Track car aerodynamics help

[PhillipM]

You've just got so little room to play with on a hatch for underbody stuff without chopping portions of the shell away or widening things away from the sills. As Kev says, with what you have available for working with for diffuser expansion, etc, you have to be running pretty low, and more importantly, be able to control your pitch when running that low.

 

[s.mac]

Long term project and work in progress. Won’t really know if there’s any benefits on track but will help cooling.

 

[s.mac]

I mean won’t really know till we get it on track.

 

[Nathan Evans]

Not really. Think you’ve got the wrong end of the stick. It’s a spec series that needed to be affordable for those coming out of karting and sit below touring cars in terms of laptime. Depending on the era the Clio cup cars also needed to be slower & cheaper than the V6 Trophy and later Megane Trophy race cars that competed in the Renault World Series. All of the cars are identical and Renault aren’t competing against another manufacturer so there is no need for Renault to design a lot of pace into the car through very very expensive aero. Plus marketing wise it’s in their interest to make the race cars look not dissimilar to the road cars.

Current WRC is probably the best example of what works on a hatchback. Like a 182 track car they are relatively slow in a straight line with a relatively high ride height, compared to say a WTCC spec TCR touring car.

Haha the last bit about WRC is so wrong so many levels. Far from slow in a straight line.

Also engine wise specs are pretty identical. 380bhp 1.6 turbo in both

 

[Steven103]

Missed the point.

Lift squares with speed. A given wing profile will generate 4 times as much downforce at 120mph than it does at 60mph.

The average and top speed of WRC car on a stage is much closer to that of a track clio on a typical circuit. Hence the aero on a WRC car being optimised for slow speeds is a far more relevant case study for this thread than conventional aero cars like GT, LMP, single seaters or the obvious comparison: a 1.6T ~380bhp TCR.



FWD hatch is unfortunately a terrible start for an aero car. Key ingredients being low ride height, stable body in pitch/roll and high average speeds. Clio has literally none of those from the factory and pitch control in particular is ruined when you fit stiff rear springs to turn it into a track car.

 

[PhillipM]

^'this is why we don't bother too much with aero on the racers bar flat floor and a barn door of a rear wing optimised to work at low reynolds numbers - the average speeds are only 50-60mph, so you need massive amounts of wing that will work at low speed to make a significant difference.

 

[Hollidog]

Long term project and work in progress. Won’t really know if there’s any benefits on track but will help cooling.

This looks slick! Are you running a flat floor as well?

For me, I think the benefit of adding a splitter and flat floor is not so much to increase downforce, but to reduce drag. The underside of a road car is a mess with flow separation all over the place which slows down the speed of the air passing underneath the car increasing drag. The problem you then run into is engine bay cooling, your only choice really being venting out of the bonnet, or ducting your radiator out somewhere. Any diffuser you would add, maximum angle you want is about 12 degrees before you start getting flow separation.

In terms of actually creating downforce, as other posters have pointed out, at the speed our Clio's can travel, and the ride heights you can realistically achieve, there isn't much you can do. That being said, dive planes/canards at the front and a gurney flap added to the rear - I think - would give you a minor increase in downforce for a slight gain in drag.

Kyle Drives on youtube has some great videos about the basics of aero, with CFD examples to show pressure spots and air velocity across the surfaces.

 

[scullyg40]

Crazy aero on a hillclimb Clio

 

[eon172]

I mean won’t really know till we get it on track.

Looks good, would love to read more about this, have you got a blog or something elsewhere?

 

[s.mac]

Looks good, would love to read more about this, have you got a blog or something elsewhere?

Got a Facebook page but it’s not the best....
Team88 Motorsport. It’s been on going for 3 years so lost a bit of interest. Finally finished and at Croft on Wednesday to check nothing falls off.

 

[eon172]

Got a Facebook page but it’s not the best....
Team88 Motorsport. It’s been on going for 3 years so lost a bit of interest. Finally finished and at Croft on Wednesday to check nothing falls off.

i know the feeling, I'm trying to get back in to working on mine, best of luck, do report back [emoji106]


P.s. I'm intrigued with your front valance bits and splitter, looks great and functional for cooling. I can see you've dropped the rad and splitter lower and put the corner bits in to fill the gap (rather neatly too!), what did you use for these - the lower parts of a donor front bumper or something? I also see the air intake going down to the ground too.