Just for those ever wanted to know the difference between the two pistons.

Whent to the dyno today with these results.

Dotted line - Singe
Solid line - Double

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

O and worth mentioning is a 28 !

EDIT : Ok so to show a closer comparison I went to the dyno again with these results..

1st Graph : Dotted line(Run13) - Single ring pistons with lightened flywheel.
: Solid lind(Run18) - Double ring pistons with lightened flywheel.

2nd Graph : Dotted line(Run19) - Double ring pistons with lightened flywheel.
: Solid line(Run20) - Double ring pistons with total loss rotor.

Reason for the small difference between run 18 and 20 is because I changed one jet size.





Last edited by Alzazorq on Wed Jul 13, 2011 8:01 pm; edited 2 times in total

What pistons were they?

Did you check combustion chamber volumes and squish were consistent?
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Hi Font,

Actually the motor is not 100% setup yet because there is a .10 difference between the two squishes because of the one barrel being a tad shorter than the other. The one head volume is also not 100% the same as the other.

It does not really matter in this comparison since the differences where there with the single ring pistons a year ago too...

Will have these sorted in the near future and some more mods, will post my findings.

The single ring pistons were Wiseco GP. (RM125)

Cheers
Mario

Good luck , do 1 mod at a time and you will get a beter comparison .

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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Vampire?

Did both pistons and rings have the same number of miles on them?

NSR-lizard wrote:The post title should read "Double ring pistons/lightened flywheel vs. Single ring pistons/total loss flywheel"

Don't forget different squish and presumably different combustion chamber volumes....


We've seen 0.2mm varience in sqish (with stock chamber profiles so 0.4cc difference in volume) make a difference of 4bhp on it's own.


What you need to do this comparision properly is;

Dyno the bike on the twin ring piston (with fresh rings).
Measure the squish.
Fit the single ring piston with fresh rings, set the squish the same.
Dyno the bike again.

I don't know what the exact measurments of the single ring pistons you're using so have no idea if this is easily achieved. If the single ring pistons are shorter then you may have to machine the barrels to suit the single ring pistons and pack it with gaskets to run the twin ring setup.
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Yes, all good and true, just so you know this was done within a 20min window so couldn't do too much fiddling with customers breathing down my neck waiting to get their bikes on the dyno.

Yeah both runs was done with fresh top ends, will see if I can get another one with the flywheel back on.

Actually the motor is not 100% setup yet because there is a .10 difference between the two squishes because of the one barrel being a tad shorter than the other. The one head volume is also not 100% the same as the other.

It does not really matter in this comparison since the differences where there with the single ring pistons a year ago too...

- some reading glasses perhaps ?

http://i561.photobucket.com/albums/ss56/deon42_bucket/NSR300STDFlywheelvsSkimmed.jpg

thats a beter comparison between stock flywheel and a skimmed unit , forget hp though

Updated to see closer comparison, please read the EDIT part in the 1st post.

Now that's a beter comparison , good work there ! Maybe I need to try a total loss unit on my setup ? Have you sent this to oom ?

Hey Bud,

Oom as in Neels ? Yes I have, waiting on his reply...

I thought you are selling your "fix" ?

Gotta love the 1.23 correction factor.

The gain with a total loss flywheel is impressive.

The huge mid range gain in the first graph (7bhp at 9000 rpm) and slight loss at peak is NOT due to piston weight, there was either a sizeable change in compression or something else was amiss.
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