> > Regarding run, I say stick to whatever the
> > manufacturer recommends. If there is no
> > recommendation, then the important thing is to
> vary
> > RPM and never let it really sit still at a certain
> RPM
> > for too long (like cruising constant 90km/h on the
> > highway at say 2500 RPM). Keep RPM changing as
> much
> > as is practical. 1000-1500 RPM variation every 5
> > seconds or so should be enough. Loading - just
> run
> > average to low loads. Do not load heavily till
> car is
> > THOROUGHLY warmed up. Do not load heavily on
> purpose.
> > If you accidentally load heavily (after fully
> warmed
> > up) by accident for a few seconds it is not a big
> deal
> > but do not do it intentionally and/or for extended
> > periods of time. Manufacturer recommendation
> rules
> > all. If they have a max RPM limit, you still want
> to
> > vary RPM as much as practical within that limit.
======
Not runing in properly can lead to anything from
increase load on the cooling system from ring-wall
friction, excess blowby leading to poor quality oil
and oil consumption, etc. etc. Things don't usually
get very bad with poor run in, but they certainly can
snowball out of control once any factor is set off.
==========
There are too many variables in an engine for which to specify a generic break in procedure. Cylinder bore finish (hatch depth, frequency, peak flatness, crosshatch angle), ring material, ring width, cylinder wall material, ring coatings, ring tension, combustion pressure, etc. Only the manafacturer knows this and only they are fit to recommend a run in procedure.
Note that motoman is talking about bike engines - which develop considerably less cylinder pressure than most automotive engines . Even then he cannot possibly have more test/teardown data than the bike manafacturers. Again, all the variables in the first paragraph apply.
Run in is also not only for cylinder seal, but for other areas of the car.
=============
> You are certainly right about break-in
> being
> > a contentious
> > > topic. No offense, but I don't really think
> we
> > should be promoting
> > > the message of any-run-in because for each of
> the
> > hundreds of
> > > thousands of permutations of factors like ring
> > materials, tensions,
> > > coatings, designs - bore materials, finishes
> (highly
> > specific), oil
> > > properties - combustion pressures, there are in
> fact
> > good and bad ways
> > > to run them in.
> > >
> > > There have been a few proponents of the hard
> run-in
> > process (most
> > > prominently the credibility-lacking Motoman) ,
> but
> > I've never seen one
> > > that can speak for all permutations or even know
> > exactly which
> > > permutation a specific model engine runs and one
> > processes the factory
> > > has run. Only the factory has access to all the
> > information and has a
> > > wide enough span of testing which ends up in a
> > recommendation that is
> > > closest to ideal.
> > >
> > > So I think I will stick to factory
> recommendations
> > on my factory engines.
> > > In other builds where I have control of how I'm
> > building the engine
> > > and have my own or my community test results
> with
> > very specific engine
> > > combinations running the same permutation, we'll
> run
> > our own run-in
> > > process. If there is a friendly and more
> successful
> > company that has
> > > done more testing on that specific combination,
> I'll
> > test out their
> > > recommendation. In the case of OEM stuff, there
> is
> > none bigger than
> > > the manufacturer. If I had say a production car and a
> > friend of mine also
> > > had the same model and he already ran his in hard and was
> > experiencing no
> > > problems, I still would stick to the
> manufacturer
> > recommendations
> > > because manufacturer tolerances are still
> relatively
> > poor and they can
> > > easily stack up and get really bad. The
> manufacturer
> > recommendations
> > > are in all likelyhood tailored to the mean
> product -
> > and since we
> > > don't know what we get without tearing the new
> > engine apart and
> > > measuring and re-assembling everything
> ourselves, I
> > believe we're
> > > better off listening to the manufacturer.
============