RE: Octane, Compression Ratio, and Detonation.
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RE: Octane, Compression Ratio, and Detonation. - 10/10/2006 12:07:00 PM
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voodoochyl
Posts: 6166
Joined: 7/31/2006
From: Grants Pass, Oregon
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The dealer I bought my bike from recommended 91 (are they in bed with the oil companies?). I am considering going down a grade, but I read somewhere about unplugging your battery when you change octane to "re-set" the bike. Any validity to this?
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RE: Octane, Compression Ratio, and Detonation. - 10/10/2006 12:20:27 PM
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HondaCBR600RRhunk
Posts: 79
Joined: 10/5/2006
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Sounds like hog wash to me, about resetting with the battery and sh*t. Go to the other post I mentioned above, its causing a lot of controversy, what fun!!!
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RE: Octane, Compression Ratio, and Detonation. - 10/12/2006 12:30:39 AM
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bushmasterAR15
Posts: 1040
Joined: 8/11/2006
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Dthomspon:
quote:
There will be someone in here that wants to argue. i have argued in 2 different threads about how you should run what they recomend. Everyone else seems to think its a matter of being cheap or something. I think its funny really. There are alot of people on this forum that "think they know, but they have no idea."
HAHA
quote:
I always run 93 octane in my bike no matter what anyone on here says. Always worked for me.
Seems like you should be arguing this one DThompson, wait, are you for or against it??
< Message edited by bushmasterAR15 -- 10/12/2006 12:36:42 AM >
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RE: Octane, Compression Ratio, and Detonation. - 10/12/2006 2:00:24 AM
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chainstretcher
Posts: 3850
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bushmaster -- what you trying to do ... stir the pot?
Eventually I'll change my tune and go along with the '93 is best no matter what anybody says' mentality. I figure with all the peeps buying the 93 then my 87 will be much cheaper
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RE: Octane, Compression Ratio, and Detonation. - 10/12/2006 2:09:00 PM
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bushmasterAR15
Posts: 1040
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No, just thought his posts were funny,
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RE: Octane, Compression Ratio, and Detonation. - 3/29/2007 1:59:28 PM
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mkhaynesaz
Posts: 313
Joined: 7/6/2006
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ok i am stll a little confused should i run 91-or 87 on my 061krr?i have only ran 91 or better beacuse that is what the dealer told me. i had a turbo car a while back that need 91 but it was turboed. i read this post and still very confused 
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RE: Octane, Compression Ratio, and Detonation. - 3/29/2007 2:20:51 PM
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Jaybird180
Posts: 2521
Joined: 5/12/2006
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Read the manual. Your dealer may not be as informed as he purports to be. But then again, he may know something about the gas in your local area.....
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RE: Octane, Compression Ratio, and Detonation. - 3/29/2007 4:42:20 PM
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Tahoe SC
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check with your manual...it'll tell you exactly what you need to run, but make sure you are not confusing RON for PON, etc.
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RE: Octane, Compression Ratio, and Detonation. - 3/30/2007 1:05:53 AM
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slipper
Posts: 159
Joined: 8/19/2006
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mkhaynesaz, im not sure about a 1000RR. If im not mistaken they actually do require 91 octane. Check your owners manual.
< Message edited by slipper -- 3/30/2007 1:07:05 AM >
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RE: Octane, Compression Ratio, and Detonation. - 3/30/2007 11:14:30 AM
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bmg velocity
Posts: 1353
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I understand the argument...or a better word...reason...to use low octane fuel.
I also understand how an engine works...haven't repaired or rebuilt every single one made...but have some and understand...
Intake..the piston in a given cylinder is traveling down...creating a vaccum...thus INTAKING...the fuel...
Compression...piston is beginning to travel up...making the cylinder area smaller and smaller as the piston rises...and gets closer to both
the intake valves and the spark plug, which ignites the gas molecules, tiny droplets of both fuel and air, aka atomized mixture.
This gets all that wonderful gasoline and air mixture, which is what explodes/burns and forces the piston to turn the crankshaft,
into the most compact and efficient gaseous form possible.
Ignition...this starts just about when the piston is at it's highest point...just before top...dead...center...or TDC.
When the piston is at full TDC...ideally this is when the fuel and air mixture should be at it's most dense, causing the cleanest burn
(controlled explosion) possible.
(Before TDC is how you set the timing for a particular engine...but that's another topic.)
Exhaust...any unspent energy not efficient enough to turn the crank, which turns the sprockets, which drive the chain,
which turns the rear wheel, which propels you forward....wheeeeeeeee....
the waste products from the unburned fuel, fuel is not absolutely pristine and sterile stuff afterall...
...and to dis-allow a build up of so much pressure that the enitre engine would eventually explode...
The Exhaust valve opens...the gases run out the valves...into the headers...down the pipe(s)...and out the exhaust canister.
That is what is known in laymen's terms as Suck...Squeeze...Bang...Blow.
Having said all that....?
My 94 F2 run better on 93 octane fuel...whether it's supposed to or not.
The engine has more power...has less naturally occuring stumble...and makes a lovelier hum on 93.
On 86...it runs like ass.
