Alterative fuels

[Gypo Logger]

Hi There, I found this article while surfing the net. Some of the posts are chainsaw specific.
John
http://yarchive.net/car/alternative_fuels.html

 

[Walt Galer]

Thanks Gypo,

I disagree with only one very small point, and that is the multiple ignition points comment. That happens in lean tunned compression ignition engines (diesel) but if it occurs in a gas engine, when the flame fronts meet, you get the condition known as detonation. This is when your piston developes a mysterious hole through it or you imbed bearings in their races, or parts break, etc. No small thing, the results.

As I mentioned in previous posts, I like to use 100 octane AVGas in demo chainsaws, especially in hot weather enviroments. I avoid 125 octane, and I retune of course. The saws have to be set back for return to the real world with regular gas, or someone will fry the engine. This is why I do not recommend the fuel for everyday use.

Again, when you go to the general aviation airport to get the fuel, you have to face the fear of the Government Nazi's however. The state is afraid you might use the stuff in your auto and try to duck their tax pile that they put on every gallon of auto gas. As if anyone would pay $2.25 per gallon or so to put it into a car. While you're at the airport, buy a bit of Jet 'A' fuel for your kerosene latterns or catalytic heaters. (This is white kerosene). The wicks will last longer, and it is usually cheaper than what they try to hit you with for regular kerosene at the service station.

Regards,
Walt Galer

 

[homelite360]

the only thing about avgas is that it is rated at that octane at 15000 feet above sea level. so 100 octane at sea level it is no better than 94 octane pump. the only benfit is the lack of road taxes.

 

[Walt Galer]

Howdy 360,

Sorry old boy, I'd have to disagree. The difference with 100 Av gas is great enough that you have to tune very significantly leanner. (Different stoiciometeric ratio, if you like two bit words).

It also means no vapor lock. The saw will start first pull everytime, even with intermitent demo use on a log pile in the sun in 90F weather, such as at the Louisville show.

All that is nice, but totally impracticle since if some yo-yo gets hold of the saw, and puts normal gas in it, and tries to do some work with it, It will be so lean as to burn up and sieze the piston/cylinder. When set up for AV-gas, you never let the saw out of your sight until it is tuned back to normal. This amounts to as much as a 1/4 turn of highspeed adjustment on most saws!

Regards,
Walt Galer

 

[Mouse trap Engineer]

Howdy Boys,

Walt is correct about the octane, Actually octane requirements decrease with altitude! One thing to remember about octane, its only functional use is to retard combustion in gasoline. Cetane does that part for diesel fuel. Now for the biggy, There are more BTU's in a gallon of 87 octane than there are BTU's in a gallon of 100 octane. HA HA i can hear it now, but yes you can and will go further on a gallon of 87 than you will a gallon of 100.


Johnny Scales

 

[HUSKYMAN]

Youre right Johnny, 87 octane will get you much farther than 100 octane, that is until there is a hole in the piston! Remember the saw will cut the best it ever has right before she welds the piston to the cylinder. Had a buddy riding an Artic Cat sno Pro, put some hot plugs in it and was amazed at how sweet it ran. 20 miles later the piston and head became one and that was all she wrote.

 

[Gypo Logger]

Animated two- stroke

Heres a description of a 2 stroke, but i dont believe the polution this if the engine is set up right.
john
http://www.keveney.com/twostroke.html

 

[Fish]

Huskyman,
I thought you all were claiming that engines run worse on regular
fuel, but there you just say it ran great right before it died.
I seriously doubt the octane of the fuel had anything to do with it.
Sounds like your buddy was an experimenter, so there were
probably many factors to his engine failure, and I seriously
doubt octane was one of them.
This "debate" on octane is really a non-issue, as I haven't seen
a plague on chainsaws that is attributable to octane, lean
seizures due to playing with carbs or problems in the fuel
system claim the majority of 2-cycles. But the guys around here that use saws for a living use regular with no problems, but
use whatever makes you happy.
Fish

 

[Rick Stafford]

I don't remember having fuel problems until the early 80's,Thats when sachs,husky,stihl,and many others started to encounter the "HOT RESTART PROBLEM".Back then I tried many different things to avoid the return of new saws that would'nt run when hot.I could'nt argue with the customers and no distributer knew what was going on !! I remembered then that we ran avgas in our racing jeeps when it was 95-100 degrees outside.So I called sachs-dolmar and asked if I could try aviation fuel at then 25:1.They laughed and said that I was afraid it would blow the cylinder head off and I was just looking for a way out of responsabilty.I said ya ???? right!Anyway LLOONNGG story made short is that the lowest aviation octane fuel is made from "good " stock and not all the ahlcohol and crap thats in our "gas" at the pumps.I mean ya don't see little cesnas falling out of the sky due to there fuel componets vaporizng the gas before it's time to fire.

