I disagree.

The piston ring does not adequately seal into the bore as the pressures in the combustion cycle at idle or zero load are insufficient to enable the ring to develop the correct forces to allow it to bed in to the cylinder.

I will repeat the comments made about break-in procedures made by Shell many years ago.

When a cylinder is manufactured, a cross-hatch hone is used to score a diamond pattern into the surface of the liner; this is necessary to allow an oil film to be held on the surface of the cylinder wall and lubricate the piston during operation.

If glazing of these honing grooves occurs before the break-in period is complete then the piston ring will not seal properly, and the cylinder wall will no longer have the surface groves necessary to carry lubricant, and the combination will result in a poor gas seal and high oil consumption. The only way to remove such a glaze is by re-honing the cylinder wall - meaning expensive and avoidable additional maintenance.

However, successful break-in not only means the use of a straight oil of the correct grade but also the use of high power settings. High power settings mean high combustion pressures which, due t piston ring design, forces the piston ring out to rupture the oil film. This is the key to the break-in process.

I can understand why you don't believe my comments but surely Shell have some idea?

Yes, or use a start-up map, but that is related to rpm (cams), not load (break in)

Starting an engine first on an engine stand and do the "walk-around" oil leak test and running some cam rpm's is in no way wrong

Hereafter you do the tuning and break with wheels turning some backpressure

Now we are saying the same thing :) Define please "initial startup"

... initial start-up, could be on an engine stand, right?

Bore glaizing is most likely to happen from cold engines running looong periods with low loads, and most incidents are found on new watercooled engines. And it is not burned oil from blow by (there is no oil in 4 stroked gas), it is condensation of burned combustion products that fills the cross hatch on the wall. Having air-cooled engines we dont run much cold for loong periods, not even on idling.

You still have load on the pistons when idling. The question is in which direction and how much, how do you think you get vertical downwards or directional horizontal load on the rings?

Why would you think that there is more blow-by on new rings vs. used rings?
Why would you think you can force the rings to the cylinder any differently using old rings?
Why would you think glazing only happens on new rings and fresh cross hatch?

For the record, I didn't load my engine and babied it for 500 miles. I had no blowby and the rings seated within minutes.

To Jakob

Sorry, you are wrong and appear to not understand the basics.

You get pressure on the back side of the ring from the chamber pressure that gets behind the ring and forces it into the wall. You want to maximize that pressure to get the rings to bed into the wall. Now tell me that the pressure behind the ring is going to be the same at idle as at WOT under load...

Glazing IS a hard coating created by oil burned on the cylinder wall that fills in the cross hatch. Doesn't matter if it is air cooled or water cooled.

" (there is no oil in 4 stroked gas)" Really ? Do you run a 4 stroke without any oil in the crankcase?? The oil gets on the bores from the lube oil in the case.

"Why would you think that there is more blow-by on new rings vs. used rings? Where did I say that? I said new rings will have a lot of blow-by because they have not bedded in to the bore.

"Why would you think you can force the rings to the cylinder any differently using old rings?"
Again, where did I say anything about old rings?? I said to get the new rings to seat you want max gas pressure on the back of the ring.

"Why would you think glazing only happens on new rings and fresh cross hatch? " Where did I say that?

It's your engine, let it idle for a couple hours to break it in..

Jakob,

Your three questions are not really sensible and bear no relationship to the situation regarding a 'fresh' engine.

No-one has made any comments about the other situations that create issues although there is much published work on the subject of diesel engine problems due to time spent idling.

The first question I responded to was about a test stand to setup carbs with respect to jetting and exhaust system comparison.

I believe that to carry out these procedures on a fresh engine at zero load is a mistake. You clearly don't agree.

The next statement was that Break-In with load or at zero load was an option. I still disagree.

You then suggested that I should know better than to run fresh engines with empty maps at full load - a ridiculous statement.

You are now trying to question my meaning of 'initial start up' which somehow seems quite obvious.

I think this entire debate has become futile and frankly life is too short.

I will stick to my opinion which is that 'zero load' running of a fresh engine should be avoided whenever possible and the time spent in these conditions kept to a minimum.

