Turbochargers

What is a Turbocharger?

After years of research and several trials of commercially using them, turbochargers have successfully been installed onto an internal combustion engine in 1925 by a Swiss Engineer called Alfred Büchi. Initially used in aviation industry to reduce the power loss at hight altitudes, they have made their way into automotive industry on multiple occasions. Due to size, quality, responsiveness, and economic feasibility issues they have been revoked from the market several times. The final breakthrough happened in the late 1970’s when turbochargers were introduced in some of the, at that time, latest models of passenger vehicles. Ever since, the turbocharger application on internal combustion engines has grown and has infiltrated majority of the industries utilising internal combustion engines for several reasons. Turbochargers do not have to be powered by external device as they are directly connected onto the exhaust manifold of the engine. This way high velocity exhaust gasses are repurposed and reused as “free” energy used to turn the so-called hot end. As the turbocharger is connected through the shaft to the so-called cold end i.e. the air intake, it uses the rotation caused by exhaust gasses to draw in the cold air from the atmosphere and push it towards the air intake manifold. This way larger amount of dense air is introduced into the air intake of the internal combustion engine improving the engine performance and fuel efficiency, while reducing the harmful emissions.

What are different types of turbochargers?

The downside of the turbochargers and a common misconception is that the larger the turbocharger, better the performance. The turbocharger, just like any other engine component, has to be specifically tailored to the engine that is using it in order to have the best performance. Having turbocharger that is too large will take more exhaust gasses and a longer time for a turbocharger to start rotating. If the turbocharger does not start rotating until it reaches higher revolutions, meaning it does not directly react to the throttle input, the engine is not capable of utilising its full capability and efficiency. This side effect is called turbo lag and can be solved in several different ways, hence for this and many other reasons there are different types of turbochargers.

Single turbochargers are the basic turbochargers that come in smaller and larger sizes depending on the purpose they are being used for and the outcome the manufacturer or the end customer expect.

Twin turbo just as its name says consists of two turbochargers. They can either be two separate turbocharging units feeding two-cylinder banks in a case of the V type engine or they can be a single unit. Single unit containing smaller and larger turbocharger, also known as sequential turbocharger, is the complex but very efficient type of turbocharger covering a wide span of RPM’s. The smaller turbocharger is used at the starts when torque is needed at lower revolutions while the larger turbocharger kicks in and provides it with that extra power needed at higher RPM’s. This way reducing the turbo lag and improving overall performance of the engine.

In order to cover a wider span of RPM’s the turbocharger does not necessarily need to be a twin turbo. Another form of turbocharger is Variable Nozzle Turbocharger (VNT) or Variable Geometry Turbocharger (VGT). This type of turbocharger has sets of adjustable aerodynamically designed vanes used to control the flow of the gasses through the hot end of the turbocharger. This means that at the lower RPM the area between the vanes is contracted, restricting the volume of the flow, but increasing its speed. This way the rotation of the turbocharger shaft is possible with higher efficiency and responsiveness to the throttle input. The downside of VNT turbochargers is that they are utilised mostly in diesel engines as the temperatures of the exhaust gasses do not reach such high temperatures as the petrol engine ones do.

In order to efficiently use the supply of the exhaust gasses from the engine and keep it as consistent as possible, another type of turbocharger, called Twin-Scroll turbo was developed. This turbocharger is fed depending on the firing order of the cylinders and due to this fact, it improves the efficiency and performance of the engine.

Using the combination of the ideas behind Variable Geometry Turbocharger and Twin-Scroll Turbocharger, a Variable Twin-Scroll Turbocharger was developed. It uses the advantages of the Twin-Scroll Turbocharger, splitting the flow of the exhaust gasses depending on the cylinder firing order with the advantage of a valve directing the flow in one or both of the scrolls.

