Hi Octane Gas

rocksolid · 05-08-2008, 07:17 PM

It has been suggested that using Hi-octane gas solves undetected knocking in a engine. This is the first time I've ever heard that the factory recommended gas grade is wrong. If anybody has evidence of this, I'd appreciate the opportunity to read it.
Rocksolid

CaptCrashIdaho · 05-08-2008, 07:26 PM

Yeah...and eating caviar cures undetectable heart disease...I have several cans I can sell you at a 'discounted' rate...wink nudge...

cmonSTART · 05-08-2008, 07:34 PM

The proper grade of gas for you to use is the lowest octane possible without audible knocking.

CaptCrashIdaho · 05-08-2008, 07:38 PM

My 2bits: http://www.youtube.com/watch?v=ZZx5w1jVUDA

rocksolid · 05-08-2008, 07:57 PM

Crash, PM sent

Wrangler212 · 05-08-2008, 08:15 PM

Quote:

Originally Posted by rocksolid

It has been suggested that using Hi-octane gas solves undetected knocking in a engine. This is the first time I've ever heard that the factory recommended gas grade is wrong. If anybody has evidence of this, I'd appreciate the opportunity to read it.
Rocksolid

That depends. The octane rating simply signifies the resistance to knock. So if you have a higher compression ratio, then the vehicle needs higher octane fuel. If you have a higher compression ratio than the octane you're running, then the heat generated by the pressure in the combustion chamber will cause the fuel to go bang before the spark plug sets it off.

Now, if you have a lower compression ratio and you're getting a knock, yes, a higher octane fuel might get rid of the knock but that means you're treating the symptom instead of the problem. You probably developed a carbon deposit or something like that which creates a hot spot in the combustion chamber setting off the fuel before the spark does it.

If this is the case, I would run the higher octane until you can take care of it properly because continued pre-ignition could do all sorts of bad things to the engine. If it's popping too soon the combustion is putting the down force on the piston too soon trying to push it backwards. The power of the other cylinders will keep it going in the right direction but this just isn't good in the long run.

dieseltech · 05-09-2008, 07:08 AM

What kind of bike do you have? has anything been done to the engine?

rocksolid · 05-09-2008, 10:56 AM

It's not that I think I need higher octane gas. It's that one of our members said that he has proof that we aren't giving our engines the octane they need to run properly. So, I started this thread to give him the opportunity to post the findings of his research. So far he hasn't posted, but I hope he will. I would like to read what he found out.
Rocksolid

shelzmike · 05-09-2008, 11:13 AM

CaptCrash -

Funny vid you made - where can I get a talking microwave?!

Mike

CaptCrashIdaho · 05-09-2008, 07:38 PM

Quote:

Originally Posted by shelzmike

CaptCrash -

Funny vid you made - where can I get a talking microwave?!

Mike

Cheap ones can be made with tequila...expensive ones need software....

rocksolid · 05-09-2008, 08:56 PM

Crash, PM sent

cdg · 05-10-2008, 06:21 AM

I'd do what the factory recommends but keep in mind these factors:

1) Duty cycle

2) Ambient air temperature

3) Gasoline formulation

4) Make, model, year, type of motorcycle

5) Mileage and care given to the bike

Duty cycle is a measure of how much work your motorcycle is doing. Consider if you are riding with a passenger, pulling a trailer, or lugging heavily loaded saddle bags. Terrain is one of the largest factors here too. High speed drag can be a factor on bikes without fairings as well. Bottom line is that when you're riding from Philly to Harrisburg, you're not looking at a lot of serious grades, probably not packing heavy luggage. Most (road) bikes are well set up for this ride and won't be getting used hard.

Now consider where I live, in the desert southwest. Ride from Wickenburg to Prescott, or nay, Wickenburg to Flagstaff where you have drastic climbs, elevation changes of thousands of feet over a relatively short run. You're running any bike hard to make this climb. This leads to heat, which leads to detonation.

