octane?
Road Master
Joined: Feb 2006
Posts: 897
Likes: 0
From: South-Central Minnesota
RE: octane?
ORIGINAL: Jehu
Much of what makes it into the owner's manual is there to protect the MoCo, not you and your machine. All other things being equal, you will get more horsepower andmore efficiency from a lower octane fuel, absent predetonation. Getting more power form higher octane is one of the most widely misunderstood concepts in modern machinery! If you are running high compression, high heat or other conditions that warrant high octane, then you are constrained. Unless I am at en event and know that I am going to begetting stuck in traffic with high ambient temperatures, I run regular and have had no problems whatsoever. I enjoy more power and lower operating costs. Recommending higher octane in lower compression engines is a safe way for the manufacturer to avoid problems with premature detonation.
The example posted above with higher mileage is not surprising at all - in fact, it is to be expected.
I have expressed whatI do on my bike. Don't try this at home - YMMV.
Much of what makes it into the owner's manual is there to protect the MoCo, not you and your machine. All other things being equal, you will get more horsepower andmore efficiency from a lower octane fuel, absent predetonation. Getting more power form higher octane is one of the most widely misunderstood concepts in modern machinery! If you are running high compression, high heat or other conditions that warrant high octane, then you are constrained. Unless I am at en event and know that I am going to begetting stuck in traffic with high ambient temperatures, I run regular and have had no problems whatsoever. I enjoy more power and lower operating costs. Recommending higher octane in lower compression engines is a safe way for the manufacturer to avoid problems with premature detonation.
The example posted above with higher mileage is not surprising at all - in fact, it is to be expected.
I have expressed whatI do on my bike. Don't try this at home - YMMV.
Road Warrior
Joined: Dec 2007
Posts: 1,437
Likes: 0
From:
RE: octane?
ORIGINAL: Jehu
Much of what makes it into the owner's manual is there to protect the MoCo, not you and your machine. All other things being equal, you will get more horsepower andmore efficiency from a lower octane fuel, absent predetonation. Getting more power form higher octane is one of the most widely misunderstood concepts in modern machinery! If you are running high compression, high heat or other conditions that warrant high octane, then you are constrained. Unless I am at en event and know that I am going to begetting stuck in traffic with high ambient temperatures, I run regular and have had no problems whatsoever. I enjoy more power and lower operating costs. Recommending higher octane in lower compression engines is a safe way for the manufacturer to avoid problems with premature detonation.
The example posted above with higher mileage is not surprising at all - in fact, it is to be expected.
I have expressed whatI do on my bike. Don't try this at home - YMMV.
Much of what makes it into the owner's manual is there to protect the MoCo, not you and your machine. All other things being equal, you will get more horsepower andmore efficiency from a lower octane fuel, absent predetonation. Getting more power form higher octane is one of the most widely misunderstood concepts in modern machinery! If you are running high compression, high heat or other conditions that warrant high octane, then you are constrained. Unless I am at en event and know that I am going to begetting stuck in traffic with high ambient temperatures, I run regular and have had no problems whatsoever. I enjoy more power and lower operating costs. Recommending higher octane in lower compression engines is a safe way for the manufacturer to avoid problems with premature detonation.
The example posted above with higher mileage is not surprising at all - in fact, it is to be expected.
I have expressed whatI do on my bike. Don't try this at home - YMMV.
Higher octane fuels burn badly and slowly in low compression, low temp engine, yelding less power and fouling plugs and valve sockets.
Higher octane, per se, is useless.
It can benefit only an engine tuned to exploit its properties.
An egine will be tuned to work properly, and without detonation, with a certain grade of gas.
Detonation occurs when pressure and temperature conditions in the firing chamber exceed those intended for the fuel rating being used.
Temperature and pressure are interdependent, but the main factor that causes detonation in an engine is temperature.
If an engine is tuned for 91 Octane fuel, using 100 octane fuel will give no benefit, and may even have drawbacks.
