TurboCharger?

 
 
What is the simple principle of a modern turbocharger? 
 
Increasing airflow to engine at above atmospheric pressure to provide more combustion 
 
Describe the terms engine torque and power? 
 
Torque is basically pulling power, it is defined as force around a given point, applied at a radius of that point. 
 
Basically the twisting force of the engine. 
 
 
Power is the force, over a given time, that question is actually really hard to answer. 
 
Horsepower is the measurement of that power. 
 
How much oxygen is there at sea level? 
 
20.9% at about 14.7psi air pressure 
 
At altitude what diffculties are faced by an engine? 
 
The higher you go, the thinner the air gets, and less air means less bang, turbo-normalizing is using a turbo to maintain sealevel air pressure (14.7psi) at a constant rate, so no matter what altitude your at in your plane or car, the engine still gets the same amount of air. 
 
When fuel is mixed with insufficent oxygen what happens to the fuel? 
 
The fuel dosent get burnt and the car runs rich 
 
An engine is said to be black smoking, what is the cause? 
 
The engine is running rich and fuel is getting into the exhaust 
 
simply put how does a turbocharger help supply air? 
 
The compressor wheel sucks air at a high rate, then after the air is compressed it is sucked down the turbo piping and then through the intercooler (to cool some of the hot air after its been compressed) then after going through some more piping it goes through the intake and into the cylinder. 
 
why is a turbo engine still able to maintain the same air-fuel ratio as at sea level? 
 
Because the extra air the turbo supplies the motor is the same amount of air that there is at sea level, no matter how thin the air gets, the turbo will spin fast enough to provide the engine with the same amount of air it needs to run comfortably. 
 
How were mechanical superchargers driven? 
 
Superchargers need to be driven off the crankshaft of the engine, this robs the engine of power, because that power is needed to turn the supercharger itself, but the supercharger increases the power, so it is worth it, it makes alot more than it robs. 
 
Why is the supercharger described as an engine parasite? 
 
Because it needs the turning power of the crankshaft to turn itselfs (connected via a belt or gear) it takes power away from the engine, depending on the size of the engine and the size of the supercharger, some may take up to 200hp to turn, but then in turn will provide the engine with another 500hp. 
 
Give an example about how much power the engine takes from the engine? 
 
The Rolls Royce Merlin, for instance, the supercharger uses up about 150 hp. Without a supercharger, the engine would produce 750 hp, with a supercharger, it produces 1,000 hp, a total increase of 400 hp (750 hp — 150 + 400), or a net gain of 250 hp. 
 
Why is the turbocharger considered more effecient? 
 
because its using wasted energy (exhaust flow), where the supercharger is taking perfectly good twisting force away from the engine 
 
Inside the turbo where is the exhaust gas channeled? 
 
The exhaust gas is channeled into the exhaust turbine of the turbo, spinning it, then it goes out and carries on down the rest of the exhaust, the exhaust housing of the turbo forces the exhaust into the exhaust turbine. 
 
then what happens to the exhaust? 
 
as said above, goes down the exhaust, going past the o2 sensor, through the cat, through the resonator then finally out the muffler 
 
the gas enters the turbine wheel, what happens to the flow of the gas? 
 
Its slowed, turbo's are bad in this sense because compared to a non-turbo car, its like having a big block in the exhaust when the turbo isnt spinning at the desired boost, this causes them to be a bit worse on gas because of the block in the exhaust system they cause. 
 
The commen shaft connects the two turbines, what are they called? 
 
Exhaust turbine and compressor turbine. 
 
During the turbo process whats the compressor wheel doing? 
 
The compressor wheel is sucking in air at a high rate while compressing it down and then sending it flying down the piping towards the intercooler (generally) 
 
The housing contains fully floating bearings, describe the bearing types? 
 
Well lets start with sleeve bearing turbos. 
 
these were popular during the 80's until nissan came up with the ball-bearing turbo design, these work by using two bronze bearings that fit around the shaft and feature small holes to allow high pressure oil to provide a cushion for the bearing, its held in by clips. 
 
They were a popular design because of the low cost, they can tolerate lots of vibration caused by the turbo because they sit on a cushion of oil, the high pressure feed of the oil also helps with general cooling of the turbo charger. 
 
The disadvantange of the sleeve bearing design, they heavily rely on oil and are very easily damaged with lack of oil or contiminated oil. They also struggle when the boost is increased from higher than stock. 
 
