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Old 08-10-2004, 06:52 PM   #16
drunken monkey
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Re: nsx and mid engine question

it's why the 911 works well.
(please excuse the oversimplified following statement...)
at rest, the weight distribution is well, a bit crazy.
however,
while it is in motion, the effective 'centre' is pushed forwards towards the centre of the car and as long as you keep accelerating, you're fine; the car is super sharp cos the rear end is absolutely pinned to the road by the engine and the front is pinned to the road by the turning effect.
it's when you decelerate or when you go over a bad camber (and the weight shifts vertically and hence cause the rear or nose to either suddenly get v.heavy or v.light) that it gets twitchy.

but that's more or less been fixed by very clever software.

put it this way.
a front engined car is easy to understand and easy to balance because of weight at the front, drive to the rear.
slip of the rear tyres is more or less totally in your hands (or should that be feet?)

a mid engined car is slightly more difficult to control because everything happens faster (you have less room for error but the rewards are 'greater').
turn-in, breaking traction etc etc, is more 'snappy'.
BUT
everything is sharper, more direct, not quite as adjustable as a front engine/rear drive but you can drive closer and longer on/near the limit.

now for the totally screwed up 911.
weight at the rear means that the front is very light.
this means very sharp turn-in
BUT
v. easy to kick the rear out.
however, clever suspension and very careful tyre choice can reduce this (assuming road is flat and perfect tarmac...)
unless you're going at speed in which case the nose gains weight and everything settles down more evenly.
basically, it's as if the faster you go, the better it drives.
but as i said before, that all changes when you want to move whilst slowing down....
in the good old days, braking and turning would've been best done with a prayer to your god/s.

it's been said that the 911 is a car that you really have to learn to drive,
mainly because its handling qualities (due to the engine placement) is almost 'not natural'
and as a result,
it takes a lot of getting used to.
one of my uncle's colleagues in lisbon has wrecked more than one 911 in his years....

anyway.
i must apologise once again for the over simplified descriptions but hopefully you get the idea.
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Old 09-28-2004, 10:06 AM   #17
deusexmachina72
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mid engine weight distrib

while i'm no expert, i've heard the subject of weight distribution discussed a lot and hopefully i don't butcher it too badly here:

when accelerating directly forward, the weight of the car "shifts to the rear" because of the inertia of sitting in one place. imagine two overlaid cars, one sitting still (the weight) and the other (the body) moving in one direction. where is the weight relative to the body? behind.

for this reason (among many others), sports cars are generally RWD, because the load will increase on the rear tires while accelerating (and we all like to do that). increasing the load on the rear tires will give them better traction (in general) because the coefficient of friction is a one-to-one correlation with the downward force (it gets stickier, which is what we want).

even in front-engined cars, 50/50 weight distribution (though i think infiniti claims 52/48 is better because of the acceleration-induced shift?) isn't too difficult to achieve. nissan's 240sx and mazda's rx-7 are both wonderful handling cars with good weight balance. in a front-wheel-drive car, like most hondas, the weight tends more to be about 60/40 front/rear. this is generally also to increase the weight over the driven wheels.

one reason MR cars are appealing is because FR cars need to get the power from the front of the car to the back, causing a little more drivetrain loss (more moving parts = more power lost as heat). think of an MR car as an FF car where the engine and driven wheels were pushed to the back of the car.

unlike an RR porsche, where the weight is actually behind the rear axle, an MR car's engine sits more or less between the four wheels. so fewer/shorter parts are required to get the power to the driven wheels from the engine, giving MR cars FF-like drivetrain efficiency while maintaining RWD dynamics.

as far as turning, there is a term 'polar moment of inertia.' my layman's understanding of this is that you want as much weight as possible as close to the center of the car and as low as possible. this is one reason sports cars are generally lower than say, an SUV (aerodynamics, etc. are other reasons).

take the following with a grain of salt, as this is purely an illustration i just thought up: imagine a hammer; the handle is light but the head is heavy. hold the handle perpendicular to the ground and rotate it 90 degrees to either side. now let's make it 50/50 weight balanced. attach another hammer, upside down, to the end of the first hammer's handle. now you have a dumbbell, basically. move it through the same 180 degrees back and forth. now let's move the weight to the pivot point. attach the heads of the hammers together. rotating them is much much easier than before, right?

hope this was of some help,
-dxm72
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Old 07-20-2005, 03:59 AM   #18
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Re: nsx and mid engine question

the nsx is based on the f1 car and driver feedback from areyton senna. The mid engine car does handle better due the weight distribution because the weight is more towards the center of the car.....that is why you don't see f1 cars with engines in the front......yes a front engine car can be set up to handle great but its not going to compare to a mid engine car......but remember driver skills are important.... nsxprime.com
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