An Observation About Using AvGas

[litefoot]

Generally these threads are a rehash of the usual.........whatever.

yep, and happens on every board I've been on.
Often a search would suffice but then there'd be 100 less threads a day :greenchainsaw:

I don't disagree with either statement. However, in the past I have been a proponent of using AvGas. Now, I'm observing performance issues that concern me a bit. So I wanted to state my personal experience. Wouldn't you agree that someone's real-world observations regarding this oft-rehashed topic might be of some value in the overall discussion?

Now where this thread has gone after my inital post is another issue altogether. LOL!

 

[Nitroman]

I don't disagree with either statement. However, in the past I have been a proponent of using AvGas. Now, I'm observing performance issues that concern me a bit. So I wanted to state my personal experience. Wouldn't you agree that someone's real-world observations regarding this oft-rehashed topic might be of some value in the overall discussion?

Now where this thread has gone after my inital post is another issue altogether. LOL!

Man I have seen so many threads like this on snowmachine forums (Snowmobilefanatics, Slednutz, Snowest and Hardcoresledder), bass-boat forums, now this forum....it goes on. Same-same stuff discussed. I ran the stuff in my air-cooled Polaris 440 GT for the 4 years I owned it, and I was the first person in this town to run it. So many people told me I'd burn down my sled...yakyakyak. I ran it in my 90hp Evinrude, 175hp Johnson, outboards no probs. I ran the stuff in my xcr-800 pulling 9000 rpm...no probs in temps from -27*F to +40*F (just have to change the jetting). I run it in my saws...no probs.

And

As I said above, on so many other forums...same-same theories, rumors and so on....and people running it with no probs.

So like I said...whatever.

I am building an inertial dynamometer which I intend to have up and running by the end of June. I will tell everyone what I find. I have crappy 87-rating here...well, I THINK it is 87. This stuff smells horrible and is purchased in Mexico by Crowley Maritime so you never know AND it sits in the bulk tanks for six months since that is how long the river is frozen. I will use 50:50, straight Av and then I'll beg some 100 and 110 and 118-rating from the local Polaris shop to see what the differences are. I'll run them in my dead-stock (I'll put a non-modded muff back on), Husky 394. We'll see.

Until then...whatever.

 

[Mad Professor]

Boats don't like ethanol either, you could try a marina for premium unleaded that is not corn fed.

If I could get that, I'd run that rather than AV gas, but I can't. When they phased in MBTE I brought a 55 gal drum of pump premium before the switch, and it lasted me quite a while.

I stopped using pump gas when they forced MBTE on us and ethanol is worse. If you can get stuff that is only 10% corn for sure and you are going to use it in a week or two with quality oil, no problem.

Concerning running richer, some of my saws do (036 038) , and some don't seem to care at all (028S, BR400 blower). In fact I'd say the 028 (stock) runs better on the AV gas and I've not touched the carb settings.

 

[ironman_gq]

on the Range up here in MN you can get it at a lot of stations they sell it to the boaters and snowmobilers and the pumps are always marked non-oxygenated and a sticker saying its not for on road use.

 

[Saw Dr.]

I don't disagree with either statement. However, in the past I have been a proponent of using AvGas. Now, I'm observing performance issues that concern me a bit. So I wanted to state my personal experience. Wouldn't you agree that someone's real-world observations regarding this oft-rehashed topic might be of some value in the overall discussion?

Now where this thread has gone after my inital post is another issue altogether. LOL!

Those of you running AVGAS just be careful. In my observation, it tends to run richer. I sold a saw a little while back that was tuned an run on AVGAS. It was a fresh rebuild. Fortunately, I checked up with the new owner a few days later. When he went back to the regular gas, it was running dangerously lean! I readjusted it and all is fine. I have also noticed the weaker idle. I am switching back to regular 93 in all my saws. Fuel lines and carb diaphragms are not that expensive.

 

[super3]

Remember dwell meters? Hope it has the adjustable distributor. I actually still have the little flexible allen tool for that.

I still have a dwell meter,one of those flex tools also. Used it last spring on an old Pontiac.

 

[backwoods12]

av gas

aint it lower octane and burns at diff temputure than premium

 

[wkpoor]

aint it lower octane and burns at diff temputure than premium

Yep its only 60octane and burns a lot hotter. It will burn up up anything you put it in.

