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Corvair conversion engines



 
 
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  #91  
Old February 4th 06, 05:28 PM posted to rec.aviation.homebuilt
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Default Corvair conversion engines

snip

However, my real problem with the valve assertion is that I really don't
know anyone who managed to run one of these little air cooled engines long
enough and hard enough to burn a valve. I do know of two broker cranks on
Corvair conversions (same person) and at least one, and possibly two, broken
cranks on VW conversions (same other person). Both are mentioned on the
FlyCorvair site, so I am really not adding much that is new. I am convinced
that all of the failures were torsional damping issues. The only burned
valve that I know of on an automotive conversion was on a liquid cooled
Geo/Suzuki engine and was traced to a carburetion problem--which was run at
a much higher power level. I was told that the carburetion problem was
corrected and has not recurred.

On the other hand, I strongly suspect that very high power levels equate to
accelerated wear; and I really dislike very short TBOs. So all of my own
scratch pad doodles are based on continuous power levels of less than 0.5
hp/cid, and usually significantly less.

Peter



I drove a harvesting machine that used hydrostatic drive and a VW engine
for power. We ran it on a governer at 3950rpm 24x7 all summer. Once I
was moving it from field to field and dropped a valve when I ratcheted
the motor up to 4100 because the machine travled at the speed of growing
grass. Of course this was after about 10 weeks of continous operation so
in terms of hours it was due.... The vale seats were pretty hammered as
I recall.

Lets see, 24*7*10=1680 hours.

Dave
PDX

  #92  
Old February 4th 06, 06:27 PM posted to rec.aviation.homebuilt
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Default Corvair conversion engines


"D.W. Taylor" wrote

I drove a harvesting machine that used hydrostatic drive and a VW engine
for power. We ran it on a governer at 3950rpm 24x7 all summer. \\\


The fact that it ran with a governor means that it was not at full HP. It
is admirable for it to run that many RPM's for that many hours, but still,
there is no indication of how long it would run at true Wide Open Throttle,
making all the HP it could.

I suspect its life would have not been as long, if it were loaded to it's
maximum output.
--
Jim in NC

  #93  
Old February 4th 06, 06:54 PM posted to rec.aviation.homebuilt
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Default Corvair conversion engines


"D.W. Taylor" wrote in message
...
snip


I drove a harvesting machine that used hydrostatic drive and a VW engine
for power. We ran it on a governer at 3950rpm 24x7 all summer. Once I was
moving it from field to field and dropped a valve when I ratcheted the
motor up to 4100 because the machine travled at the speed of growing
grass. Of course this was after about 10 weeks of continous operation so
in terms of hours it was due.... The vale seats were pretty hammered as I
recall.

Lets see, 24*7*10=1680 hours.

between overhauls or just between rests?


  #94  
Old February 4th 06, 11:32 PM posted to rec.aviation.homebuilt
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Default Corvair conversion engines

Morgans wrote:


"D.W. Taylor" wrote

I drove a harvesting machine that used hydrostatic drive and a VW engine
for power. We ran it on a governer at 3950rpm 24x7 all summer. \\\


The fact that it ran with a governor means that it was not at full HP. It
is admirable for it to run that many RPM's for that many hours, but still,
there is no indication of how long it would run at true Wide Open
Throttle, making all the HP it could.

I suspect its life would have not been as long, if it were loaded to it's
maximum output.


Jim
What airplane POH tells you to run your reciprocating engine at max/wot
throttle?
Most small airplanes run max hp for about 10 to 30 minutes for takeoff and
climb then throttle back to 75% for cruise. So expecting a VW/corvair to go
max for hours on end and not break is unrealistic. I personally think
either engine is viable in the proper application and treated properly. One
of the first things in your testing phase is to make sure your not
overheating the thing. It's quite well known a VW is not capable of
continuous operation at much more than 40 or 45 hp (let's see 75% of 65 (65
being about the highest you'll want to run a VW) is 49 hp) so your probably
only going to cruise at about 65% power which is not bad because you still
have that extra reserve for takeoff and go arounds!
I don't know what the max continuous of a corvair is but the same applies,
run it at the right level and you'll probably have a sweet little smooth
engine! This is homebuilt/experimental right? ;-)
John

  #95  
Old February 5th 06, 02:00 AM posted to rec.aviation.homebuilt
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Default Corvair conversion engines

The fact that it ran with a governor means that it was not at full HP. It
is admirable for it to run that many RPM's for that many hours, but still,
there is no indication of how long it would run at true Wide Open

Throttle,
making all the HP it could.

