Av gas

[RogersJetboat454]

Re: Av gas

If you care for your son, I would. There is a reason AV gas still has tetra ethyl lead in it instead of the now standard ethanol in auto fuels. That reason.... get ready.... moisture intrusion in the fuel! No boater has ever heard of this right? Whether you believe in phase separation or not is your deal, the FAA doesn't want to take the risk. Not a good thing when your fuel lines/carbs ice up in the much colder ambient temps at 13 thousand feet .....

 

[robert graham]

Re: Av gas

Probably true, but my son is twice as smart as me and takes no advice from the old geezer. Sound familiar? At least on the plane you're draining some gas from each tank and the fuel chamber under the engine before each take-off, at least that's what I always did, and you know what, there was always a few drops of water in that little clear plastic fuel sample bottle. Maybe he's counting big on the carb heater to save his butt, who knows?

 

[RogersJetboat454]

Re: Av gas

Lets hope that carb heater stays working .

I don't know much about the subject of small planes, only what a friend who owns a couple tells me.

He has both a Piper Cherokee Archer, and a float plane.
He is super anal about checking water content in the fuel before each flight.

 

[8hygro]

Re: Av gas

Am I better off running aviation fuel through my outboards? Im fed up with replacing floats. I have heard it has a higher lead content which could cause more build up but wouldnt that be better than using the garbage at the pumps? Thanks for any comments about using this...

The short answer...yes. Driving around the country and empirically testing pump fuel samples will blow your mind. There is absolutely no consistancy what-so-ever. It is not uncommon to see ethanol percentages exceed 20%.

LL100 is a spec fuel and tested accordingly. It is commonly sought out and used by numerous user groups because of its huge advantages compared to pump fuels. I know entire munincipalities that use it for maintenance equipment. It is a travesty what the general population is being burdened by because of the blended fuels. Were not splitting hairs here talking about light ends, end points and flame propagation...it's HUGE.

8hygro

 

[rodbolt]

Re: Av gas

short answer to AV gas in most outboards is NO.
leads to excessive carbon buildup,piston skirt deposits and a loss of WOT RPM.
most air craft engines typically run 9.0 and up compression ratios and typically turn less than 3000 RPM.
most 2 stroke outboards have relativly low,less than 8/1 compression,very short stroke from intake/ex ports closed to TDC and typically turn 5000+ RPM.
for a given compression ratio this means the higher the octane the slower it burns, at 5000 RPM its not finnished burning and leaves deposits.
most outboard fuel from land pumps at 87 octane will work fine if 87 is the callout for your outboard.
most 110 blue gas is blended to work from sealevel to about 20,000 ft above sealevel.
the reed vapor pressure and the water content must be monitored as fuel when very cold at altitute doesnt want to vaporize and can form system clogging ice crystals.
doesnt matter if its at sealevel or 20,000 ft, gasoline still MUST vaporize BEFORE it can burn and the A/F mix MUST stay between about 13/1 and 16/1 or the engine simply quits.
most boaters dont boat much above about 10,000 feet cause the water tends to get hard much above that altitude.
and yes this E scam is making millionares out of a few and killing the rest of us.
only thing worse than the E scam is the wind turbine scam.
however it makes a few feel good and a few very wealthy so all is well.

 

[8hygro]

Re: Av gas

Accepting the pump labeled octane ratings and blend ratios as fact is the first flaw. It is impossible to have a technical discussion based off data that is inacurate let alone constantly changing. The op's question basically boils down to one of the "lesser evils", as neither is optimum. Though it really is not "that" close. People have this misconception about supposed voodoo properties of Av gas (general term)...and I specifically referenced LL100 which many custom blenders use for many different applications at sea level. It does contain lead though it is be neutered as well.

The light ends of the fuel and end point are what are most applicable to our situation. The "light ends" are critical for throttle response (and starting) which becomes more important in an engine demanding good off/on throttle performance. These "light" components burn rapidly creating a chain reaction to the heavier components which do not vaporize/atomize as well. Short intake tracts, higher rpm design's and weakly controlled head/engine temps are most affected by the lack of "light ends". "End point" is the temperature of which the fuel burn's completely. If the fuel is not burned completely you have a myriad of issues from power loss, rinsed cylinders, deposits, overheating, detonation, emisions issues, etc. Pump fuels are made for engines with long intake tracts, controlled high temp chambers, computer controlled anti-knock (timing), pressurized fuel systems (atomization), catylist exhaust, etc. These designs allow the use of much less quality fuel/fuels and still perform. That is why nearly all engine design is heading the way of four stroke automobiles. It is because of the fuel people have access to. Anyone involved in engine R&D in the last 10 years has been fighting this let alone the mandated C.A.R.B and Fed requirements.

I do not care to debate this and have offered my .02. But many people are being financially hurt by this garbage and drivel coming out of the oem's does not help. Everyone is afraid of the boogeyman. The day will come shortly where we will have no choice and the engines we are clinging to will be door stops. But until then why not make life easier and cheaper if you can.

