Diesel Turbo idle down

Submitted: Monday, Sep 16, 2002 at 00:00
ThreadID: 1987 Views:2264 Replies:8 FollowUps:2
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The owner manual for my Mazda Bravo turbo diesel makes no reference to any need for an idle down period for the turbo.
Is a cooling down required for modern diesel turbos? Diesel exhaust temperatures are much lower than petrol engines. Phil
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Reply By: Darian - Monday, Sep 16, 2002 at 00:00

Monday, Sep 16, 2002 at 00:00
Its one of the big questions I reckon Phil....would car makers admit that their engine should be cooled down everytime ?....
I don't think so....they want you to be attracted to the turbo power without knowing anything about hangups......
its probably a handicap to the bulk sales they expect. Mass marketers don't want cars with hangups.
With my 99 Jack, they reckon no cool down is required, BUT I always cool it down if its been running seriously.
I reckon we all have to read between the lines these days.....dp
AnswerID: 6651

Reply By: royce - Monday, Sep 16, 2002 at 00:00

Monday, Sep 16, 2002 at 00:00
I think the style of turbo matters. Is it oil only or water and oil cooled etc. I don't idle down. But I tend to be slack in many areas! Cheers Royce
AnswerID: 6673

Reply By: johnsy - Monday, Sep 16, 2002 at 00:00

Monday, Sep 16, 2002 at 00:00
phil from driving earth moving gear/ trucks im still in the habit of idling down particulary after pulling hard through sand, hilly country or towing having said that driving in city driving a idle down would the time it takes to undo the seat belt get your things open the door and shut down.keep in mind parking the car at low revs is cooling the turbo cya johnsy
AnswerID: 6678

Follow Up By: Cobra - Tuesday, Sep 17, 2002 at 00:00

Tuesday, Sep 17, 2002 at 00:00
Agreed johnsy, follow the same procedures meself
FollowupID: 2994

Reply By: Ray - Tuesday, Sep 17, 2002 at 00:00

Tuesday, Sep 17, 2002 at 00:00
Hi Guys,

Maybe wrong here (shoot me down in flames if I am) but in my days as a fitter the term was idle down the turbo, rather than cool down. I'm not picking fault but saying there is a distint difference that is self evident with the terms. I doubt that cooling down is an issue unless required by the materials due to extreme loads. However running down a turbo is to allow the turbine, if under high loads such as high way speeds, to run down from 100k rpm to idle. From what I've been told many turbines will drop onto a set of bushes at rest, hence the need for the rpm to me as low as possible and not at max. If anyone out there has experience in this area I be interested in knowing if this is correct with respect to today's commerical turbos.


AnswerID: 6698

Reply By: dave - Wednesday, Sep 18, 2002 at 00:00

Wednesday, Sep 18, 2002 at 00:00
i found this site
when i was looking for info on turbos, very basic information and diagrams as well as heaps of links. It's a great site for any question you may have.

AnswerID: 6745

Reply By: Peter L - Wednesday, Sep 18, 2002 at 00:00

Wednesday, Sep 18, 2002 at 00:00
It's important to idle down as well as cool down a turbo, particularly if the engine has just been working hard.

As soon as the engine stops the oil pressure drops to zero - you don't want the turbo spinning with no lubrication so switch off after idleing for a few seconds at least.

As for temperature - if you switch off while the turbo is hot it can cook the oil which will leave unwanted carbon deposits on the turbo bearings.
The simple answer to both problems is go easy over the last few minutes of a journey, and once you have stopped the vehicle make sure the last thing you do before stepping from the vehicle is to turn off the engine.
AnswerID: 6764

Reply By: phil - Thursday, Sep 19, 2002 at 00:00

Thursday, Sep 19, 2002 at 00:00
Thanks everyone for the replies.
The turbo seems to have very low inertia because it responds almost instantly to throttle changes (the whine can just be heard). Because of this I will just allow the engine to work less hard before turning off. The same as I would do for any engine including lawnmowers! The last minute or so of a trip is normally at virtual idle anyway.
AnswerID: 6781

Follow Up By: Ach - Saturday, Oct 05, 2002 at 00:00

Saturday, Oct 05, 2002 at 00:00
Hi Phil,

I also have a Bravo TD and fitted a turbo timer early on in the piece (It's a kit from DSE and costs around $40). I made some mods tho', coz I didn't want anything other than the engine to be activated during the "idle down" period.

BTW, Mazda Tds are water- not oil-cooled (well at least mine is....'99 model).

ACH (himble@bigpond.com)

FollowupID: 3273

Reply By: winaje - Friday, Sep 20, 2002 at 00:00

Friday, Sep 20, 2002 at 00:00
Hi Phil, if in doubt and you want to be safer than sorry, have you looked at a turbo timer? They are user adjustable, and guarantee an idle down time from 30 seconds to 5 minutes. Something else to consider. Bill Church
AnswerID: 6794

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