RCU Forums - BME 58 Extreme

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RE: BME 58 Extreme

Quote:

ORIGINAL: RTK

Flymeaway, if you are having troubles in the air but not on the ground with run-ability then it is an air pressure problem on the carb, also as mentioned some of the carbs that came with them had very loose needles leading to problems also. If it is running hot also look at your baffling and and especially air flow, a lot of people do not pay much attention to that and any high performance engine needs a little extra in the cooling department.
I have one of the first ones made and it has not missed a beat, very smooth/linear running and gobs of power

I've been chasing this burble for five years now. New carb, tried with the velocity stack on and off, tapped and routed a pressure relief tube back to fuse, adjusted needles endlessly, new plugs, different diameter fuel lines, different oil...

The only thing I have not tried is baffling. Originally the engine was in an Extra, now it's in an MX-2. The cowls are similar so maybe baffling would help. Right now it seems that there's plenty of intake area and maybe slightly less exit area. I'll have to look into how to go about doing that since I'm completely clueless as how to do so.

Thanks.

RE: BME 58 Extreme

one thing on the preassure relief tube, you half to get the end of the tube outside the fuse in clean air.
use a piece of brass tubing on the end of the tube,with the end of tube pinch shut,then cut or drill two small holes in it and route it outside the fuse.it works great,i tried all of the other ways to do this and none of them work as well as the way i did it this last time.
engine is tuned in the air just like you tuned it on the ground.

I bought a 4th hand 30% PAU Sukohi with the BME 58 Extreme engine. This is my first gas plane of any kind (all electric before). It is swinging a Xoar 23 x 8 prop and I'' using redline oil with a 40:1 mix. Can someone tell me what max RPM's and head temperature to look for..

Thanks

Are you running a pipe or stock wrap around? With a stocker I'd say shoot for 6900 to 7200 with that prop. Higher with a pipe. your temps should be in the low 200's when you land if you rip it alot. Lower temps if you are just flying around.

Thanks! Running Pitts style. My temp was 275-280 yesterday so I richened it up today and it came down to 255. I'm gonna give it another 1/2 turn tomorrow.

I don't have BME 58 but a BME 61cc twin cylinders, also my first gas ( gasoline ) just love the engine and the sound of two cylinders reaping the skys, I'm also using red line oil at 50:1, I will be changing that to 30:1 because my new DLE uses that ratio so I can use only one gas can, it is swinging a 20X10 @ 5k

Quote:

Originally Posted by Oh no.. not again! (Post 11900122)

Thanks! Running Pitts style. My temp was 275-280 yesterday so I richened it up today and it came down to 255. I'm gonna give it another 1/2 turn tomorrow.

While you can control the temperature of a gas engine with mixture to some degree, cooling airflow through the cylinder fins is the main source of cooling. This can best be accomplished with proper baffling when needed. The BME 58 doesn't have an excess of cooling fins compared to other engines so baffling can be very important. This is not an alcohol burning engine where needle settings can have a major effect on temperatures.

Set the high speed mixture to where the engine runs the way it should (set just below or at peak RPM) and control temperature with airflow. Your engine will thank you in the long run.