gkamysz

My Feedback: (19)

The manuals list unique part numbers for the carb barrels for the 46 and 53, but they have the same venturi bore at 5.5mm. They both list the same muffler, but 53-4C appear to have been supplied with pressure fittings and the earlier 46-4C without.

Taurus Flyer

Gents,
There is a large difference between the two stroke, sucking fuel/air with the crankcase volume ratio for example 1: 3 and the four stroke sucking the mixture with the cylinder and piston, volume ratio is the reverse compression ratio , so 1 : 8.
This generates a much stronger airflow in the carburetor in the 50 % of sucking time (25 % of total cycle time instead of 50 % of the two stroke).

Generated pressure differences as result of airflow in the four stroke carburetor can be four times more than in the two stroke as result of this and the fuel level variations have less influence as result of that.

Mufflers pressure isn’t a good idea IMO, even there is a tap on the muffler because the 75 % of cycle time the engine doesn’t sucks the air but the spray bar is still open.

And the carb of my Enya 60 4C ? Also a 5,5 mm bore, see the picture.
I think the (my!) carb is originally of a little two stroke but do not know which? Who knows?
And who knows were these taps on the mufflers are coming from? Making smoke?(LOL)

At least these taps make a long thread!!!

Cees

Hobbsy

My Feedback: (102)

You have to remember that the inlet in most mufflers is about 3 times the size of the out let meaning that the blowdown of the pressure wave is not instantaneous creating a positive average pressure. Most straight pipes are crimped on the end to create this effect.

gkamysz

My Feedback: (19)

It doesn't matter if the fuel is added continuously or only during the time the valve is open. Early fuel injection systems were designed to spray fuel continuously, even if they were port injection design. The needle setting accounts for this. The pressure differential is the greatest when there is airflow through the carb, so fuel flow when there is no air flow is small. All model fourstrokes for the past 25 years have used muffler pressure. Just like any other engine the quest for more power led to the use of larger carbs. Oversize carbs can't provide the necessary fuel draw and must use muffler pressure for proper fuel flow. Extreme cases require pressurized fuel systems, like OS FS91SII-P and FS-200S-P that have carb larger than the non-pumped versions.

Taurus Flyer

Hoppsy, Greg

Two strokes first, my opinion.

I am normally more interested in the max values of the positive pulses to feed a tank by using a check valve but I do also measure averages on standard mufflers, no tuned systems.
Measured average pressures of standard mufflers are always positive, not strange because we want the smoke to leave the muffler. (pulsating pressures are complicate to calculate an average pressure with a comparable (same) flow!! that’s the reason it is more easy to show some values.

50 and 100 % throttle, 280 - 700 mmwc this is 0,42 - 1,0 PSI and of course depending of a lot of facts.

The positive average pressure we find in the fuel tank with some delay depending of the fuel level and the resistance of the connection between the exhaust and tank.
If needed to research a rich midrange of a 2 stroke it is easy to measure the RPM s also but I didn’t do that before. IMO the 280 (in this example) is relative high when compared with 700 for full power that would declare the two needle to reduce the midrange draw..

Of course it is also still possible that there are negative pulse waves that reach the crankcase on the right moment and generate a negative pressure in the crankcase, but never a 2 stroke with standard muffler will have a sucking pressure like a 4 stroke IMO.

The four stroke but all my opion!!

If we want use the exhaust muffler pressure than we have to account with the problem the mufflers pressure does not have the right relationship with the needed flow, so it is possible but with kind of fuel metering (two needle) carburetor. Not the ENYA’s we are speaking about I think although it has a fuel restrictor in the barrel. I still think the 4 stroke carburetor of the ENYA xx 4C we can compare with the standard 2 stroke bleed air with metering device for "no muffler pressure".

When you want to use muffler pressure count with the fact that the spray bar does not spray the fuel when there is no flow, (so it is dripping 75 % of time for a single cilinder ?), for me a reason not to use muffler pressure.
My engines have to suck the fuel flow. Fuel pressure is barometric but dynamic airspeed pressure is compensated.

