behind the liner vs piston port

[mike bryan]

in the 2.4 vs 2.5 thread someone made some comments about most 2.5 being behind the liner and most 2.4 being piston ported. i am really familiar with all phases of motorcycle 2 stroke port technology but could someone explain this a little further.in mc terms piston port motors didn't have reeds and the piston skirt actually controlled intake port opening.i have heard the term behind the liner many times and still don't have a clue.

[Markus]

On a piston port engine, the air/fuel mixture flows from the crank case through a hole in the piston skirt to feed the intake port in the sleeve.

A behind-the-liner engine has a channel that goes from the crank case on the outside of the sleeve (which it is why it is called behind the liner) to the intake port.

On a behind-the-liner engine, the air/fuel mixture therefore flows much straighter since it goes in a straight flow to the intake port and does not have to zigzag through ports in the piston and the sleeve to eventually end up on the right side of the piston.

If you look at a Merc 2.5 liter block, you can see the castings for the behind-the-liner channels on the outside (intake side) of the cylinders.

[H2OPERF]

Mike u are correct though the 2.4s are not true piston port engines they have reeds.dave

[yanny_haulinbass]

Markus,


Thanks for the explaining the behind the liner mystery. Much appreciated. Now if I can only figure out how they get the caramel inside a Carimilk bar...

[bigbore]

ya know i had a leaf blower that had that hmm thad be a behind the liner ryobi

[Fish]

Thanks again Marcus, another well stated, clear answer for those of us trying to learn.

fish

[WATERWINGS]

Now I think I understand, it seems like you are talking about how my CR-500 intake works.

You can see the casting for the intake on the sides of the jug.

Is this what you mean about the Mercs.?