Aero upgrades?

I'd forget about that idea. If you want to build a real down force car that is supposed to work in balance you need a lot more than a few wings or flat floors. Springs need to be different, which will compromise damping and will make the car a bit of a dog on roads/in situations that it isn't setup for.

 

Hi Neil
I was looking at one of these http://www.ebay.co.uk/itm/172401359168?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT

This is my car but i don't have it fitted, they made it look as if it was fitted without me knowing, i have also looked at the possibility of incorporating brake cooling ducts into one.

They are in the workshop across the yard from me.

 

These two go hand in hand mate. I get your idea, but why spend money on something you won't notice that much (I think you won't notice it) as if it were really needed Renault would have done it their selves. I'd go for good tires and suspension with money to spare for maintenance.

 

fwiw I go to Japan quite a lot and watch the different tv shows that they have there which show, amongst other things all the different companies that do aero work. It's quite amazing how much effort goes into it.

Yes, sure atm I have a Scenic but I'm not ruling out getting a M3RS. Which I'd definitely do an aero kit like this for.

In Australia I actually work at an Engineering company and I could convince my workmates to knock up some CAD designs in SolidWorks and get them cut out [in Europe because I come back and forth a bit too].

The RK designs look to be a bit cosmetic rather than true aero. I notice some cooling on the bonnet but no brake cooling ducts.



A different style of rear spoiler altogether on this and quite a few aero tricks.

 

Not sure if it's OEM (apologies if I assumed it was). Here is the link to the car.

Yes it is.

But for an aero car, you'd expect to see some of the elements shown here (and were on the rally car):


such as:
- flattened face
- fins to direct air around wheels
- reverse air scoop on bonnet
- side skirts

like this:



hope you can see the brake cooling holes - lol :-)

 

Not sure where all this knowledge comes from, but the Yaris WRC will have significantly more downforce, much better balanced and used than some home rapped RX8.

 

You're better off looking at time attack cars, they take aero development to a whole different level.

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UK roads are too rubbish to exploit the magic of downforce. All the bumps, dips, crests, potholes, and not to mention crosswinds affect a car's aerodynamics. An underfloor kit may help, but like it's said, the suspension set up needs to change to exploit that airflow so you don't stall it and lose downforce. Instability caused by aerodynamics is dangerous and would unsettle the car quite badly. Putting downforce on your car also affects the pressure on the tyres and how they would perform under the increased load.

If you're looking at time attack or track performance, the key is to keep your drag coefficient in the same ballpark while adding downforce. That way you'll know that the parts you're adding are giving you that benefit in speed. Otherwise it's a wasted exercise.

 

I'm mostly an aerospace engineer. I haven't researched too much into car aerodynamics so what i suggested were the basics. I don't know whether aerodynamics can solve the squirming under braking because even HEAVY downforce RWD cars will do that.

Even if it does help, it might negatively affect your performance on the other section on track.

Perhaps this problem can be solved by tuning the ABS/braking system/tyres? This isn't my area of expertise sadly

 

Based on no real knowledge....!

Would a suitable front splitter not give better flow pulsing the front end down?
From what I understand however it would have to be very close to the ground tho

 

Braking stability is also very much effected by rear toe in i.e. no rear toe in not very stable, decent amount of rear toe in more stable under braking. On RWD its a real balancing act though as adding some rear toe in makes the car corner exit understeer when on the power.

If I was trying to develop some real aero for a car I think I might stump up the cash to engage someone like Simon McBeath for a bit of consultancy:
http://www.sm-designs.co.uk/smarthome.html

 

I forgot this handling bible:
http://www.racingonthecheap.com/recommended-reading/carroll-smiths-handling-guide/

 

If i think of it as an engineer would.... Putting huge amounts of downforce on the front would give you great front end grip during high speed. But as you brake your splitter gets even lower. It doesn't give you much downforce because you're slowing down and so is the effect of the airflow over the splitter.
Furthermore the rear is lighter and wants to swing around.... And the weight transfer and subsequent moment effect is part of the reason for the squirming.

 

Most of the above is right.
Plus you need to account for suspension travel, so your aero load is dynamic. And of course horizontal load changes.

Proper aero jobs take quite some conceptional thinking. Aero stability and balance are difficult to obtain and on cars partially even more difficult than planes (suspension loads, balance F/R amongst things).

I race(d) and own(ed) mid and high downforce configuration cars. Setting them up (aero plus suspension geo plus damping/spring rates) is not an easy thing and very case specific (i.e. What works on a dry Silverstone might be a pig on a damp Silverstone).

@neilrs
I have one/two cars permanently at Nuer. Feel free to pm if you want some comments/thoughts.

Edit: fat finger typo on phone.

