Race classes- level playing field

The article left my little head spinning but its more alone the lines I think of for power > torque per mass. 45 cid Combat's seem pretty decent to make a bit over 1 lb torque per cubic inch. With some basic spiff ups can make even more. I know what ya feeling - when ya got the handling but not the power range to tackle the boring opens. Motorycling makes little sense and race rules/politics even less. Thanks for the deeper education.
 
But WILL it fit in a NORTON . :wink:

Race classes- level playing field
 
We're basically talking about power output here. Albeit theoretical using BMEP.

A 500cc two stroke twin will produce more power than a 500cc four stroke twin because it's working twice as quickly as the four stroke. A four valve/cylinder 500cc four stroke twin will produce more power than a two valve/cylinder 500cc four stroke twin because it is sucking in a greater volume of air and fuel, so more power.

You could also state that a 500cc short stroke, four stroke four will produce more power than a long stroke, 500cc four stroke single because of it's higher rpm and therefore ability to burn more fuel over a period of time than the single and therefore produce more power.

I see what you're getting at and it would make for closer racing. We would have 500cc Manxs racing against 250cc two strokes, or an inefficiently designed 750 four. But then the inefficient 750 four would be banned from that class when the race team got it working better.

I think we're stuck with the capacity classes as it is easy to work with and because that's how it's always been done. I'm not saying it's right, but basing classes on power outputs could mean an inventive design gets banned just because it wins everything. Remember the Norton Rotary?
 
I've just actually read an article on BMEP and I think I've got it arse about face.

BMEP is a method of calculating the efficiency of an engine at producing power for a given capacity, I think? So don't actually see how fair race classes could be based on this. You could have a 125cc four stroke twin with a similar BMEP as a 500 four, but the 500cc developes more BHP and so trashes the 125, I think?
 
Perhaps a Production Class for these
Race classes- level playing field
would create a level playing field .

If it didnt , sidecars with 2wd should get through any rough spots . :P :D :wink:
 
I remember. Norton claimed a 588cc twin rotor, race teams who were getting soundly beat claimed it to be closer to 1800cc because the volume of each chamber was approx 300cc x 3 (for each face of the rotor) and double it (twin rotor) = 1800cc. They chose to ignore the rotor was turning at one third engine mainshaft speed so hence Norton's claim of 588cc.
 
acotrel said:
I wonder if anyone ever remembers the concept of Brake Mean Effective Pressure when developing race classes for various bikes ? When four stroke motors of similar capacity have more valves, the BMEP is higher, and it is also higher in two stroke motors .

Sure, for modern racing classes this is fine, but it does not work when you mix modern bikes with old bikes because it does not take into account the much greater reliability that new engine designs have.

This is also why vintage racing is destroyed when people race replicas in it that have much stronger engine parts than the originals, it instantly makes real vintage bikes obsolete because they can not operate at the same power per cubic inch as the replicas without breaking down.

In AMA racing in the 50s they had the 750cc side-valve Harley and Indian twins running against 500cc OHV bikes. Someone decided that was fair, and it seemed to work out pretty well with both engine configurations taking turns winning races over twenty or so years it was enforced, and everyone seemed to have the same reliability.

In about 1968 Yvonne DuHamel ran a 250 Yamaha on a mile dirt track race in California and was as fast as the 750 Harleys and 500 Trumpets and BSA Goldstars, he finished the race with a very high placing. Maybe if the AMA would have limited 2-strokes to 250cc when it included it in that formula time would have stopped for a while longer for the Harleys and Brit bikes, but they went to 750cc across the board for all engines, so first the side-valves disappeared, then when the Japanese built 350-750cc 2-strokes, all the old bikes were obsolete of course.

No one kept up with Japanese manufacturing so the only bike that survived was the Harley xr750, and then only because the AMA simply outlawed and crippled all it's competition.
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