Vapor lock question????

[wise purchaser]

Have a cessna 150 with 150 HP conversion. I burn regular mogas for
the most part. My bird can tanker up to 60 gallons so I have very
long range capability.

The plane runs fine on the mogas not to mention the SAVINGS! Avgas
here is running as much as 5 bucks a gallon! car gas runs about $
2.45 gal

Since the airplane is gravity feed ( the engine has a engine driven
fuel pump) could I have a problem with vapor lock?? What would be
the indications of the lock? at what point could i expect vapor
lock?? start up? takeoff!!! ???

Thanks!!

By the way the 150/150 is AWSOME it kicks ass and takes names on
takeoff and cruise

with the long range can stay in the air almost 10 hours sipping the
MOGAS with regular cessna 150 100 HP cruise power ( 95 KTS ) or
6 hrs with pushing the power up till 120 KTS
9.5 gal hr

I Have the E/ I electronic flow meter coupled with the KLN 90 GPS and
I can set the fuel flow right on the nut!!!

[Ron Natalie]

wise purchaser wrote:
> Have a cessna 150 with 150 HP conversion. I burn regular mogas for
> the most part. My bird can tanker up to 60 gallons so I have very
> long range capability.

Wow, even with mogas you double the value of the aircraft by filling
up :-)

>
> The plane runs fine on the mogas not to mention the SAVINGS! Avgas
> here is running as much as 5 bucks a gallon! car gas runs about $
> 2.45 gal

It actually runs better on mogas. 100LL is not particularly low in
lead compared to anything other than the 100/130 it replaced. It's
got 4 times the lead that the old 80 grade did.
>
> Since the airplane is gravity feed ( the engine has a engine driven
> fuel pump) could I have a problem with vapor lock?? What would be
> the indications of the lock? at what point could i expect vapor
> lock?? start up? takeoff!!! ???
>
You're not likely to see it. One of the criteria for getting that
STC is to flight test for the conditions condusive to vapor locking.
Most commonly they are high ambient temperatures and very low fuel
flow rates, low pressures. In my plane (not approved for avgas) the
worst case
is a hot day, shutting down for 30minutes and letting the fuel
boil inside the lines not moving and then try to restart.

Can't vouch for 150/152's but the 172 does have a small locking
problem which was responsible for the suggestion at high altitudes
that you use LEFT or RIGHT rather than both to increase the fuel
flow rate.

[Frank Stutzman[_2_]]

Ron Natalie > wrote:
> You're not likely to see it. One of the criteria for getting that
> STC is to flight test for the conditions condusive to vapor locking.
> Most commonly they are high ambient temperatures and very low fuel
> flow rates, low pressures. In my plane (not approved for avgas) the
^^^^^^^^^^^^^^^^^^^^^^

Ah, er, don't you have a typo there, Ron?

I thought you had converted your Navion to some flavor of 550. To the
the best that I know, all such engines are approved for avgas. If anything
I would say that they are not approved for autofuel.

--
Frank Stutzman
Bonanza N494B "Hula Girl"
Hood River, OR (soon to be Boise, ID)

[rq3]

Frank Stutzman wrote:
> Ron Natalie > wrote:
>> You're not likely to see it. One of the criteria for getting that
>> STC is to flight test for the conditions condusive to vapor locking.
>> Most commonly they are high ambient temperatures and very low fuel
>> flow rates, low pressures. In my plane (not approved for avgas) the
> ^^^^^^^^^^^^^^^^^^^^^^
>
> Ah, er, don't you have a typo there, Ron?
>
> I thought you had converted your Navion to some flavor of 550. To the
> the best that I know, all such engines are approved for avgas. If anything
> I would say that they are not approved for autofuel.
>
There are two STC's required for running on mogas - one for the engine,
one for the airframe. No Navion is STC'd to run on mogas.

Rip

[Ron Natalie]

Frank Stutzman wrote:
> Ron Natalie > wrote:
>> You're not likely to see it. One of the criteria for getting that
>> STC is to flight test for the conditions condusive to vapor locking.
>> Most commonly they are high ambient temperatures and very low fuel
>> flow rates, low pressures. In my plane (not approved for avgas) the
> ^^^^^^^^^^^^^^^^^^^^^^
>
> Ah, er, don't you have a typo there, Ron?
>
> I thought you had converted your Navion to some flavor of 550. To the
> the best that I know, all such engines are approved for avgas. If anything
> I would say that they are not approved for autofuel.
>

Ooops...that should say not approved for mogas. I don't know if their
are *ANY* planes not approved for MOGAS.

There are no Navions, regardless of engine, that are approved for AVGAS.
The EAA doesn't get into anything other than 4-cyl I believe. Petersen
at one point test flew a Navion and it failed the tests. They couldn't
tell me what engine or fuel system (the Navion has probably over a dozen
different combinations AS IT CAME FROM THE FACTORY, not withstanding
those put on by STC) was the one tested and failed.

Yes the IO-550 is right out anyway.

[Ron Natalie]

Ron Natalie wrote:

> Ooops...that should say not approved for mogas. I don't know if their
> are *ANY* planes not approved for MOGAS.
>
ARGH! that should say AVGAS.

My brain is turning to cottage cheese, large curd.

