Premium ethanol gas vs. pure regular unleaded

[Andyshine77]

Uhhh I didn't say 175psi = 10:1 :bang: Not sure where you got that???? Just said if your saw is stock and blowing less than 175 psi it should be fine with the 87 ethanol free gas... I suppose I can add that would be in any stihl or husky saw from 50-90cc mid 80's or newer I'm sure if you look hard enough you can find some special application 2 stroke with a wacky bore and stroke that might not apply but who really cares? oke:

I was using 10:1 as an example. Generally, engines with high compression ratio (10:1 and higher) have less resistance to detonation and require high octane gas. The trapped method is preferred in coming up with a true compression ratio in a piston ported two cycle engine. I was simply trying to say what applies to a four stroke engine doesn't always apply in two strokes. IE a four stroke engine compression = volume at BDC over volume at TDC. You can't do this in a piston ported engine because the exhaust is open for a time during compression stroke. All of this is dependent on volumes, stroke, port timing and so on. The last numbers I saw from someone a lot smarter than I, showed a 50cc saw with 165psi had a compression ratio of about 7:1 because it had too much exhaust duration. Using the normal four stroke method it was like 14:1 which is false. Saw engine are not high performance engines, they are made to run on just about any pump fuel you can find. You need to get to 200psi in a saw before you start having issues with pump fuel IMHO.

Take this for what it is, I'm no expert and I still have a lot to learn.

 

[J.W Younger]

Saws have so much EGR, detonation ain't likely to happen. Preignition, maybe. Wonder how much 2.5 ounces of oil drops a gallon of 87 octane...

 

[Scooterbum]

I was using 10:1 as an example. Generally, engines with high compression ratio (10:1 and higher) have less resistance to detonation and require high octane gas. The trapped method is preferred in coming up with a true compression ratio in a piston ported two cycle engine. I was simply trying to say what applies to a four stroke engine doesn't always apply in two strokes. IE a four stroke engine compression = volume at BDC over volume at TDC. You can't do this in a piston ported engine because the exhaust is open for a time during compression stroke. All of this is dependent on volumes, stroke, port timing and so on. The last numbers I saw from someone a lot smarter than I, showed a 50cc saw with 165psi had a compression ratio of about 7:1 because it had too much exhaust duration. Using the normal four stroke method it was like 14:1 which is false. Saw engine are not high performance engines, they are made to run on just about any pump fuel you can find. You need to get to 200psi in a saw before you start having issues with pump fuel IMHO.

Take this for what it is, I'm no expert and I still have a lot to learn.

Now my head hurts
I'm going to another thread..........

 

[Cliff R]

No worries using 93 octane with 10 percent ethanol. I run the stuff in all my 2 stroke power equipement, and in my GTO which has a 455cid engine with 11 to 1 compression. Never the first problem one with any of it, you must have to know how to tune them. Here's a clip from the Tri Power Nationals a few weeks ago, semi-final round:

69tiger's Channel - YouTube

I know it's not a chainsaw, but that engine makes over 550hp and runs on a steady diet of 89 octane pump gas with 10 percent ethanol. I blend in some 93 when I go to the track......Cliff

 

[J.W Younger]

No worries using 93 octane with 10 percent ethanol. I run the stuff in all my 2 stroke power equipement, and in my GTO which has a 455cid engine with 11 to 1 compression. Never the first problem one with any of it, you must have to know how to tune them. Here's a clip from the Tri Power Nationals a few weeks ago, semi-final round:

69tiger's Channel - YouTube

I know it's not a chainsaw, but that engine makes over 550hp and runs on a steady diet of 89 octane pump gas with 10 percent ethanol. I blend in some 93 when I go to the track......Cliff

The main reason that eng don't eat itseff on pump gas is the cam, low gears and loose covertor. Put the stock cam,12" convertor and some 308s back in it and see how it does on 89 octane.
I doubt any amount of tuneing is gonna save a 2-stroke once the oil has seperated.

 

[Cliff R]

That car uses 3.42 gears and the converter is a custom part that is locked nearly solid above the stall speed, and about as "tight" as a stock converter for "normal" driving.

The cam has EVERYTHING to do with it, and combined with correct tuning, is the key to managing currently available pump fuel at high compression ratios.

For two stroke power equipment, most of it ends up here not running because folks leave fuel in them for many months, and often years without running them, or draining out the old fuel. Most don't know jack crap about correctly setting the carburetor "H" and "L" screws, and just run saws till they give troubles, with zero work on them other than an occassional chain tightening or replacement. I make a nice living because folks are not doing their maintenence like they should be......Cliff

 

[J.W Younger]

That car uses 3.42 gears and the converter is a custom part that is locked nearly solid above the stall speed, and about as "tight" as a stock converter for "normal" driving.

