Runaway train lol. Just ask yourself why guys pay 1000's upon 1000's for lighter cranks, rods, pistons, flywheels, driveshafts etc and you will find the answer.
Dammit Woody, stop making sense.
my 302 lost 6hp peak as well as everywhere along the curve (using the same dyno in the same conditions) with my fidanza aluminum flywheel (13lbs vs. my 24lb Ram billet steel unit) but the car was consistently .2 quicker in the 1/8 mile only picking up .3 mph.
What are the "same" conditions? Was the room temperature the same? Was the humidity the same? Was it on the same tank of gas? Was the engine at the same temp? Etc, etc. 6 HP is easy to gain or lose through even small variations.
the dyno measures torque, not hp. it calculates the hp from torque. the heavier assemblies make more torque at every point on the curve, thus make more hp. but the lighter assemblies do accellerate faster for the reasons you state. the dyno lies. what you are saying is correct, but the dynojet doesnt work that way.
Not all dynos measure torque, there is also what is known as an "inertia dyno", in which a cylinder of a known mass is accelerated by the engine/vehicle, and rate of acceleration is measured, thus determining horsepower. I believe most chassis dynos use this system. It is the same concept of estimating HP by trap speed of a car of a known race weight. Also same concept used by Dynolicious. By knowing mass and the rate of acceleration, one can determine power.
if this is the case, and the tires are hooked and the clutch does not slip, please explain to me how with the same gear ratios in a manual trans and everything else being equal other than rotating assembly weight, how the rpm will not drop a given amount?
i can see how the rpm would stay up if the clutch slipped, but if that doesnt happen in either case they should recover at the same rpm for a given shift point because of the mechanical connection of the gears, everything else being equal other than weight.
Think of it this way: If your car was sitting still and you were to rev your engine to 6K rpm, and simultaneously drop the clutch and kill the ignition, the car would move forward and experience some amount of acceleration, solely from the inertia of the moving engine parts (remember, the engine is off). I think he is trying to argue that a car in a drag race would experience the same phenomenon of acceleration due to moving engine inertia during an upshift.
... And it probably does, to some extent. However, is it enough to justify the losses of accelerating the heavier parts in the first place?
My engineering experience tells me that no mechanical system is perfect, and you never get 100% of the energy that you put into getting a mass moving back when you try to stop the mass. That's why there is no such thing as a perpetual motion machine.
So, I'm thinking that the power wasted to accelerate the heavier engine parts is probably NOT recovered during the upshift, when the mass of the car is working to decelerate the engine.
So... I still think lighter parts win.