Why a Porsche spins, a Corvette pushes, and a Lamborhini wants to kill you.

Posted on February 13, 2013

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Why a Porsche spins, a Corvette pushes, and Lamborghini wants to kill you.

By: Rob Oakman

If you, like me, are a fan of Top Gear, than you have heard Jeremy Clarkson talk about how mid engine cars like the Lamborghinis try to kill you, that Porsches have the engine in the wrong place which makes them rubbish and want to spin all the time, and that the Corvette is, well, when he isn’t trashing everything that the ‘vette is and is not you might hear him mention how the car wants to push like a lorry (That’s “Truck” in proper non-British English) unless you get on the gas. Why do these three cars handle so differently?

First as a note. No, they don’t have a 50/50 weight distribution. I have to break it to you that no well balanced car has a 50/50 weight distribution. In truth race cars and proper sports cars have a rear weight bias closer to 40/60. This is because a 50/50 balanced car will push badly. All of these cars do have a factory push, but no where near the extent a poor weight balance would have. Weight distribution itself isn’t the only factor in handling which is a complex issue on the whole, but we can narrow it down pretty simply.

When you try to get through a corner at speed you don’t drive through with your front and rear tires tracking in line with each other. You are actually driving a bit sideways. This has to do with the friction generated by the spinning tires as well as weight jacking, gyroscopic forces and technical things related to centripetal force that Newton would have a field day with. But to spare us many lectures in physics lets just say that to do this the chassis has to “Rotate”. That is it literally has to spin on a point between the wheels. The faster you can rotate the car while still in control the faster the car will change direction which means the faster you get into a corner. There are two very important things to consider. One is how far from the center the mass is, and the other is how the mass is concentrated on each end.

Let’s look at how far the mass is in relation to the center. If you have ever watched a skater perform – and who hasn’t watched figure skating, right? – you will notice that they start a spin with their arms far out, then, as they bring them in tighter to their body, the spin begins to accelerate. What’s happening isn’t that they have some turbo system hidden up their bums; it’s that by bringing their arms in close they bring more of their mass closer to their center of gravity. This makes it easier for their body to spin. They aren’t actually adding any new energy as they accelerate like the bum turbo might, it’s just that it is easier to rotate with the mass close to the center. When their arms are out, the weight has further to travel for each rotation, which takes more energy. When they move their arms closer they are travelling a shorter distance for each rotation, so as they bring them in the skater spins faster and faster until they’re arms can’t get any closer. This is true for anything that is trying to rotate.

Porsche 911 GT2 Cutaway

Porsche 911 GT2 Cutaway

All three of the example cars have the weight distributed with a rear bias, but only one of them has the weight close to the center. The Porsche has the engine, the single heaviest component bolted onto a chassis, way out behind the rear wheels. This means that the German engineers (The guys that designed a car that looks like a frog) have to put all the weight they can forward of the center to balance the chassis properly. That’s why the radiators are ahead of the front wheels. It’s a stupid and vulnerable location, but they need to get as much weight up front as they can. This means that the mass is way outside the center of the car slowing down how fast it can rotate. Then the concentrated mass of the engine wants to keep rotating resulting the the snap loose condition they are famous for when you get to the throttle.

Corvette Chassis Cutaway

Corvette Chassis Cutaway

The Corvette has the same issue except that the engine is up front. The ‘vette’s engine isn’t ahead of the front wheels like the Porsche’s engine is behind the rear, but it is bigger and heavier. Also, because the engine is ahead of the driver’s compartment, everything has to be pushed back far enough that the pedals and the driver’s feet will fit in the foot well. This pushes the driver back away from the center as well as the heavy safety-cell that protects them. This helps balance but again, this slows down how fast you can rotate.

The Corvette acts similar to the Porsche on entry but, without the lump over the rear wheels, it doesn’t have the snap at the end. It wants to push throughout the corner. The front engine layout is considered the most user friendly because of this. The only way you get a stock ‘vette to look loose is to trail brake hard and deep into the corner which pushes the front end into the ground and lightens the rear, then jump on the throttle as soon as possible and power through the corner.

Lamborghini Chassis Cutaway

Lamborghini Chassis Cutaway

The Lamborghini has the engine right at the center of the car (Hence mid engine) with the transmission (or transaxle) out towards the rear but not hanging over the wheels. This allows the driver’s compartment to be pushed right up against the front of the engine. Because all of the heaviest pieces are in the middle you don’t have to put any smaller bits on the ends to balance the car. That’s why the radiators, battery, and accessories are all near the middle as well. Everything is concentrated close to the center. That’s also why there is so little car ahead and behind the tires in a mid engine car. There is no reason to extend the body out that far except for aerodynamic purposes. Because of this concentration of mass the Lamborghini can rotate very quickly indeed, so quickly that it can be very hard to control on the edge when you are pushing for speed. The Porsche and Corvette will rotate relatively slowly giving you time to catch the car when it loses traction. The Lamborghini will snap loose on you and spin so fast you’ll think you’re on the tea-cups ride with a bunch of jerk teenagers turning the wheel.

Right?!?!

Am I right?!?!

How they make a baby Porsche

How to make a baby Porsche

Stock Porsches and the Corvettes are fairly predictable cars. When you push them they tend to react the same way every time. The Porsche will push into the corner unless you trail brake and then very predictably it will try to spin out, so you can act accordingly. The Corvette will push like a truck the whole time unless you jump on the throttle and make it loose. Even when it does get away from you both it and the Porsche rotate fairly slowly so you have some time to react (This is relative by the way so calm down Porsche and Corvette guys). It’s like a margin of safety built into the cars.

The Lamborghini doesn’t have these margins. Because all the mass is near its center of balance what happens is that when you get to the point that you do loose traction it will snap loose and spin before you can wet yourself. The factory settings do tend to make it push a bit on entry but it rotates so fast you probably won’t catch it when it starts around. Mid-engine cars are very unpredictable in this way. Even for an experienced driver they are very difficult to run on the edge because they give so little warning before they go. Drive into a corner just a bit harder than before expecting to look like a pro and suddenly the front end digs in and around you go. If you’re really lucky you might hit something hard enough that you won’t survive and have to deal with the insurance people after the wreck.

So if you are looking for a good track car for yourself then be honest about your abilities. If you’re not particularly skilled behind the wheel then something front engine like the Corvette is best because it will push consistently, just be easy on the throttle. The Porsche is more temperamental because of the pendulum effect but is also good, just be ready for the back end to swing out around mid corner. If you are feeling suicidal or you just like lying to yourself about your skill level than anything mid-engine should suit you just fine. But remember to fill out your will first. Oh, and be a dear and leave me something nice.

If you have any questions or comments feel free to send them along below and follow OakmanOnRacing.

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