"Charles Vincent" wrote in message
. ..
Morgans wrote:
"Charles Vincent" wrote

I will bet that many of the un-certified engines being marketed out
there
couldn't finish the endurance test without swallowing an exhaust valve.

Time for someone to trot out the GM stress test for new engines.

It makes the FAA tests look like a walk in the park.

Anyone got a copy of that handy?

I have the GM Automotive Test Code for 1967 (the FAA test regime was
codified in 1964). It specifies a two hundred hour durability test,
whereas the FAA is one hundred and fifty hour endurance test for
reciprocating non supercharged engines or reciprocating single speed
supercharged engines. Two speed supercharged and helicopter engines are
longer as I recall. The GM test code requires the engine to complete a
200 hour test schedule "without major failure". The engine is cycled
between peak torque rpm and peak hp rpm +200 rpm (max rpm not to exceed
4600)on five minute intervals. Every five and a half cycles, speed to
be reduced to idle from max test speed by closing throttle for two
minutes, after which engine speed is brought up to maximum upshift speed
within 10 seconds +/- 5 seconds, the speed is then reduced again to the
peak torque rpm and the normal cycle is continued again. The engine is
inspected every twenty five hours for cranking compression, blowby, belt
tension and ignition timing. I don't have the current testing codes for
GM, and since GM isn't selling an uncertified engine for aircraft use, I
don't know the relevance and doesn't effect my belief that many of the
un-certified engines being marketed out there couldn't finish the
endurance test without swallowing an exhaust valve.

Charles


I don't know of anything that is necessarily specific to any one automotive
brand, but a test procedure from some time in the 1990s has been posted to
this NG a couple of times. As of this time, I can't find it; either because
I can't remember the file name or because it died with an older computer.

To the best of my recollection, the more recent engine testing includes a
rather long run, possibly 100 total hours, at 100% power. Interestingly,
the actual purpose is to verify the effectiveness and durability of the
torsion dampener. Failure of the torsion dampener will cause a failure of
the crankshaft and/or drive train--as will its absence or incorrect
calibration--which should be of considerable interest on this NG.

I suspect that the cycling test between maximum torque and maximum power is
also primarily a verification of harmonic dampening; but that is only a
presumption on my part--with the discalimer that I am not an automotive
engineer.

In addition, there was mention of a temperature cycling test in which the
engine is repeatedly run at full throttle until normal temperature is
reached, shut down and chilled to below freezing, then started and run
immediately at full throttle until normal temperature is reached, etc. The
purpose was stated to be verification of the head gaskets and related
clamping force--especially on engines that were all or partly aluminum.

There is also a cycling test including an automatic transmission, in which
the engine repeatedly runs up through the gears and then back down--as
though a driver accelerated through the gears in drive with the accelerator
to the floor, then pulled the lever into low and coasted back
down--repeating the process over and over. According to the account which
was given, an engine will usually outlast multiple transmissions. Obvoiusly
the test has value in predicting warranty costs, but the exact purpose is a
mystery to me.

Further disclaimer: All of this is from memory and the true original source
is unknown, as is the brand of engine(s) involved.

Peter