I suspect its life would have not been as long, if it were loaded to it's
maximum output.
--
Jim in NC

I agree with your basic point. And also feel compelled to add that there is
probably no way for anyone to know how much power the VW engine produced in
the harvesting application--unless they metered torque, which would not be
reasonable. My supposition, just from reading the post, is that at least
half of the total fuel burned was applicable to pumping losses rather from
the work done.

However, also have problems with the wide open throttle scenario. I also
suspect that if we were to discuss the issue at length, we would find that
we are completely in agreement; but that we insist on using different
"phraseology."

We really don't operate our Lycomings and Continentals at their sea level
maximum output very much of the time. My best guess is that, flying with a
fixed pitch prop on a standard day, we can achieve nearly 90 percent just
off the runway and that drops gradually to less about 75 percent by around
3000 feet msl. (My recollection on exactly were this occurs is less than
perfect as I have not flown in a long time) And 75 percent, on the aircraft
engines with which I am familiar, ranges from about a low of about 0.355 to
0.357 HP per cubic inch of the low compression Lycoming O-235 engines
through 0.375 HP per cubic inch for the Continental O-200 and their new
O-240 FADEC engine, as well as Lycomings 160 HP O-326 and 180 HP O-360
engines, up to 0.420 HP per cubic inch on the 200 HP angle valve Lycoming
O-360. Those are all engines that really were designed to run that way, for
which the cooling intake and baffling requirements are well documented, and
even so many had "teething" problems which were solved long ago.

If we apply the same specific power output to a pure stock 1600cc VW as to
the smallest Lycomings, 75 percent power should equal 34 HP; which would
result in a theoretical 45 HP engine with a take-off rating that could be as
high as 60 HP, although 55 HP is more likely--based on a 52 inch diameter
prop turning about 3600 RPM. The slightly more agressive specific output of
the O-200 would give the 1600cc VW a rating of 48 HP which would equate to a
75 percent level of 36 HP.

My point in all this is that a relatively slippery aircraft fitted with a
climb prop, to conform to the ancient formula of 0.2 G static thrust
measured with a fish scale, should fly safely with an auto conversion. I
remain a fan of auto conversions, but my advocacy has its limits.

Peter



  #96  
Old February 5th 06, 03:34 AM posted to rec.aviation.homebuilt
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Default Corvair conversion engines

"UltraJohn" wrote in message
link.net...
Morgans wrote:


"D.W. Taylor" wrote

I drove a harvesting machine that used hydrostatic drive and a VW

engine
for power. We ran it on a governer at 3950rpm 24x7 all summer. \\\


The fact that it ran with a governor means that it was not at full HP.

It
is admirable for it to run that many RPM's for that many hours, but

still,
there is no indication of how long it would run at true Wide Open
Throttle, making all the HP it could.

I suspect its life would have not been as long, if it were loaded to

it's
maximum output.


Jim
What airplane POH tells you to run your reciprocating engine at max/wot
throttle?
Most small airplanes run max hp for about 10 to 30 minutes for takeoff and
climb then throttle back to 75% for cruise. So expecting a VW/corvair to

go
max for hours on end and not break is unrealistic. I personally think
either engine is viable in the proper application and treated properly.

