Fyi- net rear wheel torque

[Silversmith]

If you are planning a engine build, or just want to know your true RWTQ. May I suggest this formula I use. It's quite accurate & saves me a trip to the chassis(cash)dyno shop!! RWTQ = Flywheel TQ X 1st/trans gear ratio X (Rear End gear ratio X 0.85) Exp: (331 X 0.85= 281.35) Flywheel TQ 500ft/lbs. X 1st/trans gear 2.87 X Rear end gear 331. Or "500 X 2.87 X 281.35 = 403737.25" True RWTQ is 403.7 ft/lbs. Hope this helps.

Da Mauler

Remember! Sex is only temporary:mad: For Ever Lasting Pleasure? DRIVE A COBRA:p

[riptide motorsport]

And how do you get your flywheel torque for free?

[ClemsonS197]

And how do you get your flywheel torque for free?

Must be some kind of Government program.

[AJ Roadster NJ]

I've never thought that rear wheel torque meant anything, nor does RWHP. In fact, I don't even think FWHP means anything, but that's another rant. Just the fact that the formula uses the ratio of 1st gear makes it questionable -- what, I only care about power from 0 to 18 mph?

When we think torque, we need to think of a curve, not a static number. On any engine, torque is measured across the rpm range. When someone says, "I have 400 ft lbs of torque" they have not finished their sentence. At what rpm? Is that peak torque? Well yes, it's peak torque (the highest reading from the dyno pull) but if that reading happened at, say, 5200 rpm, are they going to drive around all day at 5200 rpm? Of course not. They're going to be forced into using the entire lower end of the rpm range just in the course of normal driving.

So what matters, really, is the overall torque curve. A really nice dyno sheet for a street car will, IMHO, have a torque curve that shoots up like a rocket at very low rpm, plateaus out, and maintains a high reading until it starts to drop off up in the extreme highs where we hardly ever venture in a street car, like 6500 to 7000 rpm.

When we measure that on a chassis dyno, where the power (torque) is being measured at the rear wheels, the result is usually extrapolated in brake torque and brake horsepower, i.e. at the flywheel. The extrapolation uses some assumptions but is pretty easy. Using a Ford 8.8 TracLoc rear end and a some variant on a T5 or Tremec trans, the parasitic drivetrain power loss is generally accepted to be about 17% off the flywheel power (assuming all fluids were properly warmed up prior to the pull). Therefore, chassis dyno torque and hp numbers can be multiplied by about 1.205 to get good approximate flywheel numbers.

AJ

[Silversmith]

I was speaking of peak TQ listed in a crate offering, or after a self build engine dyno test. AJ is right, the overall TQ curve is a better actual rep of a engine's TQ. This is something I use to estimate overall target drivetrain goals. I'm sure there are many real engineers here; who know many procedures better than what I've listed. I'm just speaking of my own lowly procedure. Sorry for any confusion caused:o