and the aircraft I own, I routinely operate LOP.
I'm simply
not blinded by the hype

CHRIST-ON-A-BIKE, _why_? It's all HYPE, remember?

Because LOP saves fuel and keeps plugs clean. That much is proven. It
is a fact that lower combustion pressures are also proven - but how
this correlates to long term engine longevity is unknown.

Where is your long-term field study comparing LOP and ROP operations?
Deakin's "Engine Series" provides:
http://www.avweb.com/news/columns/182146-1.html
See any of them about the combustion event and TDC.

None of that says ANYTHING about longevity - at least nothing provable.
Yes, the peak pressure is lower. So? Does the difference impact
longevity? Where is your model? Absent that, where is your long term
controlled field study?

: What are your parameters to asess engine roughness in normal LOP and
: ROP operations?

As mentioned earlier:
"These subjective reports were confirmed recently when Chadwick-Helmuth
spent several days running tests on a 1993 Beech F33A instrumented with one
of C-H's latest state-of-the-art vibration analyzers hooked to multiple
accelerometers and vibration transducers. Tests were flown at a wide range
of power settings and mixtures using a set of standard TCM nozzles, then
repeated after GAMIjectors were installed. The results indicated that the
GAMIjectors reduced vibration levels at the 2nd order frequency and at the
low 1/3rd order frequency by 60% to 80%.

I guess you conveniently missed that one, huh?

Not at all. I never said that GAMIjectors do not reduce vibration at
equivalent operating conditions. The test you refer to is a validation
of a product, not an operating regime. It shows that regardless of
what you do in terms of operating a given TCM engine (and note - this
is ONE engine) it does better with GAMI's. No argument. The question
is whether it does better LOP or ROP with the same injectors, and this
test does not give you that information.

:How do you model the imperfections caused by pilot
:technique? Do you have amplitude and frequency data on engine
:vibration at various mixture settings? What kind of sensors did you
:use?
http://www.engineteststand.com/

Oh no you don't. Be technical and specific. What is the model? Where
is it specifically? What assumptions does it make?

o you have long term operational data or at least a model showing the
:long term behaviour of the engine mounts, bearings, cases, crankshaft,
:etc. under the vibration conditions? Without long-term operational
:data, I would expect at least an FEA.
http://www.engineteststand.com/ (Been running for several years).

How many engines? How many installations? And what kind? Be technical
and specific. Explain why that one given installation should be
considered proof for all (or even most).

o you have any information at all on the differences in combustion
:end-products in excess-air vs. excess-fuel combustion reactions? I can
:assure you they are differrent.
??? Nice tangent there!!!

Not a tangent at all. Since corrosion takes down a lot more engines
than wear on personal aircraft, it's a major issue.

: Are any of the combustion products
:harmful to the engine components long-term?
Like Lead Oxybromide? :~)

Maybe. Maybe others. See, unless you have a statistically significant
sample of engines being run under controlled conditiions long enough to
establish MTBF, you don't really know WHAT the real issue is, so it's
your responsibility to cover all the bases if you want to claim
anything resembling compelling evidence.

Wow!! That's real specific. Methodological, but NOT ONE PIECE OF DATA.

No, there isn't one piece of data. But then I'm not the one claiming
compelling evidence exists, one way or the other. I in fact claim just
the opposite - that no compelling evidence exists one way or the other.
There are some very compelling short-term reasons to operate LOP (save
fuel, don't have to clean the spark plugs as often) and no real
evidence one way or the other what happens in the long term

The people who claim LOP is harmful in the long term are whistling in
the wind too.

I fully expect, based on your response to questions of your assertions,
that's you'll provide a classic example of evasion.
http://www.avweb.com/news/reviews/182558-1.html (Data graphs
specifically...or are those faked?)

Not faked - just not relevant. They show no long term trends in
operation. Where are your graphs showing maintenance costs year by
year? Failures year by year?

This is twice, now, that you've challenged without providing an ounce of
data. I expect some more SPIN...

You're really not getting it. I have NO data. Anywhere. I don't
think it exists. What you've shown is data all right - but not data
you can use to project MTBF or TBO or maintenance cost.

The number we're going for is this:

An engine operated LOP (making certain assumptions about how it will be
operated) will have an hourly operating cost of x% (less/more) than an
identical engine operated ROP (making the same assumptions about the
pilot's ability to consistently control the engine, and if the LOP
engine has GAMI's, so does the ROP engine) excluding fuel (where the
case has already been made quite adequately) but including parts
replacement, overhaul, etc.

Now show me what x is, how it was derived, and what assumptions were
involved.

Michael