Question about auto gas STC

"Jay Honeck" wrote in message
news:1cMvc.36339$pt3.35172@attbi_s03...
We had create luck with autogas in the Chief. Kept the engine clean.
The lower octane really makes things run nicer too. 100LL would crud
up the works pretty fast. This is especially bad for those planes that
don't have a mixture control.

I paid $3.30 a gallon for Avgas in Ankeny today!

I paid $1.92 for mogas in Iowa City yesterday.

The math is self-evident -- mogas is the way to go!

BTW: What planes don't have mixture controls? (Beside turbines and
jets?)

Most of the Bendix/Stromberg carburetors have the mix controls wired full
rich. These carbs are found on C-85's and A-65's which power the small
aircraft like Cubs, Luscombes, Taylorcraft, Aeroncas, etc.

Even if the mixture control on a Stromberg is operative, it's ordinarily
impossible to starve the mixture. The leaning process does not occur until
the engine is turning at 1500 rpm or above.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

MikeM wrote:
: Aaron Coolidge wrote:
: I paid $2.29 for 93 octane premium unleaded in Mansfield the other day.
: I paid $2.60 for 100LL in Columbia County, NY (1B1) the other day.
: For me, the math is self evident, but the other way! (Break even with STC
: costs @ 10000 gallons or 1000 hours!)

: Something is wrong with your math.

: @ $0.31 price difference per gallon, it would only take 741 gallons to
: pay for the $230 STC (O470, 230HP, $1 per HP).

: My price difference between 100LL and 86 Octane autogas has typically been
: $0.75 to $1 per gallon. I figure that between overhauls of my engine (~2000
: hours, buring 12 gph), I saved a minimum of 12 * 2000 * 0.75 = $18,000,
: which is what the last overhaul cost...

: MikeM

Ah, to have a low compression engine. My plane is a Cherokee 180, with a
"high compression" O-360. The autofuel STC is very involved. You need to
replace the electric fuel pump with 2 different electric fuel pumps. You need
to re-plumb the left (or was it right) fuel tank with larger pipes. You
replumb the fuel selector to engine with larger pipes. You replumb the flex
hoses with larger flex hoses. You then can burn *91* Octane car fuel.
As Cory P. pointed out, the detonation margins on 91 octane are small. So,
you'd probably end up using 93 octane. The fuel tanks are placarded for
"91/96 Octane Minimum".

By the way, the STC is $2000 for this plane, with 40 hours of install time.
Saving $0.30/gal takes a lot of gallons to even pay for the STC.

I also live in an area where carrying fuel in containers is legally
challenging. You're allowed a max of 2, 5 gallon containers without hazmat
placards, etc. Besides, the oil companies seem to have choses this area
to test their "Los Angeles" style pricing!
--
Aaron Coolidge

MikeM wrote:

Something is wrong with your math.

@ $0.31 price difference per gallon, it would only take 741 gallons to
pay for the $230 STC (O470, 230HP, $1 per HP).

Perhaps he's also including the cost of the rig Jay bought and built to haul
gasoline.

George Patterson
None of us is as dumb as all of us.

" jls" wrote in message
...

"Jay Honeck" wrote in message
news:1cMvc.36339$pt3.35172@attbi_s03...
We had create luck with autogas in the Chief. Kept the engine clean.
The lower octane really makes things run nicer too. 100LL would crud
up the works pretty fast. This is especially bad for those planes that
don't have a mixture control.

I paid $3.30 a gallon for Avgas in Ankeny today!

I paid $1.92 for mogas in Iowa City yesterday.

The math is self-evident -- mogas is the way to go!

BTW: What planes don't have mixture controls? (Beside turbines and
jets?)

Most of the Bendix/Stromberg carburetors have the mix controls wired full
rich. These carbs are found on C-85's and A-65's which power the small
aircraft like Cubs, Luscombes, Taylorcraft, Aeroncas, etc.

Even if the mixture control on a Stromberg is operative, it's ordinarily
impossible to starve the mixture. The leaning process does not occur
until
the engine is turning at 1500 rpm or above.

Never the less it is an effectivfe mixture control despite what many people
think. Idle cutoff has nothing to do with effective mixture control.

Aaron Coolidge wrote:
By the way, the STC is $2000 for this plane, with 40 hours of install time.
Saving $0.30/gal takes a lot of gallons to even pay for the STC.
I also live in an area where carrying fuel in containers is legally
challenging. You're allowed a max of 2, 5 gallon containers without hazmat
placards, etc. Besides, the oil companies seem to have choses this area
to test their "Los Angeles" style pricing!

Exactly. In addition to 180s, 160hp O-320s are also included (like
Warrior 161s or Cherokee 140s modified to 160hp).

--- Jay


--
__!__
Jay and Teresa Masino ___(_)___
http://www2.ari.net/jmasino ! ! !
http://www.oceancityairport.com
http://www.oc-adolfos.com

"Dave Stadt" wrote in message
y.com...

[...]
Most of the Bendix/Stromberg carburetors have the mix controls wired
full
rich. These carbs are found on C-85's and A-65's which power the small
aircraft like Cubs, Luscombes, Taylorcraft, Aeroncas, etc.

Even if the mixture control on a Stromberg is operative, it's ordinarily
impossible to starve the mixture. The leaning process does not occur
until
the engine is turning at 1500 rpm or above.

