Kep4
Jäger
This is from the Diesel Injection Service website:
Part I
Breaking In a Diesel Engine
"Breaking-in" a new diesel engine... Many of the engine manufacturers claim that their engines do not require break-in. That is just pure baloney! Enough pestering and a few references to some of the Cummins shop manuals have painted a clearer picture. All engines require some kind of break-in period. This is even true with current technology. Although current technology provides the means of manufacturing engine parts with unimaginable precision, the manufacturer still falls far short of achieving the near perfect fit that a proper break-in will provide. “Break-in,” for the most part, is the allowance of the machined cylinder and ring surfaces to conform to each other’s shape during engine operation. This conforming or “mating” of ring and cylinder surfaces is the ultimate goal of a proper break-in. “Mating” these two specific parts will produce a very tight seal in each cylinder. A tight seal is very important because it prevents the escape of unburned fuel and pressurized gasses into the crankcase, while further preventing crankcase oil from entering the cylinder above the top compression ring. It is the intention of this article to help people understand more about the break-in process, and what happens or can happen during the first few thousand miles of engine operation.
During break-in, a small amount of compression blow-by, oil-fuel dilution, and oil consumption will be experienced. This is perfectly normal and quite common in new engines. Although acceptable at first it is imperative that these undesirable attributes be as close to zero as possible after break-in has been completed. Although the others are important, blow-by is the primary reason the ring and cylinder wall interface has to fit together so tightly. Diesel fuel needs to be introduced into an air environment that is under intense pressure in order for it to burn without an ignition source. When the fuel burns, the gasses produced multiply the compression pressure in the cylinder. Pressurized gasses that escape by means of the compression ring / cylinder wall interface are called blow-by gases. Pressure that escapes the cylinder in this manner results in a loss of energy. Whether it is pressure lost on compression or combustion, it is unable to be utilized to drive the piston through the power stroke. This loss ultimately results in a reduction of fuel mileage and power.
Today’s Diesels can take a "few" miles to fully break in. 10,000 miles is not an uncommon break-in period, especially for an engine like the Power Stroke Diesel. The reasons that break-in is such a lengthy process are generally attributed to engineering targets as well as the function of diesel combustion.
In terms of engineering targets, engine manufacturers produce diesel engines to sustain high torque loads over constant and extended load intervals. In other words, very durable parts are required to hold up to the rigors of diesel operating conditions. For example, The International Truck and Engine Company employs some very special parts in their 175 - 275 hp engines. The pistons used in these engines are manufactured from lightweight aluminum alloy, and are constructed with Ni-Resist ring inserts. The aforementioned piston combination is further complemented with keystone plasma faced rings. These rings help reduce oil consumption and can extend the life of the power cylinder further than ordinary chromium-plated rings. While chromium-plated rings continue to be produced for both diesel and gasoline applications, they are slowly becoming old technology. They still perform well but plasma faced rings have consistently shown superior performance.
When we consider the function of diesel combustion, we must first understand the engine dynamics that are associated with that process. In order for break-in to occur, a fair amount of heat, friction and resulting wear will have to take place before the compression rings will have “mated” with the cylinder walls. When the rings and cylinder wall are new, a modest amount of heat is created merely from the friction of the new rings passing over the freshly honed cylinder wall. While the heat from friction is significant, the real heat is created from combustion of fuel in the cylinder. When the fuel is burned, gasses are produced that expand and heat all of the cylinder parts. If enough fuel is introduced, the resulting combustion can create gasses that expand so much they will actually expand the cylinder wall and the compression rings. It is important to understand this because expanding these parts places additional pressure on them, which creates more friction and correspondingly more heat. This does not take into account the additional heat from combustion that will be added to the heat from friction. Heat is important to assist wear for break-in but too much can cause major problems. This is the reason we should not subject the engine to significant loading for the first 1000 miles of its operation. Loading heavily will introduce more fuel to the cylinder, and will add significant amounts of heat and pressure to the cylinder components. Couple that scenario with new rings on a freshly honed cylinder wall and we can only imagine the amount of friction and heat being produced and absorbed by the rings. Furthermore, the engine oil, lubricating the cylinder walls, will flash burn when it contacts the very hot rings. The burned oil will leave a hard, enamel like residue on the cylinder wall, commonly known as oil glazing. When the rings are permitted to operate under such high temperatures, oil glazing of the cylinder can happen very quickly. Once this glaze builds up, the only repair is a labor-intensive process that requires disassembling the engine and re-honing the effected cylinders. Oil glazing is a problem because it is typically not distributed evenly in the cylinder, and the spaces that exist between the ring and cylinder wall are either still there or new larger ones are created. Oil glazing is typically thicker towards the top of the cylinder and it builds up in the areas where heating is the greatest. The glaze has very smooth and friction free properties that do not allow it to be scraped away by the rings. This inhibits further metal-to-metal wear between the cylinder wall and rings, preventing further mating of ring and cylinder. Thus, those small gaps between ring and cylinder surface will never seal. These spaces will then allow pressurized gasses and unburned fuel to escape into the crankcase, while allowing oil from the crankcase to enter the cylinder above the top compression ring.
