Air Flow / CFM's

[Chaz]

Not really how a flow bench works .. but I guess you could put a balloon over the port and hook the crank to a spintron and see if the modifications you made blew the balloon up bigger or smaller ...

You mention RPM . A two strokes porting has generally been judged by the time angle area method as apposed to CFM ratings .
Two Yamaha engineers are credited with documenting the ability to measure the mean area of a port and Gordon Jennings took it one step further and came up with the time angle chart , knowing as RPM increased , the allotted time for a port to function decreased .
Where a port's time area falls on the chart will pretty much dictate the power characteristics and if the system is balanced ...

[powerabout]

If you are an sae member you can find lots of research and tests on this stuff. Mostly Japanese.
Gordon Blair did lots as well

[Chaz]

OK , time to move onto cons :

I'll start ..

How bout , Flywheel ................ ............. ............

Agreed , that was a skeery thought . But mine will have stainless guard's next time . Just something about a 3.0L wheel sayin "Made in Korea" that made me think of mentioning it ...

OK , air flow . So it goes in the front half , # 1, 3, 5 take the short way around the outside to the rod slot . # 2, 4, 6 have a somewhat longer way around if the air is influenced by the rotation of the crankshaft.

More importantly , why do the reed blocks burn the rubber and chip the reed's on Merc's and not so much on OMC's .... ? (professor Carson , no cheating LOL )

[powerabout]

korean rubber?

[Chaz]

LOL .... well power , ya never know ...

I think there's gotta be a pretty good reason why it happens ..

[FORBESAUTO]

Dang Koreans

[powerabout]

OK , time to move onto cons :

I'll start ..

How bout , Flywheel ................ ............. ............

Agreed , that was a skeery thought . But mine will have stainless guard's next time . Just something about a 3.0L wheel sayin "Made in Korea" that made me think of mentioning it ...

OK , air flow . So it goes in the front half , # 1, 3, 5 take the short way around the outside to the rod slot . # 2, 4, 6 have a somewhat longer way around if the air is influenced by the rotation of the crankshaft.

More importantly , why do the reed blocks burn the rubber and chip the reed's on Merc's and not so much on OMC's .... ? (professor Carson , no cheating LOL )

Fuel coming in the front helps versus crank injected?

[powerabout]

Re flywheel some wire mesh in layers of kevlar in the cowl should do it.
Maybe just kevlar?

[Chaz]

So if the air is meant to go from the crankcase up thru the rod slot , why is the crank side made with sharp corners and the cylinder side floor have the radius ... ?

Wouldn't you want it to be easy to go thru and hard to come back ...

[AZMIDLYF]

Air is being drawn in on one side and the other is compressing it? Less resistance for piston coming down?

[powerabout]

You dont want the air to go back into the crankcase via rod slot
The rod is going back in so it is increases volune a bit to help that i guess not to mention ram effect from upstream in the airflow

[CNC_Guy]

see attached. It is a merc part.
Velocity is everything, why the SVS works better than the AMS. The exhaust is a 2.5 is narrow, the exhaust has to change direction, or be bounced off the floor of the block etc

Did this mod gain anything?

[powerabout]

Did this mod gain anything?

My guess is we might see it on the caldwell when they talk 500hp?

[Chaz]

# 1 ) Why do the tips of the Mercury reeds chip and burn ?

# 2 ) If air is sposta only go up thru the rod slot , why do they flow better going the other way ?

[powerabout]

1 too much cc compression due to all the air going back into the crankcase ( do port n stb chip the same?)
2 sell lots of reeds