One
of the first things in your testing phase is to make sure your not
overheating the thing. It's quite well known a VW is not capable of
continuous operation at much more than 40 or 45 hp (let's see 75% of 65

(65
being about the highest you'll want to run a VW) is 49 hp) so your

probably
only going to cruise at about 65% power which is not bad because you still
have that extra reserve for takeoff and go arounds!
I don't know what the max continuous of a corvair is but the same applies,
run it at the right level and you'll probably have a sweet little smooth
engine! This is homebuilt/experimental right? ;-)
John

I don't know what the Corvair can really do either. But expect 40-50
percent more than an 1800cc (slightly overbored) VW. I really think I'd
cruise at more like 60 percent power, at most. I agree about that sweet
smooth little engine though, and the choice will have to depend on parts
availability and how fast I really think it has to fly when I get to that
point. 120-130 Kts should be readily feasible for the Corvair.
Peter


  #97  
Old February 5th 06, 05:26 AM posted to rec.aviation.homebuilt
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Default Corvair conversion engines


"UltraJohn" wrote

Jim
What airplane POH tells you to run your reciprocating engine at max/wot
throttle?


Very few say that you can *not* run at WOT for extended periods of time.
You can choose to run WOT, if you want to, and stay at near sea level
altitudes, or if your engine is turbo-ed, or turbo normalized, and be
putting out max HP. With most certified engines and planes, there are no
immediate concerns.

Most small airplanes run max hp for about 10 to 30 minutes for takeoff and
climb then throttle back to 75% for cruise.


True, in most instances.

Most either throttle back to 75%, or climb to altitudes that result in the
engine putting out 75%.

So expecting a VW/corvair to go
max for hours on end and not break is unrealistic.


It is only not realistic, if the operator does not know what he can, and can
not, do. Saying , or implying that the Corvair and VW are equal, or close
to equal, I do not think is accurate. IMHO, the Corvair will do much better
at dealing with the higher output levels.

I personally think
either engine is viable in the proper application and treated properly.
One
of the first things in your testing phase is to make sure your not
overheating the thing.


It is a trick to see if you are overheating, with the typical VW or Corvair
instalation, since most have no way of monitoring CHT, or more specifically,
the valves, seats and guides.

It's quite well known a VW is not capable of
continuous operation at much more than 40 or 45 hp


Not well known (or admitted) by many people/companies.

(let's see 75% of 65 (65
being about the highest you'll want to run a VW) is 49 hp) so your
probably
only going to cruise at about 65% power which is not bad because you still
have that extra reserve for takeoff and go arounds!


Knowing and admitting that the VW will burn up their valves and
surroundings, if operated at much over 45 HP for very long, is a very "good
thing" on your part. g Still, I think most people think that they can run
a certified engine at maximum HP for extended periods of time, if they keep
the mixture full rich. The same can not be said about VW engines. I think
Corvair engines behave much like their certified brethern, with their regard
to being able to tolerate extended max HP runs, with a rich mixture.

I don't know what the max continuous of a corvair is but the same applies,
run it at the right level and you'll probably have a sweet little smooth
engine!


True of any engine. If you want to run at max HP often, for long time
periods, they will not run for as many hours before an overhaul. It simply
concerns me that some people believe that they can run VW's at 65 HP (and
some rate it at significantly more than that, without mentioning any names)
and only slightly shorten the engine life.

I just hope people know what they are getting, when they choose an engine.
You obviously do.

This is homebuilt/experimental right? ;-)

This isn't "on" anything. I was just talking generalities, about a VW
running at high RPM's achieving a long life before overhaul, and the fact
that high RPM's and high HP are far from the same thing.

I can't (and won't) argue against using VW and Corvair engines on airplanes.
It has been shown to work very well on many people's planes, when flown
within their limits. The only question is "what are their limits?" Most
people running them for any period of time (and still running them) know the
answer to this question, including some people on these groups. It is the
other people contemplating putting one on an airplane (with unrealistic
expectations) that I am worried about. g
--
Jim in NC

I hope I didn't step on any toes. That was not my intention. I am just
expressing an opinion, and you know how "opinions are like buttholes."
vbg

  #98  
Old February 5th 06, 05:32 AM posted to rec.aviation.homebuilt
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Default Corvair conversion engines


"Peter Dohm" wrote

I agree about that sweet
smooth little engine though, and the choice will have to depend on parts
availability and how fast I really think it has to fly when I get to that
point. 120-130 Kts should be readily feasible for the Corvair.


