slightly long reply [Diy_efi] blown engine...

[Daniel Nicoson]

What you actually experienced was pre-ignition, your diesel had oil from the
turbo in the inlet air and that air/fuel mixture entered the cylinder just
like a spark ignition inhales air/gasoline.  Problem was as soon as the
piston started back up on the compression stroke as soon as the
temp/pressure hit ignition conditions you were trying to combust with 90 or
more degrees of rotation prior to TDC, well before you would normally time
the ignition.  This leads to HUGE temp/pressure spikes that melt whatever
gets hot the fastest.  You saw the results on your glow plugs and steel
inserts.  You're lucky you didn't get holes in the pistons.

Good to hear it is running, 'hope all is well.

Dan Nicoson

-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
Behalf Of Ian Molton
Sent: Monday, June 12, 2006 7:57 PM
To: Rick McLeod; diy_efi at diy-efi.org
Subject: Re: slightly long reply [Diy_efi] blown engine...


Hi again

Well the engines been rebuilt.

it would seem the small metal fragments I found in the cylinders are the
remains of the glowplugs. The local diesel specialist says that when
turbos go and the engine starts burning oil, the oil ignites before TDC,
and thus a flame is sucked into the combustion chamber, against the
glowplugs. this burns them away very quickly.  (normally combustion
gasses exit the combustion chamber before doing too much damage.

This also explains why the combustion chambers (hard metal inserts in
the aluminium head) had moved - they had simply overheated. they were
proud enough that a faceplate on the head actually /rocked/ on the
centre one giving a ~0.5mm gap at the edge!

so, a new set of glowplugs, turbo off ebay, and a head gasket and it is
all up and running. Total cost ~20ukp, which isnt bad - but who knows
how long this new turbo is going to run?

Next task will be to tear  apart the old turbo and see if it can be
salvaged in any way. I've heard some turbos can use ordinary
ballbearings (garrett models) so perhaps... will have to see.

TTFN!
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