Finally, the electric turbocharger has an electrical motor assisting it in lower revolutions to maximise the reduction of the turbo lag. Due to the fact it is controlled electronically it is way better in controlling the performance of the turbocharger and by that the entire engine, as there is direct electrical feedback to the engine control unit and the revolutions are adjusted accordingly. Having another component, the preventative maintenance, maintenance, and safety of use of the electrical motor increase the complexity of the turbocharger and increase its price.

How to maintain a healthy and working Turbocharger?

In order to keep your turbocharger healthy and working along with the rest of the engine, preventative maintenance is of crucial importance. Below are just a several examples of how to extend the working life of your turbocharger.

To start with, let us begin with everyday use. Starting your car and suddenly increasing the number of revolutions of the engine  can damage your turbocharger (and the rest of the engine, but as the topic is turbocharger related, lets stick to the topic). The reason for this is that the engine is still “cold” i.e. still has not reached its working temperature. Having turbocharger spin at high revolutions can increase the temperature of the shaft and the compressor whilst the rest of the engine remains cold. This will lead to thermal expansion caused either by the friction between the oil and the components of the turbocharger, or direct contact between the shaft and the bearings if the oil flow has still not reached the shaft. This will in turn cause the components to friction weld themselves to the internal bearings ceasing the turbocharger.

Secondly, the turbocharger requires for the oil to be replaced at regular intervals, not just topped up, but replaced. Of course, the oil replacement requires for the oil filter to be replaced as well. This is crucial for the extension of the working life of a turbocharger. With the time and use, small lumps, whether metal, burnt oil, sealing components or other, find their way through the system into the turbocharger. Due to turbocharger high speed of rotation, sensitivity to foreign objects entering the working space is an incredible danger. In case of such a thing occurring, there is a big chance that the turbocharger internal components will be damaged and in need for a full service.

Finally, it is of great importance to take good care of a turbocharger when shutting the engine off. Taking the example of driving the motorway speeds and coming to a stop. Even through the engine has stopped the turbo wheel keeps rotating as it is independent of the engine rotation. If the engine has been shut down straight after the coming to a stop, the oil pump has stopped pushing the lubricant and coolant, in this case oil, through the rotating turbocharger. This can once again result in thermal expansion and wear or friction welding of the turbo wheel and the rest of the internal components.

What indicates there is something wrong with a Turbocharger?

There are several different ways of being able to tell there is something wrong with a turbocharger.

First of all, there is a noticeable lack of power being generated. Engine either does not react to the input or is struggling to reach higher speeds.

Likewise, with a loss of power there could also be an engine check light indicating there is something wrong with the turbocharger. Engine check light does not necessarily mean it is a turbocharger fault, but it can be on certain occasions.

Another way of noticing a turbocharger failure is by sound. There is a distinct whistling/whining sound being produced by the turbocharger every time the throttle is pressed. Hearing this sound, especially if it is getting worse with time, indicates that a professional mechanic should take a look at the engine of your vehicle.

Visually the turbocharger failure can be noticed by change in colour of exhaust gasses. This could occur due to crack in the housing or severe wear of internal sealing components causing the oil flowing through the turbocharger to leak and burn in the exhaust.

Is just repairing a turbocharger not enough?

This is one of the most common questions that we get, and the answer is unfortunately no. Both turbocharger and the engine rely on each other to obtain a healthy and long service time. When servicing a turbocharger:

  1. ALWAYS make sure that you have replaced the oil and filters in the engine – This is important because if there are any residual particles in the oil, they will enter back into the turbocharger and contamination will cause the turbocharger to fail again.
  2. ALWAYS clean the connecting points, such as inlet and outlet – all of the contaminants have to be removed because even with the clean oil, they can enter back into the turbocharger.

ALWAYS clean the intercooler – not only particles getting to the internal components of the turbocharger are a danger. If particle of any size enters the intake of the turbocharger it can damage or completely destroy the compressor i.e. the cold part of the turbocharger.

DPF

What is a DPF?