The cam has EVERYTHING to do with it, and combined with correct tuning, is the key to managing currently available pump fuel at high compression ratios.

For two stroke power equipment, most of it ends up here not running because folks leave fuel in them for many months, and often years without running them, or draining out the old fuel. Most don't know jack crap about correctly setting the carburetor "H" and "L" screws, and just run saws till they give troubles, with zero work on them other than an occassional chain tightening or replacement. I make a nice living because folks are not doing their maintenence like they should be......Cliff

Ain't no doubt stupid kills more saws than ethanol.

 

[Cliff R]

+1

And like my buddy Tim reminds me nearly every day....."you can't fix stupid"!.......Cliff

 

[nmurph]

No worries using 93 octane with 10 percent ethanol. I run the stuff in all my 2 stroke power equipement, and in my GTO which has a 455cid engine with 11 to 1 compression. Never the first problem one with any of it, you must have to know how to tune them. Here's a clip from the Tri Power Nationals a few weeks ago, semi-final round:

69tiger's Channel - YouTube

I know it's not a chainsaw, but that engine makes over 550hp and runs on a steady diet of 89 octane pump gas with 10 percent ethanol. I blend in some 93 when I go to the track......Cliff

Thanks for the ride-along. It wasn't exactly the Goat I was thinking of, but I do remember those GTO's. My brother bought a new 70 GTO Ram Air IV when he was 16.

 

[J.W Younger]

I pumped this yesterday and added 2 measured oz waterView attachment 197875
Not very scientific but it gives me some idea of what I'm getting.

 

[ncvarmint]

is there any way to tell if you have ethanol blended gas without buying a test kit. There is a station near me that says he sells 95octane ethanol free gas.
thanks
trevor

 

[J.W Younger]

is there any way to tell if you have ethanol blended gas without buying a test kit. There is a station near me that says he sells 95octane ethanol free gas.
thanks
trevor

Look at that jug on the back of my truck, the jug is full. Just 2 oz of water caused that on the bottom to fall out of the mix. Ethanol at 10% ain't the problem, its staying at that % in an underground tank exposed to air. When the alchol reaches its saturation point it will fall out and go to the bottom.

 

[Outlaw5.0]

The main reason that eng don't eat itseff on pump gas is the cam, low gears and loose covertor. Put the stock cam,12" convertor and some 308s back in it and see how it does on 89 octane.
I doubt any amount of tuneing is gonna save a 2-stroke once the oil has seperated.

Great post. Plus accelerating down a drag strip allows more timing on lower grade fuel. Its called transient accel vs steady state. Steady state loads will cause engines to go into to detonation way before acceleration type loads on lower octane fuel . Our chainsaws are run steady state for most of the time, this is why Stihl recommends atleast 89 octane. I run a engine dyno for a living, so I see quite a bit of fuel testing and detonation damage.

 

[JustinM]

I can not tell any difference in the running of my saws between 87, 91, eth, or non-eth.

And I've run a bunch of all of it. :msp_unsure:

To be honest, Fish, I dont see a lot of difference either - at least not in how the saws handle/run. However, since i can get a 93/94 octane which is ethanol free for a few bucks more per 10 litre jerry can, I just do it. Sometimes its just easier to be safe vs. sorry in the long run.

 

[Cliff R]

"Great post. Plus accelerating down a drag strip allows more timing on lower grade fuel. Its called transient accel vs steady state. Steady state loads will cause engines to go into to detonation way before acceleration type loads on lower octane fuel . Our chainsaws are run steady state for most of the time, this is why Stihl recommends atleast 89 octane. I run a engine dyno for a living, so I see quite a bit of fuel testing and detonation damage."

Correct, however, my engines are well thought out, and use tight quench, modern combustion chamber designs, and very well chosen camshafts. I also know how to tune them, and have full control of the timing and fuel curves. I dyno all of them BEFORE placing them in service. The dyno certainly loads the piss out of them, and we don't see any detonation anyplace with "normal" timing settings, and I don't try to add more timing when we go to the track.

As far as detonation and two stroke engines, or any reciprocating engine, they are most likely to detonate at peak torque, not peak HP. Peak torque is where the highest dynamic compression occurs, so cylinder pressure is high, and engine rpm's low. Past peak torque, the events happen more quickly, and the cylinder filling abilities of the engine fall off as there is less time involved for cylinder filling(more cycles per second). This is where engine design, port timing, and port volume come into play. The idea is to produce a strong/broad power curve, without raising dynamic compression at any point too high for the octane the engine will see. Pretty tricky stuff, but the engineers seem to have a pretty good handle on it, as I've never seen any chain saw engine destroyed strictly due to detonation. Most P/C damage occurs from not enough lubrication, and A/F ratios too lean at high rpm's, or combinations of both.