 

[Harley]

Hey Mouse,

87 octane might contain more heating value, but it's not worth a darn when I increase my compression ratio by a point and run 100 octane. That way more of the heating value will be used instead of going out my tailpipe.


Here's somethin for you to chew on. How come alcohol makes power. Seeing as it has roughly half the heating value and burns colder. And for that matter what makes nitromethane worth using?

Harley

 

[bwalker]

when the flame fronts meet, you get the condition known as detonation.

Detonation has nothing to do with flame fronts meeting. Converging flame fronts can be a effect of pre ignition, but that is not deto. Detonation on a basic level starts as a normal combustion event that violently explodes just before the charge is done combusting. This rapid spike in pressure does some very bad things to a motor in a very quick manner. BTW what every happened to Walt?

 

[eyolf]

Bwalker:

Detonation has nothing to do with flame fronts meeting. Converging flame fronts can be a effect of pre ignition

I think you knew what you meant to say, but may I add this: Converging flame fronts can be a cause of knock. Multiple ignition points (as, say, from glowing carbon) can cause the converging flame fronts.

I believe Walt vacated the premises after a post of his was questioned by another netizen of this place. Probably a misunderstanding. You can read the gory details in "the great chain race" thread. BTW, hats off to Mr John L for trying hard to smooth ruffled feathers, and double to Mr. Art Martin for his incredibly graceful epilogue to the saga.

 

[bwalker]

I think you knew what you meant to say, but may I add this: Converging flame fronts can be a cause of knock. Multiple ignition points (as, say, from glowing carbon) can cause the converging flame fronts.

Eyolf, the "knock" you are talking avout is pre ignition, not detonation. Many people get these two confused , but they are very differant in nature.

 

[fun_chopper]

Fuel?

Avgas is way cool, it burns at a higher number of Brittish Thermal units than regular gasoline, because its highly refined, High octane Avgas is pale blue color when it comes down to it. Also Jet-a is a terrible idea for your kerosene appliances, it is higly volitile, and they add a stabilisation compound known as +100 that is highly corosive to steel, or any other ferrous metals. Not only can it blow you up, it has a higher flashpoint, and it vaporises at lower tempatures (83 degrees f). I recomend kerosene, or Jet b if you have to (much more stable). Dont mess around with aviation fuel its dangerous, and in the wrong hands someone can get hurt! This comment comes for a USAF Combat MC-130P Crew Chief, also a FAA rated Airframe and Powerplant mechanic, that has a FAA Pilots license. Please be careful, I have seen many people badly injured in jet fuel related mishaps!

 

[bwalker]

Av gas makes a excellant base fuel for playing around with additives like mtbe and propelene oxide because it is made from alkallayted hydrocarbons. Many small race fuel blenders actually start with av gas for a base.

 

[Rotax Robert]

I use 100 LL Av gas (Low Lead) on all my saws.. Stihls, Rotax and the Predator. I do believe that there is a gain to be seen in a saw that has at least a mild hopp-up. Without getting into all the tech talk of it I would say for the few extra bucks spent you get a cleaner more consistant fuel to work with. I just paid $2.40 a gal. at my local airstrip. I doubt going to race fuels of 110 to 119 octane would show you anything above what I run, infact it may reduce your saws performance.

 

[Crofter]

Alcoho

Harley Alcohol makes power because you can burn more of it in a given size cylinder. It has a lower btu content but only requires about an 8 to 1 air to fuel mix versus 15 to 1 for gasoline. It also has a higher octane rating than gas so can stand higher compression ratios and earlier ignition timing. Because it reqires more heat to vaporize it you have to use special manifold and carb heaters to prevent icing. Cold weather starting is dismal. It also doesn't mix with mineral oil either. Insist on Ethyl instead of Methy alcohol and mix about 3 to 1 with ginger ale. Don't put it in your saw! LOL!