Is my MPG off?

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jgra1
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Post by jgra1 »

Good post Glyn,

Jim and I went through all of this in a pleasent wiltshire town the other day when my xantia broke... found the same as you... I had been using WVO for 6 months though, although I expect the crud was from the last 9 years all told...

Yes agree with seat base, it's only 2 nuts :)

John
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Post by vince »

Thanks Glynn...good write up :wink:
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bonnyman750
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Post by bonnyman750 »

All,

Just as a bit of extra info, I noticed this morning on the way to work that now that the strainer filter has been cleaned on the gold Xantia, she doesn't seem to smoke as much when giving her a bootfull to overtake, pull away etc..!!! Coincidence??? Don't know but she pulls away much cleaner and smoother than ever before!

HTH

Glyn
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Old-Guy
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Post by Old-Guy »

Hi Glyn

It's not your imagination!

Strange as it may seem, fuel starvation was making your engine smoke. Black diesel smoke is caused by incomplete fuel combustion, which can have lots of causes apart from excess fuel.

A blocked fuel filter gives the worst of both worlds: the injection pump can't provide the full dose of fuel under larger throttle openings and what is injected doesn't burn properly. You get both poor economy and poor performance, plus an anti-social trail of smoke.

For a clean (and thus efficient) burn, the injection pump must provide a pressure pulse of fuel with a sharp cut-off so that the injector nozzle valves open fully to spray a fine mist of fuel throughout the injection, and then snap shut at the end to prevent dribbling.

If the pump is starved of fuel, the pressure tails away during each pulse so although injection may start as a fine mist, falling pressure lets the valve close slowly causing the fuel droplet size to increase during the latter part of the injection. These larger droplets take longer to burn, but have least time and less oxygen to do so; they don't burn properly causing smoke.

Guy
2011 Grand C4 Picasso VTR+ 1.6HDi in Kyanos Blue
1995 Xantia Estate SX 1.9TD in Vert Vega "The Green Lady" - after 11 years now owned by XanTom
1998 Xantia 2.1 VXD Estate in Mauritius Blue - R.I.P. (terminal tin-worm)
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