A Diesel Particulate Filter, or more commonly known as DPF, is a part of the car most of the car owners do not think about as being important or might even not know it exists. Rapid growth of internal combustion engine market, particularly the diesel engine market due to their fuel efficiency, has brought a number of issues concerning health of the overall environment. Being surrounded by millions of cars pumping harmful gasses and soot particles into the atmosphere has opened up a question of how to protect the environment from the harmful effects caused by engines that essentially run the world. Unlike catalytic converter, a flow through filter, that is used for purifying the harmful gasses, Diesel Particulate Filter (DPF), just as its name says is used for entrapping the soot particles contained within exhaust gasses. It physically restricts the further flow of particles by having the alternate ends of its honeycomb structure blocked off, forcing the air flow through the walls typically made of ceramic materials. Soot and other unburnt particles this way have no choice but to deposit onto the walls of the filter in thin layers building up with time. DPF successfully removes ultra-fine particles of up to 100 nanometres in diameter with efficiency over 95% in mass and over 99% in number of wide range engine operating conditions. Use of this filter has been introduced to majority of the diesel engine vehicles since 2009 complying with Euro 5 standard, even though some manufacturers have introduced them before.

How to maintain a healthy and working DPF?

Having a DPF that is working correctly and efficiently is just as important as any other component that makes the modern internal combustion engine operate in a safe, efficient, and environmentally friendly manner.

These filters require heat to operate correctly. If the car is often driven on short distances especially in the city centres where lower speeds are both required by law and just by the surrounding environment, the heat developed in the exhaust is not sufficient to regenerate the filter. There are three types of regeneration, spontaneous, dynamic, and service. Spontaneous regeneration happens when DPF reaches 600°C. In case where spontaneous regeneration does not occur, a light on the cluster board indicates that the dynamic regeneration is occurring. In such case the vehicle must keep moving to complete the regeneration. Stopping the regeneration increases the chance of DPF becoming clogged after a shorter period of time to a point where dynamic regeneration is not a solution anymore. Service regeneration can be done in different ways and depends entirely on the type of technology utilised by the company servicing your DPF.

What indicates there is something wrong with a DPF filter?

The initial sign that some capacity of the filter has been reached can be noticed by a warning light on the cluster board. This light indicates that the regeneration process is occurring. Furthermore, in case the regeneration light is ignored, loss of power of the engine can be noticed as well as increase in the fuel consumption. Finally, to take it one step further, the engine can go into the limp mode and even cracks can occur on the DPF metal housing. It is extremely important that regeneration processes are not interrupted as the accumulation of the soot will reach the level where the only solution is a new filter, resulting in a very costly expense.

Computer aided design(CAD)

What is CAD?

Computer Aided Design or universally known as CAD has revolutionised the world of engineering. It has allowed engineers, architects, drafters, and many other creative enthusiasts to bring their ideas to virtual reality on a screen. It has increased the complexity of visualisation and incredibly reduced the guess factor as well as opened door to what seemed impossible only a few decades ago.

What is the difference between CAD and CAE?

CAD is the design and visualisation of mechanical or any other components, while CAE or Computer Aided Engineering deals with analysing these visualisations. In CAE engineers introduce real world mechanical properties of the materials and working conditions into the computer software allowing them to test the designed creations under specific conditions. Whether static or dynamic loads, temperatures, fluid flows or even, as of recent, generative design of components used for additive manufacturing of products, it can all be done in CAE engineering softwares.

What are the benefits of CAD?

The main benefit of CAD is the unlimited number of iterations that can be created before the product satisfies all the constraints set by customer, market, manufacturing  capabilities etc. All of the mistakes made on the screen do not use resources other than time. This allows to stress free plan out all the details before committing to high manufacturing expenses.

Up to which extent can you use CAD?

Virtually, visualisation wise, the only limit is the imagination and skill of the user. Whether it can be manufactured using standard manufacturing methods or advanced manufacturing methods is questionable.

How long does it take to design part in CAD?

It all depends on the complexity of the part, required changes, manufacturing constraints etc. It can take anywhere from a few minutes to days or months.

