Dyno Questions

[SWYZ721]

How come a lot of the dyno's I see in SN member's threads the power drops off, well dyno's in general, always have the power drop off. I mean when you spin the engine, you make power, and the faster you spin the more you make. So theoretically the faster the more power, but why is it that the power drops off, I mean i understand the TQ dropping off due to the mathematics and calculation of HP. so why does the power drop off, cam selection? valve float?


Sorry for the cross posting but I wanted more traffic.

 

[TrickStang37]

cuz basically the engine is not getting enough air to support the elevated RPM's. needs better airflow.

 

[SWYZ721]

cuz basically the engine is not getting enough air to support the elevated RPM's. needs better airflow.

but as the engine spins faster doesn't it creat more vacuum, and even if it's not getting enough air then wouldn't the power just plataeu and not drop off.

Just debating because I'm looking for more than just the yes/no answer. No arguing.

 

[Ray@VSK]

Cars simply perform best @ certain range, dynos show you where that range is. If that was the case how come you don't have the same plateu as you say @ lower rpms then.. Air, fuel, gears, transmission, computer, etc, etc make the curve, what you ask is like saying how come my car ain't going no faster when I'm @ 6000 rpm as it does @ 5.

 

[SWYZ721]

Well what I'm saying is CFM=Power, True? Well the faster you spin the engine, the more air the engine breathes, so when dynoing how come the power drops off at the end like usually peak HP and TQ is reached before or around 5.5K, shouldn't the power just keep coming as you rev higher, turbo cars seem to always be gaining power in their dyno, what's the deal, is it the cam?

 

[Notched]

well the car can only suck in so much air/fuel... turbo cars, the faster u spin the motor, the more air is forced into the cylinders, and the computer compensates for this by adding in more fuel. same with a supercharger, except there is only so much air a cylinder can hold, and engine can suck in....

yes it does create more vacuum, but only a certain amount of air/fuel can fit.


i know waht your saying about it just platueing, and not dropping.

ill assume in saying that as the rpms get higher, the combustion of the mixture in the cylinders becomes less, since its being taken in, and spit out much faster, not allowing either a full burn, or wahtnot.

 

[tmoss]

the cam controls how much air the cylinder gets. The higher the rpm, the less time the valves are open and the ability of the intake/heads to fill the cylinder is reduced - so is power.