Running chainsaws (and other twostrokes) on E85

[OM617YOTA]

According to this, ethanol only contains about 2/3 of the energy (67%) of gasoline per unit volume (say gallons), so E85 is only going to have about 72% of the energy per gallon compared to straight gasoline.

Start adding altitude losses (3% per 1000 ft elevation) and tuning losses and throw a dull chain into the mix and it ain't gonna be long before you gotta start burning some of that firewood to power your saw...

That's not how that works. The saw will make the same power as it would on gasoline, you'll just have to tune super rich and burn 1/3rd more fuel on E85 to do so.

 

[HansFranz]

Low nines...

 

[OM617YOTA]

Guess altitude doesn't matter when you've got all the oxygen you need in a bottle.

 

[HansFranz]

all the oxygen you need in a bottle.

"Supports combustion but not respiration..."

 

[camel2019]

Low nines...

Wonder how long a saw would last with that. In my experience cars with it can last a short time or long time before needing a new block.

 

[ericm979]

That's not how that works. The saw will make the same power as it would on gasoline, you'll just have to tune super rich and burn 1/3rd more fuel on E85 to do so.

The air/fuel ratio has to be something that's burnable. Usually that's a bit richer than the stoichometric ratio where there's exactly enough air molecules to burn all the fuel. Stoich for gas is 14.7:1 and for E85 it's 9.7:1.. which is conveniently 1/3 more fuel. If E85 contains 1/3 less BTUs then the power would indeed be a wash.

Turbo tuner cars that make a lot of power often run E85. The advantage is the higher latent heat of vaporization of ethanol (which cools the engine) and it's higher octane rating. Both of those allow more boost. For saws those would also allow higher HP via tuning but not the massive increases seen on turbo engines. Saws are limited by relatively primitive port design, short stroke (which leaves less time/area for ports) and lack of reed valves. If saw engines were made like 1980 MX motorcycle engines they'd make at least twice the hp.

 

[ihookem]

It might work real well. Ethanol has about 116 octane. Might work real well. it does not have the BTU content though. There is a reason the race cars down the road run ethanol. A guy down the road rebuilds the engines. He said the compression is about 16/1. This is where ethanol shines. It does not shine in a gas car with 8/1 compression.

 

[Patrick1903]

Saws are limited by relatively primitive port design, short stroke (which leaves less time/area for ports) and lack of reed valves. If saw engines were made like 1980 MX motorcycle engines they'd make at least twice the hp.

Don’t some saws use reed valves?

 

[KASH]

Lots of the older saws had reed valves.
Kash

 

[ihookem]

So why dont they make engines with a longer stroke? Have they not figured this out yet? I know the ECHO's have longer strokes and many say they have more torque, but have a smaller diameter bore. What are the advantages of a shorter stroke but wider bore??? Should one kind of saw have a shorter stroke and one have a long stroke? I've had some short stroke 8 cyl. " back in the day" and had a long stroke 1969 Oldsmobile 98 with the 455 Rocket with a 4 barrel. The engine was huge, the car was huge . But it got as much as 17 mpg on the highway. Amazing for those times. Should a limbing saw have a short stroke for quick revs and a bucking saw have the longer stroke for more torque?

 

[ChillyB]

E85 suitability started as a technical discussion but becomes a political discussion once politicians mandate that doing the correct thing should be expensive and difficult.

 

[ValleyForge]

E85 suitability started as a technical discussion but becomes a political discussion once politicians mandate that doing the correct thing should be expensive and difficult.

Yep…Doing the correct thing (buying no -ethanol gas) is both expensive and difficult….

 

[blades]

more like who is lining whose pocket. without subsidies to the farm for corn to ethanol or subsidies to produce ethanol it is not sustainable. Unfortunately it is the consumers who gets the shaft 3 times, inflated cost at pump, gas taxes(fed and State), income taxes diverted to ethanol via the subsidies

 

[ericm979]

So why dont they make engines with a longer stroke? Have they not figured this out yet?

