Theoretically this should be true:
If horsepower is 'x' at the flywheel, when it is sent through each gear it should change proportionately to the gear being used correct? For example, EVO's gears are 2.93:1 (1st), 1.95:1 (2nd), 1.41:1 (3rd), 1.03:1 (4th), .72:1 (5th), with an axel ratio of 4.53. Is there some sort of formula to determine to horsepower variance between gears. Dyno pulls are usually done in 2nd gear correct, why? Is that the 'fastest' gear? Anyone got answers?

 

dyno runs are usually done with 3rd gear and i think it's also the same gear that produces the most power.

 

Well the engine is under proper load to get full boost and not be uta ger too fast.

 

dyno pulls are done at 4th gear because that is a 1:1 gearing (or direct drive). Else you have gearing multiplication and such going on.

To measure gearing you multiply to solve for an over all gear so 2.93 * 4.53 = 13.27 overall gearing in first.

Remember as Torque (though not what we are talking about here) is multiplied spead is reduced because the engine is spinning more times to produce wheel spin, thus a gear reduction in gears 1-3 where 4th is the theoretical direct drive and 5th is the overdrive gear where engine speed is slower than tires for increased ride noise reduction and fuel efficiency.

 

Guru Del >>>>>> Good post. So if hp is 271 at the flywheel, what would the equation look like for 1st gear, from 271 to hp at the wheels? 271 * 2.93(1st gear) * 4.53 (axel ratio) - % lost through drivetrain = whp ? Is that correct? Would this give the theoretical hp at the wheels? Thanks

 

i know for a fact that this is how you would calculate torque to the wheels so i assume it is the same

Torque* (2.93*4.53) - % loss = torque at the wheels in first gear.

 

Do you know how much is lost through the drivetrain, and the differential? 15%? something like that i think. Thanks for all the info by the way. helped a lot.

 

honestly i have no idea as i havent looked into loss on the evo, i only drive a regular lancer but I am smack dab in the middle of a transmission class that is talking about torque and how it is calculated at the wheels.

next month we are talking power and such so i will know then

 

i think loss through drivetrain is closer to 20% do to AWD and its less effecient then the AWD on subies.

 

Well, let's see if I can tackle this one in a way that will be clear.

First of all, the wheel horsepower on a dyno can only be used for rough calculations of crank horsepower if you are using 1:1 gear ratio. Otherwise, you need to take the gearing multipliers into effect which have not quite been properly quoted on here. I won't get into that.

Second, no one has really proved what drivetrain losses are, but I think the best speculation by many guys I've spoken with is that it isn't a fixed value. At stock power levels, it may be near 20% but I seriously doubt you are losing 200 hp on a 1000 crank hp drag EVO.

Regarding what "horsepower" your car has in different gears, I think it is better to use torque since the car itself couldn't care less what rpm your motor is spinning. Torque is the force that accelerates your car and keeps your car moving at a certain speed against friction losses, wind resistance, etc.
So, now we are talking about observed torque or perhaps tractive effort. In lower gears, your motor essentially has a better leverage on the wheels (because of the gears) and therefore your car's observed torque will be higher in lower gears. Otherwise, the only things stopping you from accelerating just as hard in higher gears would be wind and friction and that is certainly not the case.
To prove it sometime, have your dyno operator make a run in first gear. When you look at the chart, you will look like this:

Mark
www.Quantum-Racing.com