MoGas Long Term Test: 5000 gallons and counting...

In article ,
Jim Carriere wrote:

Jay Honeck wrote:
Yesterday I noticed that we had pumped more than 5000 gallons of mogas
through the Mighty Grape. This represents something like 60 complete fills
(our plane has four gas tanks, totaling 84 gallons), and around 350 hours
of
flight time over the last 2.5 years.

Awww, anecdotal evidence. Statistically speaking, you need a larger
sample size

But seriously, a good post, well documented.

'Couple questions-

Do you use the same spark plugs (and same heat range) as before going
to mogas?


I do, too -- plugs last longer without the lead in the fuel.



Do you lean, and how lean? What kind of numbers do you usually see
in different regimes of flight (EGT, CHT)? Obviously detonation
hasn't been a problem for you, I'm curious how hot you can get away
with on that engine with regular auto fuel.


Detonation is NEVER a problem when the octane is correct. If the engine
is designed for 80 octane, it will happily drink 80 octane mogas or
anything else that meets the minimum spec. The absence of lead in the
fuel simply means that there is less junk to scavenge out of the
combustion products.

BTW, how many out there are aware that 80 octane unleaded avgas used to
be available, back in the 40s and 50s?

--
Remove _'s from email address to talk to me.

BTW, how many out there are aware that 80 octane unleaded avgas used to
be available, back in the 40s and 50s?

--


Actually I think it was available up into the mid to late 70s...

80/88, and it was colored Red...

BT

BTIZ wrote:

Actually I think it was available up into the mid to late 70s...

80/88, and it was colored Red...


Red gas was available in some places until fairly recently
(historically speaking). My airport was selling it right up until
2002.

Oddly enough, I saw some red gas the other day. My tiedown
neighbor owns a 150 that never flies. Every few years, he spends
several thousand on an annual and maintenance, then ends up not flying.
The cycle repeats every other year.

Just the other day he had a team of A&Ps and IA surrounding the plane
on the ramp, getting it ready to fly again. He's finally selling it.
When he sampled the fuel and it came out red colored, everyone on the
ramp just busted out laughing. We figured he had the last surviving
example of 80/87 aviation gas in the country. Too bad such rarity
doesn't make his ramp queen worth any more :-(

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


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

I got my last tankful of 80/87 at RBL about November of last year,
awhile after the last refiner stopped producing it. It had become a
rarity over the last ten years or so - you had to know where to go to
get it.

David Johnson

: Detonation is NEVER a problem when the octane is correct. If the engine
: is designed for 80 octane, it will happily drink 80 octane mogas or
: anything else that meets the minimum spec. The absence of lead in the
: fuel simply means that there is less junk to scavenge out of the
: combustion products.

That's not completely true. Some engines are marginal on their rated fuel (in
particular, fire-breathing TGSIO-ABC-XYZ-540's putting out 350 hp or whatever). Even
some planes could be marginal on their rated fuel in the worse possible condition.
For example, long climb, just under redline CHT, fuel at the bottom of the permissible
octane rating, carb float/jets at the leanest possible configuration, etc, etc.

The bigger variable is that autofuel does not use quite the same rating as
avgas. Autofuel (in the U.S. anyway) uses an (R+M)/2 rating, or anti-knock-index
(A.K.I). The point spread between the two is not published, but is generally about
\pm 5 points, with the lower (motor) most closely similar to the aviation method.
Basically, that means that 87 AKI autogas is probably about 82 motor, 92 research.

-Cory

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