics is a good thing, but the energy for downforce must come from the engine, and that can be a bad thing, unless you have lots of power.

John

craig1410 - 11/4/09 at 03:41 PM

quote:
Originally posted by mr henderson
I think any improvment to the aerodynamics is a good thing, but the energy for downforce must come from the engine, and that can be a bad thing, unless you have lots of power.

John


Yes but I think I am right in saying that you can get a certain amount of downforce from stuff like diffusers without any increase in drag. It's only once you start adding wings then your drag goes up as does the frontal area of the car.

The Cd figure for the Caterham 7 is something like 0.76 which is pretty high but I think you have to bear in mind that the overall frontal area of a seven is quite low, especially if you have no windscreen. It is the product of these which is important (Cd.A).

One thing I would be interested in evaluating is the effect of ducting the air which flows in through the nosecone back out again rather than just let it build up pressure under the bonnet. I might look into having a couple of vents just behind the radiator to spill some air back out again and then some more vents just in front of the scuttle and down the sides of the bonnet too. The latter should help to get the hot air away from around the exhaust manifolds. At the moment, all that air which enters the nosecone must be getting pushed under the car which can't be good news I wouldn't think. Some will go down the tunnel but that's no better.

Thoughts?

Cheers,
Craig.

Guinness - 11/4/09 at 04:52 PM

quote:
Originally posted by catman
any pics?

Ed



Diffuser Rear
Diffuser Rear


Diffuser Side
Diffuser Side

HTH

Mike

[Edited on 11/4/09 by Guinness]

mr henderson - 11/4/09 at 07:41 PM

quote:
Originally posted by craig1410


Yes but I think I am right in saying that you can get a certain amount of downforce from stuff like diffusers without any increase in drag.


Downforce is, as it name suggest, a downward pressure on the car created by the effect of airflow over its aerodynamic features. The pressure for that HAS to come from the energy the engine produces and therefore results in increased drag over a similar car with less downforce.

I think though, that what you are trying to say, is that some devices produce downforce more efficiently than others, which I am sure is true

John

craig1410 - 11/4/09 at 10:39 PM

quote:
Originally posted by mr henderson
quote:
Originally posted by craig1410


Yes but I think I am right in saying that you can get a certain amount of downforce from stuff like diffusers without any increase in drag.


Downforce is, as it name suggest, a downward pressure on the car created by the effect of airflow over its aerodynamic features. The pressure for that HAS to come from the energy the engine produces and therefore results in increased drag over a similar car with less downforce.

I think though, that what you are trying to say, is that some devices produce downforce more efficiently than others, which I am sure is true

John


I understand the conservation of energy principal, but it is possible to gain downforce without requiring extra engine power by reducing drag. By using less energy to move air molecules around you can gain the energy required to provide the downforce. I'm no aerodynamicist so I'm happy to be corrected but as I understand it, the diffuser and splitter are supposed to be capable of producing downforce with little or no net increase in drag. I'm sure I picked that up during discussions about diffusers on one of the F1 programs lately. Wings on the other hand give downforce and drag in equal amounts and are a straightforward trade off.

Anyone car to agree with or correct my statement above?

Cheers,
Craig.

MikeR - 11/4/09 at 10:56 PM

another way of phrasing it .... throw a brick and its got drag, add some grp bits to the front and rear to make it like an american football. Now its got less drag - change those bits to create down force .... its got the same drag as it started with but down force as well.

craig1410 - 11/4/09 at 11:11 PM

quote:
Originally posted by MikeR
another way of phrasing it .... throw a brick and its got drag, add some grp bits to the front and rear to make it like an american football. Now its got less drag - change those bits to create down force .... its got the same drag as it started with but down force as well.


^^^^ What he said!!

mr henderson - 12/4/09 at 06:13 AM

quote:
Originally posted by MikeR
another way of phrasing it .... throw a brick and its got drag, add some grp bits to the front and rear to make it like an american football. Now its got less drag - change those bits to create down force .... its got the same drag as it started with but down force as well.


But more drag than if it had remained shaped like an american football!