Mike C

iTrader: (1)

OK then,

We all know that as soon you move, you are figthing against air resistance, basically speaking, right?

But at lower speeds, it's far less noticable than at higher speeds.

I think it would be fair to say that, although it will still have a great effect, more powerful vehicles won't be so badly affected by it until they reach a greater speed than those not so powerful.

So, on a 0-60 dash, how big a role could aerodynamics possibly play? Without looking up drag co-efficients, I could name plenty of cars that look comparatively like house bricks which can hit 60 as quick as you like. Could these 0-60 times be improved by fitting splitters, diffusers, canards, vortex generators and all that, or would it be so un-noticable it wouldn't be worth it?

What about 0-100 or the quarter mile?

Or is it only at high speeds, and you'd only notice a major difference on, say, a 0-150 sprint.

And what about handling characteristics?

These aren't specific questions as such, just a general topic of discussion!

Chip

iTrader: (3)

Ive always considered aerodynamics largely irrelevant 0-60, im sure they start to effect 0-100 though on most cars

Mike C

iTrader: (1)

By how much though? Worth worrying about on a 0-100? Could lose/gain a few tenths?

I know there are many more variable factors to consider than that, but for an average car

Luca

iTrader: (2)

HUGE subject this one, Im afriad its also one that can only be answered in a wind tunnel with the exact car.

I would agree with chip 60mph + is where it would begin to come into play.

Mike C

iTrader: (1)

Really as low as that? I know various cars that raise spoilers above 60 or 70mph, but with the rate some cars can accelerate to 100, I guess I can't grasp how much resistance the air causes.

Luca

iTrader: (2)

A simple test is when on the motorway at 60mph put your hand out the window and feel the force of the air.

Then imagine that force hitting the front of your car, directly on the windscreen, the bumper, wingmirrors etc.

J1mbo

iTrader: (1)

when we were going for good 0-60, 0-100, quater mile

we took the big spoiler off, i think the wrc spoiler of an escos is working at just under 60mhp ish

i had the steam cleaner on the escos the other day (not accurate i know) but i shot the hot water over the roof and down onto the spoiler, the water seriosly shot off the back lifting the water up !

i thought wow, just like how air would react ! i guess lol

on the 0-150 dash the escos did id did circa 15seconds iirc, rod said it could be down in the 13's with the spoiler off so around a second ssaving iirc !

-beefy-

iTrader: (6)

then you can factor in the other 1 second you would of saved by not being sat in the passenger seat fatty




love yoouuu

beef

Homer.

Just look at most of the time attack evo all running voltex front bumpers, flat floors and rear diffusers Not got a picture of the full under side but you get the idea from the below, Jspeed are now also doing an off the shelf flat floor for evos for about 500 quid,

J1mbo

iTrader: (1)

lol, how nasty

Chip

iTrader: (3)

Nearly all the aerodynamic aids you see on time attack cars make them accelerate more slowly.

-beefy-

iTrader: (6)

lol you know i dont mean it ,

parmos at my place pumpkin !!!

Homer.

Yeah I would imagine the amount of down force the voltex or varis set up for evos would have a massive effect on acceleration especially over 100 but at the same time a flat floor rear diffuser combo when applied properly would help the air under the car move through quicker with less turbulence meaning quicker acceleration due to less drag, but also if the air on the underside is moving quicker than the air over the top then it will also be creating down force so slowing the car down but that is when my eyes start going squint trying to figure aerodynamics out

Chip

iTrader: (3)

Most aerodynamic aids fitted to a time attack type car tend to be there because of:

Increased corner speed
or
Fashion

Luca

iTrader: (2)

There is a super fine line between creating downforce to combat uplift and then having too much downforce and creating drag.

Mk1-stu

Working on the theory, that one of the performance cars - is either a Merc or Porsche - has a self adjusting spoiler that lifts at above 70mph, i would say that is when aerodynamics comes into play ?

