EGR

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Originally Posted by camel_landy

Dougal...

Actually, we're both correct but it depends on the age and design of the engine concerned. Opening an EGR under load, to reduce NOx, is a fairly recent thing.

I also wanted to keep the description as simple as possible, rather than splitting hairs right from the get-go.

M

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NOx reduction by opening under load is the main reason for EGR to exist, it's not a recent change. My 13 and 15 year old vehicles all did that.

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Originally Posted by Dougal

No he's not. EGR isn't there for trailing throttle, it would produce absolutely no emissions improvement if that were the case.

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Well I guess we disagree - on a modern engine the throttle is not actually closed on trailing throttle.

Garry

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Originally Posted by garrycol

Well I guess we disagree - on a modern engine the throttle is not actually closed on trailing throttle.

Garry

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On a diesel engine there is no throttle. But fuel delivery is always cut completely on the over-run.

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Originally Posted by Dougal

On a diesel engine there is no throttle. But fuel delivery is always cut completely on the over-run.

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Now we are being pedantic and on the second point we disagree.

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Originally Posted by garrycol

Now we are being pedantic and on the second point we disagree.

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There is nothing pedantic about correcting those applying petrol engine theory to diesels.

How exactly do you disagree with the fuel cut?
The fuel use display in your own vehicles will show a big 0.0 litres/100km whenever you lift off.

What happens with an auto gear box , can the engine still be in over run when slowing down . ??

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Originally Posted by Fatso

What happens with an auto gear box , can the engine still be in over run when slowing down . ??

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Yes, just not as often as a manual.

Goodness what a diatribe!

10 seconds of Google research is interesting and while I am far from expert on this subject there would appear to be merit in both arguements whoever I am led to understand envronmental considerations especially in the "Green: heaven of Europe make it mandatory.

Exhaust Gas Recirculation (EGR), NOx and particulate measurement | Cambustion

LR also use EGR in diesels at idle to reduce combustion noise to make the engine quieter, as stated in various LR workshop manuals.

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Originally Posted by Fatso

What happens with an auto gear box , can the engine still be in over run when slowing down . ??

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The tacho in my D4 shows the engine revs dropping proportionally as speed drops until revs get down to just over 1000 rpm where it drops to the next lower gear and repeats the process until the vehicle comes to a stop, with the instantaneous fuel consumption reading zero until the vehicle is basically stopped and the engine then idles.