Why this torque curve???

[effer]

I know that an engine personality is dictated by its torque curve throughout rev, but what is the link between such a curve and the engine characteristics?

Like why is torque diminishing when rpm are increasing?

Isn't it "counterintuitive" because if something rotates faster it must posess more energy and hence could accomplish greater work... ???????

I know that torque depends on lots of variables but is there some basics explaining how torque is affected by these?

How does cylinder numbers affect torque?

...engine layout? ( V, inline, boxer,... )

...intake, exhaust,...

...valve design...

etc.

 

[Ojas]

I'll take a stab at the first few ones...

I know that an engine personality is dictated by its torque curve trhoughout rev, but what is the link between such a curve and the engine characteristics?

I'm not 100% sure what you're asking here (sorry if I insult your intelligence)...

Think of torque at a given RPM as "how quickly the engine can get to a higher RPM." This is the same as how hard the car can accelerate. A car in a given gear will accelerate at rate exactly proportional to its torque curve. This means it will "pull hardest" at its torque peak.

Like why is torque diminishing when rpm are increasing? Isn't it "counterintuitive" because if something rotates faster it must posess more energy and hence could accomplish greater work... ???????

You're thinking of horsepower, which is exactly proportional to the product of rotational speed and torque. One reason torque eventually drops off is because the engine has to breath more rapidly as revs increase and eventually runs out of breath.

How does cylinder numbers affect torque?

Not mentioned: displacement and compression ratio affect torque. Number of cylinders and engine layout has a lesser (I think) effect on torque, but do affect smoothness.

Good intro. reading...
http://vettenet.org/torquehp.html
http://www.allpar.com/eek/hp-vs-torque.html
http://autozine.kyul.net/technical_school/tech_index.htm

 

[effer]

I'm not 100% sure what you're asking here (sorry if I insult your intelligence)...

No problem! As long as you only insult my intelligence and not me personally!

I am asking why X engine @ ( a, b, c, ... , n ) characteristics is showing a Y torque curve throughout its effective rpm range.

I already know about the meaning of torque and power but do not know why an engine is having its particular torque curve.

Your explanation about breathing is the type of answer/analysis I was looking for.

I would also like to understand more how displacement and compression ratio can affect torque curve.

You're thinking of horsepower, which is exactly proportional to the product of rotational speed and torque. One reason torque eventually drops off is because the engine has to breath more rapidly as revs increase and eventually runs out of breath.

Not mentioned: displacement and compression ratio affect torque. Number of cylinders and engine layout has a lesser (I think) effect on torque, but do affect smoothness.

Thanks Ojas for the links!

I also read that motorcycle engine are showing two torque peak and two power peak.

How is this possible?

You also wrote that an engine is running out of breath as revs increase. Why not designing it to not do so?


Sorry for so candidly showing my ignorance !!!