Break In ABC Engine
05-06-2002 | 07:07 AM
#1
Thread Starter
Break In ABC Engine
There's been lots of discussion about this for ABC engines in various places but the very high quality manufacturers (I'm talking things like Jett and Rossi) say to give at least 30 to 40 minutes on the bench with shortish runs followed by a cool down period and running rich. Of course what's rich to one guy is lean to another so the concensus was that if it was a little leaner than where it breaks in and out of a 4 stroke (by only a click or so on the needle) it was just about right. The fuel should have plenty of oil (20% or even more) and definitely some castor in it. The castor protects the rod bearings as they run in.
Use the smallest recommended prop to keep the revs up close to what you'll eventually fly at.
Personally I'd remove the backplate before you run it and flush everything out with fuel in case there's any particles left over from machining. And use an old plug for the running in...if any aluminium gets on the coil it'll ruin the plug.
Use the smallest recommended prop to keep the revs up close to what you'll eventually fly at.
Personally I'd remove the backplate before you run it and flush everything out with fuel in case there's any particles left over from machining. And use an old plug for the running in...if any aluminium gets on the coil it'll ruin the plug.
05-14-2002 | 05:34 AM
#2
Break In ABC Engine
FCC,
One more opinion:
A two cycle ABC (ABN, etc.) engine is designed with a tapered cylinder. When you start it, you want to get it up to operating temperature as soon as possible. This causes the cylinder to open up at the top and lessen the tightness/friction.
The first runs should have the engine running in a fast two cycle, but not full lean. This causes the cylinder to expand and allow the connecting rod and other bearings to have a smaller load, which is much better for the rod bearings. Light loading is the same reason you should use a smaller prop.
After the first few short (minute or two) runs with complete cool down between runs, the bearings are better able to handle the stress of rich runs.
Remember that tapered cylinder? If you run-in the engine rich, the cylinder will cause excessive friction because of the tight fit and will eventually wear a fit at that temperature. When you lean it out you will then cause the cylinder to expand and the fit may be too loose to have a good seal which means you have worn out your engine.
If you are flying a sport engine, this may not affect you as much as if flying a competition engine.
Remember, this is just an opinion, your mileage may vary
One more opinion:
A two cycle ABC (ABN, etc.) engine is designed with a tapered cylinder. When you start it, you want to get it up to operating temperature as soon as possible. This causes the cylinder to open up at the top and lessen the tightness/friction.
The first runs should have the engine running in a fast two cycle, but not full lean. This causes the cylinder to expand and allow the connecting rod and other bearings to have a smaller load, which is much better for the rod bearings. Light loading is the same reason you should use a smaller prop.
After the first few short (minute or two) runs with complete cool down between runs, the bearings are better able to handle the stress of rich runs.
Remember that tapered cylinder? If you run-in the engine rich, the cylinder will cause excessive friction because of the tight fit and will eventually wear a fit at that temperature. When you lean it out you will then cause the cylinder to expand and the fit may be too loose to have a good seal which means you have worn out your engine.
If you are flying a sport engine, this may not affect you as much as if flying a competition engine.
Remember, this is just an opinion, your mileage may vary
05-26-2002 | 11:56 PM
#3
Break In ABC Engine
Richard,
Full throttle. Bushing type bearings, such as the connecting rod, should be broken-in fast. At full throttle, running a bit rich and with a smaller than normal prop, the bushings build up good film pressure with the oil on the bearing surfaces.
Full throttle also allows the cylinder to get up to operating temp and expand the needed amount.
The smoothing and rubbing of parts is greatest during the first few minutes. That is why an ABC engine runs much better after a few runs. The wear-in procedure will continue for about an hour to a lesser extent and you may notice the engine running better and better during this time.
I think the amount of improvement you see during the first hour, after the initial runs, is partly determined by how well you did those initial runs.
This is personal opinion, there is rarely only one way of doing things.
George
Full throttle. Bushing type bearings, such as the connecting rod, should be broken-in fast. At full throttle, running a bit rich and with a smaller than normal prop, the bushings build up good film pressure with the oil on the bearing surfaces.
Full throttle also allows the cylinder to get up to operating temp and expand the needed amount.
The smoothing and rubbing of parts is greatest during the first few minutes. That is why an ABC engine runs much better after a few runs. The wear-in procedure will continue for about an hour to a lesser extent and you may notice the engine running better and better during this time.
I think the amount of improvement you see during the first hour, after the initial runs, is partly determined by how well you did those initial runs.
This is personal opinion, there is rarely only one way of doing things.
George
