Turbo's and one minute idling

amit · 8th November 2005, 07:11

Mod Note : Please continue the discussion in our Turbos & Idling Article. Thanks

When turbo engines were develeoped, engineers recommended that there should be at least one minute idling after starting and before switching off the engine to keep the turbo running properly and to prevent it from blowing pre-maturely. More improtant to have it idling before switching off the engine so that the turbo cools down. I don't know how many actually do it though. Now this is what I was planning to recommend customers buying a turbo charged car but from what I learn VW has engineered the new 2.0 Turbo in such a way that you no longer need to idle the engine.

This is what I got after doing some research from owner manuals and VW's training site. The new engines have a coolant/(water?) cooled turbo. Even after you switch off the engine a little pump circulates coolant through the turbo for some time to cool it down. The user manual of both the turbo Jetta & Passat doesn't recommend the one minute idling thing for this new engine. I am quoting from the training site :

To prevent carbon build-up on the turbine shaft in the turbocharger, an auxiliary coolant pump provides additional coolant circulation for a certain time after the engine is shut off hot. The pump forces the lower temperature coolant against the normal direction of flow. The coolant flows from the radiator through the turbocharger to the engine block and back to the cooler.

The service manager has gone a small vacation so I still need to talk to him about this and I don't know if the older 1.8 Turbo engine had the same technology. The only pre-owned 1.8T Jetta on our lot is missing the owner manual so Octavia RS owners,

, does your manual state anything about the one minute idling? Do all Turbo engines now no longer need this idling thing? This is the first time I am dealing with turbo engines so I am in unchartered territory here.

ajmat · 8th November 2005, 08:34

In the UK, you find a lot of BMW diesels with blown turbos because of this very point

Steeroid · 8th November 2005, 08:44

I'm a bit concerned here - the Safari Dicors manual doesnt suggest this kind of idling, not does it carry a sticker that says its required. I've seen this sticker on the older Scorpio though...I still idle the vehicle before and after use, though.

However, even after idling for say a minute or so there's a very distinctive hum of a turbine winding down AFTER the engine has stopped...

On the Smart, I can hear the water pump humming away for about 1/2 a minute after I stop the engine.

GTO · 8th November 2005, 09:40

Quote:

More improtant to have it idling before switching off the engine so that the turbo cools down.

Incorrect. The reason you have to idle for a minute is NOT cooling down, but lubrication. Turbos get their lubrication from the engine oil, and spin at a much higher rpm than the engine does. If you switch off immediately after coming to a halt, the turbo is still spinning at several thousand rpm without lubrication.

Cooling may be one of the reasons, but certainly not the main reason.

GTO

amit · 8th November 2005, 10:09

Quote:

Incorrect. The reason you have to idle for a minute is NOT cooling down, but lubrication. Turbos get their lubrication from the engine oil, and spin at a much higher rpm than the engine does. If you switch off immediately after coming to a halt, the turbo is still spinning at several thousand rpm without lubrication.

I know that part GTO but I guess I didn't put it down the way you did since I, guess, I was more interested in coming to the main point.

Quote:

On the Smart, I can hear the water pump humming away for about 1/2 a minute after I stop the engine.

Going by what's mentioned on the VW training site, that's what should happen in the Passat and Jetta too. I guess, I will take the Passat for a long drive tomorrow and switch off the engine immediately and check if the coolant pump hums away for a minute too lubricate and cool down the turbo. Will revert back on this tomorrow. Let's seee what the Passat's engine does.

ananthkamath · 8th November 2005, 10:28

Quote:

Originally Posted by GTO

Incorrect. The reason you have to idle for a minute is NOT cooling down, but lubrication. Turbos get their lubrication from the engine oil, and spin at a much higher rpm than the engine does. If you switch off immediately after coming to a halt, the turbo is still spinning at several thousand rpm without lubrication.

Cooling may be one of the reasons, but certainly not the main reason.

GTO

Actually the issue has more to do with a combination of both cooling and lubrication.

