I just want to tell me what is with that "auxiliary pressure port in the picture".

....that "pressure port" is used to pressurize the fuel. When you supercharge an engine
you drastically increase the air flow into the engine. In order to get enough fuel into the
engine to get the proper fuel/air ratio when it is being supercharged (with air) you must
have a way to increase the fuel flow to match. This method works in a manner in which....

...as the boost is applied to the engine, the same ampount of boost (pressure) is applied
to the fuel (pressure). As the RPM (and boost) is increased, the pressure to the fuel is
increase the same amount. This is a way to get around the added complication (and expense)
of having fuel injection added to the engines as well.

FBD.

So is this piped straight to the tank like muffler pressure is in an aero engine?

As with the rest of the "supercharger" this is purely an advertising gimmick designed to suck money out of impressionable newbies. This thing straight out doesn't work. Read the car engine forum here in RCU and you'll find pages and pages about this thing.

I am with downunder, i will say the "super charger" in 2 stroke model engine will not work.

Because the transferport and exhaustport are open ,and there are atmosferic pressure in the cylinder, hi pressured air/fuel mix are blowing out of exhaustport. The "supercharger" are not blowing the air/fuel pressure in the cylinder with pressure since the induction valve in crankshaft are allready closed.

You are throwing money out of window for the 2 stroke engine with "super charger" who are not more powerful than normal 2 stroke engine.

Better to run 2 stroke engine with tuned pipe.

....I agree with you Guys. Boosting the pressure to the top end of a two stroke can
only be accopmplished by boosting the pressure to the crankcase. The problem is,
when the piston drops down far enough to allow the transfers to open, the exhaust
port is open as well. That would let all the extra pressure from the "supercharger"
to exit the exhaust port.

Keep in mind that the compression of the two stroke engine does not start until the
exhaust port closes....in any case. The system doesn't need help scavanging the
cylinder either....it already suffers from an aprox. 20% loss of the fresh fuel charge
as it is, in normal operation.

If one was to "supercharge" an engine....he would have to lower the compression
from the start. The two stroke is already a low compression engine. Raising the
compression above the normal level won't help, and in most cases is counter productive.

So like Motorboy has alluded to....a good pipe will extract more power than overheating
and overcompressing the engine.

FBD.

Not doubting any of the above comments, but one time I was farting aroound with a .20~something (heck, it could'a been a .40~something, but I digress...) engine on a break in stand. I took our air compressor and blasted air into the prop as it was running to "simulate" flight (read: unload the prop some). Noticable RPM increase (understandable) I then (carefully) shot the air from the nozzle directly into the carb venturi and got a very noticable RPM increase, just as if it were supercharged...well, it was, just not a mechanically driven SC from the crank.

What about the OS Max 120 that was cupercharged with it's own little mini Roots blower? Wasn't it inline with the intake?

Neat topic, don't let it die.

Jon

The OS FS120SP is a four stroke engine with a Roots type supercharger.

I have a 1/8 nitro buggy that I installed an electric supercharger on. I know, I know, I could have gotten a larger engine, more nitro, different tuned pipe, etc etc blah blah blah........ I do not wish to re-hash the merits or demerits of supercharging two stroke engines.

However, part of being a gearhead for me is playing around with, well, gears! So I installed this thing and FWIW, on 20% nitro fuel it required the HS needle to be opened a 1/2 turn richer than normal. It can probably be even richer, but I have not experimented with it any more yet. Without the supercharger, 1/2 turn richer on the needle caused the engine to bog down significantly.

Did it cause this 2-stroke engine to make more power? I dunno, I don't have an engine dyno. It had a lot more 'bark' to it and it certainly seemed to be making more rpm. In any case, it sure did have a positive placebo effect if anything!

And under other circumstances, more fuel being burned means more power.

Regardless, it looks cool, and it does not harm the performance in any way. So it is a fun thing to have and play around with.

The classic supercharged model airplane engine of all time!

.....now, turbocharging might be a different ball game.

........except for a turbocharger small enough it'd have to spin at over half a million rpm

Actually I think a supercharger might work on a 2 stroke given suitable port timing changes because one of the things needed anyway is a positive crankcase pressure. Our engines are already timed to match this positive pressure (and the inlet port is timed to match the negative pressure). Maybe it might only give better scavenging but even that would add some power. Whether the extra power is enough to drive the supercharger is another thing though .

....yes, Downunder....I agree. You would need increased port timing on the transfer ports,
maybe an additional boost port. A long stroke engine might be the way to go too. With the
additional crankcase pressure involved, a reed valve plate would really be good. Of course
with a rear intake/carb engine, the rear disc valve engine might do the job of holding the
boost pressure in satisfactorily....but a reed valve wouldn't hurt back there either.

The whole question is whether or not the system would overcome the mechanical losses or
not....the electric blower is a good idea.

On a four stroke there is much more time during the 180 degrees allotted rotation time to
charge the cylinder.

FBD.

I've got a couple of engines that might suit if it was only to have the transfer port timing closer to the exhaust. By eyeballing them (I haven't used a degree wheel yet) the transfers on both open at virtually the same time as the exhaust port. I've never seen any other engine like this. The engines in question? Believe it or not, the ST G20/15 and ST G15....hardly what you'd call wimps .

.....that's where an additional boost port with a reed assy. would work good. Generally
speaking, it's not wise to mess with the transfer ports too much. You can raise them a tad,
but don't mess with the angles.

But like Motorboy said, the pipe does the most benefit. Once the compression is set, and
the optimum port timing is settled in, it's all about the fuel and the pipe.

I put a reed plate, a Mikuni carb, and a homemade pipe on this Grand Prix racing bike of
mine and won some races in my younger days. I was a good port-man too.

I had this old four speed Bultaco factory bike cranking as hard a humanly possible. I determined
later that a good piston port engine will make more HP than the reed set-up, but this worked
good in this application, because I only had 4 speeds. Reed plates help with the torque though.

I would venture a guess, that if we were going to pressurize the crancase with a supercharger,
a reed system would be needed to keep from losing pressure back out the intake.

FBD.

The only way to supercharge a two stroke is to put a cam operated exhaust valve in the head and close it before the fresh mixture makes it out the exhaust. That is how it's done in the big boys, though they rarely are able to actually build any significant pressure.

http://auto.howstuffworks.com/diesel-two-stroke1.htm

The opposed-piston two-stroke diesel engines for ships has turbocharger to example in Burmeister & Wain marine engine, but not for pressurized air in the cylinder as in turbocharged 4 stroke or cam operated exhaust valve 2 stroke engine. It improve shavening in the cylinder.

Jens, I was searching for a good link for an opposed piston engine and couldn't find one. They do the same kind of thing. Super or turbo chargers are not meant to pressurize the charge in these large diesels. They provide primary compression that takes place of the crankcase which is running in an oil bath.

Jens, have you ever looked at the Napier Deltic engines? What a piece of engieneering.

I think all you did was to lean out the mixture because you only added air, leaning out the mixture will of course raise rpm`s. I don`t think you actually supercharged anything

I saw first time the opposed piston engine marine engine was in the ship "Harald Jarl" (now "Andrea" ), the engine was 5 cylinder opposed piston engine with 2 turbocharger. It was in 1986. The engine was licencebuilded (B&W) in Aker Mekanisk Verksted, Oslo in 1960. See pic. of the top of piston in engine room.
http://www.elegantcruises.com/andrea.html

Yes, i saw the pic of the Napier Deltic engines, a really master engineering.

Kmot do you know who built this engine?