Tater Schuld wrote:
wrote in message
oups.com...
as far as automotive engines go, they tend to run as reliably, and with
less
attention. with oil changes at every 66 hours and inspection at 1700 hours
(assuming an average 45mph), they seem to match aircraft.

But they aren't running at the much higher constant power
settings that aircraft engines do.

I understand that, but is it because the aircraft engines are under-rated
due to their designed purpose?

and If one designes the pro and such to run at less than redline, the issues
you commented about woudl disapear. the issue of weight vs horsepower rear
their heads, but it isn't the issue I was looking at.

the issue i was looking at was lowest price point versus power, not price
point per horsepower per pound.

example, I get an engine that weights 400 pounds and cranks 150 hp at a
consistent RPM for $100, or I can get a 200 pound engine that does the same
thing for $5000. or maybe a 300 pound engine that does it for $1000. which
woudl be best? the 200 pound one. which would work? depends on the design of
the plane.

There have been a few auto conversions run at max power for long
periods as part of their testing, and the results have been good with
some. Cooling is a usual issue, since the car's radiator isn't usually
designed to dissipate that sort of heat

so use an oversize radiator, not the stock one used by the car with that
engine. more fiddling but not impossible.

but I get in my 01 car, turn the key and go. even my 86 truck I can do
this.

That's because it has about 50 pounds of computers and
injector solenoids and sensors and so on, and in an airplane that
weight is unwelcome and those systems add more failure points.

but if it works, wouldnt it justify it's extra weight? and how much of that
extra weight can be cut of? cases, cables shrouds, and such are designed
with reliability in mind, not weight consiousness.

any my 86 truck uses maybe 25 pounds of electronics gear, the oil pressure
sensor dont work, and doesnt use injectors. If it was a 4 cyl instead of a 6
i'd use it for an example. those ford inline six's are nearlying
indestructable and never seem to fail. maybe on the 2nd plane i design. too
bad they are going the way of the VW engine.

When it
quits, it quits without any warning, unlike most ancient aircraft
engine systems.

and those systems dont have EGT or CHT senors, not do their inspections have
you number the spark plugs as they are removed to evaluate each cylinder.
nor do Autos let you control fuel mixture on the fly.

take an auto engine, add some aircraft engine technology and you'd get teh
same reliability.

Further, the homebuilder prides himself on his ability
to fix anything on his airplane, and those electronic systems are
unfriendly to the average homebuilder.

yeah, I'd agree, but the black boxes that cars use are SOOOOO much easier to
replace, wallet wise.

You need to Google this group re auto engine conversions. All of
your arguments have ben discussed ad nauseum here for years, and many
people have done conversions of just about every auto engine imaginable
and have encountered many more problems than they ever anticipated.
Some spend many thousands of dollars on these projects, only to give up
in disgust and buy a Lycoming. Might as well learn from the
efforts/mistakes/research of others. If you just want to tinker,
converting's a good way to spend lots of tinker time.
A Ford 300 six is about 450-500 lbs and produces about 130 HP
at 3400 RPM. 3400 is too fast for a prop so it either has to run slower
and sacrifice power, which further increases the already-poor
weight-to-horsepower ratio, or install a redrive, which adds weight and
costs some power. I have a 300 that I put in my antique truck, and
believe me, it's heavy. A Chev 350 is a better machine to convert, but
will still be awfully heavy. Exceptionally heavy engines need
airtframes designed to handle them while keeping the CG where it needs
to be.
Big radiators need room and intelligent baffling to route the
air properly without creating a lot of drag, and depending on the rad's
position and location, coolant vapor control and removal becomes
difficult.

Dan