Scooterotica

The software itself is pretty simplistic, but has some cool features....as well as the angle area graphs in the previous post, it helps you cut to the chase with all the calcs for port area, time area, angle area, degrees timing, BMEP etc etc

You can just feed in your standard settings, and it will calc the Jennings/Blair details....you can then make alts to see how various tuning options will affect the power delivery.


There is also a CAD feature for ports, the stats change as you bend the ports about.



It just helps you to get a rough guide to what standard ports are doing and how they are working with each other at any given rev range, and helps you figure out where you are going with your porting work without butchering too many cylinders first. Just an additional tool to give a tad more info before you start with the carbide bur!

sean brady scooters wrote:quite a while ago now dan.............i tried to broach the subject of BMEP............
but unfortunatly i think it was maybe a step too far..............for most..............even smiffy let me down.............
think it was somewhere at the end of the good old "long stroke/short stroke " topic.........

Knew we'd get down to length of stroke or something eventually.

rog60 wrote:

sean brady scooters wrote:quite a while ago now dan.............i tried to broach the subject of BMEP............
but unfortunatly i think it was maybe a step too far..............for most..............even smiffy let me down.............
think it was somewhere at the end of the good old "long stroke/short stroke " topic.........

Knew we'd get down to length of stroke or something eventually.

what about rod/stroke ratio!!

drunkmunkey6969 wrote:

rog60 wrote:

sean brady scooters wrote:quite a while ago now dan.............i tried to broach the subject of BMEP............
but unfortunatly i think it was maybe a step too far..............for most..............even smiffy let me down.............
think it was somewhere at the end of the good old "long stroke/short stroke " topic.........

Knew we'd get down to length of stroke or something eventually.

what about rod/stroke ratio!!

Too technical for me, leave that to your 'expertise'

It`s a nice set of pictures, and I am impressed by the mighty white mans magic,
but as an engineer who has been to big word school, I still prefer to get my calculator out and reach for the definative manual by Mr. A.G.Bell, Gorden Jennings or the german work by Helmut Faff.

stroke to rod ratio really only affects the maximum revs before the rings start to run into difficulties. while the length of the rod will affect the rotational aceleration of the big end.

Long rods are good. what about the pcr? I hear you say.
damned good question.
One more can and I`ll go to bed.
Take this post seriously at your peril!!

More seriously that is obviously a nice bit of software which few of us will ever get to use, in the real world we try it and if it works we use it. be it white walled tyres or pink tartan two stroke.

now back to pcr hi or low????????????

BMEP has nothing much to do with rod /stroke..................combinations
and everything to do with port/area /time in relation to bore size.......and stroke..........
BMEP is used to compare the efficiency of one motor against another..........irrispective of size/cc...............
this goes in some ways to explain why a 152cc motor can be more efficient than say a 250cc motor.......in a scooter around a race track.............
many other things of course ,should be taken into account...........such as power to weight ratio/areodynamics.................

fancy stuff.
i've read and re-read Jennings but always get lost in the math.

so what program is this? it seems to do quite a bit.

and FWIW, i figure the first graph is the 200, the second is the piston port, and the third the 225 reed.

guygrrr wrote:and FWIW, i figure the first graph is the 200, the second is the piston port, and the third the 225 reed.

No.

Any other takers?

Did you measure transfere area across the chord...
Or did you square the angle of entry into the bore in relation to actual area.. If so how..??

Not trying to sound cleaver just wondered how you had gone about it..

I used to use modeling clay pushed into the port entries and using thin pieces of steel rod pushed into the corners top and bottom work out the areas square to the transfere as I could never find a better way....

Tell me there is an easier way.. PLEASE.. Thanx in advance...

I'd say the 3rd is the 200...........

The only differential in the cylinders that you've told us is capacity and induction type, and as far as I can see, induction isn't factored into the model anyway