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MLD-28 gasoline engine

Old 02-10-2012, 04:53 PM
  #1326  
rexbirk
 
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Default RE: MLD-28 gasoline engine


ORIGINAL: AA5BY

If the engine is tuned without pressure influence on the carb... then put in a cowling where pressure increases for lack of outflow, the mixture will go rich at high rpm as the pressure inside the cowl anvils the metering needle more open. If the engine is tuned for running inside such a restricted cowl, it will get leaned to counter that richening tendency but then as the rpms fall back, the high needle will be too lean and it will stumble on transition. That then gets countered with too rich of a LS needle to avoid the spooling up problem and then the idle is too rich. Neither needle ends up being set where it ought.

Quite right. Causes one to scratch his head and wonder if he has offended the creator!

Seriously, I noticed that on many 3W Engine Photos I see that they run the carb vent to the velocity stack. I assume it's because that will allow the carb to see a more constant air pressure. Whatever the reason it seems to work. Also hear that some run the hose from the carb vent back into the fuselage for the same reason.

I first tried turning the carb vent cover to different positions but that did not work.
Old 02-13-2012, 01:16 PM
  #1327  
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Default RE: MLD-28 gasoline engine

flight report.... I went out Sunday afternoon... I used clear packing tape to close off the inlets around the motor shaft opening on the cowling... She flew so much better! I'm picking up some more thin plexiglass to fit some permanent covers.

I still have a stumble with the low to mid throttle transition... it's definitely something to do with the low needle setting. I'll do a bit more fiddling after installing the cowling covers.

Full thottle response was the best yet.... strong vertical power, consistant horizontal power.

Flyracer
Old 02-20-2012, 05:09 PM
  #1328  
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Default RE: MLD-28 gasoline engine

plexiglass covers cut and glued into place to block the openings around the nose/prop area.... I also enlarged the opening on the bottom of the cowling behind the cylinder head.

Hand held tach is reading 7850 rpm consistently on the top with no hiccups.... hope to get back out to the airpark Friday or Saturday this coming week.


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Old 02-21-2012, 09:54 AM
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Default RE: MLD-28 gasoline engine

Good to hear that you have the problem solved. btw... it is always nice to get a report back that a problem was solved... thanks.
Old 02-21-2012, 02:27 PM
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Default RE: MLD-28 gasoline engine

once the aircraft is in the air, we'll know for sure the fruits of the baffle work and latest tuning! I'm optimistic ;-)


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Old 03-03-2012, 11:42 AM
  #1331  
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Default RE: MLD-28 gasoline engine

Jimeni,

After idling for 30 seconds does your MLD 28 sputter a bit until it clears out!

I think I'm trying to adjust out a problem that is inherent to a piston port 2 stroke with no reed valves.

If I don't let it idle for an extended period throttle response is fine.
Old 03-03-2012, 01:04 PM
  #1332  
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Default RE: MLD-28 gasoline engine

No, it does not load up at all. Sorry. Maybe your low end is a little rich, or oil ratio is too high. What's your plug electrode look like? Last year I switched to stihl ultra at 50:1. I am going back to amsoil at 100:1. Does not run as well at 50. I used the 100 for a long time, and kept a close eye on the engine. No extra wear noted. If your using amsoil at less than a 100:1, that could possibly cause it also, its too thick. I tried it at 80:1 for a bit, did not cause performance issues, but it did make a mess of the plane.
Old 03-03-2012, 02:48 PM
  #1333  
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Default RE: MLD-28 gasoline engine

Im using Amsoil Dominator at 50:1. The plug does look rich but leaning it further seems to cause hesitation. Myabe I should switch back to Sabre at 100:1.
Old 03-03-2012, 03:02 PM
  #1334  
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Default RE: MLD-28 gasoline engine

Jimeni,

What rpm do you idle yours at? Seems if I idle it at 2100 it doesn't load up as much. If I idle at 1900 it does.
Old 03-03-2012, 08:00 PM
  #1335  
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Default RE: MLD-28 gasoline engine

I did check with a tach once, 1800. I put throttle trim up for start, then bring it back, so I am sure it varies. I just listen, and drop it until the plane dont roll. I actually don't use a tach at all on gas engines, tune by ear, and its worked well for me. Don't worry about idle rpm so much, 2000 is pretty good. If your plane rolls a little, just put small pieces of fuel tubing between your axle nut and wheels. Have you tried a new plug, or cleaning the one you have?

My 28 seems to prefer sabre at 100:1. Weird, none of my other ones seem to care.
Old 03-04-2012, 07:56 PM
  #1336  
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Default RE: MLD-28 gasoline engine

Well... I got the Extra into the air this weekend... still having some issues with the tuning changing in flight :-( Seems to get worse going into the wind.


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Old 04-02-2012, 06:05 AM
  #1337  
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Default RE: MLD-28 gasoline engine

After another frustrating day of chasing the needles and having a high rpm misfire (with two different MLD Ignitions) I got frustrated and installed an RcExcel Ignition. I set the crank sensor to the same position as the mld sensor. Hooked it all up and it started immediately. Not only was my missfire gone but my throttle response was much better. So far with 30 minutes of run time on the ground it runs great. We will see when I can get it out to the field. I can tell it is much improved already though. I have gone thru at least 4 ignitions on my MLD Engines. Hope this is the cure. I have replaced modules and a crank sensor (original MLD parts and some replacement modules)

Crossing my fingers!
Old 04-02-2012, 06:50 AM
  #1338  
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Default RE: MLD-28 gasoline engine


ORIGINAL: rexbirk

After another frustrating day of chasing the needles and having a high rpm misfire (with two different MLD Ignitions) I got frustrated and installed an RcExcel Ignition. I set the crank sensor to the same position as the mld sensor. Hooked it all up and it started immediately. Not only was my missfire gone but my throttle response was much better. So far with 30 minutes of run time on the ground it runs great. We will see when I can get it out to the field. I can tell it is much improved already though. I have gone thru at least 4 ignitions on my MLD Engines. Hope this is the cure. I have replaced modules and a crank sensor (original MLD parts and some replacement modules)

Crossing my fingers!
REX,
you said you have installed the sensor at the same place as original?
I thought original MLD sensor position is about 40 degree advance, and RCEXL's is at 28 degree.

