# How to Calculate Engine Torque from Wheel Torque?

Not sure if this is the right place to post - so feel free to tell me to go away :)

Im trying to understand how I can use wheel torque curves to estimate the engine torque vs engine rpm relationship.

My understanding is that the following equation relates wheel torque $T_w$ to engine torque $T_e$ where $i_g$ and $i_a$ are the gear and final drive ratio respectively:

$T_w = T_e \cdot i_g \cdot i_a$

Then taking a curve like from http://rototest-research.eu/popup/performancegraphs.php?ChartsID=715 select the [Kw / Nm] option. Can I use the above equation to produce a reasonable engine torque curve estimate?

The graphs from that particular site are presented as follows, "The sum of the torques measured at each wheel hub is presented as total drive wheel torque divided by the total transmission reduction (i.e. the gear ratio times the final drive ratio)"

Furthermore, the chosen gear ratio is always the gear that is closest to 1:1, therefore $i_g$ and $i_a$ are known.