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Paul Workman · 07-23-2013

Strong numbers, to be sure.

Researching dyno calibration specs a bit, it appears (cutting to the chase) that a 4% variance exists between STD & SAE correction factors, stemming from the fact that SAE normalizes to 77ºF whereas STD normalizes to 60ºF

Also, the SAE 1349 spec requires correction for torque, relative to the mechanical efficiency (ME), or estimated at 85% at peak torque ONLY.

It is still a little vague (to me) how ME is affected when the engine is producing other than peak torque, but intuition tells me as counter rotational force (drive train inertia) diminishes, ME increases. The result would be a reduction in calculated hp at those non-peak torque regions of the rpm band.

In any case, the dyno operator was obviously conditioned to lift when his ear told him he'd reached the limit of conventional pushrod motors. The sound of the LT5 screaming past 5500 on its way to 7k+ scares the crap outta some operators, and the unaccustomed as well.

Well...Now that the hook is set, it is time for some FBI top end porting...and then...and then... Yeah, speed is addicting!

P.

07-23-2013	#9
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,466	Re: 1990 #2180 Dyno pull Strong numbers, to be sure. Researching dyno calibration specs a bit, it appears (cutting to the chase) that a 4% variance exists between STD & SAE correction factors, stemming from the fact that SAE normalizes to 77ºF whereas STD normalizes to 60ºF Also, the SAE 1349 spec requires correction for torque, relative to the mechanical efficiency (ME), or estimated at 85% at peak torque ONLY. It is still a little vague (to me) how ME is affected when the engine is producing other than peak torque, but intuition tells me as counter rotational force (drive train inertia) diminishes, ME increases. The result would be a reduction in calculated hp at those non-peak torque regions of the rpm band. In any case, the dyno operator was obviously conditioned to lift when his ear told him he'd reached the limit of conventional pushrod motors. The sound of the LT5 screaming past 5500 on its way to 7k+ scares the crap outta some operators, and the unaccustomed as well. Well...Now that the hook is set, it is time for some FBI top end porting...and then...and then... Yeah, speed is addicting! P.