Down force problem

[dai capp]

I had the 4.5 Cerbie, in fact if you go to //www.davidgeraldtvr.com and look under used cars the one pictured is my old one. It\'s sold again now but it\'s one mighty motor.

Whilst I can drive the RX and it is more then a match for Tuscs and Griffs, nothing beats that Cerbera. 180mph on the way to Le Mans was easy for it. In fact once over 140 it pushed down into the road even more. And the noise - mine was decatted with a sports exhaust and it was measured at 128.9db at 4500 rpm standing 1m away. Mind blowing.

If ever funds permit every petrol head should own one. Absolutely stunning to drive.

Ahhhh I miss it - must get the RX out tonight...

All the best

DC

[dai capp]

Originally posted by Mr_7
but when they are devolped they do incoperate airpockets into the chasis

I\'m not sure on that one - it\'s not something I\'ve heard mention before. There\'s an interview with one of the designers in Sprint (the TVRCC mag) I\'ll see if there\'s any mention...

Cheers

DC

[Mr_7]

i was in a chipped a TT 225 when i went up against one it was 4.5 round a corner on to a dual carriage way he missed third then found it on the straight it was level untill it came on cam i have never seen a car like it in my life ever it was mad the fastest car i have seen a challange for a stallion

[SCOOMER]

You must be a hell of a  driver to get the full potential out of a FD and then ask for more down force!

Heres a few pics of whats out there, not sure you going to gain much using them but here you are.

Scott

[SCOOMER]

and another

[SCOOMER]

heres another

[Mr_7]

You dont have to be much of a driver to hit the top speed in a car just need bollox and that sort of speed they both look lovely particually like the black one but looks like cosmetic the top one looks usefull fins to it straight and high level exit do you know the makers of those diffusers

[SCOOMER]

last one.

[SCOOMER]

mmm, you just mean straight line speed not going around a track let you off then.

They are both RE Amemiya but im not sure if they make the first one anymore (yellow car). The lastest one is carbon fibre or you can get it in fibre glass also has an adition to it called some thing like a bow tech generator.

I think your wrong about just being cosmetic though.

[jinx]

Definitely no expert but just read a magazine piece about this by Lotus aerodynamics guy.  Said that rear aerofoils need to be high and to rear of body to develop any useful downforce.  (Like the Exige - all designed around the aerodynamics) It means even the biggest rear spoilers on RX\'s are of dubious benefit except possibly the ones that sit up and back on the alloy uprights.

The front splitter on the RX was included to improve low speed cooling - especially on twin oil cooler cars according to the Brian Long book (I think) so probably not much ground effect intended out of that.

If you are talking about ground effects to generate negative lift under the car, from (very) limited experience with a Le Mans car, you need to design/build the whole underside of the car with this in mind - not just add the exit venturi that most of the aftermarket bits seem to be.  Is there some benefit to smoothing airflow just around the back axle?

Be interested if anyone can say if the RX\'s rear spoiler actually delivers downforce based on their experience of running with and without.
A

[wookie]

If you want a good place to start with aerodynamics then the following books may be of use:
Race car aerodynamics:designing for speed   by Joseph Katz
isbn no. 0-8376-0142-8
Competition car downforce by Simon McBeath
isbn no. 1 85960 662 8
and mainly aerofoil design but very interesting
Theory of wing sections by Abbott and Doenhoff
isbn no. 0-486-60586-8
these are all available in the uk try amazon for the top two the other one i ordered from waterstones.
Bear in mind aerodynamics can be a minefield even for experts.
You can hire a wind tunnel in this country, and no not with a formula 1 budget either. I saw a peice in a magazine (i think it was Race Car Engineering?) about a hill climber with an elise who hired a tunnel for a day. Don\'t quote me but i think it might have been at MIRA the vehicle reserch bods.
 Or instead of a day at a wind tunnel buy a CFD programme and play to your hearts content without making anything. Then when you figure out what you want, go ahead and make it/have it made.

[Initial-D]

I had my FD with and without spoiler and the rear end was lighter without the wing. It depends alot on the angle of the wing as to how much downforce is applied. I currently have a RE Amemiya rear diffuser as well as an Auto Exe rear wing and the Feed front canards - the car is stable at high speeds but nothing drastically different to running without them. The rear wing made the most difference I noticed as said above.

I think that sorting the suspension will help masses, which will reduce body movement of the car when accelerating, although this would place more strain on the trailing arms etc..

As said earlier the Mazdaspeed kit was tested for high speed usage, but RE Amemiya, Feed, Pan Speed all test their products on track in Japan. Even my Feed Canards where tested before being sent over to me, the first batch I was gonna get broke when they tested them so I had to wait for the next batch!

[Mr_7]

thatnks everyone for your help i will look in to it more and let you know what i go for

[mikeeech]

How much would a vented bonnet affect the downforce by allowing the air in the engine bay to pass over the car rather than exit out underneath it. Any thoughts as to the overall affect on the car?

[Mr_7]

If you think about it its not going to affect it at all im wondering if your being sarcastic