Consider your ambient air temperature. The hotter the intake charge and cooling air is means the less efficiently the engine will cool. This is especially true with air cooled motorcycles. I saw a comic once that had a Harley Davidson with it's cooling fins melting down in the Arizona sun. The truth is that detonation is going to hit it long before the engine "melts". It's the pistons that will be melting...

Think about your gasoline blends - ethanol blends, anti-knocking aditives. Formulation plays a role in engine knock beyond simple measures of octane or "anti-knock index" as fuel is measured today.

Ride the dirt in the desert southwest on a '74 air cooled Suzuki TS 125. I'd be willing to bet that on 87 octane gas you're going to be walking home. Well with that bike I'm willing to bet you're going to be walking, or at least using your leatherman tool twice along the trail, but that's neither here nor there. The point is that under harsh offroad conditions, detonation is an extremely real concern, and a cause for alarm. Some bikes are obviously more proned to problems than other. Consider cooling system type, how tightly cowled the engine is, and a number of other factors. Also remember that with small radiators bugs and road grime can clog up the works in short order. Air cooled bikes must be kept similarly clean in order for the cooling fins to do their job.

Carbon deposits and other such problems can also cause uneven heat buildup, "hotspots" and similar issues that ultimately cause detonation. In extreme instances of hotspotting, I've seen an older 2 stroke "run away" once - a situation in which a hot spot will build up and cause the engine to run at excessive RPMs until the fuel runs out of the carb or the air intake is blocked - much like a glowhead engine. In this case the runaway was caused by a combination of crappy old gasoline and an improperly lean mixture. They were lucky they didn't burn up the bike having this happen not once, but twice.

Age can also bring the "dummy mechanic" factor. Spark plug heat range, ignition timing, fuel/oil ratio, and numerous other improper adjustments can all lead to detonation.

In conclusion, YES, high octane fuels can right many wrongs that lead up to detonation. In some cases you must use a high octane fuel to overcome a fundamental design issue. In many of these cases manufacturers recommend high octane gasoline because they feel it is important, and able to overcome whatever design issues may exist.

I would recommend high octane fuel always be used in severe climates and riding conditions that would generally cause hot temperatures on your bike. I also normally use high octane gasoline in all air cooled applications to be on the safe side, but again, I'm in the desert southwest so I feel this is a worthwhile precaution.

Hope this helps explain some of the detonation related issues and why higher octane gasoline is sometimes required.

CaptCrashIdaho · 05-10-2008, 11:02 AM

I'm gonna stick my neck out a little here...

Most folks run high Octane for two reasons:

1. They have the impression that Octane is like "Proof". I.E. 180 proof means more alcohol...therefore 93 Octane has more power.

2. It costs more. So it MUST be better.

These are common misconceptions. I work at a high school. Do you know why most kids want an IPod? 'Cause it's an IPod. ANY Mp3 player will do the same thing...but it's the mystic/status of the IPod they want.

Same with gas.

One interesting aside here, it's my understanding that internationally, octane ratings are generally lower than they are here in the states. I have a friend who's involved in a medical/missionary outreach. They send KLRs abroad. One of the first things they do is lower the compression to handle looooow octane gas sold in the 3rd world.

TFee3 · 05-10-2008, 10:08 PM

My Suzuki calls for 87 octane, and I'm sticking with it. It runs fine! Maybe this has been asked before, but if a knock can't be detected, then how do you know it's helping to run higher octane gas? Believe me, I'm not trying to be a wise guy, but in this case, I feel it's a valid question.

cdg · 05-10-2008, 10:47 PM

Quote:

Originally Posted by TFee3

My Suzuki calls for 87 octane, and I'm sticking with it. It runs fine! Maybe this has been asked before, but if a knock can't be detected, then how do you know it's helping to run higher octane gas? Believe me, I'm not trying to be a wise guy, but in this case, I feel it's a valid question.

