How Can I run 87 Octane Fuel?


46 replies to this topic
  • chrispy1202

Posted June 12, 2008 - 12:50 AM

#21

If you really want to run 87 octane, all you have to do is modify the engine mounts and strap in a klr 650 engine......
I couldn't help myself-- sorry!

  • wayfarer103

Posted June 12, 2008 - 04:38 PM

#22

my local gas station has 92(i think). i only do trail/woods riding. am i ok with that?

  • glasseye

Posted June 12, 2008 - 04:47 PM

#23

Try 87 octane and see how it performs. I just started running 87 in my 12.5:1 comperssion sport bike and it actually runs stronger and gets better gas milage.

If it pings or runs hotter, then you are SOL on the lower octane.

  • grayracer513

Posted June 12, 2008 - 04:53 PM

#24

my local gas station has 92(i think). i only do trail/woods riding. am i ok with that?

Yes you are. That's actually a higher octane than the manual calls for.

  • MountainMax

Posted June 12, 2008 - 05:34 PM

#25

lower octane fuel actually makes more power, the problem is in our bikes it can be hard to hear detonation, especially with a YZ muffler on there.

  • grayracer513

Posted June 12, 2008 - 09:03 PM

#26

lower octane fuel actually makes more power,

That is also incorrect. Octane is completely unrelated to the burn speed or energy content of a fuel. Read the link I posted.

  • MountainMax

Posted June 13, 2008 - 01:52 AM

#27

I was told, and read, that you should use the lowest octane fuel you can to make more power, too high of an octane fuel will cause it the fuel to burn more slowly and actually make you loose power.

  • grayracer513

Posted June 13, 2008 - 08:16 AM

#28

I was told, and read, that you should use the lowest octane fuel you can to make more power, too high of an octane fuel will cause it the fuel to burn more slowly and actually make you loose power.

Nope, that's wrong. You can run the lowest octane fuel the engine will tolerate, and you will save money doing that, but there's no gain in power. Conversely, you can run as high an octane number as you like with no problems under most circumstances, but there is no advantage to it beyond the point that the engine ceases to ping.

Octane measures detonation resistance. That is, the fuel's resistance to igniting from exposure to pressure and heat, rather than an open flame. Detonation differs from combustion in that combustion moves from one molecule to the next, like a wave, like igniting the edge of a piece of paper, whereas detonation is the spontaneous combustion of all of the fuel at the same instant.

In the worst possible case, fuel with an extremely low octane number would detonate from the heat of the compression stroke before the spark occurred. This is extremely rare, and extraordinarily destructive. Almost all detonation occurs after normal ignition takes place. The spark ignites the fuel, and the flame spreads outward. As the flame spreads, the pressures in the combustion chamber build rapidly, but the unburned fuel ahead of the flame front must not burn until contacted by the flame itself. If the octane number of the fuel is too low, it will ignite from the heat and pressure before the flame reaches it, and the detonation of the unburned portion of the fuel will cause a "ping".

If you had two fuels that both had the same octane number, but one burns faster, the faster burning fuel will show a greater tendency to ping in spite of the fact that the actual octane is the same between them. Why? Both fuels would tolerate the same amount of heat and pressure before detonating without a spark. But the faster fuel would be more prone to pinging because it would be the same as running the slower fuel with more spark advance. Combustion pressures would rise to critical levels earlier, and even though its tolerance for that would be the same as the slower fuel, it would be more apt to ping. In a true technical sense, this is slightly over simplified, but I did that to make the point.

Where you run into this most often is during spring and fall, when fuel blenders switch from summer blended fuels to winter blended, or vice-versa. It most often shows up as a complaint from car drivers in the first cold snap that their car has to crank longer to start, and doesn't stay running until it warms up a little, which is caused by the slower vaporization and combustion rates of summer fuels. At one time, say 35 years ago, there was one blend of fuel, and the correction for ambient temperature was routinely handled by getting your timing adjusted during a $20 minor tune-up, but with almost all modern ignitions having non-adjustable timing, that can't be done anymore. The solution was to tweak the gas.

