F1technical.net

I'm almost sure that the 3.2 v6 brera is 4x4, and the engine is not from the GTA, its a new one from the GM group
http://en.wikipedia.org/wiki/Alfa_Romeo_Brera

More than 300hp,in a road car, would be largely unusable but possible, ate least in a strait line.
It depends on the stiffness of the chassi, the suspencion geometry, the stering geometry, the dif, the power and torq curves and off course the tires grip avaiable.
Se the autodelta 147 gta, 3.7l v6 and +/-320hp, not so good handling and beaten the m3 on topgear.
I remenber seing vw corrado's with 400+ too.
This one for ex. Ax turbo +/-500hp

ds.raikkonen:

Trust me on this one Tom, the cars we were talking about cannot perform 360s...ill give you a snap of the 800, so that youre satisfied..

Give me 20 mins with that car and alot of tarmac, I'll get at least a 360 out of it, it doesn't need to be fast to spin it maddly out of control.

While getting ready of heaps of oversteer can be as easy as easing off the throttle if its power-on oversteer.. there's definately ways of dealing with understeer, though it depends on where you get it in the turn. I don't drive passenger cars to the limit.. usually anyway haha.. but there's ways of mitigating US.

Tom wrote:Give me 20 mins with that car and alot of tarmac, I'll get at least a 360 out of it, it doesn't need to be fast to spin it maddly out of control.

Come over to india then...

These can race with 2Litres NA and 350BHP like if it was nothing....
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But as someone already posted, it depends on suspension, tyres, chassis, etc. and I think it is not wise to put more that 300BHP in a road car.

Please, someone, make a list of 10 road standard cars with 300BHP++ and FWD...

No one replied? So there are not 10 300HP FWD cars!!!

Its just a matter of mass transference:

Mass Tranfs [Kg] = acceleration [G] * gravity center height [m] * Weight [N] / longitudinal axe distance [m]

So, for example a common FWD car that accelerates 0-100KMH in 8 secs, this means 0.35G

MT = 0.35G * 0.4m * 13000N / 4m = 460KG

Do you think a car can get grip and traction with a 460KG "upforce"?

You are correct Belatti, the numbers do not lie. Because of weight transfer, a RWD car maintains better traction under acceleration. That's why you don't see F1 cars with FWD.
But when comparing RWD to FWD, it's like comparing apples to oranges, because each type of design fills different market needs. A FWD car is less expensive to produce compared to an equivalent RWD, because a FWD does not need a driveshaft, as well the powertrain packaging is much more compact.
So at the lower end of the economics scale, FWD is more appealing. But as the weight and power goes up, there comes a time when RWD starts to make more sense. Especially when you heap on powerful engines.

One thing I still don't get is why FWD are (considered) better on the snow...
one reason is because the have more weight on the front wheels, so they have more grip under very light acceleration, then?

Yes, plus they don't fishtail making them easier to control.

DaveKillens wrote:But when comparing RWD to FWD, it's like comparing apples to oranges, because each type of design fills different market needs. A FWD car is less expensive to produce compared to an equivalent RWD, because a FWD does not need a driveshaft, as well the powertrain packaging is much more compact.
So at the lower end of the economics scale, FWD is more appealing. But as the weight and power goes up, there comes a time when RWD starts to make more sense. Especially when you heap on powerful engines.

