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Discussion Starter #1
Last winter picked up two blowers, Simplicity 8-60 8hp and an older Ariens 6hp both with Tecumseh's. The Simplicity after a overhaul, grease job, carb clean- runs like a champ, the Ariens ran OK. Decided to look into an ignition upgrade to solid state. After waiting for parts forever, installed a new coil and a Nova2 module, had a problem with no power, spitting, general running like crap. After trying to find a timing problem, finally switched over the pos/neg terminals on the module and night turned to day- runs very well. From the reading I found on switching ignition, I was under the impression that the engine would either run or not if the wiring was wrong, also the complaints of hard starting by hand are true- since I also found a deal on a oe electric starter, this is a non issue. On small engines I prefer to use premium fuel, and with timing advanced seems to run fine.
Very pleased with the results and looking forward to testing out next winter.
 

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The "Nova" brand is not that good. There are others that look like the Nova and are much better. Stens has a good module that is better than the "Nova".
As for premium fuel, high octane gas has a slower burn requiring more timing advance to make it fire and burn more completely. Small engines do not have enough timing advance and are of low compression to need high octane fuel. The only thing high octane fuel will do is cause hard starting, and cost you more money. Actually give you less power and lower fuel "Mileage".
Sometimes the ignition system will advance slightly with higher speed on certain model engines, so you would have to spin the engine over much faster to get it to fire hard enough to keep the engine running.
Low or regular octane gas has a faster more complete burn to make starting easier, give more power with a more complete burn in the cylinder, more volumetric BTU efficiency to push the piston down harder, causing more power, better fuel economy and less cost.
Most all of your small engines are designed for "regular" gas. Even your newer engines with higher compression are designed for regular gas. The combustion chamber are designed for that with less "quench area" to cause knocking or pre-ignition. Many of your motorcycle engines are designed and run better with regular gas without any problems, and they have compression ratios up over 10 to one.
 

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Which bring up a dillema for a lot of folks. E0 is often available in only 91 octane or above, so 91 octane E0 or 87 octane E?? ?
 

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Higher octane fuel does not burn slower. It's simply harder to ignite. Which means you can run more ignition timing (up to the point where the engine can't benefit from more) without risking damage due to pre-ignition. Most small engines run less timing than ideal to avoid having too much timing at idle (because there's no advance mechanism). So running premium fuel will allow you to advance the timing a little bit (and gain some power and efficiency) without risking issues when at less than full RPM.

Fuel also loses octane while sitting (even with stabilizer, although this helps), so high octane gas gives more margin for error if you're running gas that's a few months old (as it would have to lose more octane before it becomes a problem). And generally, most of us don't put enough fuel through our small engines for cost to be a big concern. If you keep your fuel fresh and aren't going to advance the timing, I'll agree that there's nothing to gain from high octane, so might as well use the cheap stuff.
 

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Discussion Starter #6 (Edited)
You're right- my bad, I appreciate photo's when I read and I will see if I have any of the completed project.

So.... here in Canada we don't seem to have all the products you have access to in the US, the Nova I ended up getting was shipped here. My choice would have been an obscure Aussie colour coded make- but the application description was too vague. As for brand, I found little info out there between Oregon, Nova, Stens, etc., in fact what I ordered is not what I recieved. Besides timing difference with higher octane, I believe the fuel is better quality with less ethanol. Anyway- it runs far better than it did when it first showed up. I'm not really aware that the H60 has quench as a flathead.
 

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...... Besides timing difference with higher octane, I believe the fuel is better quality with less ethanol. Anyway- it runs far better than it did when it first showed up. I'm not really aware that the H60 has quench as a flathead.
I am not familiar with all the technicalities of engine design theory, but in real life, premium 91 octane fuel without ethanol works perfectly in all engines whether specified or not. My Ariens starts first pull on the mildest and coldest days of winter and runs strongly for however long I want. There are extra cleaners in premium gas and in Canada the fuel is spec'd to cover a wider range of temperatures for better vaporisation. Any gas left over from winter goes into the lawnmower and other summer engines seamlessly. And the same with leftover summer gas going into the snowblower. My car is never a dumping ground for fuel.

This link shows gas stations in Alberta that sell non ethanol gas: https://www.pure-gas.org/index.jsp?stateprov=AB so you have options for regular and premium without any ethanol. In Canada as a whole all Shell 91 and Esso 91 and Canadian Tire 91 have no ethanol.

I use Premium gas without ethanol because it is stable over a year (or more) long period and does not need any stabilisers or other treatments. Keeps carbs and the entire fuel system clean so gas can remain in the system between snowfalls. All of the dealers and individuals here recommend non-ethanol gas which means premium because of the quick deterioration of ethanol in gas leading to non start and fuel system issues.
 

