Marc '99T/A

iTrader: (22)

From what I understand, the higher the rear end gear ratio, the lower the #'s will be on the dyno. Is this correct, and can anyone explain why it is so? Thanks,
-Marc

Marc '99T/A

iTrader: (22)

Uhhh...........anyone???

BirdofPreyBandit

I always heard that gears do not affect dyno numbers. I don't understand how that can be but I've always been told that. Can anyone shed some light on this?

ninetres

iTrader: (35)

In general.......I have heard that they don't effect dyno numbers. Then the same experienced people who told me this have later said,"Wellllllllllll tehy do, but only a little bit. Like maybe 10whp less reading when switching from 3.42s to 4.10s."

Whoknows.

Cool Z

It's my understanding that the HP numbers will read slightly less, but the torque will be higher. Auto cars with a higher stall tend to lose a few ponies to the rear wheels, but the torque increases due to the torque multiplication produced by the higher stall. So in essence, it would make sense that a higher numerical gear ratio increases torque multiplication to the rear wheels. As far as the a slight HP loss, I do not know the technical answer. A friend with a 2002 Z28 went from 3.42 to 3.73. He gained 10 RWTQ and lost like 3 RWHP on average.

01RedT/A

your gears (or final drive ratio) should be figured into before you do your run. if i remember right, the operator should input that into the dyno. overall though, if you dont factor in the ratio, the higher the ratio, the more torque you should read, since the mechanical advantage is "higher". anyone know for sure?

Grimes

iTrader: (3)

In terms of drivetrain loss, it will affect the numbers only a tiny bit.

A dyno dosen't care what is spinning the rollers, so a dyno will spit out hp numbers no matter what car (or gear ratio) is turning it.

CHRISPY

There is parasitic loss running a deeper (numerically higher) gear ratio. Typically you'll see 8-10RWHP loss going from 3.42 to 4.10 in a 10 bolt. With a swap from a 10 bolt with 3.42s to a 12 bolt with 4.10s and heavy DS you'll see slightly more.

9 inch rears are the worst due to offset pinion location. 9 inch rears are the strongest though.

To help offset the loss you can run gun drilled axles, alum gears etc. Most just live with the slight loss for greatly increased strength.

davered00ss

iTrader: (4)

Yes, you do lose HP with gears.

Denom

iTrader: (2)

I believe you lose horsepower to the wheels, but not to the engine with a gear swap.

I may have my car dynoed again to see what horsepower loss I have since I had the 4.10's put in.

Marc '99T/A

iTrader: (22)

So overall, you do, lose some but it could be minor. Then again, it could be inputed into the computer when the dyno is set up, resulting in a more corrected number. Uhhh...right?

Denom

iTrader: (2)

I wouldn't think of it that way. I'd say think of a 10 speed bicycle. You go to a lower gear (Or taller gear if you would), so that you can get up the hill a little easier, although at a slower pace. That would be my view on it. Basically anything over your 3.23/3.42 gearing is a taller gear. You can get outta the hole alot easier, but you suffer in the top end.

ninetres

iTrader: (35)

Like top speed top end.....not the 1/4 mile top end from my ecperience. Pulls harder all the way through the traps (3.42---> 4.10 swap)

BirdofPreyBandit

I think you'll only lose top speed not top end in the 1/4. I'm trapping 117 mph and before the 4.11's, I was trapping about 115 mph.