But then at the same time - to counter my own comment, it could literally be, that the shape of said vehicle means that anything over 70 would require some downforce.

i'll shut up and go over there -------->

Rod-Tarry

I agree, XSport want to do mods like those shown above on mine, but without highspeed testing who knows if it works, I remember that Merc at Lemans taking off, it scares me. Best left alone.

foreigneRS

it's quite simple to grasp how much resistance the air has. if an average family car is using practically all of it's 100 bhp to do about 100 mph, it doesn't take a lot of calculation to tell you that it needs about 12.5 bhp to do 50 mph. so if you could eliminate all wind resistance at 50 mph, you would gain the same acceleration as having an extra 12.5 bhp which is quite significant in a 1.6 mondeo, but not so significant in harvey's escort or rod's sierra.

addressing another point in the thread, changing downforce does not necessarily change drag in the same way.

having said that, 'spoilers' that pop up at speed are mostly to reduce rear lift rather than decrease drag, and they probably usually increase drag.

Chip

iTrader: (3)

Broadly speaking I beleive that wind resistance is generally accepted as being related to the speed cubed.
So by 200mph, even a very aerodynamic car will be starting to lose a lot of power and at 10mph even a very unaerodynamic car will have no problems.

Where between those 10 and 200 points you are has as much to do with power as aerodynamics, with a car like Rod's for example, it has so much power that even with bad aerodynamics and doing 100mph, those aerodynamic effects have little effect on its ability to still accelerate as it has such a large amount of power that even if it takes 70bhp (my guess not an actual figure) to maintain his speed its still a drop in the ocean but at 200mph and 560bhp to maintain the speed it is really starting to take its toll.

Chip

iTrader: (3)

LOL, both typed almost the same thing there nick!

Mk1-stu

so working on the above theories and using Rod's car as an example, if he were doing 200mph with the wind BEHIND him, no cross wind etc, his car would theoretically not need the same amount of bhp to do the same speed ? Although it's doubtfull that the wind would be doing similar speed, the air infront of the car would already be in a state of turbulance when he went through it allowing the car to pass through it with less drag ?

Chip

iTrader: (3)

Yes a significant tail wind would help him from the point of view of drag.

turbotoaster

well in terms of wind direction, say your doing 200mph with a 50mph tailwind you will only need enough power to reach 150mph i would imagine, but then saying that it would have to make sense that if there was a 200mph tail wind it would require no power(or maybe a couple of hp) to do 200mph which doesnt seem right to me.

Maybe then the aerodynamics of the rear of the car affects that, ie it being a brick shape at the back and it being able to channel all avaliable air onto the back, like this



but since no car is like that the effects wont be as strong, as to be fair your never really gonna be in an environment where you rely primarily on tailwind for your speed

it all depends on what you want the vehicle for, 99% of all aerodynamic aids are to gain downforce for either high speed stability or cornering, by using the air to push onto the car you will be creating drag hence you will be unable to achieve your ultimate top speed.

on tracks you may find all the parts that give you drag may actually give you a higher top speed, this might be down to the dramatic increase in cornering speed that means as you enter the straight you are already at a higher speed than a stock body car.

ermm im a bit drunk and im waffling but i really enjoy these type of threads so lets keep going

Chip

iTrader: (3)

Wind resistance isnt the only thing that increases with speed.
Heat lost through the tyres for example.
So a 200mph tailwind wouldnt see you at 200mph for that reason

turbotoaster

ah yes, my good friend friction on the road, how could i forget!!

Chip

iTrader: (3)

Not just on the road either of course, wheel bearings etc too

Psycho Warren

iTrader: (5)

mmmm i might have to get my fluid dynamics books out from my aero engineering year at uni!!!

Such aerodynamic tweeks are not something you can home bodge unless you know what you are doing and can do the maths.

Wind tunnels are FAARRRRR easier. But far more expensive.

You can play around with scale models and that would be more than good enough for the cars here. Even homemade slow speed tunnels with smoke streams are adequate for seeing the air flow, turbulent areas, where air flow splits etc etc.

Rod-Tarry

It would be good if a 50mph tailwind meant that you only needed enough Power to reach 150 to hit the double ton, if you errected a sail that may be the case .
There is no one formula because it depends on a huge number of factors, not the least of which would be the coefficient of drag on your vehicle from back to front (since it was a tailwind).

Once ran with a heavy tailwind at Brunters & the car was perhaps 1 to 2mph faster under those conditions, dont tell Mike or he will dismiss what turned out to be a record run (183.2mph).

foreigneRS

as long as the vehicle is travelling forwards faster than the tail wind, the net wind resistance is still acting on the front of the car