[Vwdiesel] Decoking pistons

[mark shepherd]

Hmm no titles are descriptive. http://img809.imageshack.us/f/imgp9942.jpg/
I'll rearrange them in the future.The photos show state of pistons when I 
took the head off .
The exhaust valve marks that have been from them tapping the pistons for 
over two years, and some 25000 miles! There are some views of the stuck 
rings, and one of the sets of rings placed in a cylinder to see the huge 
gaps.
Truely impressed by the ability of this engine to run with 200, 270 160 and 
200 psi on a compression test.
As the bores looked good when I skimmed the head a few years ago; I never 
removed the pistons to check, but some months later, I managed to rig up a 
compression tester that gave about 280  to 300 psi  for the cylinders. At 
the time I assumed the low values were down to errors in my modified 
injector adaptor, because the engine ran so well, and gave reasonable mpg of 
43 to 48. Hard starts only appeared back in July, but mileage never 
diminished.
Engine now been running for about 300 miles and first fillup gave me 51mpg 
for mixed trips, at least half of them a mile or so only.
Hopefully it willl get better, but if this is the worst, then that's a 20% 
improvement

Mark


----- Original Message ----- 
From: "mark shepherd" <mark at shepher.fsnet.co.uk>
To: "mark shepherd" <mark at shepher.fsnet.co.uk>
Sent: Friday, September 03, 2010 2:08 AM
Subject: Re: [Vwdiesel] Decoking pistons


>
> At long last I got round to uploading some pictures. Here is a picture of 
> a set of rings. Not sure if they were of the 160psi cylinder, or one of 
> the two  200psi ones, or even the 270psi one.  Has anyone run with bigger 
> gaps? The pressure was less than my old vw gasser. Scrolling should give 
> the other pictures, in no particular order, but titled according to what 
> they are.
>
> http://img809.imageshack.us/f/imgp9942.jpg/
>
> Subject: [Vwdiesel] Decoking pistons
>
>
>>
>> Greetings,
>> Hopefully someone will be up on the other side of the world.
>>
>> Just taken my pistons out for a rering, I was having a 'little difficulty 
>> starting. Fuel economy averaging about 45 to 48 UK mpg. 3 pistons have 
>> single stuck rings,top or middle some of the gaps could be as big as 
>> 1/16th- 1/8th of an inch!!
>> Bores good, and hastings rings fit to middle of VAG gap spec.  Pistons 
>> are great and so are all bearings. It loks like my nocking for the last 
>> 20 to 30 ooo miles was exhaust valve clash. I always set belt accurately, 
>> but I overskimmed the head, and so this mayexplain that.
>>
>> However my question is this.
>> Should I remove the thin layer of carbon deposit between top ring and 
>> piston face?
>>
>> Regards
>> Mark
>> _______________________________________________
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>> Vwdiesel at vwfans.com
>> http://www.audifans.com/mailman/listinfo/vwdiesel
>>
>
>
>