Well why not run the engine at idle or under no load? This is bad too. It can create a similar condition to glazing. The rings need to expand a little during this initial break-in period, just not so much that they overheat and flash the engine oil. The engine needs to be moderately loaded in order to break in correctly. Running the engine under very light or no load prevents the oil film placed on the cylinder wall from being scraped away by the expanding compression rings. The rings will instead “hydroplane” or ride over the deposited oil film, allowing it to be exposed to the cylinder combustion. The oil film will then partially burn on the cylinder leaving a residue that will build up and oxidize over time. Eventually this leaves a hard deposit on the cylinder wall that is very similar to the glaze left from flash burning. My caution to those just running the engine as a normal daily driver (without some loading) and especially those who love to idle their vehicles, expect some VERY extended break-in periods (up to 30,000 miles). Expect oil consumption forever due to oil glazing. The rings never really seat well if they cannot expand from the dynamics and heat that a load produces. Expect poor mileage due to the passing of compression and combustion gasses around the compression rings. Additionally, expect to see increased bearing wear and engine wear due to the fuel passing the rings diluting the engine oil.
Thus, we can see that heavy loading and light loading can cause some major problems. Moderate loading is the key to a proper break in for the first 1000 miles. It permits the loose fitting piston rings to expand into the cylinder walls allowing them to perform double duty: First, scraping oil off the cylinder wall, and second, to create friction that will promote wearing the two surfaces to each other’s proportions. Furthermore, moderate loading will allow the rings to get hot but not to the point where it will flash the lubricating oil supplied to the cylinder walls.
Part I
Breaking In a Diesel Engine
"Breaking-in" a new diesel engine... Many of the engine manufacturers claim that their engines do not require break-in. That is just pure baloney! Enough pestering and a few references to some of the Cummins shop manuals have painted a clearer picture. All engines require some kind of break-in period. This is even true with current technology. Although current technology provides the means of manufacturing engine parts with unimaginable precision, the manufacturer still falls far short of achieving the near perfect fit that a proper break-in will provide. “Break-in,” for the most part, is the allowance of the machined cylinder and ring surfaces to conform to each other’s shape during engine operation. This conforming or “mating” of ring and cylinder surfaces is the ultimate goal of a proper break-in. “Mating” these two specific parts will produce a very tight seal in each cylinder. A tight seal is very important because it prevents the escape of unburned fuel and pressurized gasses into the crankcase, while further preventing crankcase oil from entering the cylinder above the top compression ring. It is the intention of this article to help people understand more about the break-in process, and what happens or can happen during the first few thousand miles of engine operation.
During break-in, a small amount of compression blow-by, oil-fuel dilution, and oil consumption will be experienced. This is perfectly normal and quite common in new engines. Although acceptable at first it is imperative that these undesirable attributes be as close to zero as possible after break-in has been completed. Although the others are important, blow-by is the primary reason the ring and cylinder wall interface has to fit together so tightly. Diesel fuel needs to be introduced into an air environment that is under intense pressure in order for it to burn without an ignition source. When the fuel burns, the gasses produced multiply the compression pressure in the cylinder. Pressurized gasses that escape by means of the compression ring / cylinder wall interface are called blow-by gases. Pressure that escapes the cylinder in this manner results in a loss of energy. Whether it is pressure lost on compression or combustion, it is unable to be utilized to drive the piston through the power stroke. This loss ultimately results in a reduction of fuel mileage and power.
Today’s Diesels can take a "few" miles to fully break in. 10,000 miles is not an uncommon break-in period, especially for an engine like the Power Stroke Diesel. The reasons that break-in is such a lengthy process are generally attributed to engineering targets as well as the function of diesel combustion.
