I recently bought a used BME 110 from a member on RCU, I finally flew it this week and noted that the left cylinder is running way hotter than the right. The right is about 205-215 degrees and the left is about 280. I have the cowl baffled and opened the intake holes about 1/2 inch on the cowl. About 1/2 of the bottom of the cowl is cut-out.

This morning I went out again to try some stuff again. I turned the high-end needle out 2 turns so the engine is running rich. The left cylinder is still about 270 degrees and the right was about 195 degrees after 8 minute flight.

While I was out at the field this morning I also ran the engine up on the ground with no cowl installed and took temperature readings afterward. The right was 220 degrees and the left was 255 degrees, so even on the ground the left runs hotter.

Enclosed are pictures of cowl baffle and spark plugs after this mornings flight.

Here is the spark plugs.

Any ideas from the engine experts out there. thanks

Most twins run hotter on one side. Differences in exhaust lengths and the way each cylinder "breaths" have an effect as well. Changing the baffle may help a little but you're in an ok zone now. How's the exit area for the hot air?

You did not note the type of exhaust you are using. If you're using cans you can experiment with changing the header length on the hotter cylinder a little. The plugs in the pic have not been running rich. You might want to consider running a touch richer that what the engine had been running for most of the time before the last ground run.

This morning prior to taking the pictures of the spark plugs, the engine was running very rich. It was so rich I was getting about 6400 rpm on the ground. When it was leaned out I was getting about 6900 rpm. Yesterday when the high end was leaned out it was getting about 6900 rpm but the head temp was about 290 degrees (on l/h side) after landing.

I am running the standard BME mufflers.

Is it normal to see up to 60 degrees difference between left and right head and won't the engine get damaged running that hot?

Also, what is the normal needle settings for the BME 110, yesterday I was at 7/8 turn on low end and 1.5 turns on high end. I know this is going to change some for each engine and location but most are still going to be set in a general area.

There is NO "normal" needle settings for any engine. The thought is an absolute farce. The needles on the 110 have an effect on each other, causing varied settings. Typically the low needle will be more closed than the high. Cylinder temp spreads of 25 to 60 degrees are not uncommon on twins. Temps in the air are rarely the same as temps on the ground. A person can easily create a much greater temp spread that actually exists simply by aiming a temp gun a degree or two differently than they did on the other side.

It's very difficult to determine what's going on with your engine via a printed media. What you call rich may not be rich at all. Is it rich in level flight or on an upline? Does it peak on an upline or sag? Does it peak in level flight on on a downline? All of those factors help in making a rich or lean determination. If it's a little rich on the horizontal and peaks without sag on an extended vertical upline then it's where it needs to be. It should not be reaching peak rpm on a horizontal line.

rcairflr--Does your engine have two gaskets under one of the cylinders??

No, Is it supposed to?

The fact that your temp difference is much less with the cowl off shows me that for some reason the cowl is causing a good part of the difference in readings, you may have to put more baffels in the hot side for more even temps.

WRK

rcairflr-- some engines have an extra gasket for balancing, but I have to agree with WRK. I missed the part about when you had the cowl off the temps were close.

I am lucky I guess...my Kavan twin cylinder temps run within 2-3 degrees of each other. It is a 4 cycle though.

If the temps were close with the cowl off, then it would seem to be an airscrew induced lack of airflow through one side, the screw effect of the airflow will hit the cowl inlet holes in an upward incline on one side and a downward incline on the other, if the inlet holes are radiused or sharp on either the top or bottom this would make a difference to the flow of air into the cowl according to the turbulance created by the prop wash between the prop and cowl, so according to what cylinder is being cooled more, look at the other side to establish the correct inlet hole radius or edge, it may be that the baffles are preventing air flow also.

Mike

hey rcairflr, the intakes look pretty large, I hope the exiting is at least twice the intake area. I recently had a left cylinder melt down on my BME 102, 295.00 later I'm opening the exiting area a bit more. Its been OK for 4 years, so the error in retuning may have been at fault.

Bald Eagle makes a good point. For some reason I missed the part about cowl off temps as well.

I think you should lower the top baffle a little more just to make the air go
thru the cylinder instead of over it, remember that air will go the easiest way out
do you have a picture from the front to see both sides and from the bottom?

I also thought about that but, it only takes a few seconds on the ground to get the temperature up that high and when in the air it was flying for 8 minutes, anyway in those few seconds on the ground the difference was still 35 degrees and just like in the air it was the left side that was hotter. I will post a few more pictures when I have more time.

Approximately half of the lower cowl is removed, I originally had a 3W-80 single cylinder engine in this cowl, so it is open pretty much from the back of the carburetor to the firewall.

Is it possible that I am getting some air sucked in from the bottom of the cowl and because of that I am not getting proper airflow from inlet to outlet?

I would also suggest putting a angled lip (about 1/4 inch or so) on the exit to help create a low pressure zone and pull more air thru, but I would have to look at the pictures. If you have too much removed the air might be hitting the fire wall and actually backing up the air.

That is definitely possible. Here are a couple more pictures.

If you could close the front bottom portion a little more to just behind the mufflers and make a low pressure lip, I think that would do it.
You could also deflect the air flow down the back side of the cylinders, I have found that really helps in temps.
I don't think the size of the exit area is as important as good flow through the fins of the cylinder and out.

RTK: I like that idea and think that is the first thing to try. I'll use this beatup old cowl as the test-bed and if it cools the engine I will incorporate that into the new cowl as well as getting the upper baffle closer to the engine. Also I will play with the needles a bit more.

For everyone who has posted here, I really appreciate all the suggestions. Even if I did not comment on some posts, I still have taken in all suggestions to come up with a possible solution.

If anyone can think of anything else please keep the posts coming.

For anyone who followed this thread, this is what I did to close in the cowl, after switching to the BME 110. Hopefully the airflow will be good now and the engine will run in good temperature range. If this works I have a brand new cowl sitting here to install in place of this beat up and cut-up cowl.

BTW I ordered the new cowl from Wildhare last Wednesday after getting home from work in the afternoon, when I came home Thursday afternoon from work the cowl was already at my door. Now that's customer service.

rcairflr

Your baffling system should be OK. In my experience with BME110 and what I have seen in this forum from other twins, one cylinder tends to run hotter than the other one, here you are the latest cylinder readings I recorded yesterday from my eagle tree data logger, don’t worry too much about the temperature differences unless is way too large. (There was a hovering being executed during this session):

BTW I installed a baffle system on my BME110 as well, I think is a good idea to obtain optimal performnce on twin egines.

Albatross--Where was your sensor placed on the cylinder?? Front or rear side??

Thanks to ask.

The thermocouples are not longer facing the open front of the cowl openings.
I moved 90 degree off that position, the thermocouple is now orientated toward the bottom, of the cowl.

Albatross, that is very good info. The thermocouple with a reader gives you excellent data on your engine temp... I used a IR temp gun to get my readings. Which will not be near as accurate as yours, but it looks like your temps are not far off from mine.