Conversely, using 91 octane fuel in an engine tuned in ignition advance and compression for a 100 octane gas will produce pinging and, eventually, catastrophic engine failure.
To prevent this, modern engines have pinging sensors that reduce advance to compensate for lower grade fuel: this will yeld a noticeable decrease in power.
So, since using lesser grade fuel produces a decrease in power in engines tuned for a higher grade fuel, people is prone to think that higher octane fuel yelds more power. This is a crass misconception. It's lower grade fuel that yelds less power in engines tuned for a better grade.
In other words: an engine will yeld as much power as the octane grade it's been tuned for, and no more. It can produce less, if you use a lesser grade fuel, and if the engine has pinging detection (otherwise you'll just destroy the engine!).
It won't produce more power no matter how higher the fuel grade you use, unless you re-map the engine to exploit the extra anti-detonation properties of that fuel, and map a larger advance in the ignition map.
Hope I made things a little easier to understand.
Thread Starter
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Road Captain
Joined: May 2007
Posts: 579
Likes: 1
From: eastern NC
RE: octane?
ORIGINAL: Jehu
Much of what makes it into the owner's manual is there to protect the MoCo, not you and your machine. All other things being equal, you will get more horsepower andmore efficiency from a lower octane fuel, absent predetonation. Getting more power form higher octane is one of the most widely misunderstood concepts in modern machinery! If you are running high compression, high heat or other conditions that warrant high octane, then you are constrained. Unless I am at en event and know that I am going to begetting stuck in traffic with high ambient temperatures, I run regular and have had no problems whatsoever. I enjoy more power and lower operating costs. Recommending higher octane in lower compression engines is a safe way for the manufacturer to avoid problems with premature detonation.
The example posted above with higher mileage is not surprising at all - in fact, it is to be expected.
I have expressed whatI do on my bike. Don't try this at home - YMMV.
Much of what makes it into the owner's manual is there to protect the MoCo, not you and your machine. All other things being equal, you will get more horsepower andmore efficiency from a lower octane fuel, absent predetonation. Getting more power form higher octane is one of the most widely misunderstood concepts in modern machinery! If you are running high compression, high heat or other conditions that warrant high octane, then you are constrained. Unless I am at en event and know that I am going to begetting stuck in traffic with high ambient temperatures, I run regular and have had no problems whatsoever. I enjoy more power and lower operating costs. Recommending higher octane in lower compression engines is a safe way for the manufacturer to avoid problems with premature detonation.
The example posted above with higher mileage is not surprising at all - in fact, it is to be expected.
I have expressed whatI do on my bike. Don't try this at home - YMMV.
the way I understand it is that higher commpression engines produce more heat thus needing higher octane which requies higer compression/ heat to fire.
Lower octane will detonate at lower compression / heat.
So if the heat / commpression were to high for the lower octane the engine would be trying to run on / continue to run or diesel as some would say.
so as long as there is no pinging and no run on when you switch the engine off I dont think there would be any problems.
What do you think?
Road Master
Joined: Aug 2005
Posts: 1,049
Likes: 5
From: IOWA
RE: octane?
When you see the octane rating at the pump, that number is the lowest it can be. In most cases the actual rating is higher than the posted number. So 89 octane posted could actually be 90 or even 91.
Tourer
Joined: May 2007
Posts: 264
Likes: 0
RE: octane?
Well I run ancarburated evo, and here in Canada only the priemium fuel is ethanol free. I have been told that the ethanol in the regular gas is hard on the motor, (maybe notas much with the fuel injected models) but the difference in preformance is noticable. One mechanic friend has inquired and the ethanol % in regular gas is anywhere between 6 and 10 %.
Road Warrior
Joined: Dec 2007
Posts: 1,437
Likes: 0
From:
RE: octane?