I think it's for packaging reasons. All the things that make performance also make the engine larger and heavier. Longer stroke, nice fat curving transfers, modern V shaped reed valves, boost ports, and more than two transfers per side. They all take more room and metal. Adding power via a larger bore does not make the engine much larger.

Modern type reed valves are huge. Not like the little ones of old. They need to be big to get enough flow through the petals that don't open very far.

Especially in two strokes, engine powerband characteristics depend much more on the port design and timing (and exhaust and intake design) than on stroke length. An engine designer/tuner can make an undersquare (stroke longer than bore) engine super peaky with all top end power. It'll have a lower safe rpm limit than the more usual square or slightly oversquare engine but that is usually not an issue with two strokes anyhow.

 

[Wood Doctor]

Then there is the economic consideration. Nowadays the percent difference between E85 and E15 is not that great because both are priced sky high. Might as well run E15.

 

[Team FAST]

It's not uncommon to run kart racing engines on Methanol (M100) mixed with castor oil. That's even better than E85. The trick is with both fuels, you must run an oil that will mix properly with the alcohol. Some castors will not mix with alcohol at all, which would be very bad for the engine. Stoich for mehanol is down around 4:1 and so you often have to make fuel flow mods to the carbs to enable them to operate at significantly richer A/F mixtures. Methanol is very corrosive to Aluminum so after running the engine, you have to "pickle" it by running gasoline/oil through it as an after-run process.

On my stuff, there was a healthy 10-15% power increase. And the charge cooling effect is awesome too.

You can't beat the smell of Alky and racing castor either.

 

[Franny K]

It might work real well. Ethanol has about 116 octane. Might work real well. it does not have the BTU content though. There is a reason the race cars down the road run ethanol. A guy down the road rebuilds the engines. He said the compression is about 16/1. This is where ethanol shines. It does not shine in a gas car with 8/1 compression.

The octane rating of ethanol is rather variable upon an internet search. Here is a quote that mirrors yours. Sure your guy down the road does not run methanol?

Ethanol is reported as having an octane rating of 129 (RON) and 102 (MON), with a combined octane rating of 115 ((R+M)/2). Methanol reported as having an octane rating of 133 (RON) and 105 (MON), with a combined octane rating of 119 ((R+M)/2).

I believe the four valve per cylinder with the spark plug in the middle have higher compression ratios. My F150 has a flex fuel badge on the rear. The newer ones might be direct injection I think mine is less hp than the quote below.

The 5.0L V8 in the 2020 Ford F-150 is a naturally aspirated eight-cylinder powerplant from the modular engine line. With its large cylinder bore, 12:1 compression, and high-tech injection system, it generates 395 horsepower and 400 lb.-ft. of torque.

Two strokes the compression ratio can be counted using the volume of the whole stroke or the volume of the stroke once the ports are closed. I would guess that means exhaust port as opposed to transfer port or ports. Kind of have to know which for it to mean a lot.

 

[ihookem]

I'm pretty sure it was ethanol, I could be wrong, cause it was 8" yrs ago? However, I have no idea where they would get methanol around here.

 

[ValleyForge]

Then there is the economic consideration. Nowadays the percent difference between E85 and E15 is not that great because both are priced sky high. Might as well run E15.

I run E0…..

 

[Cricket]

It's not uncommon to run kart racing engines on Methanol (M100) mixed with castor oil. That's even better than E85. The trick is with both fuels, you must run an oil that will mix properly with the alcohol. Some castors will not mix with alcohol at all, which would be very bad for the engine. Stoich for mehanol is down around 4:1 and so you often have to make fuel flow mods to the carbs to enable them to operate at significantly richer A/F mixtures. Methanol is very corrosive to Aluminum so after running the engine, you have to "pickle" it by running gasoline/oil through it as an after-run process.

On my stuff, there was a healthy 10-15% power increase. And the charge cooling effect is awesome too.

You can't beat the smell of Alky and racing castor either.

Castor oil as a lubricant was used in many - maybe most - WWI military planes. Created some issues with pilots inhaling the fumes...