four wheel drift.....
I just found this little article interesting, and I do believe this is the right place to post it. Mostly applies to rear wheel drive cars, but interesting none the less.
The true four-wheel drift as used in racing is a different technique from "drifting," which is more along the lines of over-exuberant, hyper-stylized powersliding.
To discuss true four-wheel drifting in the racing context, we have to understand the definition of slip angle. Slip angle is the angle between the direction a wheel is pointing and the direction that the wheel is actually traveling on the ground. A car moving straight ahead has a 0-degree slip angle on each wheel; a car that is sliding sideways has a 90-degree slip angle.
Obviously, tires do not have much grip with huge slip angles, but it turns out that a small slip angle is actually the peak of highest grip when cornering. Some years ago, racecar drivers were going around road course with insane 8- to 10-degree slip angles. Modern low-profile tires have very small optimal slip angles (only a few degrees) and modern F1 cars, with their extreme downforce, typically have no more than 1-degree slip angle.
We need to learn and understand the concepts behind weight transfer. To simply put it, the center of gravity of a car is higher than the contact patches. So, for example, when you accelerate the car wants to lean backwards shifting weight to the rear (and increasing grip on the back tires). This is one of the well-known weaknesses of a front-wheel drive performance car.
When you are going around a corner, it's ideal to have the grip maximized everywhere. Since all four tires need to be a certain slip angle, you can see that your car should not be pointing directly down your driving line but slightly inward (inward yaw).
You will be losing a bit of speed due to tire friction, wind resistance, etc. so you need to keep adding energy (throttle) to the system. However, by adding throttle, the rears are carrying a heavier load than before because you are both cornering and accelerating simultaneously. On a rear-wheel drive car, the car would begin to oversteer since the rear slip angle becomes larger than the front.
You would expect to spin out but, luckily, you have weight transfer on your side. Weight is transferring from the front to rear under acceleration thereby increasing the total grip at the rear and decreasing the grip at the front. The balance point between all these factors is, in a well set-up rear-wheel drive car, a small stable region in which you go through the turn at the fastest allowable speed. Since it is an equilibrium state, you can continue this almost indefinitely. This works well even on modestly powered cars (like Miatas).
A front-wheel drive car does not work the same way. Clearly, you can introduce rear slip by trail braking, which transfers weight from the rear to the front. However, application of throttle always increases the demand on the front tires and simultaneously moves weight, and grip, away from the front wheels thereby resulting in understeer. When you understeer, you begin to lose yaw angle, and the whole system eventually falls apart.
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2003 Accent GT - F&R strut bars, rear PSC sway bar, Falken Azenis rubber, TWM short shifter
1998 Accent L - <b>TURBO</b> - scoupe manifold and T15 turbo pushing 5PSI, 2.0L injectors, beta MAF, beta TB, 2 1/4 exhaust(no cat), ksports, slotted rotors w/ SS lines - much more!
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Good post! Someone make sticky please!
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