Low lift & drag aero ideas for hatchback track car

[focus1.6uk]

Hi,

new member here looking for your input on low lift and low drag aero ideas for my little track car (awaiting prep when i finish uni for summer)

Being unable to make the car longer rules out boat tails/ large kamm back extensions/ nose extensions like basjoos' civic. I doubt front wheel skirts or flat wheel trims would be possible either as the front brakes in particular generate a lot of heat on track.

Im thinking along the lines of:
small roofline extension/ small kammback similar to
http://ecomodder.com/forum/showthrea...ics-312-9.html
and Piwoslaw's 307
http://ecomodder.com/forum/showthrea...read-9040.html

flat undertray and side skirts- perhaps with VGs on the undertray

front splitter

possibly perspex rear wheel skirts

aerial/ rear washer jet and sunroof will be removed

extension on the rear of the bonnet to deflect air around the wipers as per http://autospeed.com/cms/A_2445/article.html

passengers side mirror delete or replace both mirrors with smaller ones

possibly sealing off the high pressure cowl intake in front of the windscreen or using it as place to have the air intake for the engine.

Venting under-bonnet (under hood) air out of either bonnet vents, a vent in the undertray or out the wheel arches, which may also help brake cooling.


Thanks for reading, I would appreciate any suggestions, feel free to flame any of my ideas

[focus1.6uk]

Some more ideas:

front and rear tyre spats as seen on more modern cars

Front end panel gaps sealed with foam strips

Lowering the car will make the wheel arch gaps smaller and slightly reduce frontal area

[Bill in Houston]

build a rear diffuser. saw one recently around here...

[andylaurence]

Is this just for track days or for competition? If it's just track days, I don't see why you can't extend into a boat-tail. If you're competing, I suggest you thumb through the blue book before making any changes. Much of this will not be acceptable.

[focus1.6uk]

Thanks for the input, i like the rear diffuser idea, will see if i can get a reasonable angle for it or it might increase drag rather than reduce it.

Initially the car is for track days, hopefully will have the funds to take part in hill climb or road rallies or Tin tops, no real idea yet but I will check the blue book and series specific rules - I'll make sure all mods can be undone fairly easily though.

[andylaurence]

On a track day, performance doesn't really matter as there's no timing. What it feels like to you is important as the only reason you're there is to have fun. As such, I'd not bother with much aero work as it's wasted effort given that you'll not be saving much fuel. Strip the car out. Look at every part and ask yourself "do I need that?" If the answer is "no" or "maybe" then take it off. You'll get better performance from the car than anything else.

If you're planning hillclimbs, then a good few of the ideas will put you into Sports Libre, which puts you up against me in one of these. The first thing I'd say to anyone about a track/race car project is to decide what you want to do with it and then work out what you need to do to achieve that. If you don't, you'll build something that's not eligible for anything. Even taking the rear seats out will prevent you running in most AutoSolos and bump you into the modified class on the sprints/hills.

There's only so much time in the day - don't waste it doing things you have to put back. This is coming from the person who stripped out a track car, then read the regs and had to put all the interior back in again. Luckily, I'd kept all the little bolts and I'd not sold anything!

[jtbo]

But even on track day, lower air resistance will help to get higher speeds and it is bit like putting more power to engine, so I would not say that aero work would be wasted effort. Speeds nearing 100mph, then lower cd starts really working.

Recently I had to overtake one unreliable driver, first overtaking after aeromodding my car, I did overtake as before, however car did pick up more speed, so that I was doing 10 more than normally, at higher speeds even small mods seem to help much.

Of course with competition regulations one can easily do things that are wasted effort, but there is quite often modified class which would make racing possible with mods.

[andylaurence]

Yes, better aero will help, especially with a low powered engine. However, at a track day, you don't need to overtake anyone as it's not a race. The primary purpose of a track day is to have fun driving a car quickly. Going 3mph faster at the end of the straight won't help with this, in my opinion.

The original poster referred to hillclimbs and sprints. Some of these mods will put him in a class that competes with cars that are simply leagues ahead. Define your targets and you can hit them. If you design a solution before you define its criteria, you will miss the target. I speak from bitter experience.