The Effect of Dynoing in Different Gears

370Z Purist

Mechanical advantage makes a huge difference. I can now understand where you're coming from when you say the MT's should dyno in 4th. The only issue now is that everyone has to have equivalent values, including the SAE error adjustment, whether or not you're using a Mustang or Dynojet (or some other type of dyno), whether or not it's loaded, braked, etc.

You also have to factor in that anyone who is running larger wheels or heavier wheels may appear to have less torque because of the rotational inertia or rolling resistance and what not.

Overall, the gear suggestion is a good place to start, but dyno numbers are always all over the place because of the variance in testing. Temperature makes a massive difference, especially when people use CO2 extinguishers, ice bags on their turbos or superchargers. Sure, that's forced induction, but even an NA car will experience mildly better numbers in colder weather.

Also, did a bit of math:

-----RPM--Gear--Gear Ratio--Final Drive

AT--1500--5th----1.000------3.357 = 5035.5 RPM drive shaft
MT--1500--4th----1.271------3.692 = 7038.798 RPM drive shaft

Even without the diff ratio and the wheel circumferences considered, we're looking at a 2000 RPM difference in the driveshaft. It's irrelevant to power and torque but clearly there is a significant difference.

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-Phil

"Since one of my brake light bulbs just went out, the forum told me that my piston rings are about to blow."