Yoder808

I have a TH .46, was on a Tower Trainer. I have been really impressed with this engine, it seems(seemed) like a power house. I took it off of the Tower Trainer(mounted upright), and am using it temporarily on my Funtana X 50(mounted sideways). I can't seem to get it to run right. It idles fine, but when I transition to power, it runs VERY strong for about 5 secs, and then slows down. When I go to full throttle, alot of smoke comes out, and as the power fades, the smoke does too. As I come down on the throttle slowly, the power remains at the reduced level until I hit 1/4 throttle or below, then starts slowing down. I have a 12x5 Zinger on it. Is it too much prop? I am running 15% Cool Power in it, with a brand new plug. It also might be worth mentioning I can NOT back the HS needle out enough to kill it, or even make it "lope" like a 4-stroke. I found that odd. I tried one time, and backed it of till the needle came out, but I NEVER got excessive smoke, or a rough running engine. Also, I have a Slimline Pitts muffler on it. Here is a handy graph I made of what happens.

RCPAUL

My Feedback: (1)

If this is on a profile, you may be getting fuel foaming - profile fuses flex a lot more than builtup fuses. This will cause the engine to go lean at high RPMs. Try isolating the tank more and balance the prop if you have not already.

Paul

BillS

Sounds like the relationship between the CL of carb and the CL of tank has been changed.

Generally speaking the tank CL should be about 3/8 below the carb CL. And both needles will need to be reset.

Bill

infodevourer

I had this exact problem on a two-stroke mounted upright. It turned out to be a fuel feed problem, so I don't think there is necessarily a relationship with the mount position and the issue you are experiencing.

RCVFR

My Feedback: (7)

I think one part of the problem is the prop, it's a bit much. Try an APC 12X4, you should get 12K plus for good response. This is a narrow prop and I have good results with this one on a MDS .48 and Magnum XLS .46. Usually, side mounting will not give you any problems in the carb/tank position relationship compared to upright mounting. The biggest difference in moving the engine from the trainer to the Funtana would be the prop, I am guessing.

Try different props to see what happens.

MyWay

You might try an apc 11.5x4 prop an plug or reduce the muffler outlet size for more back pressure.

Yoder808

Ok, I think I will switch props, and try that. Is it normal I can't richen it up enough to "drown" it?

MyWay

If your muffler has two outlets, plug one of them. If that does not fix the problem try backing out the low speed needle.

jaka

Hi!
Why a 12x5 prop? Seems too big for a .46 engine even on slow flying high winged trainer.
Better use a 11x6 , 11,5x4 or 12x4 APC.
/Jan K

opjose

Been here, done that.

Been through this with the TH .46 on my biplanes, both side and inverted mounted engines... with and without the Slimline Pitts, the Bison Pitts, the Sport Scale Pitts, the TH .46 muffler, and the O.S. P-Box muffler... see below...


The engine runs a bit richer mounted sideways and still more when inverted even when you have the tank to carb relationship correct.

Making things still worst, is that the TH muffler (and the pitts muffler, been here too!) has no baffle. While this maximizes power, it also provides for almost no tank pressure so you will experience tuning changes based upon engine orientation. With the TH muffler and pitss muffler there is almost no difference running the muffler pressure to the fuel tank, or not.


The good news is that the TH engine will accept a good range of tunings, especially once it has been broken in.

Your best bet is to use a muffler with a baffle plate (the O.S. P-box .46 muffler is a good choice) or add one to the TH muffler.

You will need to retune the low speed and then the high speed needle.

Sideways your engine is running a bit richer throught the low range. You get an initial "burst" of power as you throttle up, because you are quickly permitting more air into the carb. The mixture leans a bit because of the initial airflow. As the fuel is sucked in however the engine goes rich and slows down, but does not shut off.

Lean out the low end a bit, and re-tune.

Then make sure that you check the engine in all aircraft orientations, nose down, nose up, etc.... waiting at least 10-15 seconds for each orientation change to kick in...

Pay particular attention to when you have the cylinder head pointed downward (inverted) as the engine goes very rich at this point.

Lean it out enough so it does not stall out.

Then check the nose up performance. Make sure that the engine does not go too lean on nose up.


A muffler that maintains a higher pressure will cure all of this, but you'll loose a few hundred RPM's on the prop.

With a baffled muffler you'll need to retune the low and high needles as the engine will be initial very rich, but fuel flow will be far more consistent in all orientations.

BTW: Blocking one of the Pitts exhaust ports had little effect with both of the TH .46 engines I own.

Also this engine seems happiest with 10% Nitro not 15%.


Once you do have it tuned, this is a POWERFUL .46 engine...

Yoder808

Yeah, I think I'll go to a 10x6 prop, and weld block off plates on the ends of the pipes. Then drill small holes in them, and open them up gradually, till I get a good balance of power vs. reliability.

scratchonly

Too lean low speed setting can cause lack of adjustment of the HS needle, or as stated earlier a lack of decent muffler pressure although the engine should run without pressure if properly adjusted.

RCVFR

My Feedback: (7)

Now you are going from over propped to under propped! 10X6 is a .40 size prop. If you want to fly your Funtana with a .40 engine, this is one way to do it. Also, before you start surgery on the muffler, get a prop that will work, first. Then, if you still want to tinker with it, have at it!

loughbd

I run my 45's on a 10x6 prop with no problem

Yoder808

Ok, I will mess with the low speed some, put a 10x6 or 11x6 on it, I have both. If nothing else works I will modify the muffler.

opjose

The 10x6 may be a little "light" for that engine, but not so much so that it will adversely affect it's tuning by much.

loughbd

A 10x6 is absolutely an acceptable prop for a 46.

NM2K

My Feedback: (14)

Guys, don't forget about the Perry/Conley VP-20 oscillating pump. While it isn't as powerful as the VP-30, it is nowhere near as finicky in set up and it DOES help when fuel draw has been lowered by removing baffles. Furthermore, it doesn't draw on anything but engine vibration to drive it. Easy hook up, maintenance free and probably no adjustment required in most situations.

Yoder808

Thanks for all the help guys.

Turk1

Ditto.Your symptoms seemed your low speed needle is blocking the spray nozzle to allow high speed adjustment.Take back low speed needle,adjust high speed needle then adjust low speed again.

Yoder808

Got it all resolved. I did several things.

1.I took the carb off, and re-tightened the nut while pressing the carb in.
2.I switched to an APC 12.25x3.75 Prop
3.Replaced the fuel line from the remote needle valve to carb. It had a TINY hole in it, right next to the carb fitting.
4.Tuned the LS needle open more, and leaned the HS.

I am now taching the APC 12.25x3.75@11650, but I am running it at 11,050(pretty rich).

Thanks for all the help guys!

RCVFR

My Feedback: (7)

Glad to see you are back in business! Enjoy the Funtana.