The exhaust-gas turbocharger: a growing business segment …
Exhaust-gas turbochargers are a key technology to enhance performance, reduce fuel consumption, and lower exhaust emissions. When fitted to direct-injection diesel engines, they reduce fuel consumption by up to 25 percent compared with similar gasoline engine with duct injection. For this reason, they have taken over almost the entire market segment. The trend with gasoline engines is toward downsizing, that is to say, a reduction in cubic capacity for the same power output. This is achievable by turbocharging, since the high power-to-capacity ratio of these engines requires an increase in the air mass supplied to the engine. This is only attainable by supercharging. Inevitably, the number of turbocharged gasoline engines will undergo a significant rise worldwide.
Experts estimate that in 10 years time, there will be about 160 million cars and roughly 16 million trucks (>3.5 metric tons) running on this key technology, and the tendency will continue to rise. As a result, the turbocharger segment represents one of the largest growth markets in the automotive industry worldwide.
A growing business segment also in the Aftermarket
However, it is not only the turbocharger itself that offers sales opportunities. Car repair shops that are service and sales-oriented also have the chance of making additional business in the segment of servicing or reconditioning, for example, filter changes.
What's important when replacing a turbocharger
A turbocharger is designed and built to match the service life of the engine. However, the high-tech components in the exhaust gas system are exposed to several risk factors which could lead to their failure: for example from foreign bodies that penetrate the turbine, dirty oil, a faulty oil supply or excessively high exhaust gas temperatures. This makes the mechanic’s know-how all that more important. There follow some practical tips and tricks for an effective replacement.
A precondition for a successful repair is that the cause of the failure has been identified and eliminated—otherwise there is a risk that the new turbocharger will fail again after a short time.
Even the smallest of foreign bodies acts like a projectile at the enormously high speeds of the turbine and compressor wheels. The air filter therefore has to be replaced in every case. Just as important is the careful cleaning of the entire intake and fresh air system to and from the charge air cooler including the removal of all foreign bodies from the exhaust pipe.
A MUST: LUBRICATION
The rotor shaft bearing needs engine oil.
TIP: pour a little engine oil into the oil inlet bore before installing the new turbocharger, place a clean cloth over this—and then distribute the oil in the bearings with a short blast from a compressed air gun (see illustrations). After installing the turbocharger and before connecting the oil supply, pour some more engine oil into the oil inlet bore. A small syringe with engine oil is enclosed with the MAHLE turbocharger sets of seals to make this work easier.
WHAT GOES IN, MUST COME OUT
The turbocharger needs engine oil for lubrication and cooling and this is supplied by the oil pump in the engine. The oil is returned to the circuit via the oil return pipe. The complete oil return pipe and connection to the crankcase must be laid without any kinks and must be free from deposits so that the oil is transported smoothly. If the return flow is disturbed this leads to blockages and the turbocharger loses oil through the turbine and compressor wheels. Imminent consequences include major engine damage.
TIP: a new oil return pipe is just as sensible an investment as a new charge air cooler.
ANOTHER TIP: there should be no excess pressure in the crankcase. If the crankcase vent is dirty an excess pressure builds up that hinders the return flow of oil in the turbocharger. The turbocharger starts to lose oil through the turbine and compressor wheels as soon as an excess pressure of only a few millibars is measured at the dipstick tube with a manometer.
All connections on the turbocharger must be tight so that oil, air, exhaust gases and, depending on the type, cooling water can be passed through the turbocharger cleanly, safely and without losses. Each MAHLE turbocharger has a matching mounting kit—consisting of seals as well as exactly fitting builton parts (for example stud bolts, nuts, etc.). Important: only ever use these original sets of gaskets. And never use the old gaskets again—they are often deformed or porous and therefore cannot guarantee the necessary seal. Sealing compound or liquid sealers are also forbidden on the turbocharger. Sealing compound may reduce the cross-section of the bores—and parts of the sealing compound may become loose and block the supply of oil. The consequence: major damage to the turbocharger.