Now I also did learn the throat of my 4 stroke 60 4C is the same as a 46 4C and 53 4C a reason more to modify them because I think ENYA didn't do much research on the carbs

Last point I do not need an on-board glower, also not for my inverted 4 stroke engine, maybe because one simple fuel drip can blow down the glowplug?.


Cees

buzzard bait

I'm not following most of this, but I always thought that muffler pressure was a way to get relatively even flow from the tank. With the middle of the tank in line with the carb, there is positive pressure when the tank is full and negative pressure when near empty. Isn't muffler pressure supposed to even out this difference?

Jim

Taurus Flyer

Jim,

I hope you don't mind we make your thread more complicated but it is all about our Enya's
We do not have a float chamber as in the internal combustion chambers of the "Old cars".
Result is the fuel air ratio is depending of level of the fuel related to the spray bar and the changes are a lot for pattern flying and less for sport flying.
Influences of level differences are less when the carburator is able to generate a good sucking pressure with the airflow . The 4 stroke does a better job than the 2 stroke for that.
When you do not want a lot of drag of the carb you also can use the tankpressure to help the fuel flow, you still have a good pressure difference for the fuel flow through the needle valve. Only the pressure is "uncontrolled" so you need a more complicated (metering) carb
The more fuel difference over the needle valve the less influences of the tank level differences. But there stiill will be small influences, that's why you can check the ratio with "nose up" of the plane (for a puller engine!)

Cees

Hobbsy

My Feedback: (102)

Exactly, plus you get the benefit of the muffler pressure/tank pressure increasing at higher throttle settings when more fuel flow is needed.

gkamysz

My Feedback: (19)

It's easy enough to try running the engine without muffler pressure. Mine ran fine without it. I run quite a few engines without muffler pressure and often reduce the venturi size to be able to do so. The only way to virtually eliminate fuel level sensitivity is through the use of a flow demand regulator as used in Walbro carbs or like the Cline or other fuel regulators available. The flow demand regulator replaces the float in this application and uses a relatively highly (2-12psi) pressurized tank to feed fuel.

Cees, regardless if the fuel is dripping into the manifold or being pulled through by the intake stroke the engine consumes it. The needle setting compensates for it. There are advantages to injecting fuel only during intake, but hardly worth discussing in a model engine.

Taurus Flyer

Greg, when you write:


Cees, regardless if the fuel is dripping into the manifold or being pulled through by the intake stroke the engine consumes it. The needle setting compensates for it. There are advantages to injecting fuel only during intake, but hardly worth discussing in a model engine.

You are right, but when the Enya is designed to operate without muffler pressure than it can be a problem when using it. I did measure the pressures and if someone has problems to keep an engine running, and that is the subject of the thread, than I have one advice.

"Operate the engine without muffler pressure before trying something else."


About the pressure regulators, I do design and built these regulators for many years for own use, but that's one more step and not for this thread we know.

Cees.

gkamysz

My Feedback: (19)

And that's why this thread exists. The engine was supplied with a muffler that has a pressure fitting. The manual implies that muffler pressure can be used. The only thing left is to try it without muffler pressure and see how things work out.

Taurus Flyer

And when it works you will never forget me!

Cees

togatoga

My Feedback: (42)

Well i can tell you I have 3 nib older enya53s still in their original boxes and they don't have pressure taps on the mufflers.I bought them in japan a long while back and used only one out of 4 I purchased.Each engine came with comprehensive tools and accessories like a head gasket/shim to lower compression. And the engine doesn't need muffler pressure to run real well.I flew one without the muffler and I can tell you they sound great!
Now my question is , did enya change the cams on the later model 53s for better performance other than the carb.The enya airbleed carbs are really good compared to others.

Hobbsy

My Feedback: (102)

Tog, here is my .53TN, it does have a factory pressure tap, the .46 MKII has a pressure tap that I installed myself. Both run exactly as they're supposed to.

Taurus Flyer

Gents,

We can start an ENYA Exhaust Museum (EEM).
It is not really my party, these are 60 4 C, but I do have one with a "pipe", original the way I bought it. Collector item?

