Premium fuel and risidual regular in the fuel hose

Discussion in 'The Perfect Line and Other Riding Myths' started by Patek, Nov 4, 2017.

  1. der_saeufer

    der_saeufer ?איפה בירה

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    The single-hose pump is the modern pump. Back in the bad old days, you'd often have three hoses--one for leaded, one for regular unleaded, and one for super unleaded. When leaded fuel was banned for sale 25-30 years ago (depending on state), most stations slowly switched from selling just regular and super to regular/mid/super. But most blenders don't actually make a midgrade product, so when you push the midgrade button you're getting a mix of regular and super at the appropriate percentages to give the advertised octane. Some stations even make 4 grades from the two grades that are delivered. Unless you're filling a scooter with a 1-gallon tank, the fuel left in the hose isn't going to make a difference... and if you have a scooter with a 1-gallon tank, it probably runs on anything that burns anyway.

    Diesel and EtOH blends over 10% get their own hose. American stations often have separate diesel pumps anyway since diesel passenger cars are still relatively uncommon--and look to remain that way as Europe gets on with trying to ban the cars they promoted so heavily just 10 years ago. When I drove diesels in the US, it was always fun to play "find the station with diesel" in a strange city.

    Europe and Australia just got rid of regular unleaded (RON 91/AKI 87) altogether, so everyone is paying for midgrade even though their vehicles generally don't need it.
    #41
  2. High Country Herb

    High Country Herb Adventure Connoiseur

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    Come on, man, try to be environmentally friendy. Spray the first half liter into the trash can next to the pump.

    :hide
    #42
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  3. Steve in Golden

    Steve in Golden Been here awhile

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    Has anyone considered the ramifications of whether one is sitting on the bike or standing while fueling, as to whether the residual fuel makes a difference or not?
    #43
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  4. VX Rider

    VX Rider Long timer

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    Yes, but only with a car tire on the back.
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  5. Steve in Golden

    Steve in Golden Been here awhile

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    And the car tire should be filled with nitrogen too.
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  6. aldend123

    aldend123 Long timer

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    Octane Boosters advertise that they raise by x points, but 1 point is a fraction of 1 octane. So to treat a full tank of gas, you may only increase by a couple octane. Instead, you can buy race gas at 100+ AKI octane.

    More importantly, they have little value to any vehicles without notable modification like increased compression ratio or a turbo. Most vehicles off the showroom floor are engineered to run on 87 to 91 AKI* octane, and won't benefit from running higher octane. I wouldn't be surprised if a newer turbo vehicle allowed some sort of 'race' mode which increased boost when run with something higher than 93. And it'd probably require some special acknowledgement in an in-dash screen menu. But I'm not aware of anything from the factory like that. There are some cars which will call for 91, but allow you to run 87 instead of something higher with the caveat that maximum power may be slightly reduced. The computer is able to retard ignition automatically using knock sensors.

    *Other countries use a different scale, like RON, and the number is slightly higher.
    #46
  7. Bar None

    Bar None Old School Dude

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    ^^^^^^^^^

    :dhorse
    #47
  8. Trailrider200

    Trailrider200 Been here awhile

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    contact your local weights and measures dept. They will know. they are also the ones that make sure the pumps are accurate and the octane dispensed is correct.
    #48
  9. randyo

    randyo Long timer

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    fwiw, 14 ft of 3/4" hose contains 0.32 gallons of fuel MAX if there is no drain back

    if you have a 1 gallon tank and are pumping 91 octane it would reduce yer octane rating to 89.7
    a 2 gallon tank would be reduced to 90.3
    3 gallon 90.6
    4 gallon 90.8
    5 gallon 90.9
    #49
  10. William Wolfen

    William Wolfen Dirt Seeker

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    Interesting thoughts there. Having owned a Subaru WRX, and having stupidly put 87 in it once when I wad distracted, I can say that octane boosters don't do shit. I tried a coupe bottles to see if it would help, but it didn't. Had to drive off a whole tank without building boost or it would retard the timing really severely.

    Also worth commenting that it was designed to run on 91. Around here, 91 is hard to get and premium is almost always 93. There is no system to take advantage of the higher octane fuel. Would be neat if there was, but I'm not sure if that would be a good idea, especially since you would likely have to tell it manually what fuel you're running. I doubt the average moron could handle that.

    As far as the ideas in the OP: but vehicles that run on 87 and don't worry about it? Saves you a load of money in the long run anyway with premium running a minimum of $0.40 more a gallon!
    #50
  11. curtis6870

    curtis6870 Long timer

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    Whole lotta do bout nuthin.
    I mean I guess if you are filling a plastic tank Duc or Ape with ethanol free and it will be sitting awhile it MIGHT be worth getting your shorts in a bunch...otherwise, not.
    #51
  12. MotoActionADV

    MotoActionADV Level 16 wizard

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    This is why I always spray the hose onto the ground for 5-10 seconds before I start filling.



    :hide
    #52
  13. High Country Herb

    High Country Herb Adventure Connoiseur

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    Many octane boost products only raise a tank of fuel by 0.1 octane or so. A few do better, but you need to put 32 oz into 10 gallons of fuel, blah, blah, blah.

    As to your comment on the 91 vs 93: you can probably get a performance program written for you ECU to make use of the 93. I recently added a "stage 1" program to my wife's Audi that added 35 hp/50 ft-lbs. That was for 91 octane. They also offered a "stage 2" tune that was for 93 octane, which is difficult to find here. So I went with stage 1. Stage 3 includes bigger turbo, injectors, etc.

    The down side is that if you drive the car to a state where 91 is the highest common grade you'll run into the timing retard problem again. You may be able to find a tune for your car that is stored on a hand held device, which will allow you to go back and forth. That's what I have; stock and stage 1 on a hand held (the brand I got only covers Audi and VW). Takes a few minutes to flash the ECU though the OBDII port.
    #53
  14. William Wolfen

    William Wolfen Dirt Seeker

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    Yeah, I had looked into all that. Don't have the car anymore. Graded it fur a truck to haul the bike since the bike is more fun. Both happily run on 87. The bike will run on anything that reasonably approximates gasoline. Much happier with that, thigh I do miss the turbo and manual transmission.
    #54
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  15. aldend123

    aldend123 Long timer

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    COBB Tuning (popular with Subarus) sells aftermarket tunes based on target maximum pump gas available. I'm pretty sure re-flashing from a 93 tune down to a 91 tune is a couple quick button pushes. Point being the technology is certainly there. And I believe at a high level, they're just taking a 91 tune and pushing the upper limits up x percent. If a stock car can be sold to run on 91, but permit 87 by automated detuning, I don't see why they can't tune it for 100? Probably a limitation in how wide the spread is.

    If knock is detected at a rate the ECU cannot correct for, it'll set a malfunction code. Have it step down to the lowest possible octane supported, and an error message appear saying they may need to confirm what octane was selected. For cars with boost, the computer could just disallow or substantially reduce boost until the operator confirms or denies the problem. To some degree, this already happens and is called limp mode. I'm getting off track with some hypothetical stuff for the future. Anyway, OBD-II cars that have knock sensors are able to manage some differences. It will constantly try to advance ignition until it detects knock to achieve maximum timing efficiency. I always forget if this occurs in both open and closed loop modes though. I want to say it happens in both, and open loop just ignores the O2 sensor input. That's 1996 tech too.

    Anyone check an owners manual on a latest model EFI motorcycle? They might even do what I'm talking about already.
    #55
  16. High Country Herb

    High Country Herb Adventure Connoiseur

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    I remember when it was a big deal when "flex fuel" vehicles came out that could deal with large variances in ethanol content. I think that is related to fuel injector capacity, though, since it takes more alcohol to deliver the same air-fuel ratio. It would be cool to have "flex performance".
    #56
  17. augerdin

    augerdin I do my own crashing

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    Specs call for premium and they do run better with premium. I use premium (93 octane around here) in all my bikes.
    #57
  18. Yossarian™

    Yossarian™ Deputy Cultural Attaché

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    As a matter of fact, yes. My Multi Enduro has two knock sensors (one for each cylinder) and the ECU will use their input to adjust ignition timing.
    #58
  19. dietDrThunder

    dietDrThunder Why so serious, son?

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    I had no idea that there were any scooters that required premium fuel. It seems counter-intuitive, as traditionally much of the point of scooters is the economic benefit of inexpensive operation.

    On a side note, if your other bikes don't require premium, you're doing yourself a disservice by using it, and wasting money. Octane is the enemy of efficient combustion/ The entire point of high octane fuel is to resist detonation that results from other factors that aren't the spark, and it accomplishes that by being harder to ignite than lower octane fuel. So, if your motor doesn't require high octane fuel, you're artificially making it harder than necessary for the fuel to ignite in the combustion chamber.

    Is this a big deal? Not at all; motors are tuned and designed to run on a variety of fuel, and do it well. The point is that in a motor that doesn't require premium, yo're just spending extra money to get 0 (or even marginally negative) 'benefit.'
    #59
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  20. Boatman

    Boatman Membership has it's privileges ;-)

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    You also need to make sure the same "method" was used to determine the rating at the pump compared to what the vehicle manufacturer suggests. If the method isn't the same the difference in rating can be 10 or more points.
    #60