Hi Guys,
I recently acquired a Fuji 19S (pics attached.) It looks old but fired up the first time and great compression. However its muffler is a bit wierd!!!

First of all, the muffler open in the front and back. I can see through it. Is this normal????

Secondly, its got a flap on the side of the muffler for god knows what!!! My guess is to increase power or is it????

While the engine runs fine, its does not suck in fuel when i flip the prop over with my finger on the air intake but once it starts the fuel flow is cool. Also it only runs straight i.e. stops on nose up or down. Suggests no back pressure from the muffler???

I know its an old engine but its got great compression and being a recent convert to fuel engines, i am keen to learn the ropes before i go to bigger and better things!!!

P.S: I also have an OS MAx 20 which runs OK on my 20 size trainer. but i can feel this Fuji engine has much more power and am keen to replace the older OS max with this old Fuji!!!

Any thoughts?

Pic of the hole in the front of the muffler....

Muffler is normal on older engines. On later ones they closed off the front. The plate on the side is to prime the engine for starting. Try opening the throttle wide open to prime with your finger over carb then go to idle. Tank may be to far behind engine for proper fuel draw tilting plane up or down. Hope this helps.

This engine dates from the 1st days of mufflers around late '69 to very early '70's. This type muffler was somewhat typical on several brands at the time.

Jim

Thanks for your quick reply guys.... Flypaper (Sorry i dont know ur name!!) one question though,
Will the side plate be open or closed for priming? What about after priming? How do i use the side plate? The fuel tank is right behind the engine but its a GP tank with the position of the fuel pipe somewhat lower than that fuel inlet on the needle valve assembly.
Also the nozzle to attach the pressure pipe has screw threads on them.

Sorry for asking so many ques guys but no one out here has seen such a muffler and hence cant help me!!

(P.S: How does the back pressure develop when running the engine if the muff is open throughout?)

Hi again guys, tried to prime the engine but still no fuel flowing in?? what position should the side plate be in for priming?

The valve is meant to be used with a rubber fuel bulb. Open the door, give it a small squirt right into the cyl. then close the door. I think Sullivan still sells them but any small plastic bottle would do. Back pressure was not a concern back then. That is one of the first engines with a muffler. Before then we didn't run mufflers. If you want to quiet it down, put a nut and bolt through the hole in the front of the muffler. Get the centre of the tank up level with the needle valve if you can. Don't know what you mean by nozzle to pressure pipe. I have a bit later Fugi 15 in a combat job. Keeps up with the rest of them on 25% nitro. Name is Gord. Holler back if any more questions. Glad to help.

Thanx a ton Gord, very helpful indeed.
By the pressure pipe, I meant the nipple on the muffler from which you connect tubing to the fuel tank. I do need to do that dont I?

One more question, once the engine is primed the way you suggest, how does the fuel get pulled from the tank once the engine starts? I have noticed that once the engine starts, it doesnt stop as long as it is straight and level.

Quietning it down is not that much of a concern as for it running properly.

Also, if there is no back pressure, how does the fuel continue to flow when the plane is in a dive or a steep climb i.e. 90 deg nose up etc?. Does getting the centre of the tank up level with the needle valve help with this? If i can't what else can I do?

The venturi in the carb produces suction on the needle valve which draws the fuel.

The pressure line you are referring to may just be a priming line like was on my old Supertigers.

Jim

Hi W8ye,
Thanx for ur inputs.
The attached pic shows the pressure pipe as i know it!! It is running from the muffler to the fuel tank and its got threads on it too.

I know that in OS and other engines it is used for providing back pressure to the tank to keep the tank pressurised.

In these old engines, how did one manage to keep the tank pressurised?

Wow dude!! What era is that from? Looks like it will have a lot of antique value!!!

To make the pressure system work, you will need to keep the exhaust auxillary door closed. The nipple does look like one for pressurizing the tank.

With the front of the muffler open, there couldn't be much pressure?

Schnurle (Flat top piston) ported engines can take more back pressure than loop scavanged engines (Baffled piston) like this one.

Jim

I have a muffler for a Webra .61 SilverLine that is open in the front, like that one. I would never use it though since a K&B Twister muffler fits right on.

These older engines had smaller carbs than now,so as w8ye says they had better fuel suction. The one I have on the combat plane didn't have a pressure fitting,so I put one on it. Just makes for more reliable running during violent maneuvers. You would have to plug the hole in the front to get enough pressure to be worthwhile. By the way w8ye, these are schnurle ported engines. Up to date for its age.

These mufflers were called venturi mufflers and a number of engines used them when mufflers first started to be used. I remember my old Taipan 61 had one. There was concern about losing power with a muffler so the idea was that the airflow from the prop would funnel down through the hole and cause a low pressure through the centre which would drag the exhaust through the slots which you might be able to see if you look through the hole.

Why has no one mentioned that the head is rotated 90 degrees? With it rotated the engine will not cool properly.
Most flow through mufflers have the exhaust travel around the center tube and exit into the center tube from oppisite the exhaust port. Plugging the front of the muffler will increase the back pressure if the priming door is closed, but it will also cut back on the power available. Some engines actually run best without the pressure line to the tank as a few actually create a vaccuum instead of pressure. On those the tank just vents to the air.

wow guys there is a virtual goldmine of good advice there. I'll keep all ur suggestions in mind and report on my progress soon.

BTW if the airflow through the muffler causes a low pressure around the centre forcing the exhaust gases (in my case more fuel less gases!!!) out thru the back, then the muffler nipple, which is towards the back (refer last pic posted) should be able to pressurise the tank? What say?

meanwhile its off to the field with my trusty OS max 20 (1971 vintage!!!) on QB15.
But i must say one thing, there is more to fuel powered flight than meets the eye and i am enjoying this conversion from electric to glo!! A totally diferent ball game!!

and i will rotate the head asap.... Thanx Mr Motor, u just saved me some future frustration!!!

Hi again, just to report on my engine testing:

1. While tuning the low end, i felt it was running too rich at first since it was spewing oil from the muffler and stopping when glo plug was removed but when i leaned it out (air bleed screw), the rpm's increased as expected but it was too fast to be called an 'idle'. Also it was idling even though the carby was fully closed!! Wonder what was happening there?? I did check for air leaks but didnt find any. Any fool froof way to check for leaks?

2. When the low end was rich, the engine blubbered and stopped during transition. When the low end was lean the transition was fine. but again the engine was not shutting off wih the carby fully closed.

3. High end tuning looked fine but it was done on a test bench so i need to put it on a plane and check nose up etc to see if the fuel flow is maintained.

Didnt have the heart to put the engine on my plane as i was not sure if i got it right yet! What do you guys think?

Keep on playing with it until you get it right.

The mixture adjustment on a air bleed carb works backwards. To screw out the needle leans it and to screw in the needle makes it richer.

Your high end may still be somewhat rich yet causing you to open the air bleed too much to where the engine will run off the bleeder at idle?

Jim