mitjaypat

Hey, just wanted to ask this. I remember when I was a kid that our friend's dad had a Mazda turbo RX7. He used to always let the car idle for about 5 minutes after parking before turning it off. He said that was to let the "turbos cool down." I have a 2014 e550 bi-turbo and was wondering if I need to do the same. And why? Thanks in advance.

MP

teksurv

It's a bit of an old school thought, but one I still follow. I let the engine idle between one to two minutes depending on how hard I ran the car before turning it off in all of my turbo cars.

Swoosht04

Not sure where the turbo's are placed in the 550. If they are pretty low in the manifold it may have been designed so that when the car shuts down the oil drains down thru the turbo's on its way back down to the pan. I know on most of the "older" turbo cars have their turbo's sitting higher on the manifold. When the car turns off the oil backs out of the turbo into the oil pan and leaves very little of it on the bearings. Also lots of the newer turbos have bearings made ceramic and other space age materials that last longer.

SteveE400

Swoosht hit most of the changes over the years. Add to his notes that we now use full synthetic oil in our engines, so the oil that sits in the turbo's bearings is less likely to overheat and fail. We used to idle turbo's so that they got fresh, cool oil into their bearings to avoid oil turning to varnish while the turbo was stopped, and thus causing the turbo to seize.


If I have been driving "gently" for the few miles prior to shut-down, I just shut it off. If I have been heavily into boost then I idle for a minute or so, then shut down.


I haven't seen any official instruction in the owners' manual about this at all, so I have to believe that MB is not concerned about it.

jonUF02

I doubt MB or other car makers who now use turbos throughout their engine lines would expect anyone to go through this process regularly, but if you feel like doing it, then it can't hurt I suppose.

SteveE400

That's kind of how I feel about it. I think the improvements in bearings, cooling systems and lubricants make the cool-down more of a "belt and suspenders" approach. Can't hurt, but probably isn't necessary - unless you've been running hard, like on the track. Then I definitely would go for the cool-down.

J.M.G.

Mercedes uses electric oil- and water-pumps as well as electric fans in their M276 and M278 engines. So even if you shut off the engine after WOT, the turbos are beeing cooled correctly.

BenzV12

JMG's reply appeases me .Still, I wait 30 seconds then shut the car off

J.M.G.

I am totally with you. Actually I am very light on the throttle ~2 miles before shutting off the engine. When driving on the Autobahn, I also reduce speed to ~90-100mph a few miles before reaching my exit in order to allow all temperatures to settle (especially the differential-temperatures).

So yes: I do not fully thrust into the systems, that MB did include in our cars. However, letting the car idle for minutes is not necessary in my opinion!

armysoldier1073

I have a modified Evo X. Back in the day when just oil fed the turbo it required cool down. New cars have the turbos running off of engine coolant aswell. If normal driving it will be fine. If you deuve it like you stole it, just drive normal for a few minutes and it will be fine. Also higher zinc content oils help longevity some.

The G Man

According to this website, the oil pump is chain driven, not sure about the water pump:


http://myautoworld.com/mercedes/cars...des-11-v8.html


New-Design Oil Pumps

A variable vane oil pump in the bottom of the engine is driven by a new chain drive. At low engine speed and load, the oil pump only generates about 28 psi (or two bar) of oil pressure, and nozzles that spray cooling oil on undersides of the pistons are off. As engine speed and load increases, oil pressure goes up, and the oil spray nozzles open. In this way, less energy is used when less cooling and lubrication is needed.

Borrowing a page from racing-type dry-sump lubrication systems, a second stage of the oil pump is designed to scavenge or suction oil out of the turbocharger units. This system helps keep oil out of the turbo's intake and exhaust passages, further reducing exhaust emissions as well as increasing oil flow through the turbos.
When the engine is cold, oil flows through a special oil-coolant heat exchanger that uses engine coolant to help the oil heat up quickly. When the engine is warm, an oil thermostat circulates the oil through an external oil cooler.

J.M.G.

Unfortunately I do only have a in depth view on the oil system in German language, but you may want to take a look into your own link:

"Not only are the exhaust-driven turbos lubricated and cooled by a special pressure-fed oil system"

beejAMG

old turbos, yep, newer models, nope. but if you feel like idling for a few minutes before shutting off, wouldnt hurt.

The G Man

It looks like the water pump is electric, and it probably runs after you shut off the car to cool the turbo, at least that is how the BMW turbo engines works anyways.

http://catalog.kleemann.dk/catalog/c...-biturbo-m278/

SteveE400

I think this settles it for me -- no need to be extreme, but no harm in a bit of cool down if you've been pushing it.

J.M.G.

After some posts in this thread, I reread the documents regarding the M278 that I collected. I have to admit, that I did not fully understand everything. So I went to a local dealership and asked the service-manager. He said, there is no need to let the turbos cool down. However, he could not explain WHY.

Finally I found a youtube video, where the chief engineer of the famous German Company HGP explained the whole issue. HGP builds Volkwagen Rabbits with 3.6 VR6 Twin Turbos and 800hp (!) as well as Volkswagen R with 2.0 TSI @ 500hp.

He says that modern turbos can not be compared to older ones. In the past, the turbo housing became very hot. So when the engine was stoped, the oil in the extremely hot housing carbonized and therefore reduced tolerances...and in the end made the Turbo fail!

Modern turbos have water cooled housings. So the housings do not get that hot. Therefore the oil can not carbonize when the engine is stopped. He does not even let the turbo cool down in his own 500 hp 2.0 TSI Volkswagen Rabbit R which does 0-125 mph in 10,x seconds and is his daily driver.

mitjaypat

Johannes, that is exactly the info for which I was looking. I appreciate your persistence in getting this answer!
Mitesh

MBSebas87

Good to know!

SteveE400

^^ +1!


Thank you!

mrmotoguzzi00

Good Info, I'm lucky though I have a mile or so of slow road thru my development before i get to my house, so it all gets cooled off....