Is the JXF 27x10 propeller a little much for breaking in a new BME 115?

[tonyc9075]

Is the JXF 27x10 propeller a little much for breaking in a new BME 115?

The JXF is the same as the Xoar propeller from what I understand. The motor is new and just now mounted in an airplane that will be a good match for this motor.

What I am seeing on the ground using a tachometer is 4900 on the high end and 1290 on the low end.

The motor runs fine, I have had the KrisW carburetor modification and I am using the Budweiser exhaust system.

My question is what kind of numbers should I see as the motor breaks in?

[sinergy]

I am pretty sure the 27x10 is actually narrower than a Xoar... either way those numbers suck


Have you tried tuning it at all? There is no way that is too much prop for that engine. I suggest you get out your screw driver and make it come to life.

[tlundstedt]

Tony,you should be well over 7000 rpm with that prop.

[Altavillan]

Hi Tony, Couple things I see, With air blowing over the carb inlet you'll loose a few hundred rpm's, The header drop is a bit close, 3" would give a couple hundred more. Maybe you need some more little holes inside the Muffler? Check your timing and adjust the needles some more. Falcon ignition should be about 4.5mm and CH should be about 26* or about 5/16" to 3/8 for starters. Header length should be between 7.5 and 9.9" from flange to start of cannister.
Here's the lengths needed http://www.rcuniverse.com/forum/m_73...tm.htm#7385806
No one seams to be stating how well keiths fix works. Or if it does work. I'd guess you should be looking at around 6800 with that prop. I still get 7300+ with a Xoar 27x10.

[tonyc9075]

	Quote: Originally Posted by Altavillan
	Hi Tony, Couple things I see, With air blowing over the carb inlet you'll loose a few hundred rpm's, The header drop is a bit close, 3" would give a couple hundred more. Maybe you need some more little holes inside the Muffler? Check your timing and adjust the needles some more. Falcon ignition should be about 4.5mm and CH should be about 26* or about 5/16" to 3/8 for starters. Header length should be between 7.5 and 9.9" from flange to start of cannister. Here's the lengths needed http://www.rcuniverse.com/forum/m_73...tm.htm#7385806 No one seams to be stating how well keiths fix works. Or if it does work. I'd guess you should be looking at around 6800 with that prop. I still get 7300+ with a Xoar 27x10.

The header drop is 1.675. Should I get a longer header? The header lenght is 8.25 from flange to the Bud bottle lip. Is this OK?

What I can do quick is pull the muffler apart and drill some more holes. I will do that for this weekend. This will be step 1 of several things that you gave me to look at.

If you are getting 7300+ on the Xoar then I would expect to see that after a few gallons on mine.

[JEFFRO503]

I'm going to let the guru's like Altavillian , RTK , Tired old man and so forth fill you in on the corrections that need to be made , but if that motor is piped right , and the needles are set correctly you can be getting close to 8000 rpm on a 28X10 Mej prop. Sounds unreal but i've already seen the video to prove it. At those rpm numbers , you'll definetly want to switch up to a 29" prop so you don't damage the engine. If the carb fix is the culprit , send that sucker in to Tom and andy and they'll get it running right.

BTW , here is the video........talk about rippin' the prop sheeeesh!! >>> http://www.youtube.com/watch?v=9wAnK...w-owner-7.html

[tonyc9075]

	Quote: Originally Posted by JEFFRO503
	I'm going to let the guru's like Altavillian , RTK , Tired old man and so forth fill you in on the corrections that need to be made , but if that motor is piped right , and the needles are set correctly you can be getting close to 8000 rpm on a 28X10 Mej prop. Sounds unreal but i've already seen the video to prove it. At those rpm numbers , you'll definetly want to switch up to a 29" prop so you don't damage the engine. If the carb fix is the culprit , send that sucker in to Tom and andy and they'll get it running right. BTW , here is the video........talk about rippin' the prop sheeeesh!! >>> http://www.youtube.com/watch?v=9wAnK...w-owner-7.html

Wow! Talk about prop rip. That was great.
Here is what I can do in the short run.
1)Improve the muffler by adding more holes for the exhaust gas.
2)Increase my drop on the header to 3 inches. Its 1.675" now.

