Given the following instantaneous parameters and constants... Known: d = air density = 1.24 Cr = rolling resistance coeffecient = 0.015 FA = frontal area = 1.48 Cd = drag coefficient = 0.29F G = gravity (mps2) = 9.80665 pi = 3.1415926 m = vehicle mass (Kg) = 1542 DL = drivetrain loss = .2 V = velocity (m/s) A = acceleration (m/s/s) Unknown: F = vehicle force (KgMps2) T = Torque (KgM) HP = horsepower Unknown, but can be found if needed: Tire radius Current gear and gear ratio ... what would be an equation that would let me estimate instantaneous engine torque (or HP) at the wheels? So far (I think) I have worked out these terms: rollDrag = G * Cr * m airDrag = .5 * Cd * FA * d * V * V F = (m * A) + airDrag + rollDrag Assuming that ^ is correct, this is where I'm stuck. Any help is greatly appreciated. I'm sure I'm just over-thinking it or something, but I've drawn a blank and have been spinning my wheels (so to speak) on this for a couple of days now. Thanks in advance!