 

This is exactly why i think suspension is witchcraft because even at university it took me longer than anybody to understand... And why i didn't go for the trophy because i wouldn't understand what I'm doing with the ohlins

 

Here's quite a good video explaining how shock-absorbers work with a teardown:

 

Oh i know dampers and springs work...I just don't know how to tamper with them to play ball with me and my scenario. I know it's trial and error pretty much which is why i can it witchcraft

 

Honestly that extra bit of info makes it sound very much to me that your suffering from one of two things:
1) dynamic sudden toe change
and/or 2) Back end lifting due to damper rebound setting being too high.

Number 2) is pretty scary btw, I spun off 5 times in a race due that after my front dampers blew. The car kept diving loads on the brakes followed by one or both of the rear tyres locking (Michelin cups which also don't like to come back after going full slip). At the time I thought my rear calipers were binding on but the only way I could complete the race was to brake really early. Later on I found the brakes were fine and noted by static tests that the rear coil overs were drooping really slowly.

 

Here's one where the aero does look like it's done pretty well:

 

Neil I am confused. In both my race car and my very mildly modified R26 I can come off of hard throttle onto hard braking as quick as my feet will move on the peddles and the car is stable, except for 2 conditions which seem to effect every car pretty much to varying degrees:
1) Braking right on the limit of adhesion although in some cars the ABS limits that more than in others which will allow wheels to lock momentary and cause the car to dart about a bit. Personally I prefer ABS which allows more room for the driver to find limits.
2) The car isn't going straight or the track isn't a flat run when the transition on the peddles is made, some tracks are a real pain like that.

Ultimately point 2 is always going to be more problematic for cars like ours as so much weight is up front and so little over the rear axle and it has beam rear suspension, my 944 race car for example whilst moving around on its tyres about 5x more than the Meg is also much more stable dynamically on slight undulations and corners. However that car is near as perfect 50:50 and has a 60kg gearbox and drive shafts where the Meg has a thin panel and not much else, I think you are going to really struggle to shift enough weight around in the car or add enough aero download to make an appreciable difference. Proper multi-link independent rear suspension would probably help but that would be a huge re-engineering of the vehicle.

 

I'm interested in doing this, and will be doing something over the next few months that's why I'm it's interesting to discuss.

Going on the Accelorator makes the front go up due to a kinetic transfer of weight to the rear and going on the brakes sends a relative weight transfer to the front because of inertia. So really, the question is better asked 'Can aero mods completely reign in vertical movement of the front and back of the car so as to negate these increases in chassis height or bring them under control?'. I think the answer is probably no.

There's a bunch of maths variables at play and I think the only/best way would be to actually measure the angle of the vehicle at various corners and then you'd be able to determine the actual angle the car is at in the mentioned circumstances.

Active suspensions are probably the best way to handle these situations and I believe they are coming on upcoming versions of the Megane IV-RS. They've already been done for years on the Nissan GT-R and RenaultSport are apparently trying to transplant whatever they can of the systems.

Still fun sometimes trying to reinvent the wheel.. especially if you aren't going to go and buy the solution already done because it would be a) better b) probably cheaper and c) not such a big waste of time.

 

@NJH also a Golf Clubsport S (comparable with the Megane, plus it has truly independent rear suspension) has similar characteristics as you described. It maybe slightly less than the Megane (or most of other hot hatches), but it still has the same tendency.

 

I am speaking to BYC designs for a wing for the race car. I will not have a flat floor as I needed the spare wheel well for the fuel pump and swirl pot. Though I will not need it for some tracks high speed corners I have found the back end can become unstable. This is not a problem sideways on a trackday but with a car on your outside not good. Again would use a Snetterton or croft but pointless at Brands Indy! I would unless you are racing or use it purely as a track toy it is a waste of money!!! Though a big wing would look cool! [emoji16]


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@ ultralight, not surprised about that for the clubsport S as my own R26 can get pretty wild if for example one lifts off on a corner or tries to take a bit of a trail brake into a corner, even when not particularly trying so I assume all 4 wheels still on the ground. Makes the car more fun though if I am being honest and that clubsport S sounds a hoot.

 

From the race cars? or Standard clio 3 cup? Can you explain and give me a part number?
Thank you!

 

I saw on here a while back a link for a Japanese site where they had a rather mad Megane with a triple or quad exhaust? Anyway...they also did much more pronounced front fender vents...anyone got a link? Wanted to see the things.

 

Do you mean RK Design or someone else?
http://www.rkdesign.co.jp/gallery/megane.html

 

I know those guys well, I've bought the bonnet vent kit off them and am planning to get the engine cover and rear wing.

No this was a random comment in a thread where someone posted a link to a japanese (I think) tuner and commented on the car having a triple exit exhaust and it looking terrible. Anyway, that same thread had the wider arches in there, they extended with clear air gaps replacing the stock ones and then continued down the side of the car as side steps I think?!?!

 

Bonkers website there, like yahoo or something. I found the twin exhaust with the weird diffuser but not the mega front vents. This is going to drive me mad now.

 

You were right Jamie!

https://ameblo.jp/carol-yoshitomo/entry-12250198600.html