8hygro

 

[rodbolt]

Re: Av gas

leaded 110 octane aircraft fuel is simply a death knell for a modern 2 stroke outboard.
burns to slow,to cool and the lead tends to stick to things we dont want it sticking to.
two strokes dont have the fuel wash effect as the oil and fuel are both either blended or metered.
I agree with the poor quality control on the E blends.
in my area I have tested fuel samples as low as 5% and as high as 30% and the pump label says MAY CONTAIN as much as 10%.
trust me, an SX225 yamaha runs very bad on an E30 blend.
it also runs nasty on av gas cause they tried that too.
light ends, dark ends heavy metal anti-matter ends, its all irrelavent if the fuel cannot vaporize before its lit.
dont belive me, clog a filter or the injector nozzle on a TBI, or MPI just TBI is easy to see with eye balls, watch what happens when instead of a pretty cone spray the fuel starts dribbling in solid shots.
fuel rail pressure good,ECU engine controls good, engine simply runs like crap cause the fuel is solid not a vapor like it was designed.
from design concept to production a modern outboard may spend 4 to 7 years in transit, only to have the fuel used changed.
by then its to late.
E fuels and wind farms are the two biggest scams ever shoved down our throats yet the average idiot on the street thinks it may help.
its simply drivel.
could it aid certain areas and certain fleet vehicles? by all means.
as a stand in for the other 99% of us, its a scam thats making a few wealthy and whacking the rest of us.

 

[jay_merrill]

Re: Av gas

While it is correct that currently available avgas is called "100LL," it is not low lead in comparison to automotive fuels. It is low lead in comparsison to fomerly available aviation gasolines.

Its also a great deal more expensive than automotive fuel. You could buy a couple more carbs and pay someone else to constantly rebuild them and rotate them off/on your engine, for the difference in price between the two fuels over time.

Beyond that, there is no reason why you should have to do this. People run E10/E15 gas in outboards all over the country. As long as your fuel lines are up to snuff and you use modern floats, you should be fine.



???

 

[jay_merrill]

Re: Av gas

My son runs 93 octane automotive pump gas in his Cessna 172 whenever he can just to avoid the $5/gallon FBO aviation gas prices. It runs just the same, but the plane does have the advantage of a mixture control on the instrument panel and an exhaust gas temperature guage, so adjustments can be made in flight for altitude and efficiencies. The 87 octane pump gas is fine for most outboards. Why heck, the compression ratio on my 90HP 2 stroke is only about 6:1 Clean, fresh fuel is lot more important to an outboard than octane ratings. My $.02...

Tell your son to discuss what he is doing with an aircraft mechanic. 100LL is not a low lead gasoline in comparison to automotive fuel. My guess is that the mechanic will have a lot to say about expected TBO (time before overhaul) and the lubricating properties of lead in gasoline, in regard to valve guides, etc.



???

 

[8hygro]

Re: Av gas

leaded 110 octane aircraft fuel is simply a death knell for a modern 2 stroke outboard.
burns to slow,to cool and the lead tends to stick to things we dont want it sticking to.
two strokes dont have the fuel wash effect as the oil and fuel are both either blended or metered.

rodbolt...I respect your knowledge and desire to spend valuable time in helping others with it. People that are good at what they do are typically very passionate about it. The passion can be a funny thing especially when conveyed through this medium.

I do however disagree with all your above points concerning the use and propereties of LL100. Flame front propagation (burn speed) in the typical outboard is a mute point. I commonly tune engines that operate at peak efficiency above 9K rpm's and pump fuel pales in comparision to LL100 when it comes to every performance parameter. Actually, you cannot keep the two stroke's together using typically blended pump fuels when pushed. Piston temps are a byproduct of many parameters as well as engine/head temps. Fuel is metered/jetted to put piston temps where they are desired typically along with ignition mapping, everything else being sound. Production engine squish measuements and component flow quality leaves alot to be desired and is also critical. Lead does create deposits. But so does incomplete burned fuel, bad production tolerances (including alignment keyways), incorrrect/bad ignitions/settings, worn parts, etc. Modern day two stroke oils which are stoichemetrically correct can be mixed at 24:1 ratios with LL100 and be very clean after 30hrs of peak performance. Not that I condone this on the typicall outboard playing on the water.

Another thing not often mentioned is that many oem's have gotten away with peddling absolute junk with no hope for long term service regardless of the fuel used. There reliance on outsourced contractors and coorporate position of customer no-service has been criminal. The real shakedown is slowly happening and some oems once the labels are removed will go the way of the dinosoars...or should. We take everything apart right out of the shipping crates and it is crazy what is accepted practice in production today. I'm near retirement from my proffesion as well or it would be career suicide to even be participating in these forums. These companies have more zealous legal/ marketing resources than they do QC departments. The end user/customer is sadly just flat being hosed.

8hygro