Ball bearing turbo's, 
 
simular in some ways to the sleeve bearing turbo, the shaft is suspended by a ballbearing which is made from stainless steel which is put inside a carrier case which is held in by a series of clips with an oil supply hole and a bolt. 
 
Most ballbearing turbo's rely on watercooling as added cooling for the turbo, but this isnt always nessesary. 
 
Oil is needed to lubricate and cool the turbo, just like in the sleeve bearing turbocharger, but they rely on it alot less than a sleeve bearing turbo. 
 
Ball bearing turbo's have less drag than sleeve bearing turbo's, and handle heat alot better. Also they can handle boost better and can generally take more punishment. 
 
The only disadvantage with ballbearing turbo's is that they cost more to produce and generally need water cooling. 
 
Lastly, I want to mention the airfoil bearing turbo. 
 
The airfoil bearing, suspends the shaft and in itself is suspensded, being surrounded by foil. 
 
The bearing has a shaft which is surrounded by a spring loaded foil, once the shaft is spinning fast enough, air pushes the foil away so there is no contact with the shaft, thus no wear, and no need for any type of lubrication or cooling, as heat is the ally with a foil bearing, not an enemy. 
 
The issue is, when the bearing is not spinning at high speed, there is contact, and wear does occur, that means during starting the engine and stopping the engine, the bearing does wear. 
 
The advantages of the foil bearing is that its efficent due to having no friction (the turbo is more free), its quiet and can handle a very wide operating temperture. It also deals with vibration very well and dosent need any oil or water to run. 
 
The disadvantes are that it wears during starting and stopping and that it cant handle as much load as a ballbearing or sleeve bearing. 
 
what other names are turbo oil seals known by? 
 
Split ring seals & piston ring seals 
 
what is a thrust bearing? 
 
A thrust bearing is a particular type of rotary bearing. Like other rotary bearings they permit rotation between parts, but they are designed to support lots of load and come in lots of variations. 
 
What govens the rate of air flow? 
 
The throttle butterfly 
 
The causes for low power, low boost and black smoke are? 
 
Poor throttle adjustment, a clog or block in the fuel or air systems. 
 
Make sure there is no blocks in the exhaust system, then cheak the turbocharger. 
 
Cheak the turbine turns freely, cheak the clearances, if the turbo has an internal wastegate, cheak the actuator. 
 
The turbo has been removed, describe the checks a technicion would perform? 
 
Cheak the side to side clearances of the turbo, cheak the turbines spin freely, cheak for marks on the inside of the housing, and cheak the actuator is working. 
 
Define the terms axial and radial? 
 
Axial means along the same line as an axis and radial means moving along a radius 
 
How do you perform a wastegate check? 
 
cheak that the acuator is working and make sure that the wastegate flat isnt damaged. 
 
what noises are associated with turbo problems? 
 
A high pitch whine normally indicates a worn bearing assembly. 
 
A surging of air noise, normally means the boost is escaping or there is a block in the piping. 
 
Turbo or supercharger? 
 
Personally, I like turbochargers better, there recycling effectivly and they dont take any power from the engine directly, they only hold up the exhaust a bit when its off boost, otherwise they are giving you lots of extra power, at no downfall, and most modern turbo's dont suffer from lag or reliability issue's either, I think the supercharger is a dieing breed. 
 
What is a wastegate? 
 
A wastegate is basically a control valve to control how fast the turbo is spinning. 
 
What role does a wastegate have? 
 
The wastegate directs exhaust flow away from the turbo to ensure that the turbo dosent spin any faster than desired, as this could cause damage to the turbo or the engine. 
 
How does a wastegate work? 
 
It is activated either by a pressure spring or boost controller on an external wastegate or an actuator on an internal wastegate and opens a valve to release some of the exhaust from the manifold straight into the exhaust, bypassing the turbo exhaust turbine. 
 
Describe the term, turbo intercooled? 
 
Well most turbocharged cars have an intercooler, this helps to cool the air that has just been through the turbo compressor, when air is compressed it becomes hot, and hot air can cause all kinds of issue's inside the engine, so an intercooler helps cool the air before it goes into the cylinders. 
 
How does the wastegate effects a vehicles performance? 
 
A wastegate helps keep the vehicle reliable and depending on the wastegate it can effect performance by how much exhaust it lets to the turbo, more exhaust means higher boost, thus more power, so the wastegate basically controls how much power you are going to get from your turbo.