In the plane the unconnected exhaust tap and what does happen with the plane, see blue oval on the belly landing protection.
For me is interesting to see the differences in the internals of the carburetors because there are two models I see.


Cees.

gkamysz

My Feedback: (19)

Nothing more interesting than muffler photos. Loose, what was with my second hand 53. NIP, 60-4C muffler as called for on the 46 and 53 parts list, no pressure fitting.

No being able to richen the idle of an air bleed carb is a sign of too much fuel pressure. At WOT the needle is screwed in to compensate for pressure. At low throttle fuel pressure is reduced, but the carb is designed for no change, so the air bleed needs to be reduced.

Taurus Flyer

gkamysz

Lean?


Cees

togatoga

My Feedback: (42)

Well hobbsy, my 53s are the older version not the black rocker cased TN version. Mine comes with 2 exhaust pipes.One for running without muffler and the other longer one for attaching the muffler to.

It is not a good idea to fix a presssure tap to the old type muffler as the muffler attachment is a clamp on type to the pipe which can cause erratic running due to the poor seal.Thats why the newer version muffler is a screw on type for a better seal.
My 46 II, 41 and 53s all seem to share the same mufflers and carb.

togatoga

My Feedback: (42)

the enya 53s that I bought in japan way back in the early 90s i think. list price was 28000yen then.Was a powerhouse then and much better throttling than the os 48 surpass even without muffler pressure.

jaka

Hi!
Silencer pressure or not does not matter!!!!
Use it if the nipple is there or forget it if the nipple isn't there! Simple as that!

You must do something wrong if that engine does not work ok.
First thing to change is the glow plug! Use an OS F plug!
Then the rpm... anything over 10000rpm is too much! Not that the engine cannot cope with it but for best performance!

Propeller: Use a 12x6 or 13x4 APC or RAM prop...These are good props. Ma is not!
Fuel: 10% nitro is fine but the engine runs equally good on just 5%.
Tank and tank size: Do not use a too large tank or a tank that sits too low...always follow "the tank mounting rule"! 170cc (6oz) is just fine, 300 cc (10oz) is much too large...
A two line clunk system is recommended (called a Uni-flow system, gives a more even pressure to the carb) But remember that the Tettra"Bubbleless" tank is the way to go if you want the best in fuel systems.

buzzard bait

My Enya 53 has improved to the point where I think it is usable on a plane, with or without muffler pressure. Deciding which to do will depend on how it behaves in flight.

This is after removing and disassembling the carb, blowing compressed air through all the little holes, tightening the back plate screws (2 were slightly loose), and re-seating the intake tube in the o-ring and the silicon sleeve. It seems that one or more of those things helped.

Now, WITH muffler pressure, I can get a little steadier idle that bounces between about 2800 - 2900 rpm, which I could live with. The unsteadiness is not nearly as bad, and the average rpm is lower than before. But the air bleed hole needed to be almost completely closed. Top rpm was up to 11,100 today.

WITHOUT muffler pressure, the idle is still not as stable as I would like, but the range is about 2700 - 2800. That's with the air bleed opened up to about half way. If I spent more time fine tuning the air bleed I might be able to get a little better yet. But when I did a pinch test it seemed about right...a very brief rise in rpm and then quit, so I think I was pretty close to the best setting. Top rpm was about 10,900, but I assume I could have gotten the same as with muffler pressure if I'd taken a little more time to adjust the HS needle.

As a reminder, I did put in a new Enya #3 glow plug, as recommended by Enya. Is an OS F really better in this engine?

Yes, I suppose I should use a prop that gives a little more load. But I thought Enya 4 strokes were designed to be able to rev a little higher than others. Manual says 12,000 is max usable, and I suppose mine could unload that high in the air.

One other thought occurs to me: what about drilling out the muffler outlet? As someone explained above, if the air bleed has to be closed, then the muffler pressure is too much for it. So if I bored out the outlet, there would be less muffler pressure. Plus, I don't need it muffled so much. I'm with whoever said he liked the sound best unmuffled. That's a possibility too, if I like it in the air without muffler pressure.

