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AVgas and pump gas

D

deepsea diver

Well-known member
I sent my input while Rick was pulling the plug!!!!!

this what Jr Jurnigan told me IRT running pump gas in an O540. He said he builds motors to run on pump gas.(straight valve 260 hp) He states that you should get 1200 to 1500 hrs before you have to open up the engine for overhaul. He recomend running pump gas but you should run a tank of AVgas every 4 to 5 tanks. He states pump gas has no lead in it. He states that Avgas has lead in it. The Avgas with the lead will lubercate the top end better. It was designed to be that way. The lead protects and lubercates the top end but it also prolongs the gaskets and seals.

I am looking at buying a engine from Jr. I also plan on following his advise on when to change the oil and what type of fuel to run. His 0540's go for $9,500.00 and thats a lot of dough. The man knows what he is doing and he stand behind his motor.

BTW, some of those chem enginerers and scientist have a hard time walking, talking and chewing gun at the same time.

Kaos, weather you run straight Avgas, or a 50/50, or every 4 to 5 tanks seems like you will be okay.

Know a guy in Xmas that has 400 hrs on his Jurnigan motor and he only run pump gas. Still runs great on his 13 ft diamond back. It's the green boat, all Al, with the Bimini top. Front operator, side by side seating.
 
For every guy who runs pump gas there is a guy who runs avgas viceverse.....just fuel it up drive the hell out of it, and fix it in the offseason. .. When we come up with one that runs on Beer then we have a debate which kind it should be..
 
Deepsea, Jr. Jurnigan told me exactly the same thing ...... every few tanks run some 100L through it for the valves. A very small amount of Marvel all along the way might do the same thing.

He's a fine builder.

olf
 
If there is ever one to run off of beer then I would have to sell my boat. I just couldn't bear the strain of thinking all that beer going somewhere else. :D
 
I am running 0540 Angle Valve I run pump gas ever 15 gal add a bottle of octane it runs 10 degree warmer than Avgas and I run my boat hard :D
 
Have 3 0540 engines stock 260 parallel valve, HO 260 parallel valve, and 260/300 angle valve.
All will burn auto gas...see little or no noticable change in power...see increased temp on all...increased fuel consumption on all...why???

Grant
 
Leo,

OK understood about the difference in energy created.
Question...could it be that in a higher compression engine lower octane causes a slight detonation, thus reducing power causing you to burn more fuel?

Grant
 
Thanks...I was pretty sure that was the case.

I recently found this ...might explain why this octane in a/c motors seems confusing.
Octane ratings for aviation gasoline
have been rated differently than automotive
gasoline in that actual fuels
are tested in aviation engines. They are
rated according to an antiknock value
or “performance number� based on
octane values lower than 100-octane or
performance-rated for fuel rated at 100-
octane or higher.
The term 80/87 describes the observed
actual performances (resis tance
to detonation) when the engine is
operated with a lean condition (80-
octane) and then rich condition (87-
octane).
Automotive fuels are not rated in
this way but use an “antiknock index�
and an average of the research octane
method, and motor method.
The antiknock index posted on
autogas pumps is approximately five
points higher than the actual octane
rating of aviation fuel�thus an antiknock
index of 87 posted on an
autogas pump would equate to about an
“average� 82-octane aviation fuel.
Autogas STCs for 80-octane aviation
engines require a minimum of 87-
antiknock index.

Grant
 
Detonation is what will cause you to burn a hole in your piston, or detonate your motor. It will hammer the crap out of it!

I don't doubt that you'll lose some power production, but the damage to the engine is what scares me the most!

How about backing the ignition timing down some.
Won't that help provide some measure of safety when running pump gas guy's?

Some lycomings timing is to be set at 25 btdc. Some H.O. models are to be timed at 20 BTDC.

I assume Lycoming dictated that, to help control detonation under the leaner settings.
 
slowing timing down could probably help...my answer to the problem is to use the proper gas if at all possible...point I was getting at is I have never seen any savings running autogas...you're right engine damage gonna happen eventually.

Grant
 
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