SWORDSN

My Feedback: (13)

Can't see that it would different from the stock muffler as far as cooling goes. Are you saying that the engine design has a cooling problem? Just asking.

Whistling Death

Well, maybe these engines will find a way to survive. I don't know how Zenoah G38's have managed to stay together and function for decades with the same rear exhaust design.

ccostant

My Feedback: (38)

I think cooling is something to be considered with the rear exhaust muffler setup. Even engines with side exhaust equipped with a wrap around muffler have this problem. Air flow will definitely be restricted in both cases, probably less with the wrap around. I've had two G38 setups and never had a problem. Although Zenoahs typically have more surface area for the cooling fins.

MTK

Not to belabor the obvious it's a matter of amount of fin area around the exhaut post and cooling air flow hitting those fins. I don't agree that there is no airflow hitting the rear fins. If one were to properly set-up some ducting around the engine, the exhaust port will get cooled adequately....

I was using the SAP180 HP, which is rear exhaust, until this past season. The fin area of this engine is rather small, yet with proper cool air ducting I didn't really have cooling problems

I also don't agree with the "side exhaust-wrap around header" comments.Most of my 30cc-60cc engines I've been using the past 3 seasons were/are side exhaust withwrap aroundheaders for tuned pipe use. And again, with proper ducting around the engine,I've had no issues with cooling in the hottest of days. The most important thing about these engines is ductingto get good air flow through the fins.

Also, if you place a short dam or hood in front of your exit holes, negative pressure is created where it is needed the most, at the exit holes. The hot air will be sucked out of the cowl. By placing the short dam in front of exit holes I minimize the exit hole area to at most 1:1

I wouldn'thardly attempt to fly some of these cavernous cowls without ducting around the engine. The scale inlets at the cheeks actuallymay becausing more harm than good in cases where single cylinder engines are used and are installed inverted. The scale inlets are there for twin opposed cylinders. Ram air goes into these and practically completely bypasses the inverted engine cylinder as it finds its way to the exit. These help only if the engine issidemounted, but I would still form a duct around the cylinder inthese set-ups too.

Ducting I use is simple 1/32" balsa fitted to barely touch the fin edges or with slight clearance of up to 1/4" and no more. Make the clearance large and air will go around the cylinder because, as is true with any fluid, it will find the path of least resistance. The ducts go as far back as the rear of the cylinder

ccostant

My Feedback: (38)

My point about side exhaust-wrap around mufflers is there will be some amount of blockage of air flow and that it's just not the rear exhaust type mufflers that may have cooling problems. Never said it could not be cooled. Yes with adequate inlet, outlet, and ducting the engine can be cooled. Totally agree with the most important thing is to force air through the cooling fins. I have many single cycle engine setups in various warbirds with radial type cowls and inline cowling, powered by Zenoah 38s-45s-62s, DA-50s, and DLE-30s and have not experienced an overheating problem. Usually some pretty simple ducting does the job.

airraptor

My Feedback: (66)

Same here I didnt mean for it to come across as the engine will run hot and sieze. The air will stagnate in front of the muffler and the cooling fins. now if you direct the airflow over the engine and then thru the fins across the exhaust fins then will be fine, but on most setups with airflow straight thru the cowl/engine it isnt at its best. You will have a stronger engine if you cool the cylinder evenly all the way around. I bet when this engine is running the cylinder temp around the exhaust is 350-400 as the front is 225 or so in the air.

Whistling Death

At least it has people talking about the importance of engine cooling.

sbrackets

I have not seen any isseus with the DLE-55RA engines overheating. We have several at our field installed in warbirds. One being a TF P-40, TF F4U Corsair, and the other in a TF P-47. The only issue has been the mufflers. No overheating problems. And none of them have any sore of baffeling in side the engine cowl area. Just ones observation.

Jim

ewalk

Hello everyone,

I received my new Bennett mufflers today. They look really good. They are smaller than the stock one, so there will not be any clearance issues. I am hoping to get one installed this weekend. If I do, I will let you know how it goes.

sbrackets

Looks good Eric!

I should be getting mine soon.

Jim

thepamster

Hey Red Falcon.
Have you got yours from J-Tec yet? Just curious for a comparison.

Red Falcon

My Feedback: (3)

No, not yet. I am having it modified a little so I don't know if that's what is taking so long. I will let you know when I get it and post some pictures. I have flown my plane with the built up stock muffler last weekend. I got three flights and nothing has fallen off yet! It has the 1/16 plate welded onto the front and back with rossettes for extra strength. Seems to be working but time will tell.

airraptor

My Feedback: (66)

I never said it had overheating issues. but I know for sure you have more power available if cooled correctly. A uneven heated cylinder will make less power than one that is the same tempature all the way around. now this would be true if the cylinder has a looser fit on the fron half of the cylinder arc and a tighter one in the rearwith the piston the same way. we know this isnt true though. anyway this think is to advanced for most. so keep it how it is as it will still run just fine.

wyo69cowboy

My Feedback: (2)

Looks good. Let us know how it sounds in comparison to the stocker, and any rpm gain/loss [8D]

Whistling Death

I have had the Bennett mufflers on a G38 and a G62. They are loud.

sbrackets

Good! That's what we want on Warbirds.

