Alzazorq wrote:Dotted line - Singe
Solid line - Double

Same bike, same setup except changed flywheel from lightened to total loss.

Wasn`t the same setup then, was it, and as a result the graph as a 'comparison' of piston types is pretty meaningless!

The post title should read "Double ring pistons/lightened flywheel vs. Single ring pistons/total loss flywheel"

Neal`s suggestion is the correct way to go about things.

A more productive and meaningful test would`ve been to leave the flywheel constant, and change only the pistons.

The ideal (dyno*) procedure would have been:

Test #1: Double ring pistons/lightened flywheel
Test #2: Double ring pistons/total loss flywheel

This would obviously demonstrate the +/- effect of the total loss flywheel, then...

Test #3: Single ring pistons/lightened flywheel (compares with test #1)
Test #4: Single ring pistons/total loss flywheel (demonstrates overall gains)

Of course it would have meant 4 runs instead of two and increased cost. It would also have been beneficial to test with a standard flywheel too, if one was available, as you can never have too much data.

*As Fontyyy has since drawn out of you, the motor is not even set up for the single-ring pistons, so that throws the comparison off even more! +/-0.1mm can seriously effect the outcome, both good and bad.

What should really have been done first was a dry assembly with the single ring pistons to make sure you knew how to assemble the top-end with the correct combustion chamber volumes and squish. A dyno run (or runs) should then have been performed to optimise the jetting with the double ring configuration. Only then should the setup have been switched, and again run up to find optimal jetting. That would give you a true comparison, and that`s why a good dyno session and operator costs so much money and time. There`s a good half a day`s work there!

The post really seems to be a troll to fire up MC18/21/28 debate, so I`ll take the bait and say I defy anyone to show me any NSR250 that will make 78rwhp! Given the motor isn`t even set up properly for the single ring pistons, even if that's an enthusiastic crank output, I find it incredibly hard to believe an MC28 would be capable of churning out 66.3hp given a worst-case 15% draw on output.

If you're telling me that it`s crank output, I say the dyno is highly optimistic, but if you're telling me that is rear wheel hp, then I'm telling you to find a better dyno/operator!
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