I am more than happy for you to disagree but please try not to alter the meaning on my comments, which I hope I try to make clear.

My last comment on this subject concerns piston ring forces and I would refer you to this work carried out by Federal Mogul.

http://www.federalmogul.com/en-US/Media/Documents/ICES200976080.pdf

If you drove it you did apply load, maybe not much but significantly more than when idling. :)

Tippy - how do you know you wouldn't have had better leak down and compression by loading it during break-in?

Interesting discussion but I've got better things to do.

kindly read again, it says gas. Do you have oil in your 4 stroked engine GAS? No. And it is the other way around when using the "blow-by" term which I am sure you know :) When engine oil lubricates the cylinder walls you dont get coating, if it goes back up in the combustion chamber (reversed blow-by), then you get blue smoke. Again the Glazing, as seen from my perspective and experience, is from burned combustion products on mostly cold running engines over long periods.

there is no reason really to put in ironic comments, no one breaks in an engine on an engine stand, only initial startup configuration, just like you would do in a car on a still sitting dyno.

I have build and tuned many water cooled race engines, I have used race cars on still sitting dynos as "engines stands" for initial start-up configurations before break in on the same dyno 5 minutes later. Initial start-up configuration using start-up maps and "walk-around" test for oil leaks is short time. Personally, I see no reason for not doing the same on a hotter idling aircooled engine.
.

Examples (no affiliation)

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I don't believe Al's engine videos there are freshly rebuilt engines. I think that is his test engine, one that's already got driven miles on it, and he uses it to develop his EFI systems.

Slightly off topic... but where do you guys buy your metal to build engine stands, etc?

If you buy from a metal supply house, its stupid expensive...

Tried to buy some material to finish off a roll bar and a 3 ft piece of tubing was close to $100 with shipping...

Do any of the local stores (home depot/menards/lowes) carry metal suitable for building engine stands?

For example: metal fence posts, 6 foot length, are $5. Need to get the galvanizing off, but plenty strong to build an engine stand with...

Menards has boxed metal tubing for building garages, its also dirt cheap...

Any other options? Would love to find a cheap source for 2inch square metal tubing... tons of uses for it, like engine stands/frames/etc...

Bo,

Try checking out metalsupermarkets.com. They have a store in Green Bay, Waukesha and Rockford. I bought a bunch of steel tubing & plate to modify my cage & reinforce the suspension in the racecar.

Good people to deal with. Can order it on line and go pick it up to save $ on shipping.

Thanks! will look into it...

"kindly read again, it says gas. Do you have oil in your 4 stroked engine GAS? No. And it is the other way around when using the "blow-by" term which I am sure you know When engine oil lubricates the cylinder walls you dont get coating, if it goes back up in the combustion chamber (reversed blow-by), then you get blue smoke. Again the Glazing, as seen from my perspective and experience, is from burned combustion products on mostly cold running engines over long periods.

I'm not going to argue with you anymore. Do you think Lycoming knows anything about air cooled engines? This is from them:

quote:

Hard Facts About Engine Break-In

Tips

Most people seem to operate on the philosophy that they can best get their money’s worth from any mechanical device by treating it with great care. This is probably true, but in many cases, it is necessary to interpret what great care really means. This is particularly applicable when considering the break-in of a modern, reciprocating aircraft engine. Aircraft owners frequently ask about the proper procedures for run-in of a new or rebuilt engine so they can carefully complete the required steps. Many of these recommended break-in procedures also apply to engines which have been overhauled or had a cylinder replaced.

The first careful consideration for engine run-in is the oil to be used. The latest revision of Lycoming Service Instruction 1014 should be consulted for this information. The basic rule which applies to most normally aspirated Lycoming piston engines is simple: use straight mineral oil of the proper viscosity for the first fifty hours or until oil consumption stabilizes. Then switch to ashless dispersant (AD) oil.