Jim

ewalk

I ran the new Bennet muffler today in my P-40. It did seem to be a little louder on the ground, but I did not notice much difference in the air from the stock muffler. I need to lean the engine out some more. I leaned it a little after the first flight. I am not sure if this is because of a difference in the muffler, or just the fact that engine is getting broken in. I really like the new muffler. It seems to be of heavier construction than the stock one. Time will tell.

roknHS

I was just finishing up the install of my DLE 55 on a Graupner Taxi 2400 and decided to check the ignition timing...........it was factory set at 42 degrees BTDC............now that's not right! I had to elongate the mounts on the hall sensor to get it back to 29 degrees. I checked it with the spark plug and the RCEXL light/buzzer tester so, I know I got it right. If some of you RA owners are having issues getting the motor to start and run right.........learn how to check your timing........the boys and girls in China don't get it right everytime...........or maybe ever.
FYI

SWORDSN

My Feedback: (13)

Is this something that you can describe or point to a web site that can?

youngguy

My Feedback: (7)

Deleted

youngguy

My Feedback: (7)

[quote]ORIGINAL: MTK

Also, if you place a short dam or hood in front of your exit holes, negative pressure is created where it is needed the most, at the exit holes. The hot air will be sucked out of the cowl. By placing the short dam in front of exit holes I minimize the exit hole area to at most 1:1

Do you have pictures of the dams/hood? I am not sure what you mean by dams in front of exits.

roknHS

For great video instruction on timing the electronic ignitions, Search this forum and use "CH Ignition timing instructions" for your search term. That will get you to a thread where you can find a fantastic tutorial that anyone can understand.

Michel

Hi
Here,s a video , http://www.youtube.com/watch?v=GBXFp...vjx3w&index=24
And here,s some written instruction

Thought I would transfer this over from tha Cirkus (RIP). It is a couple of articals that Xipp wrote in response to my engine tuning question that got a great response from the RC Community.

Xipp engine tuning method (Salsa)

Petrol (Gas) Engine Tuning
*** Carbs aren't too difficult to tune up if you know what you're doing. First of all, you need to know how the carb works and how the settings interact with each other. About 95% of all the gas airplanes I've seen at the field are somewhat out of tune. How can I tell this? Simple, at some point the engines "four cycle" in flight. Two Cycle engines are not supposed to "four cycle" PERIOD. This is caused by a rich mixture that is forcing the sparkplug to intermittently miss making it sound like a four stroke. This is not good. HOWEVER the good news is; gasoline two stroke engines are very tolerant of rich settings (most of the time) and will run fine. You'll just consume a little more gasoline than necessary, and create a little more oil mess on your plane. You may eventually foul your spark plug as well. So why do so many people leave their engines tuned like this? Simple answer, the engine will start much easier when it's cold AND there's little or no warm up time needed prior to flying. Those are pretty good reasons! But the fact is... the engine is not running like it's supposed to.

(1) The low end needle on a Walbro carb is ALWAYS the one closest to the engine, the high end needle is the closest one to the intake/choke.

(2) There is no fuel adjustment for idle fuel, only air feed set by the idle stop or servo.

(3) Both low end AND high end needles feed the top end fuel supply.

Let's tune up a Walbro!

Set the low end & high end needles to about 1 to 1 1/2 turns each. Choke the carb or prime it, until the carb is wet. Fire up the engine and let it warm up. Let's set the top end first since it's the easier of the two. Go to full throttle. Adjust the top end needle for peak RPM. Leave it wide open for about a minute to see if it changes any. Should the engine go lean, open the low end needle slightly, if this doesn't work... you will have to adjust the needle valve inside the carb.( I will explain this later) If the top end runs OK, then slowly pull the throttle down until the engine begins to "four cycle" hold the throttle there. Adjust the low end needle until the "four cycling" stops. Now lower the throttle more until it "four cycles" again, and adjust the low end again. Keep doing this until you reach full idle. Now, from full idle begin to throttle up until the engine starts to bog or hesitate. Open up the top end needle just enough to eliminate the bog or hesitation.

When this is done right, you will be able to set the throttle in any position and it won't four cycle, plus you will be able to transition from idle to full power without any hesitation at all. -Xipp, Flyingcirkus.com Member



Understanding a Walbro Carb
Ok this is for people who need a little insight into how a carburetor works in this case I will be using a Walbro for example.

Starting from the gas tank, the fuel is pumped from the fuel tank and enters the carb through the inlet. The fuel works its way through the fuel pump through a little diaphragm pump that's controlled by 2 one way valves (little flaps). The fuel then passes through a needle & seat that is controlled by the "float" diaphragm. This "float" diaphragm manages how much fuel is available for the idle, low-speed, and high-speed throttle positions. The "float" diaphragm opens & closes the needle through a small lever attached to the needle. The fuel is then "standing by" waiting in the float area for a vacuum signal at the various jets. The lever setting is very critical since it controls the available fuel to the jets. If the lever is too low, the engine will run lean, if the lever is too high, the engine will run very rich and will likely flood out at idle
The fuel starts its journey through the pump assembly first...