 

[wigglesworth]

AVgas is obviously a much more highly refined, based on the clearness and odor, and I was told that the lead also helps in lubrication. I understand that you only need the octane for high compression and that the lead is added to bump the octane level up, but to cost power??? Until I see a side by side comparison of both, like a timed video, I will not totally buy the "100ll cost power" issue. Not flaming anybody, but a lot of assumptions floating around with no proof. I have been using it since last year some time and have not noticed any Idle problems. Heck some of my older saws idle better with it.

http://www.shell.com/static/au-en/downloads/aviation/avgas_100ll_pds.pdf

 

[BuddhaKat]

AVgas is obviously a much more highly refined, based on the clearness and odor, and I was told that the lead also helps in lubrication. I understand that you only need the octane for high compression and that the lead is added to bump the octane level up, but to cost power??? Until I see a side by side comparison of both, like a timed video, I will not totally buy the "100ll cost power" issue. Not flaming anybody, but a lot of assumptions floating around with no proof. I have been using it since last year some time and have not noticed any Idle problems. Heck some of my older saws idle better with it.

http://www.shell.com/static/au-en/downloads/aviation/avgas_100ll_pds.pdf

Lead is a lubricant, nothing more. The only reason it helps increase power is because it lowers the coefficient of friction.

Basically, the big thing about AV gas is that its burn rate is slower than what a chainsaw will throw at it. The fuel doesn't have time to finish burning, thus reducing power. By how much? I don't know. I'll let you know what I find out from using the C12 race gas this weekend.

 

[Nitroman]

Lead is a lubricant, nothing more. The only reason it helps increase power is because it lowers the coefficient of friction.

Basically, the big thing about AV gas is that its burn rate is slower than what a chainsaw will throw at it. The fuel doesn't have time to finish burning, thus reducing power. By how much? I don't know. I'll let you know what I find out from using the C12 race gas this weekend.

No, no, no. TET was used originally as an aide to reduce "knocking" or pre-ignition in crappy gas back when cars and planes starting coming into widespread use. Go to a local library and read some of the 1910-1930 National Geographics. It wasn't until the '50's and higher-performance engines using overhead valves found it worked very well (along with Stellite seats), as a lube to keep the valve seats from deteriorating. GM came up with a nifty valve rotator that rotated the valves while the engine was running that helped...a little.

This is the sort of mis-information and gobble-dy-gook that blows my mind.

 

[ironman_gq]

AVgas is obviously a much more highly refined, based on the clearness and odor, and I was told that the lead also helps in lubrication. I understand that you only need the octane for high compression and that the lead is added to bump the octane level up, but to cost power??? Until I see a side by side comparison of both, like a timed video, I will not totally buy the "100ll cost power" issue. Not flaming anybody, but a lot of assumptions floating around with no proof. I have been using it since last year some time and have not noticed any Idle problems. Heck some of my older saws idle better with it.

The odor you smell in gasoline has nothing to do with how well it is refined, the smell is added at the refinery so you can smell it if you have a leak same as natural gas or propane or acetylene. The higher octane av gas will burn slower and have higher knock resistance as well as lower volitility. with the slower burn an engine can run a lot more ignition timing to take advantage of it but in an engine that doesnt require the higher octane you will lose power becuase the charge isnt done burning by the time the exhaust port opens

 

[wigglesworth]

If I leave my carb settings set for pump gas, 100LL runs way rich. When I lean out the carb, RPM returns to normal. The only way I can see a drawback is if it actually makes less power at the crankshaft. If anything, my saw is using less fuel to get the same work done. Where is the power loss? Have I lost torque? Where is spacemule when you need him. LOL We need somebody show some cut times where 100LL is slower in the same saw as 93 in an unbiased test or else all is just purely speculation.

 

[PatrickIreland]

Isn't it always going to be less powerful on an unmodded saw, though? Higher octane means a slower burn, more fuel out the exhaust. Unless you can advance the timing/up the compression to take advantage of the high octane fuel, it should always produce less power on 100LL than pump gas?
A bit like the idiots who fill their shopping cars timed for low octane fuel with the best stuff they can find, thinking it will make it faster.
The only reason AvGas is of interest to me is the storage times...

 

[wigglesworth]

Something else I just read that was interesting is that AVgas octane is measured different than regular gas, and is 5 points higher across the board, that would mean that 100LL is actually 95 octane, in automotive terms.

 

[shortlid]

87 octane pump gas for modern stock saws right??

Stocks saws should use 87boctuane for the pre-mix right? I though higher octane can reduce there power??

 

[ckr74]

I'm still trying to figure out why a person would even consider AV gas in a saw. I've never had a gas storage problem. I let my saws and trimmers set for 6 months at a time with fuel in them. No problem here. No STABIL either. So then it must be performance. Not. High octane will not make a std. engine run better. Octane raises Flash Point therefore less HP unless compression and timing is are modified. Maybe we just get better gas in the midwest. Never had a problem.

 

[wkpoor]

No one here has even considered what the intended purpose of the fuel is to an aircraft engine. They are typically very low compression and air cooled. That throws out all the logic for the the octane and any heat hype. Everyone is wrapped around the axle over the octane level it its not a big deal. The octane and the lead content keep preignition at bay.

 

[PB]

Stocks saws should use 87boctuane for the pre-mix right? I though higher octane can reduce there power??

You should be using 90 or higher octane in your saws.

 

[PB]

Since we are on the topic of AV gas, has anyone used the Sta-Bil marine formula? It is supposed to be better at preventing ethanol based problems.