 |
Matronics Email Lists Web Forum Interface to the Matronics Email Lists
|
View previous topic :: View next topic |
Author |
Message |
gmcjetpilot(at)yahoo.com Guest
|
Posted: Fri Jul 07, 2006 4:31 pm Post subject: The TRUTH about MOGAS |
|
|
I am not ANTI Mogas or anyone who uses it, but
I would like present some of the FACTS, negatives
or CON's, in addition to all the PRO drinking the
cool-aid comments for MOGAS.
I appreciate the passion and support some have
for MOgas. Hey 5,10 and 15 years of successfully
operation is not bad. I appreciate the sense of
humor as well.
Now for facts.
besides the OCTANE molecule (distilled petroleum).
Gas has 200 of chemicals in it, some are good
for aviation some not,
Auto gas has lower vapor pressure, which means it
is more susceptible to vapor lock.
Auto gas, even premium does NOT have the same
octane as 100LL Avgas by quite a bit.
Low octane can cause detonation, and uncontrolled
burning of fuel which can lead to severe engine
damage.
In the past Av gas came in grades of 80-87; 91-98,
100-130 and 115-145. That has given way to the
ubiquitous 100/100LL
Why two numbers? The low number is the lean octane
rating and the higher number is rich octane rating.
There are four ways to measure fuel for octane:
Automotive Research, Automotive Motor,
Aviation Lean and Aviation Rich.
Auto gas has one rating and is average of lean and
rich rating and there are two methods as listed
above.
Aviation gas lean is about equal to automotive motor
octane.100LL avgas if sold at the car pump would be
105. Premium 91 octane MOgas sold as Avgas
would be about equiv to 86UL.
�
STC for Mogas was when 80/86 went a way and
the low compression engines ran terrible on the
default gas grade 100/100LL. Despite the LL�
(Low Lead) designation, there's a lot of lead in
100LL. Therefor low compression engines
designed to run on low octane fuel did not
need or work well on leaded fuel. Lead boost
octane.� That was the beginning of STC's for
automotive unleaded (UL) fuels for aircraft as a substitute for low lead/UL 80 octane.
�
Just because the FAA approves STC's is not mean
much in a high compression homebuilt.
Lycomings come in to flavors, which are certified
for 80 octane and have a compression ratio about
7.2:1CR or have about 8:50:1CR and are certified
for 100/100LL gas,�or the old� 91/96 Avgas grade.
�
If you buy the Super gas at the mini-mart and it
said 92 octane it is only worth about 87 octane.
We assume you test it for ethanol and alcohol
every time of course.
Can you run your 91/96 octane Lyc on it? Well that
is subject to debate, but it does not fly in my plane.
I guess you can reduce the timing advance a little
as a precaution?
�
Lycoming strongly recommends NOT using MOGAS.
Lycoming does know about auto gas and in fact
makes a very low compression O360 for flying in
third world countries to run on low grade fuel.
Unfortunately most 320's and 360's have 8:50:1CR
and need the 91/96 (100LL) gas.
If you are willing to test, haul and store your
own auto gas and run your engine on less than the
recommended octane, than OK, do that. If you have
a low compression engine than auto gas makes more
sense.
You may want to look into reducing your timing and
all the other things I mentioned about keeping the
fuel cool, that where somewhat ridiculed by the
MOgas experts. I would do everything I could to
assure no loss of power due to vapor lock.
�
If you have a 7:1CR engine than it is safer from an
octane stand point, as long as it does not have the
alcohol and ethanol. (However�ethanol�does increase�
the octane rating, see below).
If you get a load of ethanol gas you run the risk
of water contamination since it absorbs water. Once
airborne it cools the water comes out of the fuel
and water contamination result in loss of power.
Carb ice is more likely with ethanol (alcohol).
That is why it is important to test your auto gas.
Also ethanol is not compatible with the rubber
and gaskets used in aircraft and they will swell,
which has caused aircraft engines to stop in the
past.
These are facts. If you do go auto fuel please please
ask lots of questions of those who are experts in the
topic. I think we have a few on this list (seriously
I am not an expert but than I don't have to jump of a
bridge to know it might hurt when I hit the water. I
know if your engine stops while flying in a plane it
can be a bad thing. MOgas is NOT as good as
AVgas. The debate�is it good enough. May be.�
What I know about auto gas is enough to discourage
me.�
Ethanol does help octane so if you can get some
"sub grade" fuel before the distribution puts in
the additives, like ethanol you can expect a 5% hit
on octane. So basic fuel planned for 91 octane
with ethanol is really 89 octane without the ethanol. �
This is like 84 aviation.� To get "sub grade" you need
to get it at the distribution terminal before they add
the ethanol.
�
84 octane is not enough for higher compression 91/96
engines. If you have a 80 octane�O320 140/150HP Lyc,
than by all means go for it.
�
Some debate about reducing timing for the high
compression engines.
�
Lycoming is testing UL blends and the gas companies
are working on the 95UL as a 100/100LL replacement.
Remember there are more high compression than low
compression engines. Also the real fire breathing high
end�piston engines, turbo charged and so on NEED
the high end gas,�only make up 30% of the fleet but
use 70% of the gas.�So all you C65 & C85 engine
Piper Cubs are stuck using the 95 octane but with
the UL it should be OK.
IF I HAD an 80 octane engine AND the gas prices
kept going up I would consider auto gas it. (THERE I
SAID IT, ARE YOU HAPPY....)