I would be concerned about that kind of speed with the Corvair cranks, until
the cranks cracking on the high speed airplanes (and even nitrated ones) are
more fully understood. I think caution is in order, in this case.
--
Jim in NC

  #99  
Old February 5th 06, 05:58 AM posted to rec.aviation.homebuilt
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Default Corvair conversion engines


"Peter Dohm" wrote

I agree with your basic point. And also feel compelled to add that there
is
probably no way for anyone to know how much power the VW engine produced
in
the harvesting application--unless they metered torque, which would not be
reasonable. My supposition, just from reading the post, is that at least
half of the total fuel burned was applicable to pumping losses rather from
the work done.


Agreed

However, also have problems with the wide open throttle scenario. I also
suspect that if we were to discuss the issue at length, we would find that
we are completely in agreement; but that we insist on using different
"phraseology."


Good chance that is true. g

We really don't operate our Lycomings and Continentals at their sea level
maximum output very much of the time.


True.

My best guess is that, flying with a
fixed pitch prop on a standard day, we can achieve nearly 90 percent just
off the runway and that drops gradually to less about 75 percent by around
3000 feet msl.


Close enough, for government use! g

I will add, that when one chooses, 90% to 100% can be maintained for long
(very long) periods of time, with no other penalties expected, other than
shorter than usual TBO times being seen. This is with the supposition that
the engine is correctly cooled, and run with appropriate mixtures.

It happens, with racers, and with turbo charged engines, provided that the
owner/operator does not give a hoot about fuel burns or the reduction in
engine life. These people do not expect that their engines will have an
"extremely" high chance of immediate self destruction.

If we apply the same specific power output to a pure stock 1600cc VW as to
the smallest Lycomings, 75 percent power should equal 34 HP; which would
result in a theoretical 45 HP engine with a take-off rating that could be
as
high as 60 HP, although 55 HP is more likely--based on a 52 inch diameter
prop turning about 3600 RPM. The slightly more agressive specific output
of
the O-200 would give the 1600cc VW a rating of 48 HP which would equate to
a
75 percent level of 36 HP.


Once again, reasonable figures. I will again add that the small Lycomong is
capable of running at full output with no immediate penalty. I continue to
doubt that the VW can claim the same.

My point in all this is that a relatively slippery aircraft fitted with a
climb prop, to conform to the ancient formula of 0.2 G static thrust
measured with a fish scale, should fly safely with an auto conversion. I
remain a fan of auto conversions, but my advocacy has its limits.


I am right in line with your thoughts, as long as the reduction in power for
the VW is followed.

I too, like the auto conversion concept. I think that many can exceed the
max HP outputs (especially with a redrive, for many reasons not touched on
here; that is a different, well hashed subject) outlined here (based on HP
per cubic inch, or cc) but that some reduction in output is a rational
operational concept.
--
Jim in NC

  #100  
Old February 5th 06, 06:44 PM posted to rec.aviation.homebuilt
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Default Corvair conversion engines

Morgans wrote:


It is a trick to see if you are overheating, with the typical VW or
Corvair instalation, since most have no way of monitoring CHT, or more
specifically, the valves, seats and guides.


Jim from what I've read (no personal experience!) it is not that difficult
to hook up a cht to a VW and they (whoever they are!) suggest attaching the
sendor near the exhaust valve part of the head and limiting the cht to (I
think) 400 degrees or less. This is the part that limits VW's to less than
40 -45 hp. Of course anything you can do to remove heat faster will let you
run at a higher output. Such as proper baffling and external oil cooler etc
etc. Nothing is wrong with using a VW or Corvair engine but you should be
knowledgable of their limitations!
John

As an aside, both a 1600 and a 2180 VW can put out 40hp continuous if
properly set up but the 2180 will be loafing while doing it at a lower rpm
which will let you use a bigger prop and limit you max rpm.
Life's all a big tradeoff! ;-)

 




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