HP & torque document

[TripleZee Dyno]

Ahhh right I see where you're coming from.

The way I was talking about it is where you have the same bore, same cylinder pressure. Just longer stroke. In which case you would have more torque -- not because of higher capacity causing more fuel/air being squashed and burned, but simply because there is a longer `lever' acting on the crank centre.

So we were both talking about the same thing except I didn't explain myself clearly

In the article it says you can have torque without power -- the case cited is where you apply torque to a stuck/rusted bolt and it doesn't come undone (no work is done, nothing moves -- nonetheless you are applying torque).

Thats right, if you increase the stroke you will increase the torque because you have the same pressure on a longer arm. By the same token an increase in bore will give the same result because you have more pressure on the same arm.
It will work out the same, more or less
cheers

[LBD]

. Long rods "dwell" the piston at TDC which helps with the power stroke. A lot of it is to do with manufacturing techniques and materials as to what they can do or not do.
cheers

Short rods dwell longer at the top and bottom .....

[jonbuoy]

So why do Vtwins FEEL like they have more torque? I know the dyno graphs tell a different story, is it the sound or related to the longer power pulse?

[TripleZee Dyno]

So why do Vtwins FEEL like they have more torque? I know the dyno graphs tell a different story, is it the sound or related to the longer power pulse?

Who knows? It probably has just as much to do with what they feel like, the sound, as well as the way they are tuned.a 450 deg gap in its power pulses compared to 180 is quite big. So the Vtwin will feel different and also the way the power is transferred is different. The difference between the 120 deg and 180 deg 3 cylinder Laverdas was noticeable, but I don’t think there was any significant power difference. Big cruiser vtwins tend to be up around 80-90% of their peak tq as low as 2500 rpm, maintain it for about 2-3000 rpm and the tail off fairly quickly. Big fours may start out at around 50-60% at the same revs but usually have a rising tq curve which peaks up around half the rev range and then slowly tails off for the rest of the rpm. Performance V twins usually have less peak tq than their cruiser brothers, but a better spread and at higher rpm. Eg the difference between a Vstrom and a TL1000. Ducatis have a flat tq curve, for probably 80% of the rev range they have at least 80% peak tq. Buells and Sporty tq curves follow each other for the first 4000 rpm, then the sporty tails off and the buell rises. And that is entirely down to tuning and setup. Bore, stroke, rod ratios etc have nothing to do with it because they are exactly the same. Same for the TL and Vstrom.
All engines are tuned to operate over their intended rev range and generally speaking a twin has a smaller rev range than a 4 so thats how it gets tuned.
The Rocket 3 would have more tq than any vtwin but it I dont know if it feels like it.

[TripleZee Dyno]

Short rods dwell longer at the top and bottom .....

Long rods dwell longer at the TDC and short rods dwell longer at BDC (at least they used to 20 yrs ago. maybe technology has moved on a bit more than I thought)

[T.W.R]

Someone say rods

[TripleZee Dyno]

Someone say rods

This article makes more sense than the first one. Although I doubt the long rods contributed all that much to the 44% increase in power on the V8. The engine must have been in a shocking state of tune before they started.
Long rods aren't magic by themselves, they are part of the whole package and hopefully everything works together to produce an excellent result. Sum of the parts etc
cheers