How long does it take to design an assembly in CAD?

It all depends on the complexity of the assembly, required changes, manufacturing constraints, availability of the components on the market etc. It can take anywhere from a few minutes to days or months.

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Can you integrate already existing components in CAD?

Yes, having assumed that the software used can process the format of the part/assembly being introduced to it. There are plenty of web pages providing already designed components and more manufacturers nowadays offer their components in variety of formats to allow end user to easily integrate their products in their designs.

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Can you integrate components in scanned parts or assemblies?

Yes. There are of course some limitations and quality of the end product depends on quality of the scan, but it is possible and probably the best way for complex geometries.

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Rapid prototyping (3D printing)

What is 3D printing?

3D printing, rapid prototyping, or additive manufacturing, are all synonyms of the same manufacturing technique. It is a manufacturing technique where, unlike in subtractive manufacturing where pieces of material are taken from the billet until the desires shape is obtained. In additive manufacturing, as one of the synonyms for its name says, material is added in order to form the final shape of the part. The part desired is previously designed in a CAD software or scanned from an existing object. The object is sliced into layers only a fraction of a millimeter thick and layers are deposited at a set rate and thickness until the final shape is obtained.

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How can I benefit from additive manufacturing?

Additive manufacturing has started infiltrating into all aspects of manufacturing and is literally reshaping the manufacturing industry on daily basis. From the quick prototypes to finished products 3D printing is used for both. It is extremely financially beneficial in the prototype sector as it is highly cost efficient due to no need for manufacturing expensive moulds. As much as it is cost efficient it is time efficient. It is possible to design a product and have it printed and tested in the matter of hours. As it can take only a few hours to have a product ready, re-design and re-printing are likewise both cost and time efficient. This is allowing the end user to experiment more to achieve the desired result and avoid mistakes in the final product being produced using one of the standard methods.

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What are the materials you can use for additive manufacturing?

The range of materials being printed in various industries increases on daily basis. Everything from polymers to metals can be printed. In our facility we use PLA which is the short for Polylactic acid. It is the most common polymer material used for prototype printing.

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What is the dimensional limitation?

The printer we have in our facility can print parts in maximal dimensions of 220 [mm] x 220 [mm] x 250 [mm]

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How long does it take for a part to print?

Depends on the volume of the material used for the product to be printed. When the part is designed and sliced in the software with all the parameters of the print set up, the estimated time for the part being printed is provided.

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Is any post processing required after the part has been printed?

Depending on the type of additive manufacturing method there are different needs for post processing. In the case of the FDM additive manufacturing machine used in our facility, overhangs and other shapes needing support material require for the support material to be removed once the process of additive manufacturing is completed. Depending on the required tolerances, surface finish and the overall aesthetics of the final product the methods of post processing as well as time required to do it might change.

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Engine re-manufacturing - Cylinder blocks

What is a cylinder block?

Cylinder block is the central part of the engine where the combustion occurs. It houses pistons and connecting rods which are connected to the crankshaft on the bottom side while the top section is enclosed with a cylinder head. The engine block or cylinder block maintains engine’s stability under severe loads and temperatures.

There are two types of cylinder blocks, one being inline and the other one being V-type. The number of cylinders varies depending on the power the manufacturer wanted the vehicle to have. In the past, most of the engines were only atmospheric, meaning they didn’t have any turbochargers or compressors used to increase the power of the engine by adding more cold air into the combustion chamber during the intake stroke. Because of the engines only being atmospheric the power had to be compensated with number of cylinders. Very common engines of the higher range of performance were V8 or V6. Nowadays due to rules and regulations on emissions and most of the engines having turbochargers, most commonly engines are 4 cylinder inline or even 3 cylinder having large amounts of power considering their size.

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What are the most common modes of failure of engine blocks?