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Discussion Starter #8
I use Premium gas without ethanol because it is stable over a year (or more) long period and does not need any stabilisers or other treatments. Keeps carbs and the entire fuel system clean so gas can remain in the system between snowfalls. All of the dealers and individuals here recommend non-ethanol gas which means premium because of the quick deterioration of ethanol in gas leading to non start and fuel system issues.


-This-
 

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I dunno about others, but I use 91 non-ethanol always because it's easy to find at the pump. My vehicles require 91, and all my small engines get it.

I DO find that my older Briggs engines on my lawn mowers (early 1990's vintage Quantums) detest older gas as far as starting is concerned. It gets over a month old, it probably isn't going to start. Drain the tank, pour fresh in...starts on 1st pull.

My older (early 1970's) Tecumseh's on my blowers start and run fantastic on it and I have found no age "limit" to where they don't start and run fine. Last fall I started on the 1st pull my H70-130067 on Bill - the gas being approximately 7 months old in it's tank.

YMMV...
 

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Higher octane fuel does not burn slower. It's simply harder to ignite. Which means you can run more ignition timing (up to the point where the engine can't benefit from more) without risking damage due to pre-ignition. Most small engines run less timing than ideal to avoid having too much timing at idle (because there's no advance mechanism). So running premium fuel will allow you to advance the timing a little bit (and gain some power and efficiency) without risking issues when at less than full RPM.

Fuel also loses octane while sitting (even with stabilizer, although this helps), so high octane gas gives more margin for error if you're running gas that's a few months old (as it would have to lose more octane before it becomes a problem). And generally, most of us don't put enough fuel through our small engines for cost to be a big concern. If you keep your fuel fresh and aren't going to advance the timing, I'll agree that there's nothing to gain from high octane, so might as well use the cheap stuff.
Believe it or not, Higher Octane sure does have a slower burn than Regular grade gasoline. We have been doing extensive tests on fuel for many years now. The high octane has a slower burn flash rate with a more controlled smoother burn. It takes longer for the complete burn to happen than it does for lower octane. That is why you have to use more timing advance, because of the slower burn. It ignites the same as regular, but has a slower burn rate to completely burn the mixture.
Also, gasoline does not loose octane, if anything it would gain it because the older gas would be harder to ignite and burn much slower, a common myth or "Wives Tale" that it looses octane.
A common misconception that most people think high octane gas burns faster and creates more power, but it is actually the opposite, and most people don't realize that.
Your most common octane booster is Ethanol Alcohol that is added into the fuel, which most people don't know.
Octane is not an ingredient of gasoline, it is a rating number for "Anti Knock". Most all newer gasoline uses Ethanol Alcohol as the "Octane Booster". If you find octane booster in a store that you add to gasoline, the active ingredient is alcohol.
A difference between "summer" and "winter" grade fuels is the vaporizing point. Summer grade takes more heat and is slower to vaporize and evaporate, where winter grade vaporizes and evaporates easier to make engine starting easier in cold temperatures, but it can "vapor lock" easier when it becomes hot. The boiling point is lower for winter grade gasoline, where summer grade has a higher boiling point to combat "vapor lock" in higher temps.
When gasoline ages, some of the chemicals in gas evaporate out of the mixture of chemicals and compounds that gas is made of, and some break down. When some of the highly volatile solvents and chemicals evaporate out of the mixture, the fuel becomes harder to ignite, and as it breaks down you get a sludge leftover in the bottom of the tank. That is why it is important to store fresh fuel in a sealed container.
If you ever wondered why an old hot rod car had to use such a high energy ignition system with very high voltage over stock, and a lot of extra timing advance, it was because of using the high octane gas that was required for the higher compression ratios in the modified engine that was hot rodded.
A lot of your road race motorcycles are running with regular grade octane gas because of the extra power delivered from lower octane gas than high/premium gasoline, and these bikes are using compression ratios of 12 to 1.
Almost forgot, most of your better newer small engines do have a coil that will automatically advance the ignition timing when the engine reaches a factory set speed. They will start with a lesser advance to reduce "kick back" when starting, then increase when the engine reaches a specified RPM and hold that advance until it slows below a set rpm to prevent backfiring through the intake system. Your electronic coils are built with the advance mechanism in the electronics in the coil itself. Some of your old larger engines that used points and ones that used the external magneto had a mechanical advance mechanism like an older car had in its distributor with the centrifugal flyweights and springs and special bushing to limit the advance.
Another reason that small engine manufacturers are against adding more Ethanol to fuel, say making E15 or higher, is because they at this time don't have enough timing advance built into the ignition systems because alcohol has a slower burning rate than gasoline, like high octane gas, requiring the added timing advance increase. Alcohol produces less heat and expansion, "BTU Volumetric Efficiency" than gasoline, therefor less power because it doesn't push the piston down as hard, alcohol is corrosive and also likes to absorb water out of the atmosphere causing fuel/water contamination, besides when it burns it also creates more carbon dioxide "Greenhouse gasses" than regular non ethanol gasoline, thats why your fuel milage drops from using ethanol gas.
Gasolines have pretty much the same amount of Ethanol in it, whether it is regular or premium. If anything, premium has more alcohol in it, because that is what raises the octane number.
 