Go figure.
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Does not want to debate insurance co.'s or bad drivers for at least a decade or 10. Want to argue the merits? You are a one man show. Sorry no takers here.
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RE: Octane, Compression Ratio, and Detonation. - 3/30/2007 2:13:16 PM
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jbreit
Posts: 306
Joined: 10/13/2006
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this topic needs some science...not just blather. I wrote most of this some time ago on another forum...for sleds in particular.
Tahoe mentioned the RON and (R+M)/2 versions of octane number..he's right on. The octane requirement of a straight RON number would be a higher number than an (R+M)/2....so check what the mfr calls for.
Octane is a measure of the energy it takes to ignite a fuel (resistance to detonation is a different perspective, but gets the same point across). It is NOT a measure of the energy in the fuel. Power improvements from utilizing higher octane are a result of improved effeciency in the combustion process. Energy in the cylinder has various forms and comes from the compression of the air/fuel, from the heat in the piston/head/cylinder walls/spark plug and the last energy to throw gas over the hump is from the spark itself. This energy input is necessary to create the downhill chemical process....fuel+O2+energy = water, CO2, and LOTS of energy. When you don't have enough energy to get it over the hump the combustion process is not completed in the intial event.
Ideally the fuel/air mix is ignited by the spark before TDC and the flame front travels out radially from that point....and by the time the process creates pressure, the piston is on the way down (we are talking a couple degrees after TDC). This event is obviously VERY fast...but so is the piston speed at 7000rpm.
In lean mixture, the flame front has trouble propagating. In a rich mixture, the extra fuel robs heat from the reaction, or prevents the spark from jumping the gap in the plug.
If you use a higher octane than called for, not all the fuel ignites from the initial energy put into the chamber by the spark (remember the lower octane RON number portion of the fuel)...for the rest of the fuel to ignite, it takes the added energy of heat and pressure caused by the flame front to ignite it. This can create other smaller flame fronts in remote area's that impeed progress of the initial front in the worst cases. Regardless, by the time full combustion has happened its too late for it to contribute to the power making process....well, not very efficiently anyway....you are building pressure, but the piston is already moving away.
Higher octane is not running your engine lean in the sense of mixture, but a similar effect on power....a more comparable description would be retarding your timing. You wouldn't change jetting to make the best use of higher octane, you would change your ignition timing or compression. Newer cars with knock sensors do the prior. You bike doesn't have a knock sensor, and the ecu has no data logging or avergaing capbilities...there's no reseting or whatever.
Ethanol (alcohols) actually has a higher octane rating than gasoline. Many gas station sell 87 octane with 10% ethanol added to sell you 89 octane. However, ethanol has a lower energy content and is hydrophillic (absorbs water). Yeah, thats bad. It creates a lot of difficulties for the gas companies in terms of mixing and transporting. Ethanol mixtures will run lean in carbureted engines...bikes, sleds, weed eaters...you name it. It can be compensated for in jetting.
Compression ratio alone doesn't dictate octane...though they go hand in hand. 2 strokes will always be lower compression than a 4 stroke on the same octane because the cylinder is warmer....it doesn't get a whole pumping cycle to cool off.
Static compression is the number everyone throws around, and is a ratio of the swept cylinder volume to compressed volume. And truely, running compression ratio's are mostly anything but that number....cylinder filling efficiecies are 75-80% at low rpms (and WOT) but they exceed 100% at high rpms (and Wide Open Throttle)...how is by acc
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RE: Octane, Compression Ratio, and Detonation. - 3/30/2007 3:29:48 PM
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bmg velocity
Posts: 1353
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First of all...excellent post...though some may find it a bit...wordy...
I liked it...
quote:
Ethanol (alcohols) actually has a higher octane rating than gasoline. Many gas station sell 87 octane with 10% ethanol added to sell you 89 octane. However, ethanol has a lower energy content and is hydrophillic (absorbs water). Yeah, thats bad. It creates a lot of difficulties for the gas companies in terms of mixing and transporting. Ethanol mixtures will run lean in carbureted engines...
Ethanol ruined the fuel system in my old...220k+ Mits Eclipse.
Also, it costs more to make a gallon of ethanol gas than it is sold for...so yes...politics.
Where do you get this U4 race gas...and what jetting kit are we talking?
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Does not want to debate insurance co.'s or bad drivers for at least a decade or 10. Want to argue the merits? You are a one man show. Sorry no takers here.
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RE: Octane, Compression Ratio, and Detonation. - 3/30/2007 5:24:42 PM
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Tahoe SC
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now why would a car designed to run on 87 require higher octane?
it's possible that due to age, there is enough build up of carbon deposits, etc. within the cylinders to increase operating temps dramatically, pressure, etc. lower octane fuels in this environment would combust even before TDC due to the high operating temps...so you stick in higher octane and it makes the engine run much better.
i'm not saying this is what is up with BMG's bike, but just some possible answers.
anyone remember dad's old a$$ olds or buick that always pinged and ran like crap...and if you turned off the engine, crazy car would still sit there idling for a bit?
put high octane in there and it ran great...and we stood around and said...WTF? hahahahahhah
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