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Thread: Mixing 91 with 95 together

  1. #16
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    Quote Originally Posted by sidecar bob View Post
    What if you can't get 91 Ron, & can only get 91 Darren or 91 Colin? Will that work too?
    straight to the pool room

  2. #17
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    9th May 2008 - 21:23
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    Just fill with 91. No fancy procedure.
    If the words I say offend you, imagine the ones I keep to myself...

  3. #18
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    Sweet as!

    Cheers guys

  4. #19
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    Quote Originally Posted by Akzle View Post
    as long as you get the portions right it wont be a issue. you always want whole octane numbers or you're firing order will be out by half (or whatever degrees the decimal is)

    ie if you mix 50% of 95 and 50% of 91 you end up with 93 - which is good, but if you got say 60% of 91 and 40% of 95 you'd be left with 92.5 octane which will cause irreversable engine damage cos your cam timing will be out by 5 degrees, and 5 degrees on a four stroke (5*4=20!!!) is going to lock up your rear wheel and basically kill you.
    Yet again.....Akzle is right

  5. #20
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    Quote Originally Posted by AllanB View Post
    The Hornet 900 manual states 91 or higher.


    I owned one for 8 years from new.

    I ran it for lengthy periods on both recording MPG's,

    Performance wise there was zero difference, no spluttering, pinging, or any adverse mechanical reaction.

    Mileage was likewise indistinguishable between the two.

    I ended up filing up at whatever pump was closest and free - mixing made no difference.

    My conclusion for that specific bike:

    91 & 95 differ in colour and price.

    Otherwise zero difference.

    It's a peach of a engine that will last forever if you treat it to regular fresh oil.

    PS - don't add a K&N air filter - they are noted on this specific bike to bugger up fueling unless you have a custom tune Power Commander fitted.

    Do consider talking to KSS regarding replacement front fork springs - cheapest handling improvement you can do.
    I also owned one and rated it. Best money I spent on mine was Ohlins shock and fork revalve/rebuild.

    I use 91 because 95 made no difference I could tell.
    I thought it looked like the inside of a squid tube. - Oakie

  6. #21
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    Quote Originally Posted by skippa1 View Post
    Yet again.....Akzle is right
    Jeez Skip! Don't do it! His heads big enough already.
    LOL, 91 or 98, ethanlo etc, it all works, it's the degree to which it works that is important.
    I've used Gulls 90 lately and the ol bandit loves it, you know you've put it in there for sure, milegae, well, who cares, I get there with more Omph! and no pinging or huge backfires when I decelerate.
    Every day above ground is a good day!:

  7. #22
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    Points to OAB and Gremlin. 91 and 98, basically interchangeable for a bike that is specified minimum 91. In theory, you should see better MPG with 98 because it has more oomph for each cycle. This isn't usually proven in practice because you don't run exactly the same route, temperature, wind direction, weight, etc etc - and you're usually riding on the street at part throttle.

    Octane ratings are basically guidelines, and they're measured differently across the world (we use RON, the USA uses an average of RON and MON); it's a measure that allows you to match the compression ratio and state of tune before detonation with the appropriate fuel. It's basically a measure of knock index.

    Here's kind of how it works. A softly tuned motor (sensible compression ratio and no boost) of perhaps 10:1 compression ratio will happily work on 91 all day with no problems so long as the timing is set correctly. With a Hornet, this is probably the situation. So, you can run 91, 95, or 98 with no real issue.

    If you ran 105 octane, you'd essentially be wasting your time, there would be no using the extra "bang" in the fuel.

    So, take one of my recently built motors. It runs huge boost due to a small 8/71 GMC supercharger with a lot of overdrive into 572 cubic inches. If I ran that with 91 octane at idle, or just off idle, there would likely be no real issue. But, open the throttle and bring on boost and you'd have detonation. With a effective compression ratio of way higher than 14:1, low octane gas would create much damage, very expensive damage if no timing was pulled. In modern cars, they have a knock sensor which detects detonation and retards timing. For each pound of boost, the rule of thumb is usually near on 3 degrees of timing retardation. This high performance motor needs 105+ octane, some people run Methanol in this type of set up instead because it allows a degree of safety.

    On my old GSXR1000, I ran 98 plus octane booster because it was normally aspirated, but higher compression ratio to make more power. Same point, the correct octane for the correct compression ratio with the correct timing map.


    Some simple rules:
    Diesel in a petrol motor = bad. Drain the tank and start again.
    Petrol in a diesel = very. very bad. The car needs to be taken to a good mechanic, tank drained, fuel lines drained, injector pumps cleaned. Common rail diesels with petrol in them literally blow the injector pumps apart, this can be a $15,000 repair on late model CRD's.

    91 octane in an average motor = fine (listen for pinking, if no pinking, no problem).
    91 octane in a performance motor, or turbo or supercharged motor = bad. Detonation = broken motor.

    98 octane in an average motor = fine, but a 20 cent per litre waste.
    98 in a performance motor = fine.

    91 + 98 is fine in an average motor. 91 + 98 in a performance motor, less good.

    Disclaimer. Yes I know I'm massively over simplifying it and missing a bunch of information, but it's almost 1 am and I don't give a fuck.
    Its diametrically opposed to the sanitised existence of the Lemmings around me in the Dilbert Cartoon hell I live in; its life at full volume, perfect colour with high resolution and 10,000 watts of amplification.

  8. #23
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    Quote Originally Posted by madbikeboy View Post
    Points to OAB and Gremlin. 91 and 98, basically interchangeable for a bike that is specified minimum 91. In theory, you should see better MPG with 98 because it has more oomph for each cycle. This isn't usually proven in practice because you don't run exactly the same route, temperature, wind direction, weight, etc etc - and you're usually riding on the street at part throttle.

