Calling all HMS engine builders...

[A.K. Boomer]

Somebody build this engine that's been in my head for at least a decade, it's driving me nutz and if someone does not do it im going to have too,

Abstract; A dynamically supercharged horizontally opposed twin cylinder 4 stroke engine requiring no additional moving parts for the supercharging effect...

Concept Origins; Stihl "4-mix" 4 stroke pre-mix fuel engines - no crankcase oil, uses pre-mix like a two stroke to lubricate lower end and also mild charge effect with piston also helping to fill combustion chamber upon intake stroke...

Radical; By creating a horizontally opposed twin the concept radically supercharges the engine, due to said engine being a 4 stroke, while both pistons are going towards BDC extreme crankcase pressures are realized - Yet due to one piston being on the power stroke whilst the other is on the intake - only 1 chamber at a time is being filled resulting in extreme pressure stacking.

Theory; The results would be astonishing in horsepower production, and would be the most efficient supercharging method to date, no external apparatuses or belts, just using lubricated non modified parts that are already in existence... and unlike turbocharging the exhaust would be free flow with the engine internals also benefitting from cooler intake charges passing over all compressional components...

Usage; anything that requires close to double the horsepower in a package that weighs the same amount as original design, RC aviation comes to mind, or one hell of a weedwacker...

Talk amongst yourselves, Brian, put a man on it, I want it on my desk by tomorrow morning... (as for me I think I will just take a shortcut and couple two Stihls together then have to run some extreme octane boost along with retarding the timing a little lol) AKB

[Doozer]

I would never refer to a HSM as an engine builder.

-D

[BCRider]

I don't know about "stacking" and "radical" pressures. Yes, there is certainly a pumping effect. But consider that to draw in a new mixture that the crankcase must also become a lower pressure at some point to draw in new mixture. At least if you don't want to actually use a supercharger to force in the mixture.

Due to only filling one cylinder from the combined pressure of two cylinders I then wonder about how much volume will be drawn in through the carb or injector body to re-fill the crankcase. You filled one cylinder from the swept volume compression of two pistons. So there would be some residual higher than atmospheric pressure left in the crankcase after BDC. And that means you would not get a lower crankcase pressure to draw in new mixture until further towards TDC than in a typical 2 stroke setup. So in the end I'm not sure this will give you an actual benefit since you're pulling in at most a single cylinder's worth of mixture. And depending on crankcase volume and volume under the pistons (technically part of the crankcase volume in 2 stroke speak) and the swept volume you'll get a cylinder charge pressure of higher than 1 atmosphere but a lot less than 2 atmospheres as the total crankcase and open cylinder equalizes the pressure in the crankcase. I'm thinking at best you'd see a 2 to 4 psi boost in the cylinders over atmospheric. And perhaps not even that much depending on flow resistance and RPM.

[sid pileski]

I would never refer to a HSM as an engine builder.

-D

Sid

[A.K. Boomer]

I don't know about "stacking" and "radical" pressures. Yes, there is certainly a pumping effect. But consider that to draw in a new mixture that the crankcase must also become a lower pressure at some point to draw in new mixture. At least if you don't want to actually use a supercharger to force in the mixture.

Due to only filling one cylinder from the combined pressure of two cylinders I then wonder about how much volume will be drawn in through the carb or injector body to re-fill the crankcase. You filled one cylinder from the swept volume compression of two pistons. So there would be some residual higher than atmospheric pressure left in the crankcase after BDC. And that means you would not get a lower crankcase pressure to draw in new mixture until further towards TDC than in a typical 2 stroke setup. So in the end I'm not sure this will give you an actual benefit since you're pulling in at most a single cylinder's worth of mixture. And depending on crankcase volume and volume under the pistons (technically part of the crankcase volume in 2 stroke speak) and the swept volume you'll get a cylinder charge pressure of higher than 1 atmosphere but a lot less than 2 atmospheres as the total crankcase and open cylinder equalizes the pressure in the crankcase. I'm thinking at best you'd see a 2 to 4 psi boost in the cylinders over atmospheric. And perhaps not even that much depending on flow resistance and RPM.

Those are great points BC, the results would be stunted for the reasons you state, I think the system would immediately seek out it's dynamic equilibrium and there would be sure a dividend in the form of the next intake charge but do not believe it would be approaching half of atmospheric or anything like that, if it took a 25% hit you would still be way ahead of the game, also intake plenum design could play a key role like it does in just about anything but especially two strokes...

I think it would be very interesting to attempt this and see what happens, probably take me all winter if i decide to do it...

[A.K. Boomer]

I would never refer to a HSM as an engine builder.

-D

Classic A-hole statement, they are engines made from machined materials and designs - they run, so the guys that build them are called "engine builders" your going to have to come to grips with that...

[A.K. Boomer]

Check out this opposed twin, things a mint...

https://youtu.be/VD3H7wutsfg

[Doozer]

Well one person got my funny.
Better stick to being a porn star.

-D

[sid pileski]

Check out this opposed twin, things a mint...

https://youtu.be/VD3H7wutsfg

AK- that is a commercially built engine.

Sid

[A.K. Boomer]

He cheated i know i think they go for 649 bucks or something... it's cool looking though definitely a knock off of an old BMW...

[The Artful Bodger]

He cheated i know i think they go for 649 bucks or something... it's cool looking though definitely a knock off of an old BMW...

A knock off of a knock off?

[Michael Edwards]

A knock off of a knock off?

Ed Zachary. If you want a full size knock off of a knock off you can get a Ural.

[The Artful Bodger]

If you want a full size knock off of a knock off of a knock off you can get a Ural.

[The Artful Bodger]

My non-BMW, non-Ural flat twin motorcycle made by a company that produced 70,000 flat twin motorcycles for WWI!

https://images2.imgbox.com/2c/45/6usWpWpM_o.jpg

[CarlByrns]

Originally posted by Doozer View Post
I would never refer to a HSM as an engine builder.

-D

Sid

That sound you heard was Doozer stepping on his crank.