displacement and racing - an article

[All250R]

displacement in racing and product choice (http://twostrokemotocross.com/2009/09/four-stroke-revolution-or-clever-marketing-ploy/)

[witech]

You know what I never understood is why such a big deal about displacement? It would be much easier just to race in horsepower classes and not CC classes. Then it wouldnt mean squat whay type of engine your running. 40 horse against 40 horse. What are they going to do when they start racing the electric cycles?

[axellmusic19]

i agree with the article but even more so with the horsepower against horsepower.

[headache]

why don't they just add another class and make it 250 two stroke! Then they could make everyone happy...

[All250R]

Originally posted by axellmusic19
i agree with the article but even more so with the horsepower against horsepower.
Because horsepower is a value of output at a snapshot in time. Displacement is the capacity for an engine to intake a certain amount of combustible fuel and oxygen and is why historically races have always been categorized by displacement - not peak hp. That's a bizarre idea... creative though...

[witech]

I disagree .Engine design and state of tune is the capacity of an engine burn air and fuel. To go and say an X size 2 stroke will be a good match for X sized 4 stroke will just lead to an offset power race that can go in either direction.
The end result is what an engine puts to the ground and if you want to match up machines to do a fair battle they should be measured in what its pushing it forward. Not who or what design the engine is.
Back in the old days its was fairly true that you match a 4 stroke up with a 2 stroke of half its size but those day are long gone. New designs are allowing 4 strokes to rev nearly 2 times as fast as the 2 strokes and burn just as much air /fuel.

http://www.youtube.com/watch?v=jg8QaY4YQPM
The purple banshee is just under 80hp. The Cannondale is a 61 hp 495cc. They traded wins all day . Both were top drag racers for many years. Even with the cannondale being over 200cc smaller than the old school idea of a 2 to 1 ratio.

[All250R]

Originally posted by witech
I disagree .Engine design and state of tune is the capacity of an engine burn air and fuel. To go and say an X size 2 stroke will be a good match for X sized 4 stroke will just lead to an offset power race that can go in either direction.
The end result is what an engine puts to the ground and if you want to match up machines to do a fair battle they should be measured in what its pushing it forward. Not who or what design the engine is.
Back in the old days its was fairly true that you match a 4 stroke up with a 2 stroke of half its size but those day are long gone. New designs are allowing 4 strokes to rev nearly 2 times as fast as the 2 strokes and burn just as much air /fuel.

http://www.youtube.com/watch?v=jg8QaY4YQPM
The purple banshee is just under 80hp. The Cannondale is a 61 hp 495cc. They traded wins all day . Both were top drag racers for many years. Even with the cannondale being over 200cc smaller than the old school idea of a 2 to 1 ratio.

The fundamental problem with that is that it completely ignores the running characteristics of every other point on the power line than peak hp. No one races at peak hp for the entire race. It makes no sense at all to pit engines against each other based on an arbitrary number someplace along the power time plot. MX, TT, Drag... all the different ways an engine is run, and you think it's applicable to take one value of power and make an equal match between two fundamentally different engines? Were you serious?

[witech]

Its all about getting power to the ground which is where the displacement formulas of the past just no longer apply.

[All250R]

Originally posted by witech
Its all about getting power to the ground which is where the displacement formulas of the past just no longer apply. I tried, but can't bring myself to provide a response, except to say... amazing.

[All250R]

http://twostrokemotocross.com/2009/09/more-local-racers-are-switching-how-about-you/

[DEVINF450R]

the lites classes in my district has a 250 class, 2 or 4 stroke