When you switch off the engine without doing this exercise, the turbo keeps spinning with the residual lubrication. The high temp. prevalent in the turbo causes excess carbon build-up, also called coking of the oil. This hard coating causes the shaft to wear prematurely.

So VW is combating this with cooling rather than pumping oil after switching off the engine.

tsk1979 · 8th November 2005, 11:04

The India/go turbos have this sticker on the door frame. Not a very obvious position. You can also look at unfamiliar places for the sticker. And yes you need to idle for a minute

Steeroid · 8th November 2005, 11:16

Quote:

Originally Posted by tsk1979

The India/go turbos have this sticker on the door frame. Not a very obvious position. You can also look at unfamiliar places for the sticker. And yes you need to idle for a minute

Dude, there is NO place in the car that I havent seen and that includes the underside...NO sticker on the Dicor. Period.

The only sticker they've put on is one by the drivers side of the windscreen which relates to the usage of 4WD and how to shift back to 2WD.

RJK · 8th November 2005, 12:04

Common Rail engines wouldn't require to do this idling I'm thinking.

Rtech · 8th November 2005, 12:15

CRi is the method in which fuel is injected into the cylinder and has nothing to do with the functioning of a turbo.

Rudra Sen · 8th November 2005, 12:44

Inter cooler has no role to play in this start and shut business?

Just asking all the gurus cause I don't know.

Psycho · 8th November 2005, 12:57

The turbo timer - ie. Idling the engine for a minute is specifically to let the turbo spool down and continue supplying oil to the turbo while it is doing so. If you shut the engine the oil supply is stopped hence leading to a chance of caking on the turbo shaft. You get after market turbo timers for this too. Intercoolers have not6hing to do with the spool down of the turbo.

However some cars come with oil reservoirs above the turbo which continue to gravity feed oil till the reservoir is drained, Such systems would not require to idle before shutting off. I am personally not too sure about the Dicor.

jkdas · 8th November 2005, 13:22

splendid. now i knw something more. thanks to tbhpians.

ajmat · 8th November 2005, 13:23

Quote:

Originally Posted by Steeroid

Dude, there is NO place in the car that I havent seen and that includes the underside...NO sticker on the Dicor. Period.
.

May be Tata are looking to include you in their long term service revenue income plans

Rtech · 8th November 2005, 13:29

Best to be on the safe side and always idle for about a minute before shutting down. Although the Skoda manual has no mention of this, it is a practice I try and follow, if not for a minute then atleast for 30 seconds.

However, the manual also states that its best to start driving at low rpm's as soon as possible after starting rather than letting it idle to get upto operating temperature.

8th November 2005, 07:11	#1
amit Senior - BHPian Join Date: Feb 2004 Location: Mumbai Posts: 3,717 Thanked: 449 Times	Turbo's and one minute idling Mod Note : Please continue the discussion in our Turbos & Idling Article. Thanks When turbo engines were develeoped, engineers recommended that there should be at least one minute idling after starting and before switching off the engine to keep the turbo running properly and to prevent it from blowing pre-maturely. More improtant to have it idling before switching off the engine so that the turbo cools down. I don't know how many actually do it though. Now this is what I was planning to recommend customers buying a turbo charged car but from what I learn VW has engineered the new 2.0 Turbo in such a way that you no longer need to idle the engine. This is what I got after doing some research from owner manuals and VW's training site. The new engines have a coolant/(water?) cooled turbo. Even after you switch off the engine a little pump circulates coolant through the turbo for some time to cool it down. The user manual of both the turbo Jetta & Passat doesn't recommend the one minute idling thing for this new engine. I am quoting from the training site : To prevent carbon build-up on the turbine shaft in the turbocharger, an auxiliary coolant pump provides additional coolant circulation for a certain time after the engine is shut off hot. The pump forces the lower temperature coolant against the normal direction of flow. The coolant flows from the radiator through the turbocharger to the engine block and back to the cooler. The service manager has gone a small vacation so I still need to talk to him about this and I don't know if the older 1.8 Turbo engine had the same technology. The only pre-owned 1.8T Jetta on our lot is missing the owner manual so Octavia RS owners, , does your manual state anything about the one minute idling? Do all Turbo engines now no longer need this idling thing? This is the first time I am dealing with turbo engines so I am in unchartered territory here. Last edited by GTO : 28th January 2013 at 22:53. Reason: Adding link to turbo article
	(1) Thanks

