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On Sat, 14 Mar 2009 11:15:02 -0500, wrote:

On Sat, 14 Mar 2009 08:50:53 -0400, wrote:

Back in the 1960's, Honda had a little 50 cc, twin cylinder, DOHC,
race bike that redlined at 20,000 rpm.

Yeah but those were the guys wouldn't't weigh pistons on a triple beam
because it wasn't accurate enough ;-)
We do have to credit the Germans and Japanese for making us change our
engine factories. We were still building the stuff that allowed us to
blow up all their factories. They got a clean start and kicked our
ass. My Merc is a Yamaha powerhead. American foot. Best of both
worlds in my opinion.

Those that keep talking as if 4-strokes are somehow "new technology"
simply because they are mounted on the transom of a boat are pretty
ignorant. If someone said that 4-strokes have come a long way in the
past 100 years, they might be on to something. Most of the
developments are not specific to 4-strokes. Materials, manufacturing
techniques, fuel delivery...

The biggest single advancement in 50 years for the 4 stroke was the
overhead cam. That eliminated a lot of valve train hardware.

That was a little more than 50 years ago. They were making engines
with dual overhead cams more like 100 years ago. The rest of the stuff
you list below is not specific to 4-strokes.

The real enhancement was the computer control but that has creeped
into 2 stroke design too. EFI is where most of the efficiency and
clean burning came from. They had pretty much squeezed all the juice
out of the carburetor by the end of WWII. Fuel injection was dabbled
with for a couple decades after the war but the systems were pretty
clunky until someone put a closed loop, computer controlled system in
there. Combine that with computer controlled ignition systems and we
really have a well performing engine.
Alas, the ability to fix it on the water (or side of the road) is
compromised.

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