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That's a great summary on the properties and behaviors of various types of gasoline. I have bookmarked that page and enjoyed reading it!
 

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Discussion Starter #13
Also newer design heads have 'fast burn' chamber designs that allow more controlled burn (efficient) of lower octane fuels they would not be as 'lazy' as the flatheads or bath tub chamber designs up to the late 90's.
 

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Good summary, but I disagree with one point, and it is often made: Alcohol does not "absorb water out of the air". Some info here on the topic and quoted below:

Three Ethanol Myths Clarified - BoatUS Magazine

Ethanol does not "grab water molecules out of the air." It is hydrophilic, which means ethanol holds water. With regular gasoline (E0) as well at E10, the primary cause of water collecting in tanks is condensation on tank walls. But unlike E0, which can absorb almost no moisture, E10 can hold up to half of one percent of water by volume, and the water molecules will dissolve in the fuel. The best way to avoid water condensing into the fuel is to keep the tank full.

Thanks
 

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"Hydrophilic" meaning it attracts water, which is then "Mixed" or as most people understand as "Absorbed or Absorbs". It is a confusing topic. Depending on which chemist you talk to, they will use different words like "Attract", "Mix", "Absorb". But it does the same thing, it "Grabs" water.
Alcohol does mix with water, gasoline doesn't. That's why you see it separate with gasoline. Alcohol also mixes with gasoline until the water content is too high, then it will separate.
Alcohol is like brake fluid, it likes to "Suck" water out of the surrounding atmosphere. That is one reason brake fluid gets darker in color, because it becomes contaminated with moisture. If you ever look at the top side of a rubber diaphram in a brake mastercylinder, you may notice water on it. That is because of the "Hydrophilic" effect of the "Glycerin" in the brake fluid. Glycerin is a type of alcohol. The rubber acts as a barrier to slow the absorption of water into the brake fluid. Eventually it will pass thru the tiny pores in the rubber. Glycerin is like a "Magnet" to moisture as steel is to a magnet, it "Pulls" it towards each other.
Paulm12, that is a good article you posted for people to read, and another good reason to keep the fuel tank FULL, which I always tell people to do, and for that reason.
Another thing I always tell my customers, do not use products like "Dry Gas" because your gasoline already has that ingredient in it, meaning alcohol.
Your boat owners are much more susceptible to it being around water closer and more humidity.
We all know water is bad for fuel, and most people try to take the necessary steps to avoid it, but it does happen, like filling a fuel tank outside while it is raining, or in a boats case, filling it while the boat is rocking around in splashing water and the excess humidity being that close to a large amount of water.
 

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...Octane is not an ingredient of gasoline...
Actually, it is... Octane is a hydrocarbon molecule with 8 carbon atoms and a full load of 18 hydrogen atoms (see diagram attached). The Octane Rating tells you how much Octane a given volume of gasoline contains. The higher the octane number, the more compression the fuel can withstand before detonating.
 

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Hi Tabora,
I should have said it is not a chemical additive of gasoline, like most people think it is. It is a molecular compound as part of the molecular structure that makes up of gasoline, not a separate ingredient that most people think it is. Most people wouldn't understand that, they think it is a chemical that is added to gasoline, which it is not.
There are chemicals that are called "Octane Enhancers" added to it, to enhance or raise octane levels, but not a chemical called "Octane".
When you see the octane number on the pump, it is only a research number used to compare the grade level of the fuel. There are 2 numbers, "research" and "motor", added together then divided by 2, that gives the pump octane number that is listed on the gas pump.
Your added carbon atoms in the molecule is what actually slows down the burn speed in the higher carbon content of the combined molecules. You will have a lot of hydrogen, and also a lot of carbon with more clusters of octane molecules.
The slower smoother more controlled burn helps to prevent the collision of two or more flame fronts colliding together which causes the "Knock" sound in the engine, or when it is ignited by a piece of glowing carbon left over in the combustion chamber, usually located in a "Quench area". That all happens at a very fast rate, usually just before the piston reaches top dead center at full compression.
If you can slow down the burn rate a little bit with higher octane gas, that wont happen until after the piston reaches top dead center and is on its way down in the "power stroke", so you wont hear the knock or ping sound.
If it happens too fast and not smooth you will have an uncontrolled collision of the flame fronts causing "detonation", "knock", or "pinging", that lower octane can cause, that is why the manufacturers have redesigned the combustion chambers to get rid of quench areas to do away with the detonation or pinging and be able to use lower octane rated gasoline.
That gives a little bit of an explanation of why high octane rated gasoline needs more timing advance to produce the flame front at the correct time to build cylinder pressure at the right time, and it happens very fast, almost like "the speed of light" fast.
It is a very interesting study of the fuel make up and the research that goes into it and how it affects engine operation. The Gasoline manufacturers engineers know a lot about it, but will not tell the public everything in fear of scaring them away from buying "their brand" of gasoline that they work for, because each different brand is a little bit different from the other. Little "Trade Secrets" that they have.
 