You know when you're putting in new wrist pins in your pistons more frequently than an engine that is run with lower octane fuel. I'd only put higher octane gas if you're really going to be running it hard or if you're going to be storing the gasoline in the tank for long periods of time (why I put premium gas and fuel stabilizer in the tank of my DL 650 Vstrom before I leave for college, even though the bike only calls for 87.

Octane rating is really an "anti-knock" rating. The ratings actually mean something, and you should listen to what the manufacturers say as to which gas to buy. You should also know that higher octane fuels are more resistant against breakdown from sitting around a lot, so long term storage can be a factor in deciding what to buy at the pump.

It is true that octane ratings are often lower in the third world. Ratings can also vary because internationally the rating system varies quite a bit.

You pay more for higher octane fuel because it IS HIGHER QUALITY fuel. You can say what you want, but you can't change the scientific fact that it will resist preignition more than a lower octane fuel. Drag racers don't use 87 octane pump gas - but not because they think it's fun to spend 15 bucks a gallon for racing fuel.

dwysywd · 05-10-2008, 11:09 PM

WIKIPEDIA QUOTE: "The octane rating is a measure of the autoignition resistance of gasoline and other fuels used in spark-ignition internal combustion engines. It is a measure of anti-detonation of a gasoline or fuel."

Anti-Knock and Anti-Detonation and Autoignition Resistance = All the same thing

Crash - And for the record, I thought the video was HILARIOUS... maybe you can use 151 next time and then breath fire too... make it appear even more authentic.

FULL ARTICLE

http://en.wikipedia.org/wiki/Octane_rating
The octane rating of a spark ignition engine fuel is the knock resistance (anti-knock rating) compared to a mixture of iso-octane (2,2,4-trimethylpentane, an isomer of octane) and n-heptane. By definition, iso-octane is assigned an octane rating of 100 and heptane is assigned an octane rating of zero. An 87-octane gasoline, for example, possesses the same anti-knock rating of a mixture of 87% (by volume) iso-octane and 13% (by volume) n-heptane. This does not mean, however, that the gasoline actually contains these hydrocarbons in these proportions. It simply means that it has the same autoignition resistance as the described mixture.

A high tendency to autoignite, or low octane rating, is undesirable in a spark ignition engine but desirable in a diesel engine. The standard for the combustion quality of diesel fuel is the cetane number. A diesel fuel with a high cetane number has a high tendency to autoignite, as is preferred.

It should be noted that octane rating does not relate to the energy content of the fuel (see heating value), nor the speed at which the flame initiated by the spark plug propagates across the cylinder. It is only a measure of the fuel's resistance to autoignition. It is for this reason that one highly branched form, or isomer, of octane (2,2,4-trimethylpentane) has (by definition) an octane rating of 100, whereas n-octane (see octane), which has a linear arrangement of the 8 carbon atoms, has an octane rating of -10, even though the two fuels have exactly the same chemical formula and virtually identical heating values and flame speeds.

[edit] Measurement methods
The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing these results with those for mixtures of iso-octane and n-heptane.

There is another type of octane rating, called Motor Octane Number (MON) or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, a higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON. Normally fuel specifications require both a minimum RON and a minimum MON.

In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in the United States, Canada and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, would be 91-92 in Europe. However most European pumps deliver 95 (RON) as "regular", equivalent to 90-91 US (R+M)/2, and even deliver 98 (RON) or 100 (RON).

The octane rating may also be a "trade name", with the actual figure being higher than the nominal rating.[citation needed]

It is possible for a fuel to have a RON greater than 100, because iso-octane is not the most knock-resistant substance available. Racing fuels, straight ethanol, AvGas and liquified petroleum gas (LPG) typically have octane ratings of 110 or significantly higher - ethanol's RON is 129 (MON 102, AKI 116) reference[1]. Typical "octane booster" additives include tetra-ethyl lead, MTBE and toluene. Tetra-ethyl lead is easily decomposed to its component radicals, which react with the radicals from the fuel and oxygen that would start the combustion, thereby delaying ignition. This is why leaded gasoline has a higher octane rating than unleaded.