8th November 2005, 08:34	#2
ajmat Team-BHP Support Join Date: Feb 2004 Location: Bangalore Posts: 14,865 Thanked: 27,978 Times View My Garage	In the UK, you find a lot of BMW diesels with blown turbos because of this very point
	() Thanks

8th November 2005, 08:44	#3
Steeroid Senior - BHPian Join Date: Mar 2005 Location: N.A Posts: 7,046 Thanked: 2,751 Times	I'm a bit concerned here - the Safari Dicors manual doesnt suggest this kind of idling, not does it carry a sticker that says its required. I've seen this sticker on the older Scorpio though...I still idle the vehicle before and after use, though. However, even after idling for say a minute or so there's a very distinctive hum of a turbine winding down AFTER the engine has stopped... On the Smart, I can hear the water pump humming away for about 1/2 a minute after I stop the engine.
	() Thanks

8th November 2005, 11:04	#7
tsk1979 Team-BHP Support Join Date: Feb 2005 Location: San Jose, CA Posts: 23,717 Thanked: 22,825 Times View My Garage	The India/go turbos have this sticker on the door frame. Not a very obvious position. You can also look at unfamiliar places for the sticker. And yes you need to idle for a minute
	() Thanks

8th November 2005, 12:04	#9
RJK Senior - BHPian Join Date: Feb 2004 Location: Bombay Posts: 1,140 Thanked: 701 Times	Common Rail engines wouldn't require to do this idling I'm thinking.
	() Thanks

8th November 2005, 12:15	#10
Rtech Team-BHP Support Join Date: Apr 2004 Location: Bombay Posts: 5,770 Thanked: 359 Times View My Garage	CRi is the method in which fuel is injected into the cylinder and has nothing to do with the functioning of a turbo.
	() Thanks

8th November 2005, 12:44	#11
Rudra Sen Team-BHP Support Join Date: Apr 2004 Location: Bangalore Posts: 11,590 Thanked: 6,532 Times View My Garage	Inter cooler has no role to play in this start and shut business? Just asking all the gurus cause I don't know.
	() Thanks

8th November 2005, 12:57	#12
Psycho Senior - BHPian Join Date: Jul 2004 Location: Bangalore Posts: 1,043 Thanked: 110 Times View My Garage	The turbo timer - ie. Idling the engine for a minute is specifically to let the turbo spool down and continue supplying oil to the turbo while it is doing so. If you shut the engine the oil supply is stopped hence leading to a chance of caking on the turbo shaft. You get after market turbo timers for this too. Intercoolers have not6hing to do with the spool down of the turbo. However some cars come with oil reservoirs above the turbo which continue to gravity feed oil till the reservoir is drained, Such systems would not require to idle before shutting off. I am personally not too sure about the Dicor.
	() Thanks

8th November 2005, 13:22	#13
jkdas Senior - BHPian Join Date: Sep 2005 Location: Thiruvananthapu Posts: 9,687 Thanked: 1,492 Times View My Garage	splendid. now i knw something more. thanks to tbhpians.
	() Thanks

8th November 2005, 13:29	#15
Rtech Team-BHP Support Join Date: Apr 2004 Location: Bombay Posts: 5,770 Thanked: 359 Times View My Garage	Best to be on the safe side and always idle for about a minute before shutting down. Although the Skoda manual has no mention of this, it is a practice I try and follow, if not for a minute then atleast for 30 seconds. However, the manual also states that its best to start driving at low rpm's as soon as possible after starting rather than letting it idle to get upto operating temperature.
	() Thanks