[Blueskies]

"Ron Natalie" > wrote in message ...
: Ron Natalie wrote:
:
: > Ooops...that should say not approved for mogas. I don't know if their
: > are *ANY* planes not approved for MOGAS.
: >
: ARGH! that should say AVGAS.
:
: My brain is turning to cottage cheese, large curd.

Low fat...or regular?

;-)

[[email protected]]

Vapour lock is seldom an issue with gravity-feed systems, since
the fuel is under positive pressure (though very low positive
pressure). Vapour lock happens most often when the fuel is beling
pulled rather than pushed, as in a low-wing with the tanks below the
engine's fuel pump. The lowered pressure on the fuel in the lines
lowers its boiling point, and the heat in the cowl does the rest.
Mogas in a gravity-fed system can be a problem at altitude,
since the atmospheric pressure is low, and the fuel's boiling point
comes down. If the engine is working hard and the ambient temp is high
enough, the heat in the cowl might raise the fuel to the lowered
boiling point. As the fuel boils, the vapours expand and prevent any
further fuel flow. Carburetors and fuel injectors don't work well on
vapours.
Mogas has a higher vapour pressure than avgas, which means its
boiling point will also be lower.

We used to run mogas in our O-200s and O-320s. The
Continentals didn't like it, and the valves would stick and the valve
seats would wear out sooner. The old-technology bronze valve guides
relied on the lead for lubrication, and so did the valve heads and
seats. The Lycomings gave somewhat less trouble, but we still had
exhaust valve guide wear and valve burning problems with it. Whwn the
guide wears, it lets the valve hit the seat a little off-center and
makes the seat wear to an oval, allowing it to leak and burn. The
problems went away when we went to straight 100LL.
Today's automobiles have much more advanced valve
technology that allows them to burn the harsher mogas. The
ContinentoLycosaurus prefers the diet it's been on since it was born
in prehistoric times.
Running a mix of 100LL and mogas didn't work much better than
straight mogas. Sometimes these economy measures are false and end up
costing more in the long run. We run a flight school, and besides the
cost of expensive cylinder repairs, which is bad enough, the downtime
eats into the budget real quick. 100LL is much cheaper for us.

Dan

[flynrider via AviationKB.com]

If you're going to get vapor lock running mogas, spring is probably the
time it'll happen. Oil companies formulate mogas for different seasons.
Winter mogas has a low vapor pressure which allows it to vaporize more easily
in lower temperatures. Summer blends have a higher vapor pressure to resist
vapor lock in warmer temperatures. The problem exists when using a winter
blend of mogas when temperatures have warmed up. If you're going to get
vapor lock, that's when it's most likely to happen.

It's not a problem in cars, since a typical gas station turns over its
stock one or more times a week. It can be a problem if you get your mogas
from an airport. It can take weeks or months to turnover a full load of fuel.


This was a problem with a friend of mine that runs an FBO in the southwest.
He used to have a self-serve mogas pump at his relatively small airport, and
it would take him a couple of months to sell a 2,000 gallon load of it.
Invariably, when the hot weather hit, he would get reports of vapor lock from
pilots who were buying his winter mogas. Eventually, he considered it too
much of a potential liability and shut down the mogas pump.

John Galban=====>N4BQ (PA28-180)

--
Message posted via http://www.aviationkb.com

[Montblack]

("Blueskies" wrote)
> : My brain is turning to cottage cheese, large curd.
>
> Low fat...or regular?


Expiration date?


Montblack
Best if used before: 10pm

[jerry wass]

Bryan Martin wrote:
> In article <7044e0f5b02bc@uwe>,
> "flynrider via AviationKB.com" <u32749@uwe> wrote:
>
>> If you're going to get vapor lock running mogas, spring is probably the
>> time it'll happen. Oil companies formulate mogas for different seasons.
>> Winter mogas has a low vapor pressure which allows it to vaporize more easily
>> in lower temperatures. Summer blends have a higher vapor pressure to resist
>> vapor lock in warmer temperatures. The problem exists when using a winter
>> blend of mogas when temperatures have warmed up. If you're going to get
>> vapor lock, that's when it's most likely to happen.
>>
>> It's not a problem in cars, since a typical gas station turns over its
>> stock one or more times a week. It can be a problem if you get your mogas
>> from an airport. It can take weeks or months to turnover a full load of fuel.
>>
>>
>> This was a problem with a friend of mine that runs an FBO in the southwest.
>> He used to have a self-serve mogas pump at his relatively small airport, and
>> it would take him a couple of months to sell a 2,000 gallon load of it.
>> Invariably, when the hot weather hit, he would get reports of vapor lock from
>> pilots who were buying his winter mogas. Eventually, he considered it too
>> much of a potential liability and shut down the mogas pump.
>>
>> John Galban=====>N4BQ (PA28-180)
>
> I think you got that backwards. Mogas is blended for a HIGHER vapor
> pressure in Winter than in Summer. High vapor pressure = easier to
> vaporize = easier to start your car in the winter.
>
> Bryan Martin
>

John has it right, Bryan--and your statements are correct also--i.e.
winter gas = high vapor pressure--get winter gs in spring/summer=vapor
lock!! Jerry