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Hello again Tabora,
Did you ever get a chance to tour an oil refinery? If not, I don't know if they have any up your way, but you could head down south from you a bit to the Exxon/Mobile Refinery in Bayonne, N.J. or south a little further to Sunoco refinery in Marcus Hook, Pa.
You should check that out. You would be amazed at what all they have to do to refine and produce different types of fuel, and all the different chemicals involved and added to it.
I used to work and haul out of them, it is amazing all the different processes involved in refining crude oil.
I don't know if they give the tours anymore because of insurance liability reasons, but if you knew someone who worked at them, they could probably get you in there.
Check it out if you would ever get the chance to go, it is worth it.
 

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Hello again Tabora,
Did you ever get a chance to tour an oil refinery? If not, I don't know if they have any up your way, but you could head down south from you a bit to the Exxon/Mobile Refinery in Bayonne, N.J. or south a little further to Sunoco refinery in Marcus Hook, Pa.
You should check that out. You would be amazed at what all they have to do to refine and produce different types of fuel, and all the different chemicals involved and added to it.
I used to work and haul out of them, it is amazing all the different processes involved in refining crude oil.
I don't know if they give the tours anymore because of insurance liability reasons, but if you knew someone who worked at them, they could probably get you in there.
Check it out if you would ever get the chance to go, it is worth it.
My degree is in Geology; I've been to refineries and boreholes and mines galore. Almost took a job electro-logging oil wells in Iran/Iraq back in the late 70s... Glad I decided to avoid that mess.

Octane is totally an additive to "regular" grade gasoline to reduce detonation potential. You should review a cracking tower diagram and alkylation...

In a conventional oil refinery, isobutane is alkylated with low-molecular-weight alkenes (primarily a mixture of propene and butene) in the presence of a Brønsted acid catalyst, which can include solid acids (zeolites). The catalyst protonates the alkenes (propene, butene) to produce carbocations, which alkylate isobutane. The product, called "alkylate", is composed of a mixture of high-octane, branched-chain paraffinic hydrocarbons (mostly isoheptane and isooctane). Alkylate is a premium gasoline blending stock because it has exceptional antiknock properties and is clean burning.
 

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My degree is in Geology; I've been to refineries and boreholes and mines galore. Almost took a job electro-logging oil wells in Iran/Iraq back in the late 70s... Glad I decided to avoid that mess.

Octane is totally an additive to "regular" grade gasoline to reduce detonation potential. You should review a cracking tower diagram and alkylation...

In a conventional oil refinery, isobutane is alkylated with low-molecular-weight alkenes (primarily a mixture of propene and butene) in the presence of a Brønsted acid catalyst, which can include solid acids (zeolites). The catalyst protonates the alkenes (propene, butene) to produce carbocations, which alkylate isobutane. The product, called "alkylate", is composed of a mixture of high-octane, branched-chain paraffinic hydrocarbons (mostly isoheptane and isooctane). Alkylate is a premium gasoline blending stock because it has exceptional antiknock properties and is clean burning.
Hi Tabora, good thing you didn't go to Iraq. That is a good diagram showing the basics of a refinery.
Alkylate is an additive in the refining process to enhance the octane. They don't use a chemical specifically called "Octane" that most people think it is called, that was what I was trying to explain. They used different chemicals over the years to enhance it. Now days they are actually using the Ethanol and other more environmentally friendly additives to boost "Octane".
You did show a good example of an "Octane" molecule, hopefully people will understand that.
You can't go to a store and buy a can of pure "Octane". If you could get a can of pure "Octane" it wouldn't mix to well by just dumping it in your gas tank.
Its sad that they took out all the good stuff from gasoline that used to make it perform very well, and substituted it with all the environmentally friendly crap that doesn't work that well.
You are one of the few that understands the "Refining" process, it sounds like you had a pretty interesting career.
I am sure you will confuse a lot of people with that diagram, but it is very interesting to some, thanks for putting it on there. My nephew is involved in the kind of work that you did, right now he is doing the geotechnical stuff and the borehole samples, it sounds like an interesting career.
Anyways, good communicating with you and keep up with all those technical things you post, they are interesting to a lot of people.
 
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