fuel octane

[MotoBoyMatt]

Tetra Ethyl Lead

Too bad the EPA outlawed it for on-road vehicles several years back because of it's air polution and adverse health effects. If your running a saw for a living you probly don't want be burning lead in it. MTBE(methyl tertiary-butyl ether) would be a better option

 

[klickitatsacket]

question here for those who know. What bennifits and or detractors is there with white gas. Reading it Molecule's thread and it refreshed a statement made by an old timer about running it. I am curious about it. I will also check the net for some information but if any one can give me any help here I would appriciate it.

 

[timberwolf]

Very low octane rating, think it is in the area of 60-70.

 

[bwalker]

MTBE is still used as a gasoline additive in many areas. I have a source for the stuff.

 

[timberwolf]

To follow the Naptha/white gas thought.

Naphthalene (aka mothballs) had been used in the long forgotten past when gas had low octane ratings to boost octane, and it did to an extent. The octane # for naphthalene is 90 so it won't do anything to boost priemium gas. And will only add to carbon deposits as it breaks down during combustion.

Anyway most modern moth balls use para-dichlorobenzene in place of naphthalene. No need to state what chloriene does to the metal inside a chainsaw.

 

[semi]

Semi, Re read this thread, Your post is totaly false.

actually no it is not.

Higher compression motors need high octane. Otherwise its just a waste of $$

Octane is a rating. It rates how PRONE or UN-PRONE a gasoline is to "Compression Ignition" This is also known as DETONATION..... And is when gasoline/air mixes and SPONTANEOUSLY COMBUST, due to PRESSURE exerted on the mixture. To high of a compression engine, and low octane gas, are sure to detonate, and cause problems inside your motor.

As for High octane fuel, Ideally you should burn fuel that had JUST ENOUGH octane to keep you from detonating....Reason being, the higher the octane, the LESS BTU's per gallon (less power) It is not a HUGE difference, but it is there!

 

[timberwolf]

semi, ben will eat you alive on this, good luck.

Low octane fuel does not burn at a lower flashpoint.

In general low octane fuels have a lower flashpoint. which says the fuel can be ignighted at a lower temprature because there a lower vapor pressure and hence more available fuel in the air so the LEL lower explosive limit is reached sooner.

If lower octane fuel made more HP drag cars would be burning naptha gas with engines from model A fords.

It all has to do with compression, If the engine is not detonating adding octane will do nothing but reduce output. If the engine is detonating more octane will reduce heat and allow the engine to run and therefor produce more hp.

The compression ratio and available fuel energy is what produces HP. That is why octane and oxigenating fuels are desirable in high output applications where the engine is designed to take advantage of the octane.

Semi, by the time I posted you corected yourself. But you better check your terminology before making conclusions as such, spontaneous combustion and auto ignition are not the same thing.

 

[semi]

here is what i learned right from a motor builder when i used to race sleds

GASOLINE OCTANE INFORMATION and CARBON BUILDUP

To prevent carbon build-up in the motor verify thermostats, jet checks, timing /sync checks etc...but In addition I recommend after the break in period the use of synthetic oil, AND USE LOW OCTANE FUEL. Fact is, lower octane fuel compared to higher-octane fuel has A LOWER FLASH POINT WHICH DRAMTICALLY IMPROVES IDLE AND STARTING. BURNS MORE COMPLETELY AND AT A HOTTER TEMPURATURE, which in turn leaves less CARBON in the combustion chambers and exhaust ports and LESS FOULING OF SPARK PLUGS with un-burned fuel mixture (on a stock motor). Some engine designs require a higher octane or if they are modified to run on higher than 87 octane gasoline. A common misconception even among some of the best engine gurus is: "high octane burns better" It doesn't. High-octane gasoline has a higher flash point, will ignite later, and burn longer (less piston nock) through out the power stoke causing a rough idle on a stock motor. High octane compared to a lower octane in same quantity and air fuel ratio comparison tests PROVE the high octane’s intent and purpose does burn longer through the power stroke requiring a more advanced ignition/timing setting for complete combustion. This in turn provides more power through the stroke if only the compression ratio is adequate to support this benefit. If the unit is not intended, tuned or modified for high-octane fuel, DO NOT USE IT.
So with this in mind- here is what you should do to prevent carbon build-up
Fuel conditioner/carbon guard to prevent carbon build up and stabil use all the time to prevent fuel degradation with 87 octane will provide the best protection from carbon build up and provide the best chance for complete combustion on a properly tuned, stock set up that doesn't have a compression ratio over 9.3 to 1. The primary additive in higher-octane fuels is a anti-knock compound which are less combustible than the fuel itself. Also, lower octane fuels do not have ADDITIVES taken out of them. Hope this clears things up.

I put alot of faith in this since i have seen it on a dyno.

