Super charging a reed valve engine

[mcbob]

This one for those smarter than me !!

In memory of what was achieved in 1962 by McCulloch in Supercharging or forced induction on their BP-1 What would be needed to mount a small consumer saw engine to the outer face of the intake reed intake of say a SP125 OR 101 and use the small cylinder of say 40 or 50cc to run at an overdrive ratio to supercharge the induction possibly the drive could be a belt drive .......... idle minds needed.


Its an interesting thought the second pumping engine would be basic as all it has to do is pump a fuel air mix.

McBOB

[steveohara]

Bob,

Your conventional two cycle saw motor port arrangement would not benefit much from forced induction for the simple reason that you can't increase the pressure of the fresh charge in the cylinder above the pressure in the exhaust system without it just spilling out in to the exhuast to be lost when the piston closes the exhaust port on the way up.
Unlike the four stroke with four distinct cycles represented by a complete stroke of the piston one direction or the other, the typical two cycle has overlapping functions and the fundemental problem is that the exhast sits open until the piston is half way up the bore.
There are some interesting old and new direct injection and forced induction motors that fire every time at TDC but they are much different than the stuff we play with.
Regards,
Steve O'Hara

[Jeff Campbell]

a two-stroke motor made like a two-stroke diesel can be supercharged....



The unusal IMI Milano 100 FVT motor used 4 poppet style valves as exhaust valves. This was a sleeved MC101, it was sleeved to reduce bore for 100cc European class racing and to change the porting to only have intake ports that opened near the bottom of the stroke. This type of motor would supercharge nicely.

IMI-Milano-100-FVT McCulloch3a-480.jpg

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IMI-Milano-100-FVT McCulloch1a-480.jpg

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The McCulloch Super Scavenged snowmobile engines used a second piston for increasing crankcase pumping displacement volume. Note in the article they claim only a 25% power gain, probably inflated sales speak ... maybe actual increase was 15 to 20%, which isn't much of an improvement, and on a per cc basis (including that 2nd pumping cylinder) a true twin with two firing cylinders would certainly put out more power ... and that is the reason why successful production engines are not supercharged by adding dummy pumping cylinders.


Jeff

[ted johnson]

Kinda defeats the simplicity of a 2 cycle engine, doesn't it? Think maybe that's the reason GKCA/IKF made it so difficult to run a blown engine way back when.

[Jeff Campbell]

Ted, you got it, exactly right ... the 2 cycle motor is incredibly simple, with basically only 3 major moving parts in a single cylinder engine. Significantly increasing the power, without adding any more major moving parts is a nice engineering achievement. Look at how what engineers have done over the past 4 decades, with modern racing 2-strokes putting out about 6hp per cubic inch on gasoline.

[mcbob]

Now where do i find a IMI-Milano-100-FVT McCulloch fellas ??

[mcbob]

Well i found a pair of supercharged Mac's
Anyone know anything about the setup



McBob.

[ted johnson]

It was featured in one of the magazines in '61 or '62. Never heard of it after that.

[mcbob]

I wonder if the kart following him got drenched in fuel it would be great to see the published story on this one.

[mcbob]

Just to show what a running BP-1 runs and sounds like.

http://www.youtube.com/watch?v=GkmUeO42 ... r_embedded