Rearend Gears & Dyno #'s

[Richardcoelho]

im still unsure,lets say i dynoed my car with 3.08's and pulled 200whp & 220rwt,and now i changed the gears to 3.23's and dynoed them,would i get the same numbers?i believe the torque may differ but what about the HP,please if you don't know do make up BS,please.

[Christopherrr]

Re: Rearend Gears & Dyno #'s

No, it does not affect your hp output...

For example...say you're riding your bike. You're peddling as hard as you can in one speed...but you change the final (small gear attached to your wheel), your legs don't make more power, your effort it's either harder or easier.

It's the same for your engine...doesn't make anymore power. Your final ratio just changes how the power is put down.

[Richardcoelho]

Re: Rearend Gears & Dyno #'s

No, it does not affect your hp output...

For example...say you're riding your bike. You're peddling as hard as you can in one speed...but you change the final (small gear attached to your wheel), your legs don't make more power, your effort it's either harder or easier.

It's the same for your engine...doesn't make anymore power. Your final ratio just changes how the power is put down.

but what about torque? that i believe should change,torque=force of rotation-and with smaller gears equal more torque,so when you ride a bike and your going uphill you have to go to a smaller gear to get more torque to make it up the hill,so the dyno should not affect the hp at the wheels i think,but i think it should affect the TQ numbers.The bike comparason was pretty clever,the force out to pedal is like=engine HP, and the wheels are,, well the power you put to the wheels,but thanks for shedding some quisical thinking.

[Christopherrr]

Re: Rearend Gears & Dyno #'s

I still will say no...

Picture this...in a 3.08 car, the driveshaft turns 3.08 times with 1 full rotation of the rear wheels. In a 3.73 car, 3.73 times. The wheels are connected to the differential (point of discussion) that's connected to the driveshaft that's connected to the transmission (with it's own set of ratios, but fixed), that's connected to the crank. Obviously...

With that, there's .65 in difference between the two gears. So going from 3.08s to 3.73s you're increasing .65 of driveshaft rotation for every 1 complete rotation of the wheels at any given point, which conveys power, is transferred "quicker" giving the sense of power increase.

That's why you see people say "my engine really woke up" or "burn outs are easier" or "it really digs from the line", that's because your engine/crank can "turn" ".65" more at any given moment verses to what it used to. That's why you get higher RPM at cruise, faster reving, your engine sounds beastier (cause it revs faster). Your rearend gearing doesn't add power or multiplies power...it just changes how it's transferred. You're not increasing airflow (power), fuel (power), igntion (power), compression (power)...nothing changes. It's not a power adder.

So would torque increase due to gearing - the answer is no.

__________________________________________________ _______________

Just like you trying to start from a stand still on your bike in the tallest or shortest gears. The shortest gear will give you the most trouble (you really gotta put your legs into it) verses the tallest (where you can dig out of it easier, but your legs go faster).