If you have a fuel that you know of that verifiably produces more power in your bike than another, it is either because the fuel chemistry simply contains more energy and less junk ingredients, or because the burn rate of that fuel is a better match to your ignition timing and dynamic compression. If it also does not ping, it has a high enough octane number for you. But the two issues are completely unrelated to each other.

  • wayfarer103

Posted June 13, 2008 - 01:34 PM

#29

im pretty sure my manual says run 95 or higher octane?

2000 wr 400f

  • grayracer513

Posted June 13, 2008 - 02:00 PM

#30

It does, but it also says (or should say) that that is 95 Research Octane Number (RON).

There are two methods of testing octane, Research, and Motor (MON). Both use test engines made for the purpose, but the Motor method is tougher, and more representative of a high performance engine's demands on fuel. Because of this, the Motor method produces lower octane ratings for any given fuel than the Research method. 95 RON is about like 87 MON. Research octane is common in Europe, Asia, and elsewhere, but US gas pumps are labeled with a Average of the two. That's what the notation on the pump, R+M/2, means. A US pump grade of around 90 is roughly 95 Research octane, so a US pump grade of 92 is higher than called for by the manual.

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  • rafartist

Posted June 13, 2008 - 02:42 PM

#31

I haven't posted here in a LONG time but I feel the need too about octane ratings and hp. I have personally watched dyno runs with normally aspirated engines and turbo charged applications and I have personally witnessed small hp increases with lower octane fuels. My Grand Cherokee (V8) and my 06 VFR800 both run better on lower octane fuel and get better gas mileage. I have also tried darn near every brand of gas out there too and feel that all of my vehicles run best on BP, and that is from personal experience, not from a magazine. I would like to know if anyone else out here has witnessed dyno runs with different octane fuels. BTW, the fuel purchased was from the same manufacturer, from the same pump at the same time just 87 and 91 or 93, I cant remember.

  • grayracer513

Posted June 13, 2008 - 03:07 PM

#32

Unless you can show that the only difference in the different fuel grades you tested was the octane number, the tests are not scientifically supportable. There are far too many variables in fuels, even among fuels of different grades from the same refiner, that bear on energy content that you very likely failed to evaluate prior to this test.

I can select fuels from VP (because their chemistry is available) that would either all produce the same power (within a few percent) regardless of octane number, or produce different levels of power at the same octane number. It may inadvertently have something to do with the way that the octane number was adjusted, but not with the octane. For example, toluene raises octane number and increases energy content. Tetraethyl lead and similar compounds increase octane, but are otherwise reasonably inert, and actually lower energy content by displacing energy bearing components.

If, as I said before, you have found a fuel that produces more power than another, and doesn't ping, run it. There's no reason not to. But the results you got had nothing to do with the octane number.

  • dirtrider04

Posted June 13, 2008 - 03:45 PM

#33

i run 87 in my 07 and it runs great, leave it

  • TommyTheKid

Posted June 14, 2008 - 04:10 PM

#34

Something else to consider is altitude. At sea level, the octane's available are like 87, 91 and 93. Here in the Denver area (~5280ft) its 85, 87, 91. Up in the mountains, I have seen 85, 87, 89. If you are running at a much higher elevation (8000+ ft) maybe 87 is quite fine. Just a thought.

Tommy

  • Alternative

Posted June 14, 2008 - 04:44 PM

#35

Yeah, you're right. The higher the elevation the lower the octane needed. This is because the air pressure is lower up high so the relative pressure in the cylinder is lower, reducing the requirement for high octane fuel.

  • ghrocketman

Posted June 16, 2008 - 07:11 AM

#36

I'm pretty sure that under the RON only method Shell V-Power (93 AKI US "pump octane") is 100 octane and Sunoco Ultra is 101 octane (94 AKI US "pump octane")

One thing to note that many are unaware of, AV100LL "100 octane" AV Gas is 100 MOTOR (MON) octane and is about 108-110 AKI pump octane and about 120 RON research octane.
Before they went down to 2 grams of lead per gallon from 4 grams in "Grade 100" Aviation gasoline it was called AV 100/130 which was even higher in "pump octane" at about 115.
Av Gas is rated first by the MOTOR or 'lean mixture' octane, then by the supercharge/full rich octane (which is not the same as the automotive research number) AvGas is still roughly 100/130 gasoline but they changed the designation to AV100LL when they went to the lower (but still HIGH by automotive standards) lead content.