I have just bought a new type of MLD ignition, CM-6 and 14mm->10mm adapter, but not tested yet since I crashed my plane.

Jay.
Old 04-02-2012, 07:22 AM
  #1339  
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Default RE: MLD-28 gasoline engine

I thought the Ignitions used different timing also. In a forum somewhere someone said otherwise. I mounted it in the same exact position as the MLD. Works like a charm. Good idle, Good top end.
Old 04-02-2012, 07:23 AM
  #1340  
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Default RE: MLD-28 gasoline engine

I used the RcExcel CM6 with the plug adapter and one of their Iridium Plugs. Will know more after I am able to fly it.

I have two types of MLD Ignitions. The old style and a newer smaller one. Have had issues with both.
Old 04-02-2012, 09:39 AM
  #1341  
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Default RE: MLD-28 gasoline engine

Rex
I've decided to pull the MLD28 off my 70" Extra260... I've had enough of the frustration in trying to get this engine to run. I'll be dropping in either a DLE or RCGF engine.


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Old 04-02-2012, 10:11 AM
  #1342  
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Default RE: MLD-28 gasoline engine

I probably should have done that too but It made me mad that I couldn't figure the engine out. Did not want to let the engine stump me! When they run good they are great. I think all my issues have been Ignition related. I have five of the engines. Any I am using will get on RcExel Ignition for sure.

I like the smoothness of the engine. Seems to be a lot less vibration than a DLE 30.
Old 04-02-2012, 12:07 PM
  #1343  
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Default RE: MLD-28 gasoline engine

Rex
There have been some instances where the engine seems to be fine... it will rev thru the throttle range and pulls solid on the top end... and yes, I agree there seems to be alot less vibration than my DLE30 equipped airframe (71" AJ Slick)... but I am fed up with getting out to the airfield and it won't run. In hind sight, I should have paid the extra $175 for a DLE30 or such.

Flyracer
Old 04-02-2012, 02:12 PM
  #1344  
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Default RE: MLD-28 gasoline engine

Not to beat a dead dog, but I would bet money you guys are seeing the pick up lead connector pin over crimp issue, or poor shielding to boot solder. My money is on pick up sensor. Causes exactly, EXACTLY, what you are describing, and its a 15 minute fix.
Old 04-02-2012, 04:35 PM
  #1345  
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Default RE: MLD-28 gasoline engine

Jimeni

I have changed the connector and also changed the entire pickup. My issues have seemed to be the module. A new module cured it for a while. I have seemed to attract bad modules, both the Cermark version and another version from Mile High Rc. Don't get me wrong, I love this engine, I have 5 but it does seem to have ignition issues.

Obviously you have a good one. I have had a bunch of bad ones, both bad plug boots and modules. Very frustrating. The RcExcel Ignition seems to have made a huge improvement. The needles are consistent and a cold start has no misfiring. Have not flown it yet but I suspect my high rpm misfire will be gone. We will see. If it is I will be ecstatic!

I have to say that Milehighrc.com has been great with replacement parts under warranty and Mike is very easy to reach. He answers emails quickly and is interested to hear what you have to say. His version is different than the Cermark version. Both seem to have similar power. The Milehigh version has three bearings and a different mounting pattern as well as a slightly different carb.

As a side note, I have added an adapter to two of mine to use a cm-6 10mm plug to match my 50cc planes. Got the adapters from http://rcextremepower.net/ It's nice to only have to keep one plug on the shelf! By the way, rcextremepower.net is also great to deal with. He is a wealth of knowledge! He is the one I got my RcExcel Ignitions from.

If I have my issues solved I will be a happy camper indeed.

I am a poor 3D flyer so I dont need gobs of power. This engine suits me well. Very smooth. Yes a DLE30 puts out more power but I do not need that.
Old 04-02-2012, 05:33 PM
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Default RE: MLD-28 gasoline engine

I guess i got lucky, mine has never given me trouble. All my ignition troubles were with the spe engines, same ignition though. I hope the ignition works for you, good luck.
Old 04-03-2012, 05:11 PM
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Default RE: MLD-28 gasoline engine

Just changed over my 3DHS 72" Extra MLD to RcExcel. Can't fly them yet but am optimistic.

I suppose the ignitions are built in large batches so I suppose I could have gotten a number of bad ones.
Old 04-03-2012, 05:30 PM
  #1348  
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Default RE: MLD-28 gasoline engine

REX,

I hope you won't have any trouble in the air ! Cross fingers.
Old 04-03-2012, 05:37 PM
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Default RE: MLD-28 gasoline engine

Me too! But I can't have any more trouble than I have with the standard ignitions. I can't describe how frustrated I have become with them.
Old 04-04-2012, 04:13 AM
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Default RE: MLD-28 gasoline engine

Rex... to respond to the question in your tag line... If a circle flyer is having fun and that is what his comfort zone allows... how could that be a bad thing.

We once had a left turn only circle flyer at our field... only flying with a South wind.

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