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Extreedoc

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2495cc 19J engine, compression ratio is 21:1 (NAD). Approximately 20 mpg.

2495cc 12L 200TDI or Di engine, compression ration 19.5:1. Approximately 30 mpg (in DI form). I don't know what they do with the turbo, mine is Di.

They both have the same block but different heads.

Does anybody know WHY the big difference in fuel consumption? Not much difference in compression ratio so is it less efficient injectors or pump? Different sized valves? Different cam profile? What do you think?

I've posted this same question on LRUK.
 
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2495cc 19J engine, compression ratio is 21:1 (NAD). Approximately 20 mpg.

2495cc 12L 200TDI or Di engine, compression ration 19.5:1. Approximately 30 mpg (in DI form). I don't know what they do with the turbo, mine is Di.

They both have the same block but different heads.

Does anybody know WHY the big difference in fuel consumption? Not much difference in compression ratio so is it less efficient injectors or pump? Different sized valves? Different cam profile? What do you think?
19j is a indirect injection engine ,200tdi is a direct injection engine,19j has an injection pressure of 135 bar tdi 280 bar twice the pressure
 
2495cc 19J engine, compression ratio is 21:1 (NAD). Approximately 20 mpg.

2495cc 12L 200TDI or Di engine, compression ration 19.5:1. Approximately 30 mpg (in DI form). I don't know what they do with the turbo, mine is Di.

They both have the same block but different heads.

Does anybody know WHY the big difference in fuel consumption? Not much difference in compression ratio so is it less efficient injectors or pump? Different sized valves? Different cam profile? What do you think?

I've posted this same question on LRUK.

As James says, they are slightly improved tech over a 19j.

But that is poor mileage for a 19j, I used to get nearer 30mpg out of mine, perfectly set up, and driven carefully.
And I would expect better out of a Tdi.
 
It makes me wonder what would happen if you put a 19J head on a 200 engine, for instance: how do the piston crowns differ between the two engines? Lots of other problems occur to me also. Just an exercise in thought and ideas...
 
It makes me wonder what would happen if you put a 19J head on a 200 engine, for instance: how do the piston crowns differ between the two engines? Lots of other problems occur to me also. Just an exercise in thought and ideas...

From memory, the pistons are completely different. And I would wonder why bother?
 
It makes me wonder what would happen if you put a 19J head on a 200 engine, for instance: how do the piston crowns differ between the two engines? Lots of other problems occur to me also. Just an exercise in thought and ideas...

You need to look into the differences between indirect injection and direct injection, as James mentioned.
Indirect injection have swirl chambers, and only a small cut out in the piston tops.
I dont have much to do with direct injection, but they usually have the combustion chamber in the piston crown itself.
The two don't really mix.
 
From memory, the pistons are completely different. And I would wonder why bother?
At the mo' it's just a thought that won't leave me alone but it does have a possible practical application: the alloy heads on the 200 lump; I don't like alloy heads on diesels and one day, the last alloy head will crack and it won't be possible to find a replacement. So, this is a possible source of more durable heads which it might be possible to modify to make an acceptable alternative to scrapping an otherwise good engine. Of course if it will require a change of pistons as well it might not be viable. I enjoy playing with the idea though...
 
At the mo' it's just a thought that won't leave me alone but it does have a possible practical application: the alloy heads on the 200 lump; I don't like alloy heads on diesels and one day, the last alloy head will crack and it won't be possible to find a replacement. So, this is a possible source of more durable heads which it might be possible to modify to make an acceptable alternative to scrapping an otherwise good engine. Of course if it will require a change of pistons as well it might not be viable. I enjoy playing with the idea though...
the cast heads on the 2.5s are more prone to cracking
 
I agree, all apart from that alloy head, as I said before, I don't like alloy heads on diesel engines although plenty would disagree... to me it's shades of 'chocolate teapot'. However, if the iron head is more prone to cracking as James says it is, there seems to be no viable answer.
 
I agree, all apart from that alloy head, as I said before, I don't like alloy heads on diesel engines although plenty would disagree... to me it's shades of 'chocolate teapot'. However, if the iron head is more prone to cracking as James says it is, there seems to be no viable answer.

I have seen more cracked heads on 2.5NA and TD than on Tdi. And the Tdi has been around for a long time now, and has an excellent reputation as LR engines go.
 
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