Chassis Dyno. Am I missing figures in my calc? Torque looks high!
Chassis Dyno. Am I missing figures in my calc? Torque looks high!
(OP)
Basically, for my own= information, I am looking at how chassis dyno torque is calculated. They all seem to come in below where the engine torque should be BUT there is ALWAYS a gear reduction to the final output which multiplies torque. For example, one vehicle I looked at was about a 3:1 in 2nd gear. Obviously torque would be multiplied but the RPM would also be reduced by that factor SO..... HP should remain the same as it is a product of torque and RPM.
However, the Torque to the rollers would be about 3X (assuming no Cf losses). Basically, you have a 100ft/lb motor, a 3:1 total ratio, and a 24" rear tire, you will get 300lb/ft to the rear axle. Obviously cars make MUCH more than this so thousands of lbs of torque would be seen at the load rollers. Am I missing something???
However, the Torque to the rollers would be about 3X (assuming no Cf losses). Basically, you have a 100ft/lb motor, a 3:1 total ratio, and a 24" rear tire, you will get 300lb/ft to the rear axle. Obviously cars make MUCH more than this so thousands of lbs of torque would be seen at the load rollers. Am I missing something???





RE: Chassis Dyno. Am I missing figures in my calc? Torque looks high!
Brian Bobyk - Hoerbiger Canada
RE: Chassis Dyno. Am I missing figures in my calc? Torque looks high!
At-the-wheel torque does not appear in there. At-the-wheel torque would require you to have all gear ratios, current engine power, tire size, and current vehicle speed, but that would not be (directly) related to dyno torque. Of course, increasing dyno torque output, all other things held equal, increases the at-the-wheel torque.
RE: Chassis Dyno. Am I missing figures in my calc? Torque looks high!
RE: Chassis Dyno. Am I missing figures in my calc? Torque looks high!
RE: Chassis Dyno. Am I missing figures in my calc? Torque looks high!
I think the load roller is irrelevant at this point but lets just say a 24" roller to make things easy. This means that if the engine actually makes 250lb/ft of torque at 4000rpm, and 285HP at 6000rpm, at the load roller or rear tire, we would see 2675lb/ft of torque and 285HP (2675*560/5252).
Obviously there can be some back calculations for torque but it sure seems that nearly 3000lb/ft of torque would be seen at the load roller if 1st gear was used. I realize the goal is to run a test in a higher gear to reduce the torque level but it wold still show over 1000lb/ft of torque to the load roller.
Am I missing something??
RE: Chassis Dyno. Am I missing figures in my calc? Torque looks high!
Norm
RE: Chassis Dyno. Am I missing figures in my calc? Torque looks high!
I certainly hope I am missing something but I cannot figure it out thus far....
RE: Chassis Dyno. Am I missing figures in my calc? Torque looks high!
Yes. Less a little for losses.
Norm
RE: Chassis Dyno. Am I missing figures in my calc? Torque looks high!
RE: Chassis Dyno. Am I missing figures in my calc? Torque looks high!
RE: Chassis Dyno. Am I missing figures in my calc? Torque looks high!
RE: Chassis Dyno. Am I missing figures in my calc? Torque looks high!
RE: Chassis Dyno. Am I missing figures in my calc? Torque looks high!
RE: Chassis Dyno. Am I missing figures in my calc? Torque looks high!
Regards
Pat
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