Help with break in of ABC engine

Glow/Nitro and gas engines, propellers, fuel and other stuff associated with making lots of noise and thrust.

Help with break in of ABC engine

Postby le fou » Sat Jun 12, 2010 4:01 am

Hi,

I have a Magnum 91xls that I am trying to break in but I ruined the sleeve and piston. I used a fuel containing 18% of oil which I added castor oil to bring it to 25%. Then I ran the engine on a test bench at full throttle but not too rich or not too lean. I ran the engine 5 runs of 1 minute each and I let the engine cool down completely between each run. Then I ran the engine 5 minutes three more times letting the engine once again cool off between each runs. Every run, I tried to lean the engine slightly more. I then mounted my engine in the airplane but during the flight, the engine leaned out and overheated and upon landing, the piston and the sleeve were cooked!!! The engine still works but I lost some power... Also, I measured the engine temperature while it was on the bench with a laser temp gun, temp was around 350 to 380 degree Far, On couple instances, the engine overheated at what point I made it more rich or stopped it. So I ordered a new piston and sleeve and I was wondering if somebody has an easier and safer way for the engine to be broken in. I don't want to kill the new sleeve and piston.... I need to protect the engine from the user (me) :D

Thanks,

Le fou
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Re: Help with break in of ABC engine

Postby RCModelReviews » Sat Jun 12, 2010 6:19 am

How do you know that the piston/liner are ruined?

It takes a *lot* of abuse to ruin a true ABC setup (I've tried).

Also, the quality of the oil you use is as important (if not more so) than the quantity -- however you should have been safe using a regular 18% blend of castor/synth to break in your engine.

Most of my ABC engines get a couple of minutes running on the ground (just lean of 4-stroking) then I just fly them -- making sure to vary the throttle a lot during the first few flights and not stay at full power for more than 15-20 seconds at a time.

By the third tank of fuel, they're all run in.
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Re: Help with break in of ABC engine

Postby le fou » Sat Jun 12, 2010 7:48 pm

Thank you for taking the time to answer my post. I have the feeling that I ruined my engine b/c the pinch at TDC without a glow plug is quite reduced not to say almost non existent. Also, when I compare the RPM that I get from other users, I am about 2000 below...
What procedure would you use on a test bench?

Thanks,

Le fou
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Re: Help with break in of ABC engine

Postby RCModelReviews » Sat Jun 12, 2010 9:29 pm

I've found that the Magnum/ASP engines don't hold their pinch very well when compared to other brands such as ThunderTiger.

None of my ASP (aka Magnum) 2-strokes have much in the way of ABC pinch left after they've been run a few times but they still make good power.

What prop, fuel and glow-plug are you using?

Does the engine still have compression when you turn it over slowly by hand?
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Re: Help with break in of ABC engine

Postby dawgmckay » Fri Sep 03, 2010 6:00 pm

Hold the plane vertical, nose up, at full throttle. If engine dies, you are to lean.
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Re: Help with break in of ABC engine

Postby Boolarra » Sat Sep 04, 2010 12:48 am

Please tell us how the the engine is mounted in the plane. i.e. is it fully cowelled and does it have a big enough air intake and at least twice as much outlet area as intake.
Prop. size, fuel tank height with respect to carb. Centre line of tank level with spray bar.
An engine will 99% of the time lean out in the air as the prop unloads and revs. increase.
Do you have the Manufacturers instructions?
Hope you have success, Boolarra.
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