[Jay S]

Originally Posted by Steve C.

A non expert opinion here, I was suggesting what I thought might be a normal rpm spread between peaks.


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Would probably need to see a full graph and more drive terrain details to really give more of an educated guess on what the spread actually is or why it is that wide. Wheel dynos seem like they are hard to compare numbers between other combos or dynos. It could be the torque converter multiplied the torque for a bit at a that lower rpm and the engine’s actual peak tq was higher. If it was on an engine dyno the peak tq and power would more than likely come out closer to a that 1500 spread like your suggesting.

[Steve C.]

Makes sense, thank you.

And I can relate to your comment about wheel dynos being hard to compare numbers. When I converted to direct port fuel injection on my 505 we were unable to use the engine dyno for the numbers. The dyno facility is not set up for the fuel injection. But for interest I put the car on a chassis dyno. The results were very confusing !



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[joes455]

If say peak hp numbers are correct at 3000 rpm ,How are you going to gear your car to cross the finish line at max hp ?haha,if you ever bring it to the track

[JLMounce]

If the dyno operator wasn't using an RPM signal, the software may have been using drum speed. This may be why the torque values are wrong as stated by the OP.

The HP may be close, but with the torque being wrong, it may just be an approximation. I have no doubt the engine is stout, but this is really why chassis dyno's are more for tuning than for bragging rights.

[joes455]

412hp chassis 568hp crank,I don't think so.Almost 40% gain?Bullsh..

[Formulajones]

Large differences like that between engine and chassis dynos are not unusual.

I see it all the time with our stuff as we have went from the engine dyno to a chassis dyno on several occasions.

An example is Dad's engine which made 724 HP on Tony Bischoffs engine dyno. We already know that to be very accurate and not inflated. It was even tested with the exhaust used on the car, no fancy dyno headers that Inflate numbers

Same engine in the car on a NASCAR certified chassis dyno that we've used several times with repeatable numbers he made 505 HP at the tires.
That's a big percentage difference but not out of the ordinary. He's pushing through a 4l80 with the converter unlocked, a heavy 3.5" steel driveshaft rated for 1000 HP and a 12 bolts rear

That whole 15 percent difference that is commonly thrown around on the internet is complete bs. You really can't put a number on it like that and you can't compare one chassis dyno to another. There are way too many variables. The key is to keep using the same dyno and make your tuning changes, that's what it's for. Going to different chassis dynos is going to throw you for a loop and make no sense at all.