Dyno graph with no torque

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badassracing
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Dyno graph with no torque

Post by badassracing » Mon Nov 06, 2017 12:43 pm

A buddy of mine had his car chassis dyno'd and when I asked to see the dyno graph there were no torque numbers or curve. I asked if that was all he got and he said yes...the torque readout wasn't working that day.

Is that possible?

racear2865
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Re: Dyno graph with no torque

Post by racear2865 » Mon Nov 06, 2017 12:58 pm

If u got hp numbers, you can calculate tq from HP and RPM.
reed

DaveMcLain
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Re: Dyno graph with no torque

Post by DaveMcLain » Mon Nov 06, 2017 1:15 pm

Torque * RPM/5252=horsepower. So take the horsepower number multiply that by 5252 and then divide by RPM and you'll have torque.

They had to measure torque to figure out the horsepower but they must have had their software not set to display the torque.

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Re: Dyno graph with no torque

Post by Zmechanic » Mon Nov 06, 2017 1:30 pm

If it was a purely inertial dyno, then it wouldn't technically have to read torque, but I highly doubt the software wouldn't provide it anyway. I suspect it probably wasn't inertial to begin with though. Sounds like someone just needs to spend some time with the software manual.

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Re: Dyno graph with no torque

Post by badassracing » Mon Nov 06, 2017 2:23 pm

The dyno graph doesn't have RPM. It only has speed

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John Wallace
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Re: Dyno graph with no torque

Post by John Wallace » Mon Nov 06, 2017 3:02 pm

That dyno doesn't really know what RPM the engine is turning, only what is output to the wheels against the rollers.

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Re: Dyno graph with no torque

Post by digger » Mon Nov 06, 2017 3:29 pm

Sounds like a dyno jet. If they didn't use an rpm pickup then you don't get torque just hp.

Note the dyno jet torque is a derived torque value it's not the torque at the rear wheels.

Derived torque = rwhp x 5252 / engine rpm

Good news is if you calculate gearing ratio and know tyre size you can convert back to rpm from mph assuming no slip

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