Then the fuel is regulated by the float diaphragm that controls the needle & seat.



All of these parts reside in the float cavity area as well as the fuel ready to be fed through the jets as needed. The amount of fuel available in the cavity is regulated by the lever and its relationship to the float diaphragm. So it's critical that the lever be set properly. Within the cavity, there are distribution holes that are managed by the low end and high end needles. Plus the idle circuit, which is a fixed size.

(Note) All Walbro carbs will run in any position, but they tune "best" as a side draft carb. The down draft position tends to run a little rich at idle, and the updraft tends to run a little lean at idle. No big deal though, it's easily tuned none the less.

This photo depicts one of Walbro's premier carbs, having a large bore and equipped with a high speed check valve and external fuel pump pulse inlet.



Now let's talk about the pulse signal for the fuel pump.



Your ENGINE will determine which pulse inlet type you need! If the engine "carb base" has a hole drilled into the crankcase you will use the STANDARD pulse port and the optional (if you have it) port must be closed off. If there's no hole drilled, you will find a fitting located somewhere on your crankcase. Use a piece of fuel line to connect the crankcase fitting to the fitting on the optional pulse inlet. There's no need to block off the standard port, as it's already blocked off by the engine mounting.

The carb must get a pulse signal from the engine! This signal "pushes and pulls" on the pump diaphragm which feeds the carb fuel.

Now let's check out the "float needle & seat" setting.



This is the single most critical setting on a Walbro carb! Walbro offers a "setting gauge" to properly set the height of the lever for your particular carb. If you don't have one, the setting will be a trial & error adjustment and a real pain in the butt since you have to open up the carb to make the adjustment. For general purposes, the lever will be almost perfectly parallel to the carb base. This will get you close. If the lever is too high, your engine will tend to run a little erratic at idle. If the lever is too low, your idle will be OK but it will tend to run lean on midrange and high end. It may also run the float cavity "dry" at full throttle and die, regardless of your high speed /low speed needle settings.

The needle valve seat is pressed into the carb base, and you should not remove this without having the correct tools and setting gauges. Do not remove it!

Typical PROBLEMS The engine stalls when accelerated: POSSIBLE solution: High end needle way too lean, or low end needle slightly lean
Engine goes rich in flight : Low end needle too rich, float diaphragm needle lever slightly too high
Engine goes lean in flight : High end needle slightly lean AND low end needle is rich, float needle lever may be set too low
Engine runs good, but no idle at all : There's crap in the idle jets, the carb will have to be removed and cleaned. You may also have an air leak at the base of the carb. The throttle butterfly could be damaged or worn out
carb leaks fuel when not running : float needle is bad or has crap stuck in it, or the float lever setting may be too high, or the float diaphragm is bad.
My engine four cycles momentarily when I back off the throttle, then runs normal : This is perfectly normal for carbs NOT equipped with a "check valve" high speed jet. If you do have the check valve, then your float needle setting is slightly too high, or your float needle is leaking a little
the fuel leaks back into the gas tank when it isn't running : Bad fuel pump membrane, or an air leak in the fuel line at the carb

NOTE 1:
A very common problem with cowled in engines is, the air pressure in flight changes the "natural" pressure on the float diaphragm. This causes the engine to run rich in flight. There are several possible fixes available. Most of the time you can simply tune your engine for flight by trial & error. However, the easiest fix is to open up the cowling around the carb area to lower the air pressure. You may also rotate the cover to different positions to see if that works. The "BEST" fix is to solder a piece of brass tubing where the vent is, and route the vent line to a better location. I normally route it into the fuse going through the firewall. It works perfectly every time! Plus, your ground tune doesn't change in flight!

NOTE 2
Carbs equipped with the high speed check valve are greatly superior for flying aerobatics, or flying whereby the throttle will be used extensively. The check valve prevents jet dripping when you back off the throttle. That's all it does...
Straight through (non-check valved) jets always drip a little fuel while the throttle is being backed off, and causes a momentary four stroking of the engine until the jet stabilizes to the new air flow rate. This is completely normal.
-Xipp, Flyingcirkus.com Member






Michel

wyo69cowboy

My Feedback: (2)

Any update on your JTec 55 muffler? Curious on the cost, and how it sounds...

Aeroworks has 2 30cc planes I want that would be great for a DLE35, and neither has a pipe tunnel(30cc Ultimate and Extra 260). They both do appear to have plenty of room behind and below the engine for a "big volume" muffler. Was thinking of calling JTec on price for a custom Pitts style...

thepamster

I had been waiting to hear from Red Falcon as well. I went ahead and ordered one for my dle55ra from Bennet with smoke nipples attached. It was like 55.00 total shipped.
As was said earlier it is smaller that the stock muffler but much heavier and the other guy here said it was a little louder. My plane is not yet ready to go so I have not used it yet.
You should probably contact Jtec directly yourself. I think they can custom make anythng, for a price I am sure.