Never the less it is an effectivfe mixture control despite what many
people
think. Idle cutoff has nothing to do with effective mixture control.

You are correct. I use my mixture control on my Stromberg every time I
fly. A Stromberg aficionado in the 120/140 group has published all kinds of
helpful material on the Stromberg, including how to set up a longer mixture
lever for better, more accurate control.

Amen to that... I waffled for awhile, but ended up buying the STC for ours.
I've got an A&P/IA that worked with me, so I did most of the install. It was $1500
when we did it a year ago (it had gone up from $1100 the preceeding year... DOH!).
Since I did the labor, that's about all it cost. Around here (SW-VA), "premium" is 93,
and "mid-grade" is 89... so there's only one choice. Also, 93 is $1.99 right now
(less $0.125 road-tax rebate), and base-rate 100LL is $2.50. It still makes sense.
Last year I flew 150 hours, and the fuel price difference was even more so and I've
already paid for the STC.

I've pretty much convinced myself that it's fine on the engine. In cruise,
there's absolutely no question that it's fine. If I'm flying locally, I can fly 2
hours on a single tank without making a wing too heavy. Then I don't even use any
100LL except for takeoff. It was perfect for instrument training.

Another noteworthy point is that field elevation here is 2100'. The DA is
typically 3500-4000' in the summer, when detonation potential is highest. Going
'full-rich' is *WAY* richer than necessary under those conditions and gives a bit more
margin. It's a noticable decrease in power full-rich, though.

YMMV
-Cory

Aaron Coolidge wrote:
: Ah, to have a low compression engine. My plane is a Cherokee 180, with a
: "high compression" O-360. The autofuel STC is very involved. You need to
: replace the electric fuel pump with 2 different electric fuel pumps. You need
: to re-plumb the left (or was it right) fuel tank with larger pipes. You
: replumb the fuel selector to engine with larger pipes. You replumb the flex
: hoses with larger flex hoses. You then can burn *91* Octane car fuel.
: As Cory P. pointed out, the detonation margins on 91 octane are small. So,
: you'd probably end up using 93 octane. The fuel tanks are placarded for
: "91/96 Octane Minimum".

: By the way, the STC is $2000 for this plane, with 40 hours of install time.
: Saving $0.30/gal takes a lot of gallons to even pay for the STC.

: I also live in an area where carrying fuel in containers is legally
: challenging. You're allowed a max of 2, 5 gallon containers without hazmat
: placards, etc. Besides, the oil companies seem to have choses this area
: to test their "Los Angeles" style pricing!
: --
: Aaron Coolidge


--
************************************************** ***********************
* The prime directive of Linux: *
* - learn what you don't know, *
* - teach what you do. *
* (Just my 20 USm$) *
************************************************** ***********************

Jay Masino wrote:
: Exactly. In addition to 180s, 160hp O-320s are also included (like
: Warrior 161s or Cherokee 140s modified to 160hp).

Actually, the 140's modified to 160 rarely quality. The cowling style must be
the later clamshell fiberglass version with the dual exhaust. If it's just a 140/160
with the flip-up style aluminum cowling, it doesn't qualify for the STC. Too hot back
by the muffler on the firewall.

The part that really irks me is the reason for the dual fuel pumps is
inadequate fuel flow. The logical problem is that raising the compression ratio of an
engine DOESN'T CHANGE THE FUEL FLOW! It's an O-360... it suck/squeeze/bang/blow's 360
CI of mixture every cycle... it's just that a higher CR gets a bit more bang out the
bang part. I could see the muffler issue (hotter EGT with higher CR). If a Cherokee
150's (lower compression 160 with clamshell cowling) fuel pump is adequate for the
low-compression STC at $1/hp, putting higher compression pistons doesn't change that
in the slightest.

Yet another way the FAA is keeping you safe by being inconsistent with
physics, but consistently performing CYA.

-Cory

--
************************************************** ***********************
* The prime directive of Linux: *
* - learn what you don't know, *
* - teach what you do. *
* (Just my 20 USm$) *
************************************************** ***********************

wrote:
Jay Masino wrote:
: Exactly. In addition to 180s, 160hp O-320s are also included (like
: Warrior 161s or Cherokee 140s modified to 160hp).

Actually, the 140's modified to 160 rarely quality. The cowling style must be
the later clamshell fiberglass version with the dual exhaust. If it's just a 140/160
with the flip-up style aluminum cowling, it doesn't qualify for the STC. Too hot back
by the muffler on the firewall.

Wow. That's interesting to know. I wonder if a modified/160hp 140, with
the Powerflow exhaust would qualify. The muffler is outside the cowling,
and the collector assembly is in the front, underneath the engine.

--- Jay



--
__!__
Jay and Teresa Masino ___(_)___
http://www2.ari.net/jmasino ! ! !
http://www.oceancityairport.com
http://www.oc-adolfos.com

wrote:

Yet another way the FAA is keeping you safe by being inconsistent with
physics, but consistently performing CYA.

The FAA has nothing to do with it except as the issuer of the certificate. People
like EAA and Petersen work with one of the plane/engine combos until they get it to
run reliably on car gas. These people have determined by empirical experiment that
these modifications are necessary.

George Patterson
None of us is as dumb as all of us.