I have a Moki 210 in a WM Extra 300s and I am having trouble with overheating. Engine runs great with cowl off however with cowl on It runs bad and hot. I have enclosed some pics of the setup and I am hoping somebody can tell me what the problem is.

Pic 1 shows that the left intake is closed. Also the head sits a little lower than the intake.

Pic 2 shows the huge outlet for air.

Pic 3 shows how the carb also sits down below the inlet.

I posted what I thought might be a helpful link in the other thread you have about this problem.

Crash90,

Your engine may need baffles to route the air, that comes through the cowl "nostril", around the cylinder and the head of the Moki.

Because of the helical propwash "shape", the air coming through this intake may have enough "down" quadrant, to miss the cylinder altogether.

Even full size Lycoming and TCM engines have such baffles installed.

Block of the redundent cowl in take, it's doing nothing any way.

Try a baffle plate from the good intake as suggested above. You need to force the air "through" the cylinder. As you can see clearly in your photo, the air is going over the cylinder, not through it!

If that dosn't help (it will) try this...

because you have set the moki at an angle, cut a sub hole underneath the cowl intake, directly infront of the carb and cylinder head. This doesn't need to be big, infact it get less efficient (I run fully cowled YS 1.40s with an intake size if 1x2cm and a very big outlet area. Perfect) 2x3 cm will be fine. Try that for a while. Infact , that could work so well you may even block of both cowl intakes.


Remember to keep the nitro low ie.5% with a Moki

Thanks for all of the replies. Bla Bla that sounds like its worth a shot. Quick and easy. Maybe I can close off the 2 intakes, cut a hole directly in front of the cylinder and use a piece of brass tubing that runs right back to the cylinder creating a tunnel which would force the air right into the cylinder.

I have both the 180 and the 210. My motors are cowled and a lot of my flying is during the summer. Here in Louisiana the summer is always in the high 90's and the humidity is 150%.
I use the Cline regulator for the Moki motors.

This past weekend a friend was helping me with a test flight of a new airplane. I ran the motor up and asked him to hold the plane pointed straight up, straight down, and side to side.

After the test he commented that something was wrong.
What? I asked.
He said it didn't pick up rpm's when it was pointed straight up. Well no! Thats what the regulator is for. Constant fuel flow at all angles.

In your case your motor is probably going a little lean when you fly at an up angle.

I want you to know that I am NOT a MOTOR EXPERT. This is just my opinion.

Hope this helps.
tonyc

Overheating is while on the ground trying to set high end. Not too lean.

Is your prop a 20/8? The Moki 2.10 likes to be broken in using a 20/8 prop. A 20/10 needs to be saved for later on after the motor is well broken in.
Also are you using a tach?
I run a bunch of short break-in-runs using small tanks of fuel on the ground, full out at 6000 rpm. This is a very rich setting. After this I lean it out to see if I can get up into the mid 8000 range. I hold this only for about 1 to 2 minutes and then back off to 6000 rpm again.
My test flights are at about 7500 rpm, a full 1000 rpm below peak power. This is a slow process, I am not looking for the last ounce of power until after several gallons have been used.

Over heating on the ground sounds lean to me.

There are a lot of scale builders out there, Jeff Folley mr Top Gun, that fly a Moki 210 fully cowled on 25+++ pound war birds, down in Florida heat and they do fine.

Also are you using 0% nitro? Moki runs just fine on 0%. If you are using 15% you may be cooking your motor.

On my motors I use 0% nitro, 15% oil. I run a 18/8 on the 180 and a 20/8 on the 210. Bambula props. Good props by the way.

Hope this helps

tonyc

Yes I use a tach. Motor runs great without cowl on. However I am using 20x10 APC.

I would bet you have too much prop for this motor at this time. The APC is a heavy prop and doesn't spool up as fast as a wood prop.

I traded for my Moki 210, it was almost new and came with 2 props, Zinger Pro 20/10. I think this is not the correct prop for this motor. I ordered two Bambula 20/8 props. These props run less rpm's but pull very well in the air.

In the test flight article printed in Model Airplane News the Moki did very well using a Menz Ultra 20/10. The Ultra is a thin wood prop and the Moki developed 26 lbs of thrust at about 7500 rpm.

I think if you tried a different prop, Bambula 20/8, Menz Ultra 20/8 or perhaps the 20/10 on the Ultra, I think you will be happier.

tonyc

I will give it a try. I am just going to pull the cowl and rotate the engine to a 90 degree. Should only take 20 minutes and should correct the problem.

I have a BGX installed in a 300s almost identically to your setup. I have the intakes on both sides open, but use baffles to direct the air to the engine. It runs beautifully without any sign of over heating.

John

JWN Do you have any pics?

I don't have any on hand, but will try to take some and post them in the morning.

John

Thanks.

It was my wifes birthday yesterday and taking pictures of model airplanes didn't quite make it on the list of things to do last night I'll post the pictures tonight.

John

JWN. Thats ok. I have ordered a new cowl and have already turned the engine to 90 degrees. Thanks for everything.

That may not take care of the overheating. Baffles are needed in many aircraft due to the amount of air space behind the engine. This can cause a high pressure area in the cowl which can push the incoming air away from the path you need it to flow. I'll still post the pictures as I know this is a subject which has come up from time to time.

John

Great. Thank you.

JWN.
I have decided to take your advise and put baffles in. Any pics would be very helpful. Thanks.

Here are a few pictures of my 28% Extra 300s with BGX. Note, I installed the baffles after first flying the model due to overheating. The air hole below the stock opening was present since before the very first flight. The last picture shows the main air exit. it's about 3.5" X 5" long. There is more space between the bottom of the cowl and the bottom of the engine box than appears. Also note the over head shot with the lower half of the cowl installed and how much space has effectively been eliminated by the baffles to prevent air stagnation behind the engine.

John

Head on without the cowl.
3/4 above without cowl
Side view without cowl
[IMG]http://jndneff.home.texas.net/rcplanes/DSCN0050.JPG
[/IMG] Over head with lower cowl installed
Head on with lower cowl installed
Underside of lower cowl with air exit

John,

It seems like the baffles in your aircraft are intended to extract the incoming air out of the cowl.

What our friend here, Crash90, needs are baffles that would route the incoming air, over the engine's head and cylinder cooling fins, before being drawn out.

The baffles you have shown are also needed, of course.

The baffle behind the engine is in deed intended to direct the air to the bottom of the cowl to be expelled. This is every bit as important as directing the air to the engine, which, is what the baffle on the aircrafts left side of the cowl does. It directs the air from the left side opening towards the engine.

No matter either way though. Crash 90 has his engine mounted, in his first post, exactly as I have mine mounted. The conclusion here is "What works for the goose will work for the gander".

John