Low speed sprint car aero help

[Blackpoolrock]

Aero is not really my cup of tea ! I know nothing about it !

Currently building a 700bhp Subaru sprint car and looking into aero options. This is not got a huge budget behind it but looking at the other cars in the series they all run big wings above the roof line of the car, splitters and some flat floors. Is there anyone in the uk I can turn to for advice, and also on rear wing, there are some pre built choices out there fr little money, how do these compare? I don't want something that has a negative effect !

On the flat floor, I don't see how I can keep things like the exhaust and rear diff cool and still remain a flat floor, and rear diffuser desighn has really got me scratching my head !

[Lycoming]

Aero is not really my cup of tea ! I know nothing about it !

Currently building a 700bhp Subaru sprint car and looking into aero options. This is not got a huge budget behind it but ...

Go to your local library and try to find a book by Simon Mcbeath or Racecar Aerodynamics by Katz. Both are pretty minimal on math and will serve to introduce the topic. Probably ought to read one of those before trying to get advice from somebody so you can at least communicate using the same language.

[gixxer_drew]

Honestly I think your best bet in that situation is still to hire an aero guy. Some options are very inexpensive, couple thousand dollars to get some basic advise that can make a world of difference and often seconds per lap. Trying to figure it out on your own, guess, rebuild things as you learn. It will be a lot more expensive than that. However if your goal is to learn and not to place well, heaps of literature is out there. Concentrate on repeatable test methods. Free help in a web forum will be worth every penny. My $.02

[Blanchimont]

If your car really has 700hp and you race at low speeds than drag will not be your concern. I think you can put on almost as much drag and downforce as you want, it's very likely that you'll gain from it if the added weight isn't to much.

My first aero step would be to look at the other cars in the series and analyse what wing profiles are used and at which angles of attack they are installed. Take pictures and/or ask your competitors for help, although i don't know how much of help you can expect from them.

But before thinking about aero, i would optimise the suspension, tyre choice and engine throttle control for best mechanic grip. I assume you have a lot of wheel spin with 700hp when accelerating!?

[marcush.]

first of all -what are the technical regs you are working around? This must be always your starting point.which are the surfaces and boxes you are allowed to put bits on or use for producing downforce.
From there you need to understand what you are willing to invest in that area.I don´t think if say 500Bucks are available it would make sense to go into any details -just slab on a bord at an angle so the forward motion is split up into a vertical component....

I´m sure the usual bits commercially available are not suitable - but in USA there is a Huge SprintCar industry with lots of knowledge and experience.air must be the same in the states as in the rest of the world so i´d think buying overseas will make a very efficient starting point.

[Pierce89]

first of all -what are the technical regs you are working around? This must be always your starting point.which are the surfaces and boxes you are allowed to put bits on or use for producing downforce.
From there you need to understand what you are willing to invest in that area.I don´t think if say 500Bucks are available it would make sense to go into any details -just slab on a bord at an angle so the forward motion is split up into a vertical component....

I´m sure the usual bits commercially available are not suitable - but in USA there is a Huge SprintCar industry with lots of knowledge and experience.air must be the same in the states as in the rest of the world so i´d think buying overseas will make a very efficient starting point.
http://draftingthecircuits.whoobazoo.co ... 5372_n.jpg

I think he's talking about a different type of sprintcar. Those you showed, are v8 only and 700 hp would be uncompetitive. I think he's talking about an actual Subaru car for "sprint" racing on a road course.

[Blanchimont]

Probably something like Time Attack UK.

[youtube]http://www.youtube.com/watch?v=_hwykajgeZs[/youtube]

[Pierce89]

That's the impression I got. I know sprintcars(as raced in US and AUS) don't come in a Subaru variety.

[neilbah]

I too had wondered what type of 'sprint' car the poster meant. I always thought the huge roof spoilers on the dirt oval tubular space framed cars was for advertising more than DF but it seems they do have an aero function.

If the author means an actual subaru such as impreza (saloon/hatch?) then i suppose pikes peak style solutions should be used of big front air dams with vertical end fences to force air over rather than around the front and a large/High AOA rear spoiler in clean air high up or even a lancia delta/nascar style angled flap. The rear bumper could be cut down and heavily vented to allow heat out and allow space for a rear diffuser, do the rules specify a rear exiting exhaust? reverie do some off the shelf diffusers/wings floors http://www.reverie.ltd.uk/astonmartin_reardiffusers.php

I guess some clarification on rules for the formula would be helpful and it might be worth getting some uni students involved or paying for some wind tunnel time to test the off the shelf parts - with some adjust-ability built into the mountings to see how effective different angles or positions are.

[marcush.]

my post is still valid .
If you are not restricted in terms what and where to place your downforce generating device....you can go wild....what about a sucker ?

or that one...



pikes peak mountain racer

[wesley123]

the Lovefab NSX is a great example of what you can do. But based on the budget the OP gave us(he didn't gave a number though) that seems a little out of reach.

[marcush.]

I don´t think its out of reach .
i bet with a good guesstimate you can get into the ballpark with it say 90% of what is possible.all you need is a wing profile suitable for the speeds and angles of attack you may need and some ellbow grease to mount the wings actually to the car .
even if you only manage to achieve 80% you ´d still get monster downforce levels from the huge wingarea you are using .
Everyone and his dog has a go-pro camera these days so a bit of vlow viz or tufts will show you the way to position the wings in favourable positions.You need safe and sturdy mountings for sure and if you happen to have a bit of data logging available you can even measure vertical force using the displacement of the springs as a base for your calcs ...
Yes everything will add up to something expensive ,but when was racing cheap after all?

[wesley123]

Agreed, the start on it isn't really hard or expensive. You can dump a large rear wing on it, a flat floor, a diffuser and add a large front splitter. You'll make big gains from that. But then, to improve from that, that's gonna cost a lot of money and effort.

Therefore it might be a good idea to take a look where you want to be, what your goals are(and are their achievable?), you can put all the parts on as described, but to then hope for the best wont get you anywhere.

[marcush.]

right.
a few wool tufts and a go-pro camera is already more than those who invented aero application to motorsports did hav e access to ....so be happy what you got:
-internet will be a very valuable source of information
-basic aero knowledge and common sense will get you VERY far
-keep expenses for actual parts to a minimum as long as you are not sure how to make maximum use of it.

I remember the words of a leMans Team principal who happened to stand besides Gordon Murrey when his car was going through pre qualyfying when test days were weeks before the race -half finished as it was ,barely roadworthy no underfloor let alone a diffusser ...
Murray gave a thumbs up to the car and encouraged the team -wait till you get an underfloor mounted to it ,this will give you another few seconnds per lap.
How wrong he was .The flat floor and ramp did nothing to the vehicle performance over one lap but it was not really driveable as all temps were soaring as there was no real airpath for the waste heat left...

[andylaurence]

If you're looking at wings, I assume you are going to run in Sports Libre. Is the car in road going spec with a tax disc and MOT? If not, you will need a Nat A Open licence, which is 8 signatures on your upgrade card. Easy to forget! Onto more productive things, what championship are you aiming for? This will give us an idea of the venues and the use cases associated. The spec sounds like British Sprint Championship if you're looking at 700bhp and big aero. It's a lot of work to get a production car on the pace of a Radical SR3 Turbo or a Juno and the circuits they run on are what I'd term fast; average speed at Castle Combe is over 90mph for me and I run in the smaller engine class with a 999cc engine.