200TDI compression

On or around Mon, 29 Sep 2003 15:18 +0100 (BST), snipped-for-privacy@slave.org.uk (Niamh Holding) enlightened us thusly:

I take it you've read what the HBOL says?

compression ratio is about 19.5:1, so your theoretical maximum should be about 19.5 bar, I'd think, however, you'll never actually achieve that - with that in mind, My gut feeling matches yours, that 16 bar sounds low, but without a comparison, it's hard to say. The various 10:1-ish petrol engines I've got never seem to produce very high figures, certainly never in the region of 10 bar.

According to HBOL Land Rover don't specify a figure for compression pressure, they do however give a max. variation of 70 psi (about 5 bar (!)).

RAVE hasn't got figures either, or not the one I've got.

HBOL does say that the pressure should build quickly on test - if the gauge goes up in stages, with a low reading on the first stroke which gradually increases, then this is indicative of poor ring sealing. Wet testing is not apparently conclusive either, as the oil can sit in the piston crown and not get to the rings. a low figure which doesn't increase with extra cranking is indicative of leaks - valves, head gasket or cracked head - all of which should be addressed in a major engine rebuild.

AFAIK the different head gasket thicknesses are about clearance, rather than compression. Any engine should run reasonably well with the thickest one - however, for optimum performance it should of course be measured and the correct gasket used.

The list of piston protrusion figures goes from 0.5mm to 0.8mm, so the maximum error is going to be 0.3mm, which in a stroke of 97mm, ain't gonna make much difference, really - about 0.3%. I think you can discount the "wrong gasket" theory.

Try finding someone who can do a leakdown test?

also, in terms of poor starting and poor power, how sure are you that the injection timing and pump fuelling settings are correct? In particular, low power can be due to the pump having been "turned down", which improves economy if you only drive slowly - I suspect that they're set deliberately on the low side to make sure they don't smoke, and since I assume there's a spring involved somewhere, it has to be possible that it gradually drifts out of tune one way or another. The fuelling setting is very sensitive, a half turn will take you from "low power" to "smokey", with the correct point somewhere in between...

Reply to
Austin Shackles
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Yes, it was the lack of a figure that prompted the raising of the question. Those nice people at Turner Engineering have emailed me with the answer of

24 bar which given that there is going to be some temperature rise seems a very sensible figure.

Our next approach is going to be to borrow a know working 200/300TDi and test that as a means of checking the compression tester.

Depending on the result of the above check then we'll have some idea whether we are pursuing the cause of low compression or another reason for the starting/power problems; if it is the latter then your suggestions will be amongst the first investigated.

Niamh.

Reply to
Niamh Holding

Checked with one of the techs at work today. They regularly see high 20's to low 30's when checked Ford TDCi engines.

HTH

Reply to
Adrian England

A concern which makes finding the solution a priority.

Niamh.

Reply to
Niamh Holding

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