That's actually a very good explanation of the difference between horsepower and torque, southpaw!
So, at low speeds (lugging) we need more torque to produce equivalent horsepower. Sure - and some engines like my old 427 cu in Police Interceptor were designed to produce high torque in the low RPM band so it was easy to move off from a standing start. I know diesels are weak in this regard.
But, why is a diesel so different from a gasser? Is it because the compression is so high that it "works against" the output at low rpm?
Naturally, we can only really continue to accelerate as long as the torque output of the engine exceeds the torque demand needed to maintain the current speed. And, at cruise, the torque/fuel demand is reduced, since we're no longer accelerating, but have to supply just enough to counter the force of wind resistance, friction, and other losses that try to slow us down.
The whole horsepower thing is kind of a "fiction", isn't it?
And, does the EGT go up in lugging because the fuel is "afterburning" as it leaves the cylinders? (Hasn't completed the burn during the power stroke)? Or, did it finish the burn too early, since the piston is moving too slowly? (Creating a "hot spot" effect in the cylinders that is not countered soon enough by the cooling exhaust and intake cycles)? In either case, wouldn't a gasser have the same problem?
And, getting back to the "lugging" proposition, what, specifically, is wrong with this strategy? Does it work in a gasser but not in a diesel due to the low RPM power characteristic?
I did not mean to hijack this thread and if I have, I'll start a different discussion of it elsewhere.
I'm honestly just trying to gain a better understanding of the two technologies. I'm already a diesel convert, just don't have one yet!
- Jack
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