In terms of engineering targets, engine manufacturers produce diesel engines to sustain high torque loads over constant and extended load intervals. In other words, very durable parts are required to hold up to the rigors of diesel operating conditions. For example, The International Truck and Engine Company employs some very special parts in their 175 - 275 hp engines. The pistons used in these engines are manufactured from lightweight aluminum alloy, and are constructed with Ni-Resist ring inserts. The aforementioned piston combination is further complemented with keystone plasma faced rings. These rings help reduce oil consumption and can extend the life of the power cylinder further than ordinary chromium-plated rings. While chromium-plated rings continue to be produced for both diesel and gasoline applications, they are slowly becoming old technology. They still perform well but plasma faced rings have consistently shown superior performance.
When we consider the function of diesel combustion, we must first understand the engine dynamics that are associated with that process. In order for break-in to occur, a fair amount of heat, friction and resulting wear will have to take place before the compression rings will have “mated” with the cylinder walls. When the rings and cylinder wall are new, a modest amount of heat is created merely from the friction of the new rings passing over the freshly honed cylinder wall. While the heat from friction is significant, the real heat is created from combustion of fuel in the cylinder. When the fuel is burned, gasses are produced that expand and heat all of the cylinder parts. If enough fuel is introduced, the resulting combustion can create gasses that expand so much they will actually expand the cylinder wall and the compression rings. It is important to understand this because expanding these parts places additional pressure on them, which creates more friction and correspondingly more heat. This does not take into account the additional heat from combustion that will be added to the heat from friction. Heat is important to assist wear for break-in but too much can cause major problems. This is the reason we should not subject the engine to significant loading for the first 1000 miles of its operation. Loading heavily will introduce more fuel to the cylinder, and will add significant amounts of heat and pressure to the cylinder components. Couple that scenario with new rings on a freshly honed cylinder wall and we can only imagine the amount of friction and heat being produced and absorbed by the rings. Furthermore, the engine oil, lubricating the cylinder walls, will flash burn when it contacts the very hot rings. The burned oil will leave a hard, enamel like residue on the cylinder wall, commonly known as oil glazing. When the rings are permitted to operate under such high temperatures, oil glazing of the cylinder can happen very quickly. Once this glaze builds up, the only repair is a labor-intensive process that requires disassembling the engine and re-honing the effected cylinders. Oil glazing is a problem because it is typically not distributed evenly in the cylinder, and the spaces that exist between the ring and cylinder wall are either still there or new larger ones are created. Oil glazing is typically thicker towards the top of the cylinder and it builds up in the areas where heating is the greatest. The glaze has very smooth and friction free properties that do not allow it to be scraped away by the rings. This inhibits further metal-to-metal wear between the cylinder wall and rings, preventing further mating of ring and cylinder. Thus, those small gaps between ring and cylinder surface will never seal. These spaces will then allow pressurized gasses and unburned fuel to escape into the crankcase, while allowing oil from the crankcase to enter the cylinder above the top compression ring.
Well why not run the engine at idle or under no load? This is bad too. It can create a similar condition to glazing. The rings need to expand a little during this initial break-in period, just not so much that they overheat and flash the engine oil. The engine needs to be moderately loaded in order to break in correctly. Running the engine under very light or no load prevents the oil film placed on the cylinder wall from being scraped away by the expanding compression rings. The rings will instead “hydroplane” or ride over the deposited oil film, allowing it to be exposed to the cylinder combustion. The oil film will then partially burn on the cylinder leaving a residue that will build up and oxidize over time. Eventually this leaves a hard deposit on the cylinder wall that is very similar to the glaze left from flash burning. My caution to those just running the engine as a normal daily driver (without some loading) and especially those who love to idle their vehicles, expect some VERY extended break-in periods (up to 30,000 miles). Expect oil consumption forever due to oil glazing. The rings never really seat well if they cannot expand from the dynamics and heat that a load produces. Expect poor mileage due to the passing of compression and combustion gasses around the compression rings. Additionally, expect to see increased bearing wear and engine wear due to the fuel passing the rings diluting the engine oil.
Thus, we can see that heavy loading and light loading can cause some major problems. Moderate loading is the key to a proper break in for the first 1000 miles. It permits the loose fitting piston rings to expand into the cylinder walls allowing them to perform double duty: First, scraping oil off the cylinder wall, and second, to create friction that will promote wearing the two surfaces to each other’s proportions. Furthermore, moderate loading will allow the rings to get hot but not to the point where it will flash the lubricating oil supplied to the cylinder walls.
