He's being very general. If we get too technical this discussion dies.
He was standing at a black board with engine diagrams talking about how combustion chamber dimensions, combustion speed, piston speed and stroke effect torque, I would say he was trying to make very specific statements, that I don’t agree with, unless the situation is very extreme.
I am
very aware that my post was annoyingly over the top, it’s embarrassing, but this person didn’t focus on power delivery, just torque, and his own examples didn’t even back his point.
I agree about not wanting a street bike buzzing in my ear, but if we ignore that, and many do, This short stroke bmw machine makes 83lb-ft from 999cc, and delivers approx 73ft-lb+ from 6000 to 14000rpm, that’s a lot of useful rpm.
I just don’t see examples of long stroke engines making significantly more torque (per displacement) than square or short, I am however very open to being shown such 4t engines tuned for torque making more per displacement, but only if naturally aspirated,
I am happy to say long stroke engines are more suitable for making torque, but not necessarily better at it.
I overlaid the long stroke Harley 1200 against the 999cc Bmw and ~1100cc Ducati, yes I know its a ridiculous comparison, the engines are in different states of tune, the bikes are ridden in completely different fashions, are made for different purposes and many other reasons, however, and especially for the Ducati, consider riding the bike from 4K to 14K rpm, the available torque is notably similar to the Harley between 2K and 5K rpm.
Below the BMW s1000rr comparison, a super short stroke, 17% smaller engine, ~999cc vs ~1200cc
I am not meaning to compare the raw performance of these engines, that would be crazy, I am just pointing out the similarities in torque output for each engine, while a bit bumpy, the range of 5K to 14K rpm for the BMW and the usable range of the Harley are comparable for torque output, while there designs are worlds apart.
Worth noting that considering the RPMs these bikes will be ridden at, they will both have similar instant engine torque available without shifting.
Anyway, back to two strokes, I will agree a square two stroke might have the edge over a super short one due to exchange/scavenging, but we don’t have those in the modern saw game, we might call a saw long or short stroke, but they are both short stroke really.
Related question, does anyone have a Dolmar 9000, are they good on fuel?