  • glasseye

Posted June 16, 2008 - 07:16 PM

#37

Two-strokes are entirely different, and information regarding their fuel requirements has no application in a discussion of four stroke engines. The main difference is that the 3-5% engine oil content of pre-mix fuel lowers the effective detonation resistance of the mix, so that you have to start out with a higher octane rated fuel in order to get away with it. A YZ450 with a CR or 13:75 can run 91-93 octane fuel (R+M/2 method), whereas a two-stroke running at 12:1 is often lucky to get by with 100.


Exactly what manufacturers make a 2-stroke with 12:1 compression ratio??

A couple of us here are sharing experience base on compiled data. Book smart is a good starting point, but every just out of school engineer I have worked with made more blunders in thier first year than I have made in my 30 years because I evaluate every situation with pure data, not what some proffessor that never worked in the real world says is correct.

I don't dissagree that pre-mix lowers the effective pre-detonation resistance, but that is just because it makes the fuel leaner. Jet it properly and it is a mute point!

  • glasseye

Posted June 16, 2008 - 07:21 PM

#38

I tried 110 octane in my WR426 once and ended up draining it out under the power lines. Ran like crap and fouled plugs, made it about 15 miles.

Higher octane is only a good thing when required to reduce pre-detonation in high compression engines. Too high of octane WILL decrease performance. Too low octane will cause "pinging" due topre-detonation.

  • grayracer513

Posted June 16, 2008 - 09:33 PM

#39

Exactly what manufacturers make a 2-stroke with 12:1 compression ratio??

A couple of us here are sharing experience base on compiled data. Book smart is a good starting point, but every just out of school engineer I have worked with made more blunders in thier first year than I have made in my 30 years because I evaluate every situation with pure data, not what some proffessor that never worked in the real world says is correct.

Two stroke compression ratios are measured in a static condition, from the point where the exhaust port closes, and are as high as 10.9:1 when done this way. True dynamic compression is considerably higher.

As far as being a just out of school engineer, that's hysterical. I was just out of school 41 years ago, and was a professional technician, machinist, and welder for 35 years. I was a mechanic for 6 years before my professional career started, and have been for the 7 years since I quit. Have we cleared that up? :thumbsup: Maybe we can go back to the subject then.

I tried 110 octane in my WR426 once and ended up draining it out under the power lines. Ran like crap and fouled plugs, made it about 15 miles.

Higher octane is only a good thing when required to reduce pre-detonation in high compression engines. Too high of octane WILL decrease performance. Too low octane will cause "pinging" due topre-detonation.

Once again, it was the specific fuel chemistry (incorrect vaporization rates, etc.) that caused your performance problems, not the octane itself.

Higher octane is in fact only necessary when required to suppress detonation, you are correct. But an excess is no more than a waste of money. To cite examples of a particular fuel or fuels with one or more performance attributes, be those desirable or not, and attributing any of them other than detonation control to the fuel's octane is silly, and the result of a general popular misunderstanding of octane. Oil company marketing campaigns over the last 65 years are at least partly to blame for this.

Pick up a can each of VP Red (105 MON), U4.2 (102 MON), and C44 (99 MON) and try them. The Red and the C44 (the highest and lowest octane of the 3) will behave much like the fuel you complained about, will require excessively rich mixtures, and produce poor economy, while the U4.2 will run very well. This is because U4.2 is blended for use in motorcycle engines, while the other two are optimized for big car engines with long manifold runners. AV Gas often performs poorly in motorcycles for the same reason.

Detonation and pre-ignition are also two different things. Pre-ignition can be one of the causes of detonation, and it can be caused by some of the same things as can cause detonation. But, they are not synonymous, and pre-ignition need not happen in order for detonation to occur.

  • MaxPower

Posted June 17, 2008 - 01:32 AM

#40

[COLOR="Green"]Im not telling anyone to run 87
Im saying I do and I did.I know what detonation sounds like.I know when my bike is lean,I know when it is rich.I am not a A level motocrosser but am not a putt putt trail rider.I have not heard my bike detonate and can not tell the difference between regular and premium fuel[/COLOR]




 
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