Fwd...

[hotmaledotcom]

FF cars are usaully inferior, but has two exception though;the 320horse FWD Alfa Romeo 147 GTA and the integra hype R

[83-944]

"Any car with a front mounted engine will want to understeer"

Have you seen a Porsche 944? Front engine, rear transmission, 51/49 weight balance. Center of mass is about at the center of the car.

[Pavlo]

by changeing the sway bars you can tune your fwd to be really nice without any major understeer. And I read that too 2strokeblock that fwd cars are tuned to have understeer, i think thats dumb, how can you feel safer when your car does not want to go into a corner?

[-Jayson-]

on the drag strip i love my FWD car, 2.0 60FT is why. But on the street i spin the tires like crazy.

[Neutrino]

Originally Posted by 83-944

"Any car with a front mounted engine will want to understeer"

Have you seen a Porsche 944? Front engine, rear transmission, 51/49 weight balance. Center of mass is about at the center of the car.

2stroke is corect, a front mounted engine car will have a higher polar momentum and will help understeer

[Alastor187]

Originally Posted by Neutrino

2stroke is corect, a front mounted engine car will have a higher polar momentum and will help understeer

The higher polar moment of inertia will not effect the under-steer characteristics of the vehicle, but it will effect the steering responsiveness. It is still possible even with a front engine vehicle to achieve a near 50/50 weight distribution, so it possible to achieve near neutral-steer handling. With FWD under-steer is generated from the increase in front wheel slip angles as the vehicle accelerates.

[Neutrino]

Originally Posted by Alastor187

The higher polar moment of inertia will not effect the under-steer characteristics of the vehicle, but it will effect the steering responsiveness. It is still possible even with a front engine vehicle to achieve a near 50/50 weight distribution, so it possible to achieve near neutral-steer handling. With FWD under-steer is generated from the increase in front wheel slip angles as the vehicle accelerates.

Yeah it will its basic physics. The further forward the weight is the more polar momentum the car will have, meaning all that weight will resist turning. And what does it it mean when the car is resisting turning? Understeer.

This is why you want the most weight like the driver or the engine as close as posible to the rotational center of the car. This is wjy midengine designs are the best.

And the reason Most FWD cars tend to understeer, is for three reasons:
1. Most are econocars with understeer dialed in from the factory since its safer.
2. They have a lot of weight up front(engine, transmission, diff etc) causing a great polar momentum.
3. If you aplly power during a turn you can overwork the tires and lose grip, especially with an open diff.

However they can stil make good racers with good design and excelent suspension geometry setup.

[Alastor187]

Originally Posted by Neutrino

Yeah it will its basic physics. The further forward the weight is the more polar momentum the car will have, meaning all that weight will resist turning. And what does it it mean when the car is resisting turning? Understeer.

This is why you want the most weight like the driver or the engine as close as posible to the rotational center of the car. This is wjy midengine designs are the best..

I agree that a vehicle with a high inertia will resist acceleration, and with high polar inertia will resist rotation. So to achieve a given acceleration it will take more force for a vehicle with the high inertia compared to a vehicle with low inertia.

I don’t agree that this resists to rotation is the same characteristic as under-steer. For example take a vehicle with neutral steering traveling around a skidpad at a constant speed. If the vehicles speed is increased an increase in lateral force must be generated by both the front and rear tires to maintain the same radius of curvature. Since this vehicle has neutral-steering no change in steering input is required. Now if the polar moment of inertia is increased along with the speed, even more lateral force will be required than was needed previously. But the font and rear lateral forces increase proportionally and so the steering characteristics remain the same. Still the vehicle will not require any change in steering input.

In other words the PMoI effects the vehicles resists to rotations or responsiveness of the vehicle. The steering characteristics (under/over/neutral) are effected by load distribution, tire characteristics/setup, drive type (F/R/A WD).

See also:

http://autozine.kyul.net/technical_s...handling_4.htm
http://www.siu.edu/~ritzel/courses/3...ledynamics.htm
http://www.rqriley.com/suspensn.html

[Neutrino]

Originally Posted by Alastor187

I agree that a vehicle with a high inertia will resist acceleration, and with high polar inertia will resist rotation. So to achieve a given acceleration it will take more force for a vehicle with the high inertia compared to a vehicle with low inertia.

I don’t agree that this resists to rotation is the same characteristic as under-steer. For example take a vehicle with neutral steering traveling around a skidpad at a constant speed. If the vehicles speed is increased an increase in lateral force must be generated by both the front and rear tires to maintain the same radius of curvature. Since this vehicle has neutral-steering no change in steering input is required. Now if the polar moment of inertia is increased along with the speed, even more lateral force will be required than was needed previously. But the font and rear lateral forces increase proportionally and so the steering characteristics remain the same. Still the vehicle will not require any change in steering input.

In other words the PMoI effects the vehicles resists to rotations or responsiveness of the vehicle. The steering characteristics (under/over/neutral) are effected by load distribution, tire characteristics/setup, drive type (F/R/A WD).

See also:

http://autozine.kyul.net/technical_s...handling_4.htm
http://www.siu.edu/~ritzel/courses/3...ledynamics.htm
http://www.rqriley.com/suspensn.html

Well of course steps can be taken to compensate for a high polar momentum up front. And its not the only element to affect handling.

However it will still affect the car in a negative way, and the car will have higher natural tendency to understeer than a midengine car. So again its something that can be compensated for but it will always be better to start off with a superior mid engine platform that a front engine one.


Also its not that hard to make a car steer neutral around a skidpad since its a steady state corner. However in the real world corners varie infinitelly and its much harder to tune a car to steer neutrally in most of them. This is why according to Maserati engineers a rear bias is actually preferable to even the classic 50/50 distribution, and i would think a porche engineer would agree with him.