I would extend your reasoning on the "each type of design fills different market needs" statement and disagree a little, if you allow me.
The FWD configuration has a basic stability advantage that comes from the traction being applied in front of the CG of the vehicle. Is like pulling or pushing a shopping trolley: when you push it, you must hold it usually with both hands to keep it going on the desired direction. Otherwise, it is basically unstable and will steer away from control. That's the case of RWD vehicles: that configuration makes them basically unstable. When you pull a shopping trolley, you can do it with one single hand and it will follow your direction of motion. A similar situation comes with other forces applied in a vehicle: if they are applied behind the CG they will make for an unstable vehicle. That was the case with the Auto-Union record vehicle that killed Bernd Rosenmeyer: the aerodynamic forces were applied behind the CG, making the car impossible to control at high speeds and were the reason behind the fatal crash.
That's why a FWD is a better handling car in all non-ideal conditions: bad roads, gravel, unexperienced drivers... that's also why when rally cars don't have 4WD, they are usually FWD: asphalt excepted, they are fastest in every other conditions. And the less grip the road has, faster they are than a RWD.
You can see that also in the WTCC: the BMW's are usually the best cars in dry asphalt (although in very twisty circuits I'm not sure). That's because of superior traction when accelerating (because of the weight transfers and because of the grip circle of the wheels has to deal only with traction or steering, but not both). But when it rains, the advantage goes over to the FWD.
Also, I don't think it is factual that the FWD is less expensive: it demands a more complex packaging of the transmission and the use of joints to transmit power and allow wheel steering. The problem is that when you deal with high torque on the wheels, the friction circle problem above gets way more complicated and you get handling issues combining high torque and steering: torque-induced steering and heavier and less precise steering if you use big tyres to handle the torque.

Just an example, notorious gangsters in France after the war, used the Citroën 11CV, the first FWD produced in big series, to escape the police, that has big american RWD V8 cars. In the twisty roads of France back then, the FWD gave them a huge advantage in car chases. Eventually, the french police ended up buying Citroëns also, to balance the score... http://fr.wikipedia.org/wiki/Gang_des_Traction_Avant

Very well explained Dumrick.

One more advantage of FWD is under braking the CoG of the car shifts forwards, with all the weight over the front wheels there is also extra grip for braking meaning you stop quicker. (however you have to be a bit careful as the back can easily swing round.)

Also under engine braking FWD have the advantage for the same reason. However if you manage to lock the wheels under engine braking (I've done it on gravel) then you get catastrophic understeer.

In reply to ds.raikkonen's post from a few weeks back, I'd love to goto India to arse about in your car, but it's not really economically viable.

I agree with your post drumrick, well said. But I need to explain that I was referring to the different types in a production environment, where most cars go to, for everyday, family driving. In most situations for relaxed (family) driving, vehicle stability and weight transfer issues are no bother. It's when the performance envelope is pushed do these issues arise.
The first great FWD car, the immortal Mini, designed by the great Sir Alexander Issigonis was a marvel of packaging efficiency. It was basically two boxes, the front box containing the front end, wheels, and powerplant, while the larger box contained the passenger compartment. To this day, most FWD cars still follow this packaging arraingement.

Most cars in the BTTC are FWD... They do ok.. Its all about your Diff.

I've got just under 300 bhp in my FWD car, yes 1st and 2nd are limited in power but after that its all good. Besides its not the bhp that gives you wheel spin its the torque. My mappings are all the low torque versions and all mods are to increase top end bhp.

My next mot is quaife LSD like the RS focus had as standard. Then you can put the power down earlier exiting corners due to driving the loaded wheel and not the unloaded wheel. I've read reviews on the new megan F1 and they said the fwd actually tightens to the line when applying power.

Just watch the british touring cars then you'll see FWD cars beating their RWD counterparts easy out on track together.

I thought that RWD was weight penalised in BTCC..........

It looks like the answer to the thread question is; "not very many HP's" are the "practical" limit for FWD. Even if 300bhp can be handled, it still isn't much (relatively )

Lack of horsepower doesn't mean that FWD is slow on give and take roads, where most cars aren't traction limited. In fact the mini was a great example where handling could triumph over power (anyone watched Mini's & Ford Galaxies racing ).

Truthfully, FWD could handle a lot more horsepower (if you are seeking top speed) - the limitation would be that you couldn't use it all lower down the speed range.

What if you figure downforce into this discussion - then a FWD car could usefully use more power once the downforce devices are doing some work. Even then; RWD or AWD could use MORE power in the same situations.

Is this question really about performance rather than HP? And are we asking about performance in the twisties or in a straight line?

Did we mention FWD torque steer?


By the way here in holland there are a few nutters with mazda 323s if I'm not mistaken those cars have high-revving 2.5 litre V6 engines, alledgedly one guy put a turbo on it and got 600+ HP with FWD! Idiot, I can imagine what's left of his gearbox and engine; nothing!