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limpabit 28th September 2009 13:30

Rear spoiler/wing
Hi everyone.

Been looking at rear spoilers/wings. I now a couple of the guys use the blade type spoiler here. And noticed a great improvment on high speed runs.

But I've been looking at the boot type spoilers witj the rear light integrated. But would they be any good for the job in hand at high speed? I'm assuming not as TD wind tunneled Ken's one I beleive and it needed to be quite high up to be of good use. So the low boot spoilers would be useless I guess.

chrislandy 29th September 2009 18:59

John, I would work on the front splitter, lower the front suspension by 10mm or so and work on the airflow under the car (maybe add a rear difuser) so you start to get ground effect.

Spoilers work best at speed and in clean air so unless it is close to or above the highest point of the car they are not worth it. I'm up at uni at the moment pestering the Motorsport department about various thing so I'll try and get some guidance on it

limpabit 29th September 2009 19:11

Funny you should mention the front as I read that today as well.

Track developments done Ken's yellow one, and like you said, is quite high. But I beleive Ken's mainly for the track. It's on there web sight under galley.

chrislandy 1st October 2009 19:54

Hi john, got a few books from the uni library
1) competition car composites
2) competition car aerodynamics (lots of good and rather interesting info with cfd examples)
3) race car aerodynamics - pretty hardcore stuff

and I bought "race car dynamics" 700 pages of everything!

Once I've digested a couple of them I'll report back!

limpabit 1st October 2009 20:27

Happy reading mate!

KrazyKen 19th October 2009 21:09

Sorry, not been on for a while but I can shed some light on this subject. The windscreen on the 5EXi creates a hole in the air which enables us to chat and not be blown to pieces as in a 7 type car. The hole created in the air means that the air displaced by the screen then comes off the edges and back on itself thereby creating a vortex effect which will explain while you feel the heat from the engine on the back of your neck. In order for the rear spoiler to do any good it MUST be up in clean air hence why mine is up on extra high pylons.

I experimented with getting more mechanical grip earlier this year and fitted at great expense (20 off EBay) a wider twin blade spoiler. This completely altered the balance of the car in a bad way in that the handling went to pieces, the front end was too light and anything above 60mph meant that the extra drag had the engine cover bouncing up & down where the extra drag was trying to pull it off the back of the car. Needless to say I refitted the Marlin single piece spoiler and normality was restored.

My advice would be to use a single blade spoiler, only have a small angle, mine is set at 7 degrees and use the longer pylons to get it up in clean air.

Hope this helps.

limpabit 20th October 2009 12:34

Hi Ken.

Thanks very much for you input. I'm on the look out now for a single blade spoiler.:biggrin1:

Where did you get yours?

Also, what width do they need to be? The width of the car?

alackofspeed 20th October 2009 13:11

Ken's pylons are a track development item. The wing is the standard Marlin one (as also modelled by the Type-R demonstrator?).

TD had a spare set of pylons a while back, they might still have them / prepared to sell them. Worth a call, perhaps.

limpabit 20th October 2009 13:59

Having a think about it. Could do with 2 different sets of pylons.

Big ones for the track. Shorter ones when on the normal road. Just so they don't look OTT on the road. As though the long legged ones do a fine job on the track, they look OTT. In my opinion anyway.

Got me thinking anyway.:eusa_think:

KrazyKen 20th October 2009 20:35

As John correctly states my pylons were from TD whereas the wing is the original Marlin item just mounted higher. John has a wider single blade wing but I don't know where he got it from, perhaps you can advise John.

One thing to bear in mind is that the wider you go the more downforce you will get as the central part of the rear wing will still be in a certain amount of dirty air. Having extra rear downforce is not necessarily a good thing as I discovered when fitting the twin blade spoiler.

If you have more downforce on the back this may need to be balanced by extra downforce on the front. Witness the current F1 cars where you have a very wide front spoiler but a narrow rear wing yet they are balanced on track. I am no expert but what I can say is that my set up with the standard Marlin rear wing, TD pylons and no additional bodywork mods on the front works very well.

Hope this helps


KrazyKen 20th October 2009 20:47

One other relavent point having read Chrislandys comments. My front ride height is 110mm and the rear is 150mm. This was set by TD after doing a full analysis. Also I have my car corner weighted at TD every year which means that the offside is always higher than the nearside to balance the car up. With a K Series engine all the weight (Driver & engine) is on the same side of the car which makes set up more challenging. If you are running a Honda B16or B18 engine then this will not be such a challenge as the engine is on the opposite side to the driver.

alackofspeed 20th October 2009 20:57

Ken, correct me if I'm wrong, but although the lower front will help, from what I recall part of the reason your car is 40mm lower at the front, is to get the standard geometry to work as effectively as possible.

My car is ~10mm lower at the front, as advised by TD.

On the k20a2, i think the mass of the 6-speed gearbox help restore a natural balance. My car isn't corner weighted, because "there's no point" as TD put it. Basically mine is naturally within 1% across the width of the car (if the springs are set to the same compression), and 9/10 times on track I'll have a passenger on board.

limpabit 20th October 2009 21:03

Ken. Could you do me a little favor please. When you get a chance, can you measure the length&width of you spoiler?

KrazyKen 20th October 2009 21:36

John, you are correct about my front ride height, I had forgotten about that. As there are now a range of engine options in the 5EXi and suspension mods both from Marlin, TD and owners like Bigrich sorting their own setups it is probably best for each owner to go the route that best suits them. As we know both our cars have had suspension modifications by TD and are track focussed.

I am away on business at present but will measure my rear wing for Limpabit when I get back. This is unlikely to be until next week as I am heavily involved with the Stroke Association Day this Saturday at Castle Combe. Please feel free one and all to come along on the day.

limpabit 20th October 2009 21:56

No problem Ken. No rush. When ever you get a chance mate.

nutter 20th October 2009 22:07

Good post to read this one.
Ive thought about what to do for the rear wing for my 5EXi when i get that far.
hmmmmmmmmmmmmmmm, more questions than answers :)

limpabit 20th October 2009 22:16

If I had a choice, I would like one with a brake light. But can't seem to find one that will do the trick and looks ok.

chrislandy 22nd October 2009 08:20

Having read the books I found cover to cover 3 times, I think I might be getting an idea of what to do ;) Does anyone have any pictures of the underside of the finished car?

limpabit 22nd October 2009 09:23

Hi Chris.

I have none of a finished car, but I have one picture of during the build when the chassis was up side down!

If you look under build history, the first post is about riviting the floor etc. The only difference that may be different to those pictures, is that the front section is sometimes covered (under the fuel tank).

Not sure if Mr Dry cover the rear engine comparment section as well.

craig 22nd October 2009 17:07


Originally Posted by limpabit (Post 17209)

Not sure if Mr Dry cover the rear engine comparment section as well.

I don't have any pics but my underside is completely flat as front, middle and rear is all covered with undertrays!

John's is defo done aswell

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