FertBert wrote:Ok, I made a port map of the cylinder I have. It has a dual ring piston, I'm not sure why the link I posted has a different piston.

Thanks a lot!

I've placed them together in this post for a good comparison:

FertBert wrote:The exhaust port seems to be a little bit more aggressive than the one on the DR. I also calculated the area of the boost/transfer ports on the Mer Eur kit and the DR.

DR = 434 mm squared area
Mer Eur = 556 mm squared area

This is probably due to the fact that the bore or size of the Mer Eur kit is slightly bigger than the DR.

I think you're right. To bad you didn't measure the distance from the top of the cilinder to the top of the cylinder skirt transfer.

But assuming that we both made no measuring-mistakes it is likely that the Mer Eur gives max power at a higher RPM than the DR. I guess the Mer Eur cylinder is likely to give max power between 7.000 and 8.000 RPM, while the DR gives max power between 6.000 and 7.000 RPM.
[I base this on the theory of A. Graham Bell's Two Stroke Tuning, but I need the distance from the top of the cilinder to the top of the cylinder skirt transfer to confirm my assumption.]

By the way: notice that the Mer Eur has much widener transferports than the DR (17 + 9 mm vs. 11 + 8 mm). This already makes a difference of 98 mm squared area...

the fiche of polini says that the polini cylinder max goes to 6000rpm. and the LC version (with the same porting) goes to 8000rpm. and we all know that the DR cylinder not reach the top of a polini cylinder. So i'm not so sure about the revs.

metsinsons wrote:the fiche of polini says that the polini cylinder max goes to 6000rpm. and the LC version (with the same porting) goes to 8000rpm.

Yes, that's true ... That is why I want to see the portmap for the Polini cilinder, and that is why I posted the power-graph in another topic

metsinsons wrote:and we all know that the DR cylinder not reach the top of a polini cylinder. So i'm not so sure about the revs.

But the fact that the Polini gives it's max power between 5.500 and 6.500 rpm, and the assumption that the DR 65cc gives max power between approx. 6.000 and 7.000 RPM, doesn't mean that the DR gives more power...
(It has for example to do with the total area of all ports, the positioning of the ports, number of ports, compression etc).

I'm not sure, because I do not have a really clear one, but you can try to zoom in on the portmap for the Athena 70 cc for Camino. If you calculate that cylinder-timing (tranfertiming, outlet-timing and inlet-timing [although for the last one there is not enough information]) you probably find out, according to Bell's theory, that that cylinder gives max power around 10.000 RPM!
I guess not many people with that Athena cylinder on their Camino have the setup designed for 10.000 rpm.

Still I'm really interested in all these portmaps and technical data of these cylinders, to check the theory, and in the end, create a setup completely designed for the powerband of the cylinder (whatever brand I'm using). So the exhaust, the variomatic and the carburator will too be designed for specific that powerband...

But please be my guest to give your critics, that's the only way for me to learn

Twister wrote:

klainstain wrote:Is it an vlinderpoort? (butterflyexhausport )
Or just a line ?

No, it's not a "butterflyexhaustport" (mooi gevonden trouwens ). I it's called bridged port in English, and it looks like this:

Vlinderpoort.jpg

Oké, then I saw, there was that line on every port

Haha merci