CaptCrashIdaho · 05-11-2008, 12:41 AM

See there's that "quality" question again...IS Bacarti higher quality because it's higher proof?

I don't begrudge anyone using premium. In fact, I ran it in my GSXR1100 for years--and would do the same thing again if I had a high performance bike (jetted/piped) that I routinely flogged. But for what I'm riding now? Big single...heck it's a medium single...and 93 seems a bit extreme.

Here's the wierd part: I switched from premium to regular as an experiment. Guess what happened?

Gas milage jumped from 55 to 60mph. No idea why. Gonna have to talk to the microwave about it...

05-08-2008, 07:17 PM	#1
rocksolid Senior Member Join Date: Jul 2007 Location: Pittsburgh, Pa. Posts: 922	Hi Octane Gas It has been suggested that using Hi-octane gas solves undetected knocking in a engine. This is the first time I've ever heard that the factory recommended gas grade is wrong. If anybody has evidence of this, I'd appreciate the opportunity to read it. Rocksolid

05-10-2008, 11:09 PM	#16
dwysywd Vintage Forum Moderator Join Date: Feb 2008 Location: Close to Detroit Posts: 282	WIKIPEDIA QUOTE: "The octane rating is a measure of the autoignition resistance of gasoline and other fuels used in spark-ignition internal combustion engines. It is a measure of anti-detonation of a gasoline or fuel." Anti-Knock and Anti-Detonation and Autoignition Resistance = All the same thing Crash - And for the record, I thought the video was HILARIOUS... maybe you can use 151 next time and then breath fire too... make it appear even more authentic. FULL ARTICLEhttp://en.wikipedia.org/wiki/Octane_rating The octane rating of a spark ignition engine fuel is the knock resistance (anti-knock rating) compared to a mixture of iso-octane (2,2,4-trimethylpentane, an isomer of octane) and n-heptane. By definition, iso-octane is assigned an octane rating of 100 and heptane is assigned an octane rating of zero. An 87-octane gasoline, for example, possesses the same anti-knock rating of a mixture of 87% (by volume) iso-octane and 13% (by volume) n-heptane. This does not mean, however, that the gasoline actually contains these hydrocarbons in these proportions. It simply means that it has the same autoignition resistance as the described mixture. A high tendency to autoignite, or low octane rating, is undesirable in a spark ignition engine but desirable in a diesel engine. The standard for the combustion quality of diesel fuel is the cetane number. A diesel fuel with a high cetane number has a high tendency to autoignite, as is preferred. It should be noted that octane rating does not relate to the energy content of the fuel (see heating value), nor the speed at which the flame initiated by the spark plug propagates across the cylinder. It is only a measure of the fuel's resistance to autoignition. It is for this reason that one highly branched form, or isomer, of octane (2,2,4-trimethylpentane) has (by definition) an octane rating of 100, whereas n-octane (see octane), which has a linear arrangement of the 8 carbon atoms, has an octane rating of -10, even though the two fuels have exactly the same chemical formula and virtually identical heating values and flame speeds. [edit] Measurement methods The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing these results with those for mixtures of iso-octane and n-heptane. There is another type of octane rating, called Motor Octane Number (MON) or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, a higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON. Normally fuel specifications require both a minimum RON and a minimum MON. In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in the United States, Canada and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, would be 91-92 in Europe. However most European pumps deliver 95 (RON) as "regular", equivalent to 90-91 US (R+M)/2, and even deliver 98 (RON) or 100 (RON). The octane rating may also be a "trade name", with the actual figure being higher than the nominal rating.[citation needed] It is possible for a fuel to have a RON greater than 100, because iso-octane is not the most knock-resistant substance available. Racing fuels, straight ethanol, AvGas and liquified petroleum gas (LPG) typically have octane ratings of 110 or significantly higher - ethanol's RON is 129 (MON 102, AKI 116) reference[1]. Typical "octane booster" additives include tetra-ethyl lead, MTBE and toluene. Tetra-ethyl lead is easily decomposed to its component radicals, which react with the radicals from the fuel and oxygen that would start the combustion, thereby delaying ignition. This is why leaded gasoline has a higher octane rating than unleaded. __________________ To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts. Last edited by dwysywd; 05-10-2008 at 11:11 PM..

