[Vwdiesel] By hook or by crook or by the book

[James Hansen]

George:
James how do you account for different shims? Different head gaskets? These
engines are not fine tolerance; they are just acceptable tolerance!
_______


James:
Not quite.
How many engines do you know of that vary head gasket thicknesses to get
EXACTLY the right deck height, aside from real race engines that is (And
we're talking 1980, not today).
Yeah, none, other than those made by engineers that are anal about
tolerances.
It's a given that there exist differences in piston and rod length (within
tolerance), and making them all exactly the same makes for too much scrap,
so they match sets, and vary the gasket thickness to remove the differences,
and make all engines basically the same.  The different gaskets are to make
the engines the same, not different.
Valves wear, and need either hydraulic followers or an adjustment point.
I've pulled shims out of solid follower engines for the first valve set from
new.  The factory installed shims were all the same.  What was that again
about different shims?  You're talking about USED engines, that have worn
valves, so yeah, the shims will be different to account for differing rates
of wear, but the compression ratio change caused by a 0.1mmm valve face
recession is next to nothing and insignificant.
You forgot to mention paint colors.  Those vary some. :-)




IMO all engines should be set to manufacturers recommended timing
initially; and then they should be farted about with  +/- a bit
______
And that's essentially what I wrote.
If you actually read what Svend wrote, he maintains that the book settings
are crap. You should do it all by ear starting at a grossly retarded
position.
I maintain that the performance setting that is publicized in some
literature of 1.00 mm is the best overall setting. If that isn't optimum, go
ahead and tweak, but then you are starting from a known point, and adjust it
in X increments to setting Y.  When you change belts, you go to setting Y
again, takes 15 minutes, and you are driving the car, not farting away two
weeks trying to arrive at the same destination again.... maybe.



and
listened to or just simply driven to see what's best.# For you #.I look for
economy with just enough power to overtake  that troublesome truck. This
may or may not coincide with original spec.
_________

And I look for the most power period.
Guess what?
In a diesel, the setting for the most power happens to coincide with the
best efficiency.  It's what you do with your right foot that directly
influences mileage.  Put a brick under the pedal, you get mileage, put it on
top of the pedal, you get power. That's the beauty of a diesel- there is no
carbeurator to mix air/fuel at stoichiometric ratios every time the engine
runs, so only as much fuel as is needed to maintain a given rpm is used.



This is before any wear. Then
as agreed; re-fudging as slack develops.Recording results I agree is always
better than not recording it especially as the route to happiness is a long
road for some drivers. However if wear may also be a factor then the
subsequent adjustments are unique to this engine; unless you are able to
create a graph of wear adjusted timings.
-_____________

If your pump wears that fast, there is something drastically wrong.
Recording known timing values would bea way to track that as well, but then
there are better ways of diagnosing pump trouble... such as a flow bench
test.  I had a car (A2 Jetta TD) with over 580000kmson it, and the original
pump is still running fine.  I know the current owner well, and am sort of
mentoring him as he learns things diesel. Trust me in this, pumps do not
wear that fast.  perhaps theoretically they could, but not in real life.  If
they do, they need to come apart to fix what is wrong before they wreck a
set of injectors, or eat themselves.



I don't tune by ear particularly; but once I have an engine as I like it; I
'm the first to notice a change in the sounds that may be a later issue!
Call it maintenance by ear!
_____


Very valid way to keep tabs on an engine. I always listen for fresh news.
In some of my stuff, with engines at 25K a pop, you listen. I detected an
oil line come off my cummins this spring by ear- the line was internal, it
just leaks back to the pan, and is used to control injector advance.  One
was late, and I could hear it at operating RPM. Not a big deal, but stuff
like that gets caught before the line falls off and drops onto the camshaft
making a $10K noise.
Injector wear has a lot to do with things too, and new calibrated nozzles
have a lot to do with good or acceptible mileage.  I usually go a tad
overboard on injectors- as in 15 bar higher break pressure, esp on older
lower compression motors.  It starts better then, and in my opinion,
improves mileage somewhat.
-James.
--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.371 / Virus Database: 267.13.13/198 - Release Date: 12/12/2005