OT: Pinking Diesel Engine

Hi all,
How is it possible for a diesel engine (given the correct grade of fuel) to pink? Obviously with petrol, you can advance the ignition to produce the effect, but with derv, combustion is determined kind of automatically by the compression level (AFAIK) and is therefore fixed. Yet my diesel car's been pinking since the garage changed the EMU and I'm sure I'm not imagining it. How is that even possible? Any ideas?
Ta.
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Chris wrote:

I don't know much about diesel, but I expect the injection has to be timed. I think the idea is that air alone is compressed, and then the fuel sprayed into it at the appropriate moment, when the air is very hot.
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Maybe the ECU is injecting fuel too early, before the piston reaches TDC. That would have virtually the same effect as the spark plug on a petrol engine firing too soon.
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On 08/10/16 09:48, NY wrote:

It all depends utterly on the software and mapping used as to how much of a knock the engine will give. Lean early injection will be more fuel efficient, produce more NOx and pink more.
And since mapping is somewhat of a moveable feast depending on the sensors attached to the engine and their condition, and the software, I would be asking why the EMU was changed.
And what it was changed for...
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Just wondering if it's doing the engine any harm running it with this slight pinking. I haven't noticed any difference one way or the other with fuel consumption or performance.
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Older diesel designs used to knock like the clappers. We've got a bit spoilt by modern ones in this respect. Pity they've not managed to do anything about the stink, though. ;-)
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Diesels 'knock' or 'pink' to work, it's what they do. Now whether you should *hear* a noise that sounds like that is another matter.
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"Chris" wrote in message

Have you just had a VW 'fixed' for the emissions?
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On Sat, 08 Oct 2016 10:09:29 +0100, Richard wrote:

Nope. Nowt to do with VW, this is a Land Rover. The EMU was changed because the original one (which ran quietly) packed up.
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On Saturday, 8 October 2016 12:19:41 UTC+1, Chris wrote:

Diesel valves do need de-coking quite regularly. I think it just means a polish with grinding paste, which should have been done at the time but was unlikely to; however its arriving with the new part sounds fishy.
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On 09/10/2016 03:11, Weatherlawyer wrote:

Regularly as in once every million miles or so, if that? I'll admit mine have only done 200-230K, so haven't had that much time to get coked up yet.
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On 09/10/16 03:11, Weatherlawyer wrote:

every 1/4 million miles or so,. yes.
I think it just

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Eh? Don't know of any modern engine that needs de-coking regularly. Think this was more a function of older oils anyway.
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"Chris" wrote in message

If this is after a VW 'fix', take it back and get them to put it right. Daughter's 2.0 TDI Golf had similar issues post fix. They first said it was a dirty EGR which they allegedly cleaned, but the problem persisted. I had a chat with the service guy and pointed out it was their fault, and they must rectify it. After further investigation, they allegedly found some soot which was interfering with the operation of a valve or some other bollocks - but the problem has gone away for now. Dealer techs were appreciative of the learning opportunity. Check Honest John for other experiences.
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Chris wrote:

I've been looking at car code readers recently thinking of upgrading and one feature mentioned by so is the ability to reprogramme the injectors ( I know not what features can be changed) So maybe whatever programming data for the injectors in your old ECU have not been set up the same in the new one?
I'd be going back to the dealer and "discussing" it with them. Have you driven it enough to get an idea of the fuel consumption and how that compares with before? In my experience degradation in fuel consumption comes with almost anything being sub-optimal in the engine control system.
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I really can't see how a new ECU wouldn't be correct in this respect. It might well start off with a base map, and learn the actual engine's characteristics. But this isn't going to take long.
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On 08/10/2016 15:13, Dave Plowman (News) wrote:

If this engine is of the Duratorque, much of the mapping is carried out at the dealer and there is very little learning.
I believe the pinking the OP hears is the multiple injection times at part throttles. At full throttle this sound should go away.
BICBW
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On 10/7/2016 11:53 PM, Chris wrote:

You need to ask Mr Cheerful, hence the cross post. Might be helpful to mention exactly which model Land Rover.
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On 08/10/2016 16:32, newshound wrote:

The ignition cannot start until the actual moment of injection. So you first need to get the timing checked. Don't leave it as it can wreck the engine.
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On 08/10/16 17:06, MrCheerful wrote:

Do you actually know how the injection timning works on a modern diesel?
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