jordant12000

I have a Hanger 9 RV 8 with a Super Tigre 75 engine, i get 2 -3 minutes of flight then engine sputters and quits with the Cowl on. (I now land better dead stick than with power) If the cowl is removed the engine runs great. I have the proper airflow outlet, fuel is same and glow plug is same. The club members (lots of experience) don't know what to tell me. The engine is mounted sideways so air is flowing right across the carb inlet and the head. Any suggestions? Thanks

jester_s1

Can you post a picture of the setup? Maybe there's something you missed.

52larry52

My Feedback: (1)

You said you "have the proper airflow outlet". I have been taught that the air exit area should be 1.5 times the air inlet area. Is this what you have? I would try adjusting the main needle setting 1/4 to 1/3 turn richer than peak setting. This has helped me cut out dead sticks with some of my Super Tiger engines. I also warm up the ST engines before making that final needle setting prior to takeoff. Just shooting you some ideas.

invertmast

My Feedback: (23)

Build a baffle to force the air to flow directly over the engine cylinder. Air is lazy and will always take the path of least resistance, so you have to force it where you want it to go. With proper baffeling you can get away with as small as a .5:1 exit to inlet ratio

jetmech05

If the engine runs good without the cowl but runs hot with the cowl you don't have good airflow. A baffle maybe your answer.

jordant12000

Thank you all for you comments, very much appreciated. When i have the cowl on i run a little richer. Have not thought of a baffle, but as the inlet flows directly over the carb inlet and head i woul

jordant12000

Sorry, posted before i meant to. The pics above show the setup which appears to me to have ample air outlet, but i am fairly new to the hobby so i defer to more experienced pilots. Thanks again for your comments and help!

Greg Wright

My Feedback: (6)

First: off you need to close off the opening opposite the cylinder head. That will help force all the air over the motor.

Second: back the high end needle off a couple clicks from peak RPM as the engine will unload in the air.

Third: try to build a Baffle to help direct the air thru the fins on the cylinder better this will help tremendously.

Greg Wright

My Feedback: (6)

Here's an article that might help you out. The baffle doesn't have to be made out of any thing too heavy either.
Some corrugated card board would do it nicely. That way it won't add to much weight up front.

http://www.cmchobbies.co.za/cmc%20ar...%20reviers.pdf

jordant12000

Thanks Greg, will see what i can do for her!

jetmech05

Looks to me like the muffler is blocking the exit in the cowl. I agree with blocking off the intake away from the head.

JohnBuckner

My Feedback: (1)

[QUOTE=jetmech05;12102928]Looks to me like the muffler is blocking the exit in the cowl. QUOTE]

Bingo! You appear to have almost no outlet area that is not blocked by that flat muffler likely even less than inlet area. Nothing you else you do is going to help much unless you let the hot air out of that bake oven.

Of all the pictures most are of not much concern but you left out the most important one when trying to assess this type of problem and that is from the bottom with the cowl installed.

John

junkjet

My Feedback: (55)

I had this problem with st 90 in a goldberg extra. I went to 5%nitro and a warm plug and all was fixed. Flew it for years still have it 90 is warn out now.

loopdeeloop

My Feedback: (4)

I also agree that the muffler is blocking, or at least misdirecting the air flow out of the engine bay. At the trailing edge on the bottom of the cowl is sort of an air outlet. That needs to be enlarged. Even though air is entering the cowl, the air cannot get out and is just being swirled inside the cowl. I feel blocking the other inlet opening is not necessary if a better outlet path is provided. The cowl cheeks fit tight against the fuselage so air is really getting trapped. That hot, trapped, turbulent air may be upsetting carburetion as well. Change one thing at a time and try a flight or two before making another change. If you change a bunch of things you never know which one made the difference whether it was all of the changes.

jordant12000

Everyone, I really appreciate all the suggestions! I will post a pic of the plane with the cowl on.

Billy J

My Feedback: (4)

fly with out cowl first // u need 1 in and 3out on air flow , doesn't matter on side ways engine . make sure prop size is correct / u must run it rich and chop up bottom of cowl to release heat good luck!

