Does engine placement matter?

[Godlaus]

If each wheel on a car has a 25% weight load, and there's zero drivetrain loss (imagining here), does engine placement matter?

[bum]

Moment of inertia! Of course, matter. And why your think that each wheel has a 25% weight load? It's not always so.

[Matra et Alpine]

yes it matters.

Get a ruller and put a weight at each end of the ruler and try to rotate it quickly and feel the resistance caused by the "polar moment of inertia" of those weights. NOW bput the weights near the center and notice how it's easier. Cars with more centralised mass handle more predictably and controllable.

[dydzi]

If each wheel on a car has a 25% weight load, and there's zero drivetrain loss (imagining here), does engine placement matter?

not really. for example most cars have weight distribution about 60:40 between front and rear

[RacingManiac]

yes it matters.

Get a ruller and put a weight at each end of the ruler and try to rotate it quickly and feel the resistance caused by the "polar moment of inertia" of those weights. NOW bput the weights near the center and notice how it's easier. Cars with more centralised mass handle more predictably and controllable.

I think if a car has minimum polar moment of inertia it would respond well to input and change direction well, but not necessarily controllable because it might be more twitchy....

[Matra et Alpine]

It woudln't be "twitchy" unless the suspension geometry wasnt' dialed in.

Lower and centralised polar moment makes the setup easiest becaues it minimises the effects. What it does is make it less able to "flick" the car to reocver from problems. But if that's the case you just dial in a little less toe-in or alter caster to get the preferred handling.

More "twitchy" comes if you've weight away from the centres as that inertia imparts forces to over-ride the direction the wheels are pointing in.

THo' we may need to clarify what "twitchy" means as it differs with driving styles and conditions. "Twitchy" is good on loose forest surfaces In the same way that unstable flight makes for the best fighter palnes

[NSXType-R]

Of course it does. FF cars always seem to understeer in the corners because of the heavy weight in the front. FR cars (if tuned horribly or have no nannies or too much power) will have a tendancy to oversteer due to the power being directed to the rear and all the weight in the front. Also, have you seen any FR or RR F1 cars?

[Godlaus]

Of course it does. FF cars always seem to understeer in the corners because of the heavy weight in the front. FR cars (if tuned horribly or have no nannies or too much power) will have a tendancy to oversteer due to the power being directed to the rear and all the weight in the front. Also, have you seen any FR or RR F1 cars?

1. I was saying "if there was 25% weight load on each wheel". Apparently it's inertia, not weight, which is were Messes up.

2. F1 rules restrict them to MR

[NSXType-R]

But the load on each wheel will change unless if your car never moves. It is impossible to have exactly 25% weight load on each wheel when the car is constantly in motion.

[Matra et Alpine]

Also, have you seen any FR or RR F1 cars?

YES and 4WD. But just not in todays formula which mandates engine and drive position.

But the load on each wheel will change unless if your car never moves. It is impossible to have exactly 25% weight load on each wheel when the car is constantly in motion.

not when running steady state
Cornering, acceleration adn braking and THEN it's the suspensions job to assist. BUT in cornering you want the front/weight to be ideally blanced and in acceleration/braking you want left/right to be balanced. So in the both directions steady state you get close to equal corner weights. ANd in practice nobody gets EXACTLY 25% as close enough is good enough

[Alastor]

YES and 4WD. But just not in todays formula which mandates engine and drive position.

not when running steady state
Cornering, acceleration adn braking and THEN it's the suspensions job to assist. BUT in cornering you want the front/weight to be ideally blanced and in acceleration/braking you want left/right to be balanced. So in the both directions steady state you get close to equal corner weights. ANd in practice nobody gets EXACTLY 25% as close enough is good enough

I think your points about the weight/load distribution are valid, but on the track a race car is very much a transient problem. Of course it can be simplified as steady state model if you are assuming constant accelerations.

[Matra et Alpine]

I think your points about the weight/load distribution are valid, but on the track a race car is very much a transient problem. Of course it can be simplified as steady state model if you are assuming constant accelerations.

true, BUT the position of the mass is equally (sometimes more) important in the dynamic state and any decent setup will concetrate on that and a driver will judge the dynamic impact of any changes and request adjsutments accordingly. Just because we develop a starting position for setup based on static and determine how to repeat the setup by measuring the static doesn't mean the driver and engineer aren't focussed on the dynamic impact on the vehicle handling. It woudl be silly set up a car for purely stationeary reasons Try the ruler demonstration.

If the mass is at the extremities of the chassis it makes it much more difficult to control the dynamics with adjustments - if possible at all.
That's why F1 cars vary where they can locate ballast and conversely why BTCC used to mandate it went in the passenger seat area