 

[chowdozer]

Semi, that is essentially what I learned.


http://en.wikipedia.org/wiki/Octane_rating

 

[bwalker]

actually the higher octane will decrease performance but it runs cooler. I saw use what your saw calls for and be happy. Higher octane decreases knocking. The only time i would run it is if my saw was modified. again it runs cooler, but doesn't increase performance. Just the opposite.

Higher octane will not decrease performance and does NOT BURN COOLER. All gasoline has essentially the same BTU's.

Reason being, the higher the octane, the LESS BTU's per gallon (less power) It is not a HUGE difference, but it is there!

Again, this is not true.

semi, ben will eat you alive on this, good luck.

Are you a betting man, Timber wolf?

In general low octane fuels have a lower flashpoint.

Timber wolf, I might point out that flashpoint is a measurment taken for transportation purposes only. Regular and premium have simular flashpoints depending on brand, etc.

It all has to do with compression, If the engine is not detonating adding octane will do nothing but reduce output.

Once again , it will not.
Semi, Your" tuner", like most, has no idea what he is talking about in regards to fuels.
If you guys do not believe me, which being on the internet why should you? Have a look at these readings. I think you will find a lot of the common held facts in regards to fuels are not factual in basis at all.

Hydrocarbon Chemistry - Author George A. Olah - ISBN 0-471-11359-x

Automotive Fuels Reference Book - Authors Keith Owen & Trevor Coley - ISBN 1-56091-589-7

The Chemistry of Hydrocarbon Fuels - Author Harold H. Shobert - ISBN 0-7506-0384-4


BTW I think the garbage on Wiki pedia was very poorly wriiten and the author really was not qualified.
Octane is a measure of a fuels ability to resist ABNORMAL(ie detonation) combustion, not its ability to resist combustion.
I might also add that I spent several years working at Fuel sytems supplier to the auto industry, so I have a little background in the subject at hand.

 

[bwalker]

Here is some further reading. Pay specal attention to the explanation of what detonation is and when it occurs. It will become apparent after reading this part of the articlae why octane has nothing to do with flame speed, or flashpoint.
http://ericgorr.com/techarticles/Fuel_Basics.htm

 

[bwalker]

Another excellent article that dispells most of the crap in this post.
http://www.chevron.com/products/prodserv/fuels/bulletin/motorgas/

 

[Vman]

bwalker..........after following all the responses for several days, may it seem logical that the engine may run cooler with higher octane cause the engine ignition timing would be more consistant? i am just asking, not contradicting anything. i find this thread very interesting.

 

[timberwolf]

I'l give you that one, too many exceptions to make that generalization that lower octane fuels have lower flashpoints. Flash point is more to do with vapor pressure and minimum ignition energy than octane.

Don't think you saw what semi posted and quickly corrected.

 

[bwalker]

that the engine may run cooler with higher octane cause the engine ignition timing would be more consistant?

As long as pre ignition isnt present, timing should be consistant. Incidently pre igntion is apparent when its happening. Often called spark knock of pinging.
Timber wolf, I didnt see what Semi retracted. I amsure Semi is a good guy, its just that so much information gets passed around, even by people who should know better that its hard for the average Joe to know what the facts are.

 

[bwalker]

I forgot one thing, Timber wolf. Vapour pressure, and distallation curve( I think what uoi are refering to as flashpoint is really the 10% distallation temp) are mandated by the EPA for pump gas in order to reduce evaporative emmissions. All pump gas has to meet these standards regardless of grade. FWIW these standards change be given geographic area and season.

 

[timberwolf]

On the flash point I'm talking the minimum temprature that a transient flame will pass over a liquid pool if a pilot flame is introduced. Just a bit below flame point where the flame becomes self sustaining rather than transient.

 

[semi]

the reason i corrected what i posted was that i didn't state it the way i wanted to. I was too busy trying to get my point across. The article that i posted is what i am trying to say. That is what i learned from two factory reps that used to build my motors and other people's motors. They were all two strokes that had to remain stock. I have seen lower octane produce higher numbers on a dyno and higher octane actually decrease performance.

 

[timberwolf]

Marketing of these octane boost products sure sucks alot of people in, 99 times out of 100 they are adding something the engine can't take advantage of or reduces output, and 99 times out of 100 they are paying too much for what it is.

Funny the same factory that makes octane boost makes paint thinner.

I wonder as "peak oil" unfolds and they add more mazola or other junk to the gas how our high compression saws will be doing. Sounds like only a couple years from now 5% ethanol will be law in Canada. The day may not be far off that pump gas will not cut it.

Oh yeh, "increases octane 7 points" got to love that line! I guess it would not sell if it read"7 tenths of a point"

 

[bwalker]

Semi, The guys giving you info and the author of that "article" are flat out wrong. I have provided ample resources in this pos for you to become informed of the facts. Do with it what you will.
And have have seena lot of high jinx on a dyno.