AEM 30-6905 Universal Programmable EMS-4 - Manual (Page 233)

Page 233 of 279 EMS-4 Install and Tuning Guide_Rev 1.6
Traction Control
Most OEM and available aftermarket traction control systems use the differential of a front and
rear wheel speed sensor to determine traction conditions. While this is great way to control
wheel slippage, it does not address all wheel drive (AWD) vehicles as all wheels spin at the
same rate. AWD manufacturers do not use traction control on their vehicles as power
distributing to four wheels is typically sufficient. However, AWD racing in snow, dirt, and gravel
like WRC and Pike's Peak is a whole different story.
The AEM EMS traction control is the solution for all types of vehicles including 2WD and AWD.
The EMS uses "acceleration" as the basis for traction control as all applications have an engine
speed and vehicle speed input. And because most vehicles do not come standard with wheel
speed sensors, this is the obvious choice for plug n' play traction control.
Under optimum traction conditions with no wheel slippage, the maximum rate of acceleration
can be determined by:

Engine performance

Transmission gear ratios

Final drive ratio

Drive train losses

Tire size and tread pattern

Vehicle gross weight
If a loss of traction occurs during hard vehicle acceleration, the acceleration rate will exceed the
rate possible under optimum conditions.
Theory of Operation
The EMS uses several different methods to calculate acceleration. The following are definitions
for each calculation method:
A. Option TC Timebase OFF:
1. Option TC Speed/Time ON:
2. Option TC Speed/Time OFF: