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Gotta love high octane fuel

Discussion in 'Moto Club' started by fireman jb, May 14, 2006.

  1. fireman jb

    fireman jb

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    I had some work done on my bike and found a shop that sells 116 octane race fuel.:alien: So of course I had to get some for the bike. Not cheap at all $8 a gallon. Here in Anchorage you can only get 90 octane and with the motor work done to my bike I wanted some thing with a higher octane so now I just mix. Today was my first ride with the mix and I could tell a difference. A little more pep, a lot better smell. I love the smell of race fuel. My tank is only 3 gallons so I'm mixing 1 gallon of 116 to 2 gallons of 90. The guy at the race show said it should put me around in the 98-100 octane range. I think that should be good. After one tank it's even turning the insides of my exhaust that nice grey color. No more nasty black ashy pipes. I also just changed my oil and put in some Royal Purple. All I've heard is good stuff about it so hopefully that will have good results just like the fuel. Anyway just wanted to tell anyone that would listen. The wife doesn't really understand and truthly doesn't really care as long as I'm happy with it. Anyone else mix race fuel?
     
  2. F14Scott

    F14Scott Luggage CLM

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    What kind of bike are you running? I ask because I'm curious about the performance differences you believe the race fuel is giving you.

    As I understand octane ratings, they actually have a slightly inverse effect on fuel energy. That is, the higher the octane, the less volatle the fuel.

    Octane refers to a fuel's ability to resist detonation, called knock. Detonation is usually caused by some combination of increased pressure and/or increased heat inside an engine. Highly tuned race bikes, ones with turbos or otherwise high compression ratios, or ones with hot spots like hot spark plug or exhaust valve parts, have a tendency to light off the air/fuel mixture explosively, instead of as a fast, smooth burn. This slaps the piston, harming it and making a knocking sound.

    By decreasing a fuel's tendency to light off, raising octane actually lowers a fuel's volatility. For maximum performance, one should use the fuel with the highest volatility possible without knock. Therefore, one should try to use the lowest octane possible without knock.

    If your bike wasn't knocking (or trying to knock before a knock-sensing system sensed the knock and detuned the engine to prevent it), then adding racing fuel shouldn't make any difference or could even hamper the engine slightly, because of decreased volitility.

    Race fuel shouldn't have much to do with the color of your exhaust soot, as that is caused primarily by the mixture and temperature of the combustion chamber.
     

  3. RonC

    RonC

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    Ditto F14Scott.

    The advantage of higher octane is to allow higher compression, which doesn't happen automatically. You have to do something to the engine, like increase piston travel, add domed pistons or up the boost on the turbo charger.

    The effects can be quite dramatic. For example at the beginning of WWII, the famed Merlin engine, used in Spitfires and, under license, in the P-51, was rated at 1000 hp using whatever octane fuel was then available, no higher than 90.

    With the advent of catalytic cracking and hence higher octane in the range of 110 to 120, the same engine was developing near 2000 hp by the end of the war, by allowing higher supercharger boost before preignition endangered the engine.

    As I recall, the Merlin supercharger could provide greater than 150 inches of boost!
     
  4. fireman jb

    fireman jb

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    I've posted pics and upgrades on a few of my posts. Like the I won post. But we'll go throught it again. I have an American Ironhorse with a 111" S&S motor. The motor has been balanced, ported and polished, heads have been decked ( higher compression) and a custom cam. I personly think that is plenty of motor work to run more then the highest you can buy at the pump, 90 octane here in Alaska. What do you guys think? As I said in my first post I've had a little motor work done. No I don't have a knock sencor yet but I'm going to be insalling one this winter. S&S has come out with a very nice ignition that sences knock and adjusts timing according to ride style and the needs of the motor. And yes a higher octane more efficient fuel in a worked motor will turn the inside of the exhaust pipes a different color. Check any drag bikes out the track or better yet check any AMA bikes out at the road races there tail pipes will have a nice grey almost white exhaust tip. A very pretty site. Ot's just another way to tell how your engine is running. Just like reading your plugs.
     
  5. wolfy692005

    wolfy692005 pro tinkerer

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    if you run 10:1 or higher you are supposed to run 92 + octane... i have 10:1 in my 100" v-twin motor as well..
     
  6. fireman jb

    fireman jb

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    I'm not sure the compression I'm running now but a stock 111" S&S runs 9.5:1 so I know I'm running well over 10:1 now. But the highest pump gas you can buy in Anchorage is 90. Hence the reason I'm mixing fuel.
    Wolf what octane do you run in your twin? There is a guy here with a fatboy that has a Supercharged Nitrous fed 100" S&S he splits his fuel 50/50 116/90 octane. But he has even more work done then mine. In South Carolina I could get 93 octane at the pump then would usually bump it up with some NOS octane booster.
     
  7. DaisyCutter

    DaisyCutter

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    I've experimented with race gas in my race bike. It smells faster, that's about it. ;)
     
  8. fireman jb

    fireman jb

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    You have any motor work done? I guess that would depend on what classes and sanctioning body you race under.
     
  9. fiveoboy01

    fiveoboy01

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    You should use the lowest octane fuel which will allow your engine/its tuneup to run under load without detonation.

    Any more octane is a waste of $ and equals less power.
     
  10. DaisyCutter

    DaisyCutter

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  11. fireman jb

    fireman jb

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    I see how you could feel obligated. That is a clean looking bike. Trick race fuel is the fuel I'm running in my bike. I used to run VP race fuel in my race bike.
     
  12. kengps

    kengps

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    I haven't been there in a year or so, but the filling station on King's road behind Costco was selling Avgas there. It is 100 octane. That is equal to about 95 using the automotive rating. Might want to give that a try.

    I have to say that the smell of burned race gas is something that I love. Put at least a thousand miles on the track at Daytona back when I was racing. The smell of burned race gas in the morning when the air is still brings back a lot of memories.
     
  13. fireman jb

    fireman jb

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    Thanks Ken, I'll have to check that place out.
     
  14. gixxer11

    gixxer11 bbrrraaapppppp!

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    Hey fireman, does whoever did the engine work know how many cc's your heads are? 10cc head on a 100cc cylinder is 10:1 for example. The white stuff you see is usually lead in the fuel. Sometimes a bike needs to be jetted when you change fuel due to O2 content. Check you exhaust temps compared to pump fuel. lower temps mean a richer mixture(i.e less O2). Also compression ratios aren't as important as cylinder pressure when running. If you have a dual plug head it makes it easy to find out. My 1340cc GSXR has 275psi @ idle. The pistons are rated @ 14:1 but after all the other stuff, that number is thrown out the window. It's probably slightly lower than that. For example I have very big cams that are advanced, so I need more clearance, which lowers the comp ratio. I've run VP Ultima 4 with "only" 90 octane (IIRC) and had to up my jet sizes. Made approx 10 more HP at the wheel. An '02 GSXR 1K I had built made almost 15 more on the stuff. It's low octane but very high in O2. I've even seen stock bikes make more power with it. If your bike likes it, why argue. Just my .02
     
  15. fireman jb

    fireman jb

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    Gixxer I don't know how big the heads are. The guy that I bought the bike from had all the engine work done. I don't even know how to contact him now.