Ratdat said:
Trouble with rear spoilers is you get a trade of between downforce and drag. I think this reflects in the relatively poor drag coefficient of Skylines. I doubt the bulk of production car spoilers are all that effective at all in terms of downforce because if they were to generate a lot of downforce it would mean an increase in drag and subsequent drop in fuel economy. Aftermarket spoilers offer improved efficiency but are probably not needed on the majority of cars. If the car is able to put the power down and is stable then no real benefit to be had.
I know when I fitted a front spoiler to my 510 it had an incredible effect on stability at 130mph+. The car felt absolutely rock solid compared to how it did without it. Unfortunately, I discovered another trade off shortly after fitting it...it caused the front brakes to run very hot on the track...bugger
the front lip would have only reduced the air flow under the car thus the overall effect of lift the cars shape creates is reduced. but as you say, the air is often used to cool the sump, brakes and exhaust. why didn’t you add break ducts? did you see a change in water/engine temps after fitting the part?
most road cars don’t have wings. they have spoilers. their main function is to 'spoil' the air flow over the car. they make sure the air leaving the tail of the car doesn’t join up with the air that went under the car. this creates drag but it also keeps the car on the ground. the s13 spoiler is one of these.
mini wings like on the e36 m3 are too small to do anything useful. they are more likely to be there to act like spoilers than wings. also for a wing to work and produce lift (negative lift for car wings) you need space around the longer side of the wing.
so a tiny little wing on the back of an m3 with about 2inches of space between it and the boot lid is useless as a wing. no lift to be had here.
a wing needs to be mounted either high up or off the back of the car. this gives it the space it needs below the wing to move the air that creates the lift.
Bon Bon said:
So at what speed would you say a rear aerofoil becomes affective? I reckon at motorway speeds they can have a significant affect, certainly did make a difference to the stability or my mates E36 M3 having a rear spoiler around the Nurburgring.
Remember, on the Skyline for example, 80kg of downforce is a LOT...because the car will generate lift, so first the wing is counteracting the lift, then adding downforce.
However inverted wings wouldn't work, especially once the airflow was redirected once the car went sideways, but, it's an excuse to argue.......
around 80mph is when most smaller wings become useful. if you had a huge wing with a long surface then it would work at much lower speeds. they also need clean air. if there is turbulence then there is little benefit to be had from the wing.
an inverted wing would work. lift is lift. if you turn the wing up the other way it will still work. so long as there is space for it to move the air. but the low speed of drifting and the sideways action of the car doesn’t help. a massive 'V' shaped wing on the tail could create lift at speeds above about 30mph. but it would need to be quite a big wing and would look very odd indeed. i spose some drifting is much faster than 30, so a wing that worked at 50 would be much smaller and you could add extra elements to the wing to help double up the effect it has. but you would need to mount it quite high up to get clean air to help reduce the size of the wing.
another way would be to add smaller wings to the sides of the car. there is a fair bit of air flow down the sides and they are high pressure areas. this means there is more air in a set space to create lift from. this plus a smaller rear mounted wing could get you more lift.
how much lift is needed to help the rear tyres lose grip? and would lift really help? if you flick into a drift at 80mph and then the rear wheels don’t have enough grip to stop sliding straight on, you may not be able to catch the drift.
i spose if you only want to remove some of the weight from the rear, then a small wing setup may give you just that little bit of a helping hand. but its defo not worth the effort if you haven’t removed all the weight from the rear of the car that would can.
do you really need them big lights with all their bulbs and glass? cant you just use LED's. they are much lighter and use less power. it would also help the alternator work less hard and free up some power for the wheels. not much tho. every little helps eh.
how about plexi glass for the rear window and rear sides? might be a bit of a security issue if you use your drift car on the road. and then you still have the rear hatch/boot lid made of steel. dump it and get some light composites.
playing with the aerodynamics of your car to create less rear end grip could land you in a world of trouble at motorway speeds if you use your drift car on the road. 90mph and a 30mph head wind.. doomed.
L.
if you know how they generate downforce 
I never replaced it as track speeds were never high enough to warrent it really and I'd stopped using the car on the road by then.
The standard wing is like you say just a spoiler to reduce lift and tidy up the airflow, along with the rear bumper splitters, etc.
