Lotus Elise Rear Wing/Separator ?

[DrCarbon]

Hi Guys,

Composite builder/engineer and require some advice on what to do with increasing down force on the new toy car.

Lotus Elise - not the greatest shape car too push through the air and prone to rear end lift at speeds over 100 mph.

My attempts to date are -

Rear under tray diffuser which I have copied from other designs and am presently recreating in pre preg carbon. This should go some way too improve the down force create by the additional diffuser area and veins.

http://autozine.kyul.net/gallery/lotus/elise2.htm

Front splitter to eliminate some of the air volume traveling under the car and create a low pressure area immediately behind the splitter to help keep the front down.
To improve this I am profiling the shape and faiing it under the forward part of the front overhang.

http://www.eliseparts.com/products_pages/carbon/elisespliter.htm

Now after all that comes the question -

Rear Wing or not too rear wing.
Now apart from the drag and the obvious "eye sore" a rear wing can create on a road going sports car of this type, plus the engine doesn't generate enough H.P. to counter such a large drag addition !

Now the guy's at Mclaren played with an Elise and came up with the following alternative to the rear wing -

(web page - scroll to the black car at the bottom) -

http://www.geocities.com/MotorCity/Track/1926/factory/elise/elise.htm

OR direct to a rear pic of the offending area.

(jpeg link)-

http://www.geocities.com/MotorCity/Track/1926/factory/elise/3004.jpg

Now is this -

a. worth doing ?

b. helping with down force or reducing drag ? or both ?

c. helping with break away and reducing low pressure drag effect in behind the car ?

Need help here guys, is this a waste of time or a good substitute for an ugly large rear wing ?

Thanks in advance……

 

[matt00000]

Have you heard of the exige? dont they race them? what do they do on that? If I reacall corectly it has a massive rear wing. the wing increases downforce on the car which increases cornering velocity and breaking force (at high speed). if you want your car to look like a racer and consequently get stopped by the police more then get one!

http://www.btinternet.com/~tjthompson/myexige/exige.htm

Now thats what you call a rear wing!
Good Luck

Matt

 

[DrCarbon]

Matt,

Thanks for the reply but it doesn't really answer the question, I don't want to put a rear wing on the car and as you say attract the atention of the local law.

I want to know if the small rear spoiler lip on my Elise - (link to pic below) is worth doing to increase down force ?

http://www.geocities.com/MotorCity/Track/1926/factory/elise/3004.jpg

The car at high speed has rear end lift and would like to make some attractive changes to try and reduce this problem. Any other ideas would be appreciated.

 

[matt00000]

I had a look at the picture. Is that an add on by lotus?
whats the profie of it? How do you attach it? It looks as though its a 'gurney flap type affair'
Yes it will increase downforce. Will you notice it? I doubt that it does a great deal below say about 90mph. If you want downforce then the wing is the way to go. The lip in the picture will help a little but its just designed to improve the airflow and stability at high speed. Yes the high speed lift is the same as for the Audi TT Porche Boxter... and quite a few other similar cars.
I understand there is a racing suspension package you can fit. That would probably help more but then the ride would be even harder!
There is also a boost available for the engine to increase the bhp. I dont think the flap will make a great deal of difference to overall top speed or acceleration.

 

[Buckie]

Dr Carbon,
Put a wing on it, but make sure u can feather it for the desired downforce. If your tracking it you'll end up finding what sort of angles will be required to find max grip for a desired sort of drive.
Ive got a nissan Pulsar Gti-R which comes complete with large front wing and rear. These make a huge difference on the ride above 85, although more horses are felt to be required after 130+, the wing on the back is very angled!
Ive seen adjustable wings on nortons, maybe theyd give some info??

 

[DanT]

What are you using as evidence that there is less rear downforce at speed? Oversteer could be more front downforce/less front lift. What do yarn tufts do over those rear deck vents ? Tape a scale to the rear wheel well opening and Get a buddy in another car to take pictures to see if the rear ride height is really increasing at speed.

If this was 1968 another couple of inches of rear spoiler would be worth a try. Still might be.
Vertical or horizontal.