As I said for the real world guy $400-$800 is about
what you can expect to save per year. Some of the
guys who live where fuel is cheap and ethanol is not
forced down their throat, good for them. If you have a
High compression engine and ethanol free fuel is hard
to find at the pump than not so good.
For the convenience of pulling up to the airport pump,
filling with very high octane fuel, with very high vapor
pressure and knowing there's no bad chemicals in it
with out having to test it, is worth it to me.
To each his own, I'll never say never but at some
point I just will not fly as much or at all, sadly.
Sneak preview the [url=http://us.rd.yahoo.com/evt=40762/*http://www.yahoo.com/preview] all-new Yahoo.com[/url]. It's not radically different. Just radically better.
| - The Matronics RV-List Email Forum - | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
Back to top |
|
 |
ogoodwin(at)comcast.net Guest
|
Posted: Fri Jul 07, 2006 5:01 pm Post subject: The TRUTH about MOGAS |
|
|
I haven't researched enough to know which has the higher vapor pressure...auto or aviation fuel...but the higher the vapor pressure, the more likely to vapor lock, not the other way around.� If indeed the auto gas has lower vapor pressure as you say, it would be less likely to vapor lock than avgas.
[quote] ---
| - The Matronics RV-List Email Forum - | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
Back to top |
|
 |
dsvs(at)comcast.net Guest
|
Posted: Fri Jul 07, 2006 5:01 pm Post subject: The TRUTH about MOGAS |
|
|
, snip
Quote: |
Auto gas has lower vapor pressure, which means it
is more susceptible to vapor lock.
>
Get it straight George. The higher the vapor pressure the more chance of vapor lock. And BTW av gas does have lower vapor pressure for that exact reason.
|
Don
| - The Matronics RV-List Email Forum - | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
Back to top |
|
 |
pcowper(at)webtv.net (Pet Guest
|
Posted: Sat Jul 08, 2006 11:38 am Post subject: The TRUTH about MOGAS |
|
|
The seasonal blending and geographical blending by automotive gasoline
refiners does have a significant effect on the operation of the engines.
When I was Terminal Superintendent of the Union 76 tank farms at San
Diego and Imperial (El Centro) Terminals back in the early 1980's, we
used to back haul the Imperial "desert gasoline" for the coastal San
Diego's California Highway Patrol during certain seasons of the year for
fuelling the 24/7 patrolcars that ran severe duty periods of idling and
high speed pursuits.
As engines used in aircraft adopt modern automotive computers utilizing
such monitors as temperature probes and O2 sensors, the engines will be
able to finely tune themselves as they encounter differing weather and
altitudes. With the 1930's technology of many of our Lycoming &
Continental aircraft engines, this thread has been informative with its
cautions and could prevent damage from unexpected power off landings or
even save some lives.
If a plane is based on a private strip at a rural home, farm or ranch
where automotive gasoline for vehicles and equipment can be delivered by
commercial tankwagon, the savings can be measurable if the automotive
fuel is found to be adequate for the aircraft engine.
Our local fairly busy airport, with commercial airline service on its
6,559 foot runway with ILS, only pumps 150,000 gallons of Aviation
gasoline a year. If this were a corner filling station pumping only
150,000 gallons in just a month - it would be facing closure for being
uneconomical. Refiners are making aviation gasoline more as a service
than a profit center. We need to continue to educate ourselves about
alternate fuels as aviation gasoline will no doubt have to change from
the currently available 100LL to a fuel that has other shared
applications to make it at least marginally profitable to produce and
distribute.
As to the flamers and naysayers . . . "Don't confuse me with the facts,
I've already made up my mind."
Pete Cowper
RV-8 #81139 (working on fuselage)
| - The Matronics RV-List Email Forum - | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
Back to top |
|
 |
Bill Schlatterer
Joined: 09 Jan 2006 Posts: 195
|
Posted: Sun Jul 09, 2006 7:34 am Post subject: The TRUTH about MOGAS |
|
|
Pete, just curious and you sound like someone who would really know so I
have a question. I understand adding the "local content" for season and
geography in the auto fuel side but I am under the impression that 100LL is
the same everywhere.
Is 100LL blended at the tank farms and then delivered locally, in which case
the transportation/distribution costs would be slightly higher or does it
come from one main refinery and then get trucked across the country in which
case the difference in price might be very recognizable?
Also wondered if 100LL and Jet goes through the normal pipeline distribution
system or is it land-hauled because of the extremely low volumes compared to
auto fuel?
We appear to have a pretty amazing system for auto fuel distribution but I
am wondering if there is a drastically different distribution cost to av
fuel?
Thanks Bill S
7a Ark
--
| - The Matronics RV-List Email Forum - | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
Back to top |
|
 |
aerobubba(at)earthlink.ne Guest
|
Posted: Fri Jul 14, 2006 4:04 am Post subject: The TRUTH about MOGAS |
|
|
HI Tim-
This is getting interesting and closer to answering my curiosity. What is
the "squish" you referred to?
glen matejcek
aerobubba(at)earthlink.net
| - The Matronics RV-List Email Forum - | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
Back to top |
|
 |
chaztuna(at)adelphia.net Guest
|
|
Back to top |
|
 |
aerobubba(at)earthlink.ne Guest
|
Posted: Sun Jul 16, 2006 5:31 am Post subject: The TRUTH about MOGAS |
|
|
Hi Charlie-
Thanks for the links. They gave me just what I needed-
glen matejcek
aerobubba(at)earthlink.net
| - The Matronics RV-List Email Forum - | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
Back to top |
|
 |
|
|
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum You cannot attach files in this forum You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|