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05-08-2008, 07:26 PM	#2
CaptCrashIdaho Safety Hooligan Join Date: Sep 2007 Location: SW Idaho! Posts: 1,679	Yeah...and eating caviar cures undetectable heart disease...I have several cans I can sell you at a 'discounted' rate...wink nudge...

05-08-2008, 07:34 PM	#3
cmonSTART Rider of old stuff Join Date: Apr 2008 Location: Antrim, NH Posts: 812	The proper grade of gas for you to use is the lowest octane possible without audible knocking.

05-08-2008, 07:38 PM	#4
CaptCrashIdaho Safety Hooligan Join Date: Sep 2007 Location: SW Idaho! Posts: 1,679	My 2bits: http://www.youtube.com/watch?v=ZZx5w1jVUDA

05-08-2008, 07:57 PM	#5
rocksolid Senior Member Join Date: Jul 2007 Location: Pittsburgh, Pa. Posts: 922	Crash, PM sent

05-09-2008, 07:08 AM	#7
dieseltech Senior Member Join Date: Feb 2008 Location: Hutchinson Ks Posts: 215	What kind of bike do you have? has anything been done to the engine?

05-09-2008, 10:56 AM	#8
rocksolid Senior Member Join Date: Jul 2007 Location: Pittsburgh, Pa. Posts: 922	It's not that I think I need higher octane gas. It's that one of our members said that he has proof that we aren't giving our engines the octane they need to run properly. So, I started this thread to give him the opportunity to post the findings of his research. So far he hasn't posted, but I hope he will. I would like to read what he found out. Rocksolid

05-09-2008, 11:13 AM	#9
shelzmike Senior Member Join Date: May 2008 Location: Rocky Mount, VA Posts: 753	CaptCrash - Funny vid you made - where can I get a talking microwave?! Mike

05-09-2008, 08:56 PM	#11
rocksolid Senior Member Join Date: Jul 2007 Location: Pittsburgh, Pa. Posts: 922	Crash, PM sent