Thanks to everyone who contributed your thoughts and experiences. I don't mean that as a closing necessarily, and I will report back when I've had some experience with it in the air.

Jim

Hobbsy

My Feedback: (102)

Jim, the OS-f will never be as good as an Enya #3, 2,700 is a pretty lousy idle, 2,000 to 2,100 is much better. If it were mine I'd try closing the throttle more at idle and opening the air bleed to half way.

buzzard bait

I think something is still wrong, and the only thing I can think of at this point is an air leak. If I open up the air bleed and try to close the throttle it just quits. That's been the problem all along. It's better now, but not as good as it should be.

I'm thinking about just putting some RTV around the intake pipe connections, at the carb and the intake hole. I don't want to try to take the O ring out to see what size it is for fear of damaging it getting it out. It isn't brittle.

Yeah, I'm not happy about the idle. I'd like to see it ticking away at 2400 or better.

Jim

Taurus Flyer

Jim,

For me it is clear you still do not understand the bleed air carburetor of your Enya.
See your bolt phrase.
So here is my last attempt.

When you want to close the inlet of your carburetor and run the engine only with bleed air it has to quit.
This is the way Enya did designed the carburetor, so it is possible to stop the engine.
When the inlet is closed the outlet is closed too, see the red circles, so no air. Also not by bleed air adjustment
If the inlet of the barrel was closed and the outlet still open you will find in no time all the fuel in the muffler!!!!.

So how to handle?
Basic combustion air is supplied by inlet and outlet of carburetor (red circles), and the fine adjustment of air to adjust the right ratio is by bleed air adjustment valve.

When you use muffler pressure there is a chance the carburetor does supply too much fuel as result of tank pressure of the muffler (How much? I did measured a lot of pressures). The Enya G type carburetor is not a two needle carburetor so you cannot reduce that fuel flow. Only try to keep the engine running however. Result can be, too high RPM at idle or un stabile adjustments as result of too rich mixture.
Risk also, one drip of fuel can change your little candle called glowplug in a blowplug (LOL), especially when running inverted.

Can people run the bleed air with muffler pressure? Of course! I see a lot of tricks.


When you do not use muffler pressure, you have the normal and right amount of fuel in idle position and have to close the carburetor NEARLY for that (CL engines do have a blocking? adjustment for that either!), then fine adjust bleed air.
How low can you go? Depending of the fuel, plug, propeller, quality of engine and a lot of other facts.


I modify the my carbs by making small exactly V cut outs in the in and outlet of the barrel so I have a better control of flow adjustment in idle. What you have to do is make an exactly throttle linkage so you can control barrel rotation exactly, the linkage might not have (too much) play.

The precisely machine v groove on the surface of the barrel is for fuel flow metering and is made by ENYA to prevent lean running in midrange. Lean running is very destructive for engines. The V groove gives the engine some rich running in the whole throttling range after full power is adjusted!

But now when use the muffler pressurized systems combine with the ENYA G type carburetor?
Muffler pressurized systems normally already do have a rich mixture in midrange, so you might guess.

We Dutch people hate anything with “rich” in it and we have to pay for it so I did start with shortcut the groove, possible when using a fuel pressure controller.


Jim, success with your engine and use a pipe instead of a muffler, most spectacular. ENYA already did designed for you.
Be careful with drilling holes in engines, I did see that before.

Cees

buzzard bait

I appreciate all the efforts, but the bottom line is that without muffler pressure, or with muffler pressure, the engine won't idle reliably much below 3000. I've been quite careful to adjust the air bleed screw.

The one thing I notice on this engine that doesn't look right is the HS needle. It had a bit of discoloration, which I cleaned up, but there remains a pit on the needle. I'm wondering if that pit interferes somehow with proper carburation. Unfortunately it's too small to photograph with my camera. It can be seen without magnification, but with a hand lens it really stands out as a significant pit on the tapered portion of the needle.

This is quite frustrating, especially after reading about the guy who found one in the woods and it runs perfectly!

Jim