Fongu

Another thing to consider is the locating the engine close to the drive wheels. Rear-mid engine cars have shorter driveshafts (less mass in the drivetrain) to the rear wheels. This also helps packaging of the car since on low cars, the driveshaft doesn't have to cut through the passenger cabin. The rear-mid engine placement is required for single seat race cars (CART, F1) to make a clean chassis.

pierceman

, but what happens when that mass is in motion, then you slam on the brakes. 50-50 only works while the car is at a standstill. in motion everything changes, or am I way off here?

RACER

Typically, when you brake, a large majority of weight transfers from the rear to the front of the car. On a race car you can adjust brake bias(amount of braking in front vs. rear) A race car has two master cylinders. You can also adjust bias by having a larger or smaller piston in the master cylinder or larger or smaller diameter brake line. Typically on a fine tuned race car, there is 60 percent bias to the front and 40 percent to the rear(this is a rough estimate) A Indy car can go from 100 mph to a complete stop in exactly 1 second. yes 1 second. One advantage of having the rear mid engine is that you can move some brake bias to the rear of the car(thats one reason they achieve the 60 40 front and rear bias) more weight on the rear vs. front or front mid mounted engine. Keep in mind, when you accelerate, weight transfers from front to rear(putting downforce on the drive wheels), therfore the mid engine helps to achieve a nice balance(allows you to hammer it out of a corner)

ellisnc

You ever wonder why Porsche gets raves about brakes on the 911 all the time? It's because they can put large discs and calipers at each wheel and actually use them under braking because of the weight distribution of the car.

Same thing in getting drives out of corners... ever been behind a good driver in one at a race track? I wouldn't say they're as good as 4wd for corner exit speed, but they're pretty darn good!

Patdeisa

Everyone here's pretty much said it- lower moment of inertia, braking, acceleration, and proximity to drive wheels.

When racing, you want 50/50 during turning and braking, while acceleration is better for a rear-wheel drive car when the weight's more in back. With a mid-engine car, you can get better acceleration and braking due to weight shifting, at the small cost of turning under neither. Let's say it's typically 40/60 distribution. Under acceleration, you might be able to get 30/70 which provides better traction than 40/60, giving good launches. Under braking, you might get 50/50, which is optimum to have the weight distributed to each wheel for maximum braking. If you're turning under braking, a mid-engine car can get about the best possible weight distribution (50/50 under brake and turn). Turning under accleration gives a car good traction for acceleration while keeping understeer down. All this gives for good racing potential.

JonBoy

[QUOTE]Originally posted by ellisnc
You ever wonder why Porsche gets raves about brakes on the 911 all the time?

suvh8r

Look at the mustang for the other extreme. A car that is very nose heavy has trouble transferring weight to the rear wheels which hinders traction.

Penforhire

The older 911's were known as "tail-happy" because of what happens with rear bias in fast transitions. If you want a balanced car, as much as possible, you want 50-50 because anything else helps somewhere and hurts somewhere else. You could argue that braking into turns and applying power out of them are more important in road racing, where Porsche does excell partly from the rear bias.

tafka TMB

Longitudinal mid engine is better (like the new VW roadster and most of the top end mid engined cars). If you want to do it on the cheap just grab a transverse FWD package and swap it to the rear (Lotus Elise, Toyota MR2, Fiat X19, MGF, Lancia Scorpion, etc).

Ferrari went from transverse mid engined in the 308 GTB to the 360 Modena (and also picked up a bit of underfloor venturi space at the same time).

Have a look at the Lamborghini Countach and the Ferrari Boxer/Testarossa as 2 different ways of getting a longitudinal engine and a gearbox within the wheelbase of a car.

Also watch Centre of Gravity and Centre of Aerodynamic Pressure (load?) and drastic changes of front wheel load if your mid or rear engined car has it's fuel tank way out in the nose. Early Porsche 911 had lead weights in the nose until they sorted things out a bit better.

I'd rather have a well balanced front engined car with high polar moments of inertia than a poorly set up "superior" twitchy mid engined car (although I do still love the rally car version of the Lancia Stratos).

Ultimately a properly designed mid engined car is the go, there is still a lot of crap out there that claims to be "superior" because they are mid engined.

nodisguise

Anyone remember that thread about article that guy wrote in that magazine (heh)? He talked about the superiority of a rear-engine setup in a race car. My search couldn't turn it up, but if anyone has it bookmarked or anything, they should share; it was pretty interesting.