b4chow

is it necessary to let the supercharger cool down before you turn off the engine... this is our first kompressor, and I know for a turbo-charged car it is better to cool down the turbos before turning off the car. any other tips on taking care of the supercharger?

White Knight II

A turbocharger has a lot of hot gasses going through the turbine at one end of it, at least when the waste gate is closed. That heat travels down the shaft towards the compressor turbine, and that entire shaft is bathed in oil. (The shaft is supported totally by the oil bath; there are no bearings in there.) Shut down a hot turbocharged engine before it cools down, and you cook that oil, which will cut down on its lubricity and possibly coke up the shaft. Hence the instruction not to shut down a turbocharged car immediately after driving it hard. If you let the car idle for a few minutes (Lycomimg advises 4 minutes for its turbocharged aircraft engines) after it's driven hard, you give the turbocharger some time to cool down and the engine some time to pump cooler oil onto the shaft. By the way, the oil used to cool/lubricate a turbocharger comes out of (and goes back to) the engine oil sump, so if you screw up this oil, it's not just the turbocharger you're hurting.

None of that applies to a supercharger. It is powered by a belt or gears off the crankshaft, and no exhaust gasses get near it. So it doesn't get hot enough to coke its lubricating oil. It's still not a good idea to drive any car hard and then immediately shut it down, since there is a lot of residual heat buildup left in the block which can boil the coolant if left to its own devices, but the cool-down period for a supercharged engine is considerably shorter than for a turbocharged engine.

b4chow

thanks for the info...

Bilal

White Knight, I drive a Mercedes A170 CDI. You may not know what one is, but it has a diesel engine, adn I think If I am not mistaken it has a turbocharger, since I am always doing the school run, and regularly doing short trips, how long should I wait in idle before shutting it off?

White Knight II

If you haven't driven a turbocharged car hard within the last five minutes before you park the car, I wouldn't worry about cooling down the engine. I'm guessing, but I would think that 3 to 5 minutes of idle or normal driving are required to cool down a turbocharger that has been spun up and worked hard for any significant amount of time.

As to whether your car is turbocharged, I don't know, but your owner's manual should make that clear immediately. If the engine specs say nothing about a turbocharger, maximum boost pressure (measured in BAR) or the name of the turbocharger builder (it's not M-B), your engine isn't turbocharged.

Also, you could look under the hood - a turbocharger is easy to spot if you've seen one before. If you haven't, it may just look like intake manifold plumbing. You might be able to find it by looking for a gizmo near the top of the engine at the rear of the engine compartment that would fit inside an 8 inch cube and that says "Garrett" or "Rootes" on it. The name is cast into one of the plenums, not stuck on a placard.

Bilal

Thank you so much for the information. Does this affect all turbo cars, because the Maybach/MB V12's have turbo's and so does Porsche?

Thanks again

blueSL

WKII's exactly right. When you switch off the engine, the coolant stops circulating and you only have convection to cool it. The residual heat is what drives the residual heating function which can keep the interior of the car warm after you've left it.

In the early days of Porsche's turbos, they used to have a small electric pump that continued to pump coolant around the turbo to stop it cooking from the heat soak.

theine

originally posted by blueSL
In the early days of Porsche's turbos, they used to have a small electric pump that continued to pump coolant around the turbo to stop it cooking from the heat soak.

I am sure that MB thought about this when releasing the Bi-Turbo.

Steve Clark

the supercharger itself,the cool-down time is ZERO.If the blower is running hot enough to have cooling concerns,you've got other,more immediate problems.