If this doesn't get me into the 6000+ RPM range then sending it to Tom and Andy would be next.
For what is worth the KrisW fix was used by another BME owner here in Louisiana and it works fine. I really think that I have choked the motor with a restricted muffler. Easy to find out and I will this weekend.

[why_fly_high]

I have flown Tom's plane and the power is stupid. I call it the mejzlik abuser.

Dan

[JEFFRO503]

	Quote: Originally Posted by tonyc9075
	Wow! Talk about prop rip. That was great. Here is what I can do in the short run. 1)Improve the muffler by adding more holes for the exhaust gas. 2)Increase my drop on the header to 3 inches. Its 1.675" now. If this doesn't get me into the 6000+ RPM range then sending it to Tom and Andy would be next. For what is worth the KrisW fix was used by another BME owner here in Louisiana and it works fine. I really think that I have choked the motor with a restricted muffler. Easy to find out and I will this weekend.

Well , Altavillian would know more than me , but i can't see how the standard 1' ( 25mm) exhaust can be restricting the motor? Your headers look fine to me ( little short) but fine.

GUY....shorter headers can restrict the motor? I was thinking more along the lines it would just move the power/rpm curve around a little , but how is it restricting the flow of the exhaust?

When i had my BME 115 , i thought i was told to run a header length of about 11" or so? Guy , what is the length you have used for best performance? I'm getting a new one here pretty soon and will be running a MTW , K&S or something similar canister setup.

[tonyc9075]

	Quote: Originally Posted by JEFFRO503
	Well , Altavillian would know more than me , but i can't see how the standard 1' ( 25mm) exhaust can be restricting the motor? Your headers look fine to me ( little short) but fine. GUY....shorter headers can restrict the motor? I was thinking more along the lines it would just move the power/rpm curve around a little , but how is it restricting the flow of the exhaust? When i had my BME 115 , i thought i was told to run a header length of about 11" or so? Guy , what is the length you have used for best performance? I'm getting a new one here pretty soon and will be running a MTW , K&S or something similar canister setup.

The 1 inch header goes into a 1 inch aluminum pipe that goes into the Budweiser can muffler. Inside the can the exhaust is released into the can but the exit out of the can is a "bunch" of small 1/16 " drilled holes in the back part of the pipe. The pipe is pluged 1/2 way into the can and the exit holes are on the back 1/2 of the pipe. The exit out the can is the same pipe, curved without obstruction.

If I did not drill enough holes, its restricted.

[tonyc9075]

Here is a another picture of the muffler.

[Flyinrazrback]

I don't know anything about those home made cans, but every can is designed/tuned around a certain length header. The cans may be very restrictive compared to others. What I would do is take the cans out of the equation. It will be loud, but run the motor on just the headers and see what kind of rpm you get, then add the cans on and see how it compares. With that prop you should be spinning mid 6K easily on the ground. If you turn those numbers on just straight headers, and then add the cans and it drops back down to what you are seeing, the header length will need to be experimented with and/or the cannister is too restrictive for that engine. The 115 needs a healthy size can to breathe correct, otherwise you are just choking it up. Most success comes with a 10-12" header on MTW 75K cans or short headers on 3W LL cans. Try just the headers and tune for max rpm first though, then same process with the cans.

[RTK]

I definitely would do as razrback mentioned. Run the engine open exhaust, if you are not in the mid to high 6's you've got something else wrong. I would also double check the timing if the open exhaust numbers aren't there. Depending on which ignition you have they are timed differently. 28*BTDC for CH, and "I believe" but double check me, 4* BTDC for Falcon.
Are you also sure your tach is functioning properly?

[LanceLKs]

From the pictures ,it looks as if you have a WB series carb . This carb doesnt work very well with this engine. The WGA9 is a much better carb to use.

[tonyc9075]

	Quote: Originally Posted by RTK
	I definitely would do as razrback mentioned. Run the engine open exhaust, if you are not in the mid to high 6's you've got something else wrong. I would also double check the timing if the open exhaust numbers aren't there. Depending on which ignition you have they are timed differently. 28*BTDC for CH, and "I believe" but double check me, 4* BTDC for Falcon. Are you also sure your tach is functioning properly?

What raxrback suggested would be the logical 1st step. I can do both, run open without header and run with header and no Budweiser muffler.

For the tach test the Florescent light bulb test is the one I am fimilare with. I think I should see 2400 rpm off the light bulb. Is there another way?