Just thinking out loud here how programs like Top Gear don't really understand torque. Like a big Chevy V8 produces loads of torque and a honda vtec for example doesn't come close.. Why don't they realize that power (hp, Kw whatever) is actually more important? A V8 big block producing 500Nm torque at 3500rpm versus a modern jap engine producing 250Nm at 7000rpm; losses aside, these would put exactly the same traction force on the road! The 7000rpm engine needs twice shorter gearing, doubling the effective torque!

Same with downforce; Since when do people actually believe that road cars produce downforce? Only a handfull do, and those are the 'supercars', certainly not your Civic! And even those few like the Ferrari 430, specify downforce at 300km/h, choosing this extreme speed to make the numbers two or perhaps juuuuuuuuuuuuuust 3 digits in kilos.. At 100 or 150km/h the numbers would be pretty pathetic..

end of semi mild shrug type semi rant.

I agree for track use, but revving to 7k rpm on a regular basis gets old real fast. I'd like 700Nm at 3500rpm, thank you very much.

So if I put my hand out of a car window on the motorway, with my palm facing the ground and fingers outstretched, may I ask what the force is thats pushing my hand downwards?

Just wondering thats all.

The point is that cars by default create lift (they get lighter at speed), and almost all of the "wings"/spoilers slapped on non-racecars actually just help reducing the lift, but are not creating downforce.

Quote from richy :

So if I put my hand out of a car window on the motorway, with my palm facing the ground and fingers outstretched, may I ask what the force is thats pushing my hand downwards?

Just wondering thats all.

That makes almost no difference at all! (but it is downforce, yes!) Otherwise Mr. Schumacher would have spent his races doing that in the corners

The car doesn't actually produce any downforce.

Downforce is the 'Use of air to puch a car down onto the road, e.g with wings.'


I have no idea what torque is. And neither does Mr. Clarkson!

Quote from richy :

So if I put my hand out of a car window on the motorway, with my palm facing the ground and fingers outstretched, may I ask what the force is thats pushing my hand downwards?

Just wondering thats all.

Downforce.

Yup, that's downforce. Unfortunately, cars are the same shape as your hand, so whilst your hand will make downforce (and lots of drag), your car will create lots of drag and a bit of lift. To make downforce creates a lot of drag, and drag is the enemy of road cars, where economy is [meant] to be a priority.

Ricers with wings just add drag, and probably some lift too. I doubt many, if any, generate any meaningful downforce.

Im confused I think.

Reducing the lift is not downforce? Aircraft can fly at some pretty slow speeds, if a plane can lift off at those speeds then surely a car can be pushed down at those speeds? Some light aircraft take off around 60mph because of their shape, surely the shape of a car comes into play at the same speeds?

edit: by the way not trying to justify ricer wings or such, just that production cars have spoilers wings etc.

Lets say your car produces it's weight in lift - i.e. the wheels are *just* coming off the ground at 100mph.

Now, decrease lift so that at 100mph it produces 90% of the car's weight - still lift, just less of it. You will have less grip that at slower speeds, but not quite as little as above.

Now decrease lift so much that at 100mph it presses the car down at 100mph by 5% of the cars weight - THAT is downforce.

Of course it does. If you look at an airplane wing and a car from the side, they have the same basic form. Air can pass unhindered below, but has to take a detour around the top, creating a low pressure area on top which pushes the car/wing upwards.

Thankfully the shape of a car is far from an ideal wing and the amount of air that goes below it is limited, so the car doesn't take off at 60mph.

Well, think in terms of net lift.

Let's say we have a car body that, at a certain speed, produces 1000N of lift.

You could add a spoiler, that changes the shape of the body, and might reduce lift to 750N. The spoiler itself is not actually producing (250N of) downforce, it's lift reduction from the change in shape of the car body.

You could add a wing. This will create downforce in it's own right but if it, at whatever speed this car is travelling, produces 400N of downforce (or more correctly, -400N of lift), the car will still be experiencing 600N of lift, so the overall effect of the wing when placed on the car, is to reduce lift.

Edit: beaten twice, but I think I covered a different angle

Torque and BHP ... Simply put, The amount of Horsepower you have determines how fast you can go, the amount of Torque determines how quickly you get there.