05-10-2008, 06:21 AM	#12
cdg Senior Member Join Date: Apr 2008 Posts: 268	I'd do what the factory recommends but keep in mind these factors: 1) Duty cycle 2) Ambient air temperature 3) Gasoline formulation 4) Make, model, year, type of motorcycle 5) Mileage and care given to the bike Duty cycle is a measure of how much work your motorcycle is doing. Consider if you are riding with a passenger, pulling a trailer, or lugging heavily loaded saddle bags. Terrain is one of the largest factors here too. High speed drag can be a factor on bikes without fairings as well. Bottom line is that when you're riding from Philly to Harrisburg, you're not looking at a lot of serious grades, probably not packing heavy luggage. Most (road) bikes are well set up for this ride and won't be getting used hard. Now consider where I live, in the desert southwest. Ride from Wickenburg to Prescott, or nay, Wickenburg to Flagstaff where you have drastic climbs, elevation changes of thousands of feet over a relatively short run. You're running any bike hard to make this climb. This leads to heat, which leads to detonation. Consider your ambient air temperature. The hotter the intake charge and cooling air is means the less efficiently the engine will cool. This is especially true with air cooled motorcycles. I saw a comic once that had a Harley Davidson with it's cooling fins melting down in the Arizona sun. The truth is that detonation is going to hit it long before the engine "melts". It's the pistons that will be melting... Think about your gasoline blends - ethanol blends, anti-knocking aditives. Formulation plays a role in engine knock beyond simple measures of octane or "anti-knock index" as fuel is measured today. Ride the dirt in the desert southwest on a '74 air cooled Suzuki TS 125. I'd be willing to bet that on 87 octane gas you're going to be walking home. Well with that bike I'm willing to bet you're going to be walking, or at least using your leatherman tool twice along the trail, but that's neither here nor there. The point is that under harsh offroad conditions, detonation is an extremely real concern, and a cause for alarm. Some bikes are obviously more proned to problems than other. Consider cooling system type, how tightly cowled the engine is, and a number of other factors. Also remember that with small radiators bugs and road grime can clog up the works in short order. Air cooled bikes must be kept similarly clean in order for the cooling fins to do their job. Carbon deposits and other such problems can also cause uneven heat buildup, "hotspots" and similar issues that ultimately cause detonation. In extreme instances of hotspotting, I've seen an older 2 stroke "run away" once - a situation in which a hot spot will build up and cause the engine to run at excessive RPMs until the fuel runs out of the carb or the air intake is blocked - much like a glowhead engine. In this case the runaway was caused by a combination of crappy old gasoline and an improperly lean mixture. They were lucky they didn't burn up the bike having this happen not once, but twice. Age can also bring the "dummy mechanic" factor. Spark plug heat range, ignition timing, fuel/oil ratio, and numerous other improper adjustments can all lead to detonation. In conclusion, YES, high octane fuels can right many wrongs that lead up to detonation. In some cases you must use a high octane fuel to overcome a fundamental design issue. In many of these cases manufacturers recommend high octane gasoline because they feel it is important, and able to overcome whatever design issues may exist. I would recommend high octane fuel always be used in severe climates and riding conditions that would generally cause hot temperatures on your bike. I also normally use high octane gasoline in all air cooled applications to be on the safe side, but again, I'm in the desert southwest so I feel this is a worthwhile precaution. Hope this helps explain some of the detonation related issues and why higher octane gasoline is sometimes required.

05-10-2008, 11:02 AM	#13
CaptCrashIdaho Safety Hooligan Join Date: Sep 2007 Location: SW Idaho! Posts: 1,679	I'm gonna stick my neck out a little here... Most folks run high Octane for two reasons: 1. They have the impression that Octane is like "Proof". I.E. 180 proof means more alcohol...therefore 93 Octane has more power. 2. It costs more. So it MUST be better. These are common misconceptions. I work at a high school. Do you know why most kids want an IPod? 'Cause it's an IPod. ANY Mp3 player will do the same thing...but it's the mystic/status of the IPod they want. Same with gas. One interesting aside here, it's my understanding that internationally, octane ratings are generally lower than they are here in the states. I have a friend who's involved in a medical/missionary outreach. They send KLRs abroad. One of the first things they do is lower the compression to handle looooow octane gas sold in the 3rd world.

05-10-2008, 10:08 PM	#14
TFee3 Senior Member Join Date: Aug 2007 Location: Gravois Mills MO Posts: 1,890	My Suzuki calls for 87 octane, and I'm sticking with it. It runs fine! Maybe this has been asked before, but if a knock can't be detected, then how do you know it's helping to run higher octane gas? Believe me, I'm not trying to be a wise guy, but in this case, I feel it's a valid question.

05-11-2008, 12:41 AM	#17
CaptCrashIdaho Safety Hooligan Join Date: Sep 2007 Location: SW Idaho! Posts: 1,679	See there's that "quality" question again...IS Bacarti higher quality because it's higher proof? I don't begrudge anyone using premium. In fact, I ran it in my GSXR1100 for years--and would do the same thing again if I had a high performance bike (jetted/piped) that I routinely flogged. But for what I'm riding now? Big single...heck it's a medium single...and 93 seems a bit extreme. Here's the wierd part: I switched from premium to regular as an experiment. Guess what happened? Gas milage jumped from 55 to 60mph. No idea why. Gonna have to talk to the microwave about it...