Despite the bad publicity these new fuels get, we have had ZERO issues using it in anything. Ethanol has both good and bad qualities, but at 10 percent isn't a problem for 2 stroke power equipment, at least from what I've seen here.

What I have seen here, is every single piece of power equipment we've worked on, required custom carburetor settings a tad richer than what they were as delivered from the factory, no exceptions.

Echo stuff is the WORST, and probably why we continue to see bellyaching about smoked P/C's and "anemic" for power production. If you have an Echo chainsaw, remove the limiter caps and throw some fuel at it. You will be rewarded with easier start/warm-up, and stronger power at every rpm. Ya, I know, probably voids the warranty, but it's unlikely you'll need it and the saw will love you for it......IMHO.....Cliff

 

[Red Elm]

is there any way to tell if you have ethanol blended gas without buying a test kit. There is a station near me that says he sells 95octane ethanol free gas.
thanks
trevor

Yes there is Trevor, and it's very easy to do. All you need is a tall narrow clear glass bottle with a cap (an olive jar works great), and a permanant marker like a sharpie. In the clean bottle put in about an inch of water, tap water is fine. Set the jar on a level surface and then with the marker put a mark on the side of the jar at the waterline. Next, fill the jar to within an inch or so of the top with the gas you want to test and put the lid on tight. Now shake the contents for a few minutes and then let it sit on the level surface for 10-15 minutes (rarely takes this long). If there is alcohol (ethanol) in the gas it will leave the gasoline and combine with the water. The "water" level will now be above the mark on the jar.

This is how ethanol can ruin a saw. In a mix of ethanol enriched gasoline and saw lubricant, we have alcohol, gasoline and lubricant. The gas and lubricant want to be together because they are both petroleum based. The alcohol stays with them basically because it has no other option at this point, and alcohols will stay suspended in petroleum. If any water (ie condensation) enters this mixture the alcohol prefers to blend or bind with it and seperates from the gas and lube. When this alcohol goes into the cylinder it will usually fire but carries no lubricant with it and a scored piston and/or cylinder is the result.

You can also test suspect saw mixtures of gas and lubricant with the same method.

 

[nmurph]

Pouring water in a jar and shaking it is quite different than what happens to fuel exposed to the humidity in the atmosphere. There is little transfer of water into the fuel even at high ambient humidities. Further, the amount of water that 10% ethanol gasoline can absorb is very small.

 

[Roofgunner]

Heat

Question: Does ethanol laced fuel run hotter than non-ethanol fuel all other things being equal??

 

[Dalmatian90]

Saw Troll's post made me go look it up:

Aspen 2 alkylate petrol - Aspen alkylate petrol - Environmental fuels - Motor racing fuel & racing oil from Anglo American Oils UK: Suppliers of high performance motor sports fuels - oils & Lubricants.

Looks like it's roughly $28 for 2.5 gallons.

Non non-ethanol gas around here. It's all required to be oxygenated (archaic law from the days of carbuerated cars), when they banned MBTE everyone switched to ethanol.

 

[Cliff R]

"Heat
Question: Does ethanol laced fuel run hotter than non-ethanol fuel all other things being equal??"

If anything it would run slightly cooler. This assumes tune was correct once the switch to the 10 percent ethanol was made.

From what I see here in automotive applications, it takes about 5 to 7 percent more E-10 to do about the same thing as straight gasoline. For E-85, about 30 percent more. Users of E-85 also report that they MUST keep their engines fully warmed up, and fully heat soaked or performance suffers considerably. They also report that their engines run very cool on E-85 as compared to gasoline. With this in mind, one should consider that the possibility of lube oil dilution exists, as the more difficult to burn ethanol may tend to "wash" the cylinders some on cold starts, thru warm up cycles.

E-10 has good and bad qualities. Absorbing water was mentioned, but it also evaporates very quickly. In a carbureted automotive application, with a vented system, you've got about 5-7 days after shutdown before the carb is empty. Of course a carburetor with a huge bowl capacity would take a bit longer, and smaller bowl capacity a bit less, but the overall average is about a week from what we've seen.

To date I've had zero issues here with E-10 and two stroke power equipment. I make sure every piece of equipment is used or at least started and warmed up every month or so, and I use up the mix often enough it never stays around to loose octane or settle out, absorb a lot of water, etc......Cliff