Need Information To Do A 150 Hp Conversion On My C-150

Max Conrad (ferried Pipers all over the world in the 40s and 50s) ran
fully leaned & with full carb heat when he was in his max range mode.
Do you know of any reason not to, assuming a low power setting? It
would improve the mixture distribution, something the O-470s are
notoriously poor at. It would also reduce the inlet air density,
allowing things to operate with less pumping loss.

nrp

In rec.aviation.owning nrp wrote:
: Max Conrad (ferried Pipers all over the world in the 40s and 50s) ran
: fully leaned & with full carb heat when he was in his max range mode.
: Do you know of any reason not to, assuming a low power setting? It
: would improve the mixture distribution, something the O-470s are
: notoriously poor at. It would also reduce the inlet air density,
: allowing things to operate with less pumping loss.

Unless the CHT's get too high in that configuration (causing poor valve
cooling and cylinder badness), there's not much that says it's bad except:
- No filtration of the air with carb heat. Shouldn't be a big deal in cruise (unless
you have a *really* dirty cowling).
- If flying in cold enough weather, you could get carb ice when normally ice crystals
would flow through unmelted. (I generally don't like to use carb heat until I know
it's necessary)
- Sudden power requirement will cause the engine to falter... get used to a quick red
knob, then throttle.

The real disadvantage of the arrangement on my fixed-pitch plane is 65% is
only obtainable at that mixture up to about 7000-8000'. "Best power" of 50 ROP will
get you 75% or so at that altitude.

-Cory

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

In rec.aviation.owning wrote:
: The real disadvantage of the arrangement on my fixed-pitch plane is 65% is
: only obtainable at that mixture up to about 7000-8000'. "Best power" of 50 ROP will
: get you 75% or so at that altitude.

Cory, this I don't understand. You don't have to run WOT to use LOP. Or, are
you saying that you can't get over 65% LOP above 7000'? The maximum possible
power from a non-turbo engine at 7000' is 75%, perhaps that's what you're
saying?
--
Aaron C.

nrp wrote:

Max Conrad (ferried Pipers all over the world in the 40s and 50s) ran
fully leaned & with full carb heat when he was in his max range mode.
Do you know of any reason not to, assuming a low power setting? It
would improve the mixture distribution, something the O-470s are
notoriously poor at. It would also reduce the inlet air density,
allowing things to operate with less pumping loss.

On the 470's, in cruise, you give it whatever carb heat gets you a carb
temp of 40-45F. Running at full carb heat makes no sense whatsoever.

Newps wrote:
On the 470's, in cruise, you give it whatever carb heat gets you a
carb
temp of 40-45F. Running at full carb heat makes no sense whatsoever.

Why not? Using full carb heat would seem to promote better mixture
distribution. The reduced charge density would allow you to run a
higher manifold pressure for the same mass flow, reducing the pumping
loss for a given power setting.

Obviously aggressive leaning probably to at least peak would be
desirable, although who knows where the non-instrumented cylinders
would be running.

I'd be a little concerned running partial carb heat as there would
possibly be a considerable temperature gradient in the air intake
system, given how the carb heat is crudely modulated with that
humongous flapper valve. In other words, some cyls might get a hot
mixture, and some might get cold mixture.

This is assuming the purpose of all this is to reduce the fuel
consumption to get maximum endurance or range under low power settings.
I don't think cyl temp would be a limiting factor.

I don't normally fly my 172M this way (w carb heat always on), but if
it was a question of making it or not, I'd sure use it.'

Thoughts of others?

Most pilots don't know how to get the absolute maximum range or
endurance out of their aircraft.

In rec.aviation.owning nrp wrote:
: Max Conrad (ferried Pipers all over the world in the 40s and 50s) ran
: fully leaned & with full carb heat when he was in his max range mode.
: Do you know of any reason not to, assuming a low power setting? It
: would improve the mixture distribution, something the O-470s are
: notoriously poor at. It would also reduce the inlet air density,
: allowing things to operate with less pumping loss.

I find that I can run my Cherokee's O-360 LOP quite effectively using full
carb heat. Attempts to do so without carb heat lead to unacceptable engine
roughness. With the carb heat on, I can reduce the RPM down several hundred
RPM from peak RPM with good smoothness. Without the carb heat, the RPM
peaks as the mixture gets leaner, then as the RPM begins to drop the engine
gets progressively rougher.

I have not run the engine LOP for any appreciable length of time as I have
no CHT or EGT instrumentation. I have done it for a minute or so to see if
it is possible.
--
Aaron C.