The exceptions to the basic rule above are the O-320-H and the O/LO-360-E series. These engines may be operated using either straight mineral oil or ashless dispersant oil; however, if the engine is delivered with ashless dispersant oil installed, it must remain on ashless dispersant oil. The Lycoming oil additive P/N LW-16702 must be added to the O-320-H and O/LO-360-E engines at airframe installation, and every 50 hours thereafter or at every oil change. An FAA-approved lubricating oil that contains, in the proper amount, an oil additive equivalent to LW-16702 will meet the requirements for the additive as stated in Lycoming Service Instruction No. 1014M.

All Lycoming turbocharged engines must be broken in with ashless dispersant oil only

When taking delivery of a new aircraft, there is another point which must be emphasized. Some aircraft manufacturers add approved preservative lubricating oil to protect new engines from rust and corrosion at the time the aircraft leaves the factory. This preservative oil must be removed by the end of the first 25 hours of operation.

Each new or rebuilt engine is given a production test run at the factory before the engine is delivered to an aircraft manufacturer or customer. After installation in the aircraft, the engine is run again during the test flights. These test runs will ensure that the engine is operating normally and will provide an opportunity to locate small oil leaks or other minor discrepancies. In addition, these test runs do the initial seating of the piston rings. The rest of the break-in is the responsibility of the pilot who flies the aircraft during the next 50 hours.

A new, rebuilt or overhauled engine should receive the same start, warm-up and preflight checks as any other engine. There are some aircraft owners and pilots who would prefer to use low power settings for cruise during the break-in period. This is not recommended. A good break-in requires that the piston rings expand sufficiently to seat with the cylinder walls. This seating of the ring with the cylinder wall will only occur when pressures inside the cylinder are great enough to cause expansion of the piston rings. Pressures in the cylinder only become great enough for a good break-in when power settings above 65% are used.

Full power for takeoff and climb during the break-in period is not harmful; it is beneficial, although engine temperatures should be monitored closely to ensure that overheating does not occur. Cruise power settings above 65%, and preferably in the 70% to 75% of rated power range, should be used to achieve a good engine break-in.

Remember that if the new or rebuilt engine is normally aspirated (non-turbocharged), it will be necessary to cruise at lower altitudes to obtain the required cruise power levels. Density altitudes in excess of 8000 feet (5000 feet is recommended) will not allow the engine to develop sufficient cruise power for a good break-in.

For those who still think that running the engine hard during break-in falls into the category of cruel and unusual punishment, there is one more argument for high power settings during engine break-in. The use of low power settings does not expand the piston rings enough, and a film of oil is left on the cylinder walls. The high temperatures in the combustion chamber will oxidize this oil film so that it creates a condition commonly known as glazing of the cylinder walls. When this happens, the ring break-in process stops, and excessive oil consumption frequently occurs. The bad news is that extensive glazing can only be corrected by removing the cylinders and rehoning the walls. This is expensive, and it is an expense that can be avoided by proper break-in procedures.

To summarize, there are just a few items to remember about engine break-in:

If a preservative oil has been added by the aircraft manufacturer, drain it no later than the first 25 hours of operation;
Follow the engine manufacturer’s recommendation regarding the oil to be used for break-in and the period between changes;
Run the engine at high cruise power levels for best piston ring/ cylinder wall mating;
Continue break-in operation for 50 hours or until oil consumption stabilizes. These simple procedures should eliminate the possibility of cylinder wall glazing and should prepare the engine for a long and satisfactory service life.


The oil that blows by the new rings IS what causes the glazing of the bores.

end of quote.

This is sorta like being in a strip club (i've heard...).

Everybody has an opinion of what works and what doesn't....


sorry for asking.....................

I'll take Shell and Lycoming's opinion on what works....

You will be a lot sorrier if you try breaking in a new engine on a test stand.

Alright. So bolt it in, start it up, and check for oil loss. Then drive (LOAD) it at reasonable rpm's under 3.5 maybe but do this for how many miles?

The 3.0 SC Weber 20/21 webcam regrind data from WC says do not allow the engine to idle below 2k for the first 15 minutes of use.... That would be easy if the carbs were tuned prior to break in... conundrum 101 ....???