AWD Drifting Tech[nique] - Curteousy of Drifting.com

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D1champ

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AWD Drifting Tech[nique] - A Difinitive Guide

Step 1 - finding that every single AWD system in the world is completely different from any other system...

I drifted my AWD 91 Legacy Turbo for years, and it's no easy thing (IMO, harder than the RWD kind). My AWD was a viscous coupling type and not necessarily front-biased, there were things that I could do to hold the drift since the rear wheels were pretty much always getting power. However, in a front-biased system like the 4G63T's or CR-V’s, your rears will only get power when the fronts are slipping, as I'd imagine you know by now.

Part of All-wheel-drifting is exactly what the name says: all of the wheels drift. If you watch AWD rally cars you don't usually see the front wheels following the "best line" on the course like RWD cars do (for the most part). A lot of the time the midpoint of an AWD car will be following the best line but the fronts and rears will all be spinning and the steering is toggled back and fourth between almost aimed straight and almost fully counter-steered. This coupled with the insanely high rates of entrance speed helps the car to stay sliding through the turn rather than grinding to a halt on the gravel, but high entry speeds also help keep the car sliding on pavement as well. Most of the time you won’t need to give as much steering input as you feel that you should after the initial “shock” of input to transfer the weight - sometimes only a third to half of a full counter-steer will be plenty to keep you sliding and a full steer will be too much and will whip you back around to the other side.

Although AWD's purpose is to prevent cars from losing traction, you can really use it to your advantage to keep the wheels spinning. If you recall the "traction circle" that you learned in performance-driving kindergarten, you'll remember that the East and West directions represent steering right and left and the North and South directions represent acceleration and braking (respectively). Now, to make a car lose traction, the load on the tires must exceed their ability in any one of those directions or as a combination of two (or more, but that's a bit more advanced).

Let's consider 2 cars with the same specifications, car A having RWD and car B having AWD. When accelerating from a standstill, car A will be sending 100% of the power to the rear wheels only. Granted that car A has the ability to load the tires beyond their capacity, it will break the traction circle and spin the rear wheels. If car B were to send 100% of its power to the driveline, it would momentarily go 100% to the front wheels (in the TSi's case) and break the traction circle causing wheel slippage. The slip sensor will detect this and tell the transmission to take up to 50% from the front and send it to the rear. (NOTE: The initial driving wheels and amount of power distribution will always depend on the AWD system in question) When it does this, the load on the front tires will move to inside the traction circle and the rear wheels' traction circle will look exactly like the front's (ignoring weight and transfer). Simple, right?

Now imagine when a car is going around a turn and power is being applied while there is a constant lateral load on the traction circles of all tires on both cars, during a left turn for example (meaning that the work done on the tires is along the East-West line on the West side). While cornering at half of the capacity of the tires, car A can apply enough power to exceed the traction circle of the rear wheels (the work done by the tires is outside of the traction circle on the upper left side). Meanwhile, the front tires will stay at their half-capacity of lateral load without ever knowing what is happening to the rears. Once a driver counter steers, the direction of lateral load on the front tires is reversed (to the right in a left-turn drift) and they are now working to prevent the car from going off of the track to the left - there's a split second in a feint where the rear is sliding and the fronts are pointed straight just after the body roll has passed neutral. In our left turn, if the driver does a power-over and applies just enough power for the rears to break traction, he can keep the work asked of the tires just beyond the traction circle and maintain control of it, but if he applies too much power the tires will be overwhelmed and the driver will lose control -- this is why higher-powered drift cars need to have the power modulated in order to keep control and keep from spinning while lower power cars can be floored and stay in control.

Ok, the same left turn example with car B and AWD. If the driver applies power in a turn, it may cause the front wheels to exceed the traction circle and transfer power to the rears, which in turn brings both front and rear back within the load limits of the tires, since half of the power is going to the front wheels and half to the back wheels. This would essentially be like driving car A in the same manner but with half the power at the driver's disposal (65hp for a Nissan 240SX, probably not enough to exceed even the stock tires). Even if your TSi has 200hp to the wheels, each set of wheels will see only half of that during a drift, and to get it to slide you either have to be turning harder or going faster to have the work exceed the capabilities of the tires (or use less-sticky tires).

Unless you have tons of power, All-Wheel Drifting techniques require knowledge of vehicle dynamics, your drivetrain, your AWD system, and your traction circle (the best drivers are subliminally imagining all 4 traction circles of all 4 wheels all at the same time all the time). I find that the majority of the time all wheel drifting is spent trying to find ways to "trick" the computer into giving more power to the rear wheels than they can handle. Rocking the steering wheel between neutral and counter-steered one direction is a pretty good way to keep constant load on the outside tires and to find the best steering angle.

You may also want to try doing a moment of very hard braking during the moment of the feint that has the front wheels pointed straight just before turn-in, and then applying maximum power through the apex. Try also varying this so that you don't feint but do sharp braking before the turn-in at a high enough rate of speed that the rear and will swing out, and then try a small steering angle while applying maximum power.

Try getting up some speed (more than you think necessary) and cutting the wheel to one side and then counter steering with favor towards a small steering angle.

You may be able to trick the AWD by pulsing the E-brake but not yanking it when you think the car is close to it’s lateral traction limit when approaching the apex. If you can, try to replicate the effect that rear-only ABS would have but make sure that you fully release before each pull - if your AWD computer is slow enough, it may see the braking moments as representing the “wheels that grip” and send power to those wheels with the power arriving at the rear axle just as you are releasing the brake pressure. Try this technique with the foot brake as well at various times through the turn, both with and without pressing the gas.

I found that most of the operations in drifting an AWD car were pretty full on: full on the gas, full on the brake, etc. In racing they say that you should use smooth motions as to not upset the car's tenuous grip at the limit of traction, but in AWD drifting sometimes you will need to wrestle the car out of traction. Most of the time you will find that unsettling the car will be your best way to break traction while your manipulation of the AWD system will be your best way to maintain control.

MOST IMPORTANTLY: BE SAFE!!! Don’t practice where you may run into something or someone or even where road surfaces are beyond an accepted level of safety. Don’t try and take on more than you feel confident with – drifting may be to-the-limit extreme, but that does not mean being stupid.

Hope this helps and let us know how you make out!

-MR

Thread: http://www.drifting.com/forums/showthread.php?s=&threadid=6479
 
Thanks a bunch needed that little reading to help me understand some reaction of my WRX . Next summer ill get bald tires to practice ... Thanks again !
 
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