If you want a quick idea to think of. An aeroplane wing produces lots of downforce - but in the wrong direction.

It uses the downforce to lift up into the air.

Quote from F.Rizzo :

Torque and BHP ... Simply put, The amount of Horsepower you have determines how fast you can go, the amount of Torque determines how quickly you get there.

I hear that a lot, but don't understand it. Please explain.

Im struggling to see the difference.

lets go back to the examples in the thread topic.

What is the ferrari doing that makes it have downforce that any other production car isnt doing in a smaller amount? As i see it the exact same principles are in place, its just the ferrari is better at doing it than say, the civic which is actually doing downforce just not as well.

Quote from sinbad :

I hear that a lot, but don't understand it. Please explain.

Ummm thought it was pretty clear ^^ ....

Your Top Speed is limited by the amount of bhp you have, and of course the weight and shape of the car, wheel/tyre diameter etc.

If you have a lot of torque, you will get to your top speed quicker.

"In theory", a car with 200bhp will accellerate no faster than an identical car with 150bhp (if they had the same amount of torque).

Yes that is the misconception imo! Of course torque curves aren't identical but if you imagine a variomatic, a 7000rpm 250Nm engine would accelerate the car just as quickly as a 3500rpm 500Nm engine! So torque doesn't tell you how fast you'll accelerate at all, because torque gets divided through the gearbox and final drive.

Ferrari probably uses the wind tunnel and computers to optimize the car body shape and most of all some underbody diffuser, accelerating the air out of the back.

What Niels said.

That's why I never quite understand why everyone says that popular phrase.

Quote from richy :

lets go back to the examples in the thread topic.

What is the ferrari doing that makes it have downforce that any other production car isnt doing in a smaller amount? As i see it the exact same principles are in place, its just the ferrari is better at doing it than say, the civic which is actually doing downforce just not as well.

A Ferrari gets popped in a wind tunnel to optimise downforce. Drag isn't as important, because it's a high performance car, although it does come into it a lot regardless. A Ferrari will have a sealed underside (as opposed to the open underside of a Civic), and tunnels, proper diffusers etc to generate a sort of 'ground effect'. It's upper body is designed to work the air where it matters, and to channel the air where downforce can be made.

A Civic is meant to be cheap, easier to work on, and carry more people and luggage, with low running costs and good fuel economy, as well as low wind noise at speed. With a taller, narrower frontal area, a short body, and all the shapes associated with passenger cars, in short it creates lift. Not much perhaps, but it won't produce downforce.

E-Types, when fitted with a 'legal' numberplate, will virtually lift the front wheels of the ground over 120mph!!!!!!!!!!! A Ferrari F340 will get lower on it's suspension at speed as the downforce crushes it into the air.

If you can't understand the difference, the world of cars isn't beckoning.

Edit: Re Torque and Power. If comparing different cars I tend to look at power, as it's not altered by gearing or tyre sizes, and takes rpm into account. If comparing the same car (for tuning, development etc) I either look at engine torque, for engine work, or wheel torque, for everything else. And when simulating performance on Excel I use torque, as it can tell you more.

Quote from Niels Heusinkveld :

Yes that is the misconception imo! Of course torque curves aren't identical but if you imagine a variomatic, a 7000rpm 250Nm engine would accelerate the car just as quickly as a 3500rpm 500Nm engine! So torque doesn't tell you how fast you'll accelerate at all, because torque gets divided through the gearbox and final drive.

Ferrari probably uses the wind tunnel and computers to optimize the car body shape and most of all some underbody diffuser, accelerating the air out of the back.

Ok, I said in simple terms. If we are going to start throwing gearbox drive ratios rpm and god knows what into the equasion than you are not talking about simple torque / bhp figures anymore.

But when comparing different cars (which is what you were doing) you HAVE to take gearing, rpm ranges etc into account. If you don't then any comparison is MEANINGLESS.

Face it, you don't understand torque/power as well as you thought you did.

So all production cars produce lift, and dont produce any downforce?

Pretty much, yes.

\/\/\/ lol

Pretty much, yes.



EDIT: LOL!!!