The oil supply and return lines often run very close to the turbocharger. Car manufacturers thus protect the oils pipes with shielding. This should also be checked when replacing the turbocharger: is it still in place and undamaged?
NEW TURBOCHARGER—NEW OIL
A new turbocharger should always be given new oil—and a new oil filter. This ensures that any foreign bodies in the oil system are eliminated and cannot damage the new turbocharger. (After all, the old turbocharger is faulty—which may be due to infiltrated foreign bodies or particles.)
TIP: “If a little is good, then more is better” does not hold true for the oil level! Because if the oil level in the engine is too high this leads to disturbances of the compression ratio in the engine. This forces engine oil into the turbine and compressor of the turbocharger where it collects in the charge air cooler. If this oil is sucked in and burnt again by the engine this could lead to major engine damage.
MAN THE PUMPS
Once the turbocharger has been fitted, the oil and possibly water lines connected and the air and exhaust gas line connected to the turbocharger, the oil can be changed and the cooling system vented.
Ignition must be prevented when the engine is started—for example by removing the fuel pump’s fuse or relay. Then turn the engine with the starter until oil pressure has been built up. If the engine is being started for the first time we recommend that you leave the engine idling for 2 minutes before opening the throttle to ensure the supply of oil.
A SCREW LOOSE?
You then have to check whether all screws and connections are tight and that there are no leaks.
TIP: check the tight fit of all screws again after running for approx. 20 hours or 1,000 km.
Every engine profits from being run for a longer period of time. A turbocharged engine takes poorly to short trips because after a cold start the unburnt fuel and condensation water collects in the engine oil. This worsens the tribological properties of the oil and reduces the carrying capacity of the lube oil film. These unwanted companions only disappear at oil temperatures over 80 °C. If the oil temperature stays below this level for a longer period of time, as is the case with short trips, this constitutes a risk for the turbocharger: the bearings of the crankshaft and camshaft and rotor shaft in the turbocharger become worn. At low outside temperatures the emulsion of engine oil and condensation water in the oil return pipe of the turbocharger and in the crankcase vent can also freeze leading to disturbed engine compression ratios.
BIODIESEL? A HIGHER RISK FOR ENGINE OIL AND TURBOCHARGER
Vegetable oils do not evaporate—and unburnt vegetable oils collect in the engine oil. This becomes viscous as of a certain concentration and the lubrication system collapses soon afterwards. This means much shorter intervals between oil changes if vegetable oils are used as a fuel.
|Pour in a little engine oil before installation to lubricate the rotor shaft bearing.|
Then place a clean cloth over the oil inlet bore …
… and distribute the oil in the bearings with a shot of compressed air.
Customer care: good to know
Idling prophylaxis: let the engine run at idling speed for around 30 seconds before setting off to ensure the supply of oil to the turbocharger – and 30 seconds idling after a fast trip on the motorway cools the turbocharger.
Short trip compensation: drivers whose journeys are mainly short trips should take a longer trip at least once a week to give the engine oil the chance to regenerate.
Heater output optimisation: to help get the engine up to working temperature faster in winter you should wait for 3 minutes before switching the heater on – it will then heat up quicker too.
MAHLE OE technologies for the aftermarket
MAHLE is one of the technology leaders and system developers in the field of internal combustion engines and engine peripherals. It is also a long-standing business partner to international automotive and engine manufacturers in the development and production of high-loaded turbocharger components.
In particular, efficiency profits from downsizing engines. Efficiency is all the higher, the better the technologies involved are matched, such as exhaust-gas turbocharger, fuel injection technology, variable valve timing, exhaust-gas recirculation, and charge-air cooling. The MAHLE Downsizing Engine was specially designed and certainly made an impressive statement as a technology demonstrator—it is capable of achieving a CO2 reduction of up to 30 percent.
As part of the systematic enhancement of the product portfolio for the aftermarket, we are now supplementing our range with turbocharger systems for high-performance and high fuel-economy diesel and gasoline engines. Not only that, we are placing our innovative MAHLE turbocharger technologies at the disposal of the retail trade and to car repair shops.