ORIGINAL: rydermike
Ethanol itself is about 115-117 Octane , yet has on;y about 1/2 the energy level of similar ocatane gas
Ethanol itself is about 115-117 Octane , yet has on;y about 1/2 the energy level of similar ocatane gas
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Stellar HDF Member
Joined: Jan 2007
Posts: 2,626
Likes: 1,347
From:
RE: octane?
99, You are correct but I respectfully disagree with one small statement, that temperature and pressure are independant of eachother.
Boyles Law dictates that a gas when compressed heats up and when expanded cools; gas when heated expands and when cooled contracts. It is for this reason that higher compression will yield higher heat.
Also, because heat is a mandated by=product of power in an internal combustion engine, the only ways to get more power are:
1. Move more oxygen through the engine within a confined time period through
a) Displacement, b) more intake cycles or revs, c) pressurized intake such as turbo or blower, d)vooler/denser intake air through environmental factors, intercooler, etctera.
2. A more vilent explosion and push of the piston on the power stroke through things like compression and tweaked ignition/cam timing.
Of course, these things may be combined and oftentimes are.
Higher octane works against a more violent explosion and more forcefult hrow of the piston on the power stroke. It does, as you state, burn slower,cooler and longer which, while counter-performance is better for reliability.
Like the S&S engineer said to me when we were talking about the then-prototype X-Wedge engine a few years agao, I asked "What horsepower ratings will it be capable of and ultimately released in?" He said as to the latter about three different numbers which I forget - but, most importantly, as to the first part of my question, he said, "How long do you want it to last."
Top fuel drag engines last a pass or three and their existance is completed. General Aviation aircraft air/oil cooled piston engines generally develop one-half hoprsepower per cubic inch. i.e. a Lycoming O-360 (4 cylinder Opposed 360 cubic inch) will typically be only rated for 180 horsepower - but they last foreverburning 100 octane low lead fuel.
Boyles Law dictates that a gas when compressed heats up and when expanded cools; gas when heated expands and when cooled contracts. It is for this reason that higher compression will yield higher heat.
Also, because heat is a mandated by=product of power in an internal combustion engine, the only ways to get more power are:
1. Move more oxygen through the engine within a confined time period through
a) Displacement, b) more intake cycles or revs, c) pressurized intake such as turbo or blower, d)vooler/denser intake air through environmental factors, intercooler, etctera.
2. A more vilent explosion and push of the piston on the power stroke through things like compression and tweaked ignition/cam timing.
Of course, these things may be combined and oftentimes are.
Higher octane works against a more violent explosion and more forcefult hrow of the piston on the power stroke. It does, as you state, burn slower,cooler and longer which, while counter-performance is better for reliability.
Like the S&S engineer said to me when we were talking about the then-prototype X-Wedge engine a few years agao, I asked "What horsepower ratings will it be capable of and ultimately released in?" He said as to the latter about three different numbers which I forget - but, most importantly, as to the first part of my question, he said, "How long do you want it to last."
Top fuel drag engines last a pass or three and their existance is completed. General Aviation aircraft air/oil cooled piston engines generally develop one-half hoprsepower per cubic inch. i.e. a Lycoming O-360 (4 cylinder Opposed 360 cubic inch) will typically be only rated for 180 horsepower - but they last foreverburning 100 octane low lead fuel.
Road Warrior
Joined: Nov 2005
Posts: 1,942
Likes: 2
From: LAKESIDE CA.
RE: octane?
I don't know but I have been running mid graae for years and have had no problems
mileage is mid to hi 40"s yes it will ping if I lug it, so I don'y only got just over 40 thou on bike so things may change
[IMG]local://upfiles/5757/CC5C4EA0D52E4255863A35F45B6DCF0C.jpg[/IMG]
mileage is mid to hi 40"s yes it will ping if I lug it, so I don'y only got just over 40 thou on bike so things may change
[IMG]local://upfiles/5757/CC5C4EA0D52E4255863A35F45B6DCF0C.jpg[/IMG]