Who Does a Turbocharger Work?

http://auto.howstuffworks.com/turbo.htm

You keep the engine running/idling before shutting down to allow the turbo wheel time to slow down - if you immediately shut off the engine after spinning the turbo hard, you lose oil flow/pressure to the wheel and it can burn the oil that it is sitting in.

Slightly wrong! you should have written that you need to keep the engine running at tick over for a minute or so, to allow the Turbo to cool down with the aid of the engine oil flowing through its bearings.

Turning the engine off while the Turbo is still red hot (they glow visibly under quite normal conditions of usage) causes the residual heat to possibly over heat the bearings and maybe carbonize the residual oil in them, so ruining the turbo for future usage.....

Some (not all!) modern turbos are watercooled and as far as I am aware, this precaution is then not required.

This guy didn't deserve an off topic score.

He gave an answer to the guy's question. Which is on Topic.

He didn't give an answer that is as thorough as many of the rest of you but he still answered the question for the most part. He also included a link for a more thorough explaination.

A Turbo charger is designed to increase the volume of air in a combustion chamber to improve efficiency and more complete combustion.

You need to idle an engine with turbo on startup to allow oil to reach the bearings which is critical on a component that rotates at enormous speeds however, the reason to idle the engine with a turbo on shutdown is completely different. As the turbo and its central shaft run white hot, if you shut down the engine instantly, you run the danger of shaft warp/droop! The next time you start up the engine, it wouldn't sound too good so, let it cool off a bit before pulling the plug!

Hope this helps

a little sematics here. A turbo charger doesn't increase volume, it increases MASS. An ICE engine is a constant VOLUME compressore.

Tomatos and Tomatoes Volume or Mass, either way the point is as 50 was making is you are pumping more air into the combustion chamber rather than the piston having to simply "suck"· it in.

I seriously doubt much more could be added to this subject other than just picking each others coments apart. Although some are more detailed than others, none can actualy be pegged as wrong.

A Turbocharger compresses the air before injecting it in the cylinder so there is more oxygen when gasoline ignites, making it a better combustion

Correct on the shutdown.

Idling allows the turbo to cool, and not "coke" the oil in the housing.

They use sleeve bearings, and can be scored easily.

It is common for the exhaust section of a turbo under load to be hot enough to glow.

Hi Ash,

A turbocharger is a component used on an engine to increase the volumetric efficiency and thereby the horse power of that engine. It's main function is to change an engine from naturally aspirated intake syatem, to have a pressurised intake system.

It works by utilising the waste gas products from the combustion process - exhaust - to spin a turbine inside the exhaust housing of the turbocharger. This turbine wheel is connected via a shaft running in very high precission brass bushings inside the main body of the turbocharger to the impellor wheel inside the intake housing of the turbocharger. This impellor wheel when spun at high velocity creates a positive pressure in the intake system of the engine's manifold. When the inlet valve opens the pressure in the cylinder is therefore more than the total volume of the cylinder at atmospheric pressure.

The principle of turbochaging means there is more oxygen for the combustion process - so many technical advantages are gained, cleaner burning, higher efficiency, and more power from a smaller engine.

The reason a turbo charged engine must be idled for a perod of time before shutdown is to prevent premature failure of the component. The turbine inside is spinning at extreme velocities when it is functioning. If a "hot" shutdown occurs, the oil pressure from the engine stops flowing around the shaft when the engine is turned off. It is the oils job to lubricate and cool the shaft. If no oil is flowing around the shaft it will obviously burn the residual oil in the body and eventually lead to scouring of the bushes and slip rings.

I hope this helps you to understand the basic principles. Many related topics - intercooling, aftercooling, wastegateing and such are all relevant but for now the above is a simple explanation for you.

in addition to above comments i would like to add that you will improve weight to power ratio of the engine by turbocharging,In simple language for same given size and weight of the engine you will squeeze higher power from the same engine when naturally aspirated and when turbo charged.

crm

GA.. If Ash Brandy doesnt know the basics, a good visual aid is worth a thousand words

One small point I'd like to include to this excellent answer, a turbo takes some of the normally wasted energy of the pressurized exhaust gasses to create the intake manifold pressure. One of the reasons that turbos improve engine efficiency. This typically means that the exhaust gas speed and volume must be sufficient to pressurize the intake manifold. This is the root of the concept of turbo lag. For on most turbo charged systems, the exhaust gasses of an idling engine will be insufficient to pressurize the intake. When the throttle is opened for more power on an idling engine, more unpressurized air and fuel enter the cylinders, get burned, produce more exhaust gasses and now pressurize the intake manifold.

Hmm I guess that was actually two small points.

That has been fixed to a great degree by the turbo blades (probably on the "cold side" being adjustable, so that at low exhaust rates, the pressure produced is still correct and at higher rates, the blades are partially folded, to stop the Turbo from "over speeding/over pressurizing"...

I could easily believe it is a simple mechanical "speed control" of the Turbo itself (probably using intake manifold pressure), but up to now, I have not managed to see one in real life........it may of course be controlled from the motor management system, but I personally doubt that......sounds too complicated, but I have been wrong before, it could (and will!) happen again!!

The waste gate was an earlier attempt at basically the same thing, but with less than optimum result as we all know.....perhaps the waste gate still works together with the variable geometry turbo blades.....

Here are a few websites that mention these modern Turbo Chargers:-

http://www.carsandtuning.org/hybrid-turbo-blower/

http://www.turbotechnics.com/docs/turbo/hybridinfo.htm

http://wikicars.org/en/Turbo_Engine

I hope this helps.

Three readily available books I would recommend reading are:

Street Turbocharging by Mark Warner, P.E. by HP Books (includes much in regards to today's electronic control systems and programing and upgrades for today's ECU's and generally a good read on the subject)

Turbochargers by Hugh Maclnnes also by HP Books (well put together for basic understanding and systems.)

Maximum Boost by Corky Bell. Bently Publishers (contains much more technical aspects to the different applications and even though somewhat opinionated at times, really good information on the subject on a wide scale.)

When the oil gets "cooked" in the center turbo bearing housing it is commonly called "coking" the oil.

Aside from Turbos increasing power output, I personally think all vehicles should have one simply due to the increase in operational efficiencies via from heat and ading volumeteric efficiencies. (A custom made Holset/Schwitzer combo for my 318 mopar)

Something I would like to add is that we need a method to "bleed off" excess turbo boost in certain circumstances. Too much boost can damage an engine, so we use a wastegate (or often in racing, a simple pop-off value) to bleed off a calibrated amount of the boost.

Turbos run at tremendously high rpms, and very hot as well; those are major reasons to idle for a minute before shutting down. Also, bearing clearances tend to be very small, and we need to cautious about shut down because bearing scoring/flaking/other damage often occurs when we shut down immediately. Coking can also occur with hot oil and small oiling passages.

A one minute idle is just good insurance, along with a quality oil changed at recommended intervals; usually "severe" service intervals.

Correct, which is why I have ONLY used fully synthetic oils on all my cars since the early 1990s....

Synthetics can take higher temperatures and eventually only evaporate with no residue.....many do not know that!!