Rocketman612

My Feedback: (85)

+1

bipe II

My Feedback: (25)

Jordan

Also you may want to take a closer look at your fuel filter. Can't tell for sure but, it looks like your filter could be touching the fins of the cylinder, if so it could be boiling the fuel in time. Easy fix... good luck

vertical grimmace

My Feedback: (1)

If you can add one of these it will help tremendously. The low pressure created actually sucks the hot air out of your cowl. I have used them successfully in in hot scale installs, and the Late PE Reivers did a thread here showing his research on the benefits of cooling louvers. These are particularly handy with hotter running gasoline engines.

http://www.taildraggerrc.com/cooling...l-2-7-8-x-2-5/

thumbnstick

My Feedback: (169)

All Good Comments, also try some fresh fuel. Alchohol absorbs moisture into the fuel and causes the engine to run hotter. You can not see it or really test for it that I know of. Keep you fuel lids tight. Seems like your engine is on the edge of the problem. Any one of the above solutions may solve it.

wcmorrison

My Feedback: (2)

It seems to me looking at your pictures you have a cowl vent in the wrong place on the bottom of the cowl. You need the cowl vent near and around engine head. That is where the heat is generated and thus needs the maximum cooling. That you have provided a larger vent area is good but all the airflow is no where near the head. I think you need add a vent above the head and you need a baffle to direct air toward the head. I would not close off any entrance areas, as the engine needs all the cooling it can get. As said the air is lazy it will take the shortest route out of the cowl, so you are cooling the muffler not the engine. Good luck.

vertical grimmace

My Feedback: (1)

I will say that your pictures tell us very little with the cowling not installed. I am going to guess from what I see that you essentially have little or no exit air. It the air does not have a easy way out, it will pool up or eddy inside the cowl. If you add a louver behind the engine head, and block the air in on that left side of the cowl, this will force air in over the head, and the louver will suck it out.

jester_s1

There is a common misunderstanding that I've seen shared in this thread a couple of times already that I'd like to try and help with. That misunderstanding is that more airflow is always better. It's not true because the limiting factor of how much air can flow through your cowl is the size and efficiency of the exit. Air does not flow though much of anything by being pushed. It flows mostly by being pulled. So good airflow depends more than anything else on an exit that creates a vacuum in the cowl at flying speeds. That's why louvers and NACA ducts help so much; they are designed to create a vacuum when air flows over them. So that's the first part of the equation- make an air exit that creates a vacuum.
Where the "more is better" mistake is made is at the intake side. Your cowl has two air intakes. As mentioned above, air will take the path of least resistance. So in your setup, most of the airflow through your cowl is going from the non engine side of your cowling through the bottom where it does you no good at all. Remember the limiting factor is how much of a vacuum your exit can create or how much air your exit can suck out. So if your exit was capable of 10 CFM of flow, you probably would have 8 CFM bypassing your engine entirely and only 2 CFM going through your cooling fins. If you will block the right cooling intake you will preserve the vacuum inside your cowl and cause more air to flow to your head where you need it. Ducts will help too by forcing the air to go through the fins instead of just turning down and heading straight for the exit. It seems weird until you understand the fluid dynamics involved in the situation, but keeping your engine cool is mostly about blocking all airflow through your cowl except for the air that actually cools your engine. Everything else just makes it stay hotter.

tacx

My Feedback: (1)

Jordant12000,

I had the same exact problem with my Goldberg Staudacher with a 91 Super Tigre. All I did was to block off the opening opposite the engine side so the air flow was more directed over the engine body and it solved my overheating problem. In the attached photo you can see where I epoxied in a piece of clear plastic. It made a big difference.


Others have also given you good advice as to making sure you are on the rich side etc, etc.

jetmech05

Ok gents let's look at a recip engine cowl. Nice round opening exposing all the cylinders.
For controlling CHT (cylinder head temp) there are cowl flaps. These are located at the aft of the cowl area. Cowl flaps closed no airflow through the cowl. CHT rises right now.
Open the cowl flaps and there is airflow over the cylinders and CHT falls. I used to fly a C-131 in the Marine Corps as a first mech.
you have to have an exit.