The focus will first be on turbochargers for truck applications, for example, for brands such as Mercedes-Benz, MAN, Volvo, and Scania. The product range will be constantly expanded. By the year 2012 it will cover roughly 70 percent of all fast mover applications and will be supplemented by car applications. The wide range of different sizes and types with power outputs from 75 through 1000 KW guarantee optimized compatibility with the most diverse requirements of car, truck, construction, and agricultural engines.
Cutting-edge quality through integrated development and manufacturing processes
Speeds of over 300,000 rpm, exhaust-gas temperatures of more than 1,000°C. To achieve high efficiency under such extreme conditions over a wide map of characteristics requires extremely high development competence and manufacturing precision.
Our engineers therefore utilize state-of-the-art simulation tools in the initial phase to guarantee the required thermodynamic and thermo-mechanical characteristics of components over the complete integrated development process. Thermo-mechanical calculations are conducted to determine the durability of the turbine housing. After the design and calculation phase, the exhaust-gas turbocharger is subjected to an extensive series of tests on hot-gas test benches and engine test benches. The criteria here include thermodynamic maps, shaft displacement curves, and product life cycle.
MAHLE Original exhaust-gas turbochargers are manufactured at production locations in Germany and Austria based on standards that are universal throughout the Group. Modern, computer-controlled production machines guarantee optimized precision to machine housing components made of aluminum and cast steel. Turbines are manufactured from high-temperature resistant materials and feature premium cast quality and precision balancing. This is the only way in which they can withstand extreme conditions in the long term.
|Using what is known as field balancing, specific in-service conditions are simulated and dynamic unbalance is detected.|
Since the shaft and the turbine wheel are made of different materials, welding these two components together represents a special challenge. MAHLE engineers found the solution: electron beam welding—a process that permits extremely precise and reliable joining.
To comply with very high quality standards in turbocharger production, a team of product and process engineers are permanently deployed to continue development in production, assembly, and test processes, such as high-speed machining, joining technology, coating with fluid and solid materials, or balancing. The team can harness the wide range of production competence gained from all previous product areas.
MAHLE Original turbochargers – Production quality without compromises
Sustainability as obligation
When it comes to environment protection, MAHLE is also one of the leading automotive suppliers in this discipline. Our mission is to promote technical progress and human future in harmony with our environment. We have sealed our obligation to this commitment through certification of our locations in compliance with DIN EN ISO 14001. Besides the economical deployment of resources and ecological production processes, it is our core products that make the greatest contribution to environmental protection. They produce a sustainable positive impact on the ecological balance since they are installed in millions of vehicles worldwide to reduce fuel consumption and lower exhaust-gas emissions.
Design and function of turbochargers
The power output of an internal combustion engine mainly depends on the air mass supplied to the combustion process and this is achieved by employing a turbocharger. It utilizes exhaust-gas energy to precompress the intake air and supply a greater air mass—and therefore more oxygen—to the engine, achieving greater efficiency in the combustion process.
Exhaust-gas turbocharging permits an increase in maximum torque and maximum power output (while retaining constant work volume), and a rise in mean pressure, without requiring any mechanical drive output from the engine that normally occurs with mechanical supercharging, e.g. a compressor. This increase can be harnessed to fit a more powerful engine with approximately the same dimensions as the original engine. Alternatively—and the trend is pointing in this direction—it can be utilized to implement downsizing concepts that can lower fuel consumption and CO2 emissions without a tradeoff on power output.
The exhaust-gas turbocharger is driven by engine exhaust gases that are supplied to the turbine blades or the turbine wheel (red) at high speed and high temperatures of up to 950°C. In turn, the turbine wheel drives the compressor wheel that is mounted on the same rotor shaft. During the resulting rotation, the compressor wheel draws in ambient air through the intake duct and from there the air is routed to the cylinders (blue). The yellow marking shows the oil circuit—from the inlet to the return pipe.