Cylinder blocks can fail in many different ways:

  • Just like everything else with time and use, cylinder wear out.
  • If the engine is not serviced regularly. Oil, filters, timing belt replacement, coolant, all have to be replaced in a timely manner in order for engine to run smoothly
  • If the cylinder block overheats it can crack or deform
  • Pistons if overheated can expand and seize in the cylinders, damaging the surface of the cylinders
  • If the vehicle is pushed to its limit at all times the load on the crankshaft can crack the bearing saddles
  • Overloading can also deform the crankshaft and run the pistons into the sidewalls of the cylinders etc.

What to do if cylinders are worn out?

  1. Cylinders have to be measured and visually inspected to determine how out of tolerance they are.
  2. Cylinders have to be checked for the out-of-roundness and taper to determine can they be overbored to the next size specified.
  3. If cylinders are out of all the allowed tolerance, they have to be bored and sleeved. If they can be bored to the next specified size they are and in both cases they are honed

Engine re-manufacturing - Cylinder heads

What is a cylinder head?

Cylinder head is a part of the internal combustion engine responsible for so called “breathing” of the engine. Having the intake and exhaust valves sitting on the valve seats and camshaft, cylinder head is adjusted to open and close the valves in a timely manner.

What are the most common modes of failure of cylinder heads?

Cylinder head can fail in many different ways:

  • Valve guides wear out or get damaged
  • Valve seats get damaged and do not seal properly
  • Valves wear out, hit the piston and bend, or just get eroded on some occasions
  • Intake and exhaust ports get clogged
  • If overheated cylinder head can crack
  • If the engine is not serviced regularly. Oil, filters, timing belt replacement, coolant, all have to be replaced in a timely manner in order for engine to run smoothly etc.

What to do if cylinder head needs a repair?

  1. If engine got overheated it has to be pressure tested or if for any other reason it is suspected that it might be cracked, cylinder head has to be pressure tested.
  2. In order to inspect it thoroughly cylinder head has to be taken apart, thoroughly cleaned, and visually inspected
  3. Valves, valve seats and valve guides have to be measured and visually inspected to determine how out of tolerance and damaged they are.

Crankshafts

What are crankshafts?

Expansion cycle of the internal combustion engine creates linear motion of the piston. This linear motion of the piston pushes onto the connecting rod and converts the linear motion of the piston into the rotational motion of the crankshaft. Crankshafts are responsible for transmitting the power of the engine.

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What are the most common modes of failure of crankshafts?

Crankshafts can fail in many different ways:

  • Just like everything else with time and use, bearings and crankshaft rod journals wear out.
  • If the engine is not serviced regularly. Oil, filters, timing belt replacement, coolant, all have to be replaced in a timely manner in order for engine to run smoothly
  • If the engine overheats it can deform the crankshaft as well
  • If the vehicle is pushed to its limit at all times the load on the crankshaft can bend and twist etc.

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What to do if crankshaft needs a repair?

  1. Bearing journals have to be measured and visually inspected to determine how out of tolerance and damaged they are.
  2. Journals have to be checked for the runout and taper to determine can they be ground to the downsize dimension specified.

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Connecting rods

What are connecting rods?

Connecting rods are used as a connection between piston and crankshaft. They are vital components of the internal combustion engine undergoing large stresses and temperatures. During the compression stroke majority of the stress is induced from the crankshaft side while during firing stroke it suffers stresses from the piston side.

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What are most common modes of failure of connecting rods?

Being constantly in motion and under large stresses combined with large temperatures there are several most common ways connecting rods fail. Failure of the connecting rods can lead to complete engine failure and thus good care has to be taken for this not to happen.

If engine overheats, connecting rods might overheat as well and they might change colour. This typically means the material properties within the connecting rod has changes and it has to be replaced fully.

Due to large forces it withstands while in motion and absorbing heat from the engine it can also twist and bend. If it bends or twists by a certain amount, it has to be replaced with a new connecting rod

Harsh conditions can also deform big end and small end of the connecting rod. Any deformation has to be checked for both in big and small end. Depending on the magnitude of the wear, the two ends can be

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