    Octane ratings are basically guidelines, and they're measured differently across the world (we use RON, the USA uses an average of RON and MON); it's a measure that allows you to match the compression ratio and state of tune before detonation with the appropriate fuel. It's basically a measure of knock index.

    Here's kind of how it works. A softly tuned motor (sensible compression ratio and no boost) of perhaps 10:1 compression ratio will happily work on 91 all day with no problems so long as the timing is set correctly. With a Hornet, this is probably the situation. So, you can run 91, 95, or 98 with no real issue.

    If you ran 105 octane, you'd essentially be wasting your time, there would be no using the extra "bang" in the fuel.

    So, take one of my recently built motors. It runs huge boost due to a small 8/71 GMC supercharger with a lot of overdrive into 572 cubic inches. If I ran that with 91 octane at idle, or just off idle, there would likely be no real issue. But, open the throttle and bring on boost and you'd have detonation. With a effective compression ratio of way higher than 14:1, low octane gas would create much damage, very expensive damage if no timing was pulled. In modern cars, they have a knock sensor which detects detonation and retards timing. For each pound of boost, the rule of thumb is usually near on 3 degrees of timing retardation. This high performance motor needs 105+ octane, some people run Methanol in this type of set up instead because it allows a degree of safety.

    On my old GSXR1000, I ran 98 plus octane booster because it was normally aspirated, but higher compression ratio to make more power. Same point, the correct octane for the correct compression ratio with the correct timing map.


    Some simple rules:
    Diesel in a petrol motor = bad. Drain the tank and start again.
    Petrol in a diesel = very. very bad. The car needs to be taken to a good mechanic, tank drained, fuel lines drained, injector pumps cleaned. Common rail diesels with petrol in them literally blow the injector pumps apart, this can be a $15,000 repair on late model CRD's.

    91 octane in an average motor = fine (listen for pinking, if no pinking, no problem).
    91 octane in a performance motor, or turbo or supercharged motor = bad. Detonation = broken motor.

    98 octane in an average motor = fine, but a 20 cent per litre waste.
    98 in a performance motor = fine.

    91 + 98 is fine in an average motor. 91 + 98 in a performance motor, less good.

    Disclaimer. Yes I know I'm massively over simplifying it and missing a bunch of information, but it's almost 1 am and I don't give a fuck.
    Given the OP asked what is a very basic question...most of the above just sailed straight over his head
    If the words I say offend you, imagine the ones I keep to myself...

  9. #24
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    Ahemmm.....

    You need to check your set up & tune. My bike is tuned for a minimum 95RON only. It was fine for 91RON before, however I found it a little snatchy on the throttle.

    If your bike is stock, then 91 is fine, but there must be a reason why the previous owner decided to use 95? Perhaps it was retuned for 95RON OR perhaps he just found it ran a little better?
    PHEW.....JUST MADE IT...........................UP"

  10. #25
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    Quote Originally Posted by caspernz View Post
    Given the OP asked what is a very basic question...most of the above just sailed straight over his head
    Basic question was met with a mix of right and sort of right answers. Thought adding a better answer would help others who see this post.
    Its diametrically opposed to the sanitised existence of the Lemmings around me in the Dilbert Cartoon hell I live in; its life at full volume, perfect colour with high resolution and 10,000 watts of amplification.

  11. #26
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    Quote Originally Posted by madbikeboy View Post
    Basic question was met with a mix of right and sort of right answers. Thought adding a better answer would help others who see this post.
    My eyes glazed over after the 3rd word and I skimmed the rest...

  12. #27
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    Quote Originally Posted by caspernz View Post
    Given the OP asked what is a very basic question...most of the above just sailed straight over his head
    Well, he talked about both octane ratings, but didn't say if you could mix them... and did mention about blowing stuff up
    Quote Originally Posted by Jane Omorogbe from UK MSN on the KTM990SM
    It's barking mad and if it doesn't turn you into a complete loon within half an hour of cocking a leg over the lofty 875mm seat height, I'll eat my Arai.

  13. #28
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    Quote Originally Posted by Gremlin View Post
    Well, he talked about both octane ratings, but didn't say if you could mix them... and did mention about blowing stuff up
    Read the last line before the disclaimer. And the first line. And a few lines in the middle.
    Its diametrically opposed to the sanitised existence of the Lemmings around me in the Dilbert Cartoon hell I live in; its life at full volume, perfect colour with high resolution and 10,000 watts of amplification.

  14. #29
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    Quote Originally Posted by madbikeboy View Post
    Basic question was met with a mix of right and sort of right answers. Thought adding a better answer would help others who see this post.
    It's funny how people offered advice then admitted they couldn't follow your post.

    Just wait till they start asking about e85....
    Can I scream?

  15. #30
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    Quote Originally Posted by madbikeboy View Post
    Octane ratings are basically guidelines, and they're measured differently across the world (we use RON, the USA uses an average of RON and MON); it's a measure that allows you to match the compression ratio and state of tune before detonation with the appropriate fuel. It's basically a measure of knock index.

    Here's kind of how it works. A softly tuned motor (sensible compression ratio and no boost) of perhaps 10:1 compression ratio will happily work on 91 all day with no problems so long as the timing is set correctly. With a Hornet, this is probably the situation. So, you can run 91, 95, or 98 with no real issue.

    If you ran 105 octane, you'd essentially be wasting your time, there would be no using the extra "bang" in the fuel.

    So, take one of my recently built motors. It runs huge boost due to a small 8/71 GMC supercharger with a lot of overdrive into 572 cubic inches. If I ran that with 91 octane at idle, or just off idle, there would likely be no real issue. But, open the throttle and bring on boost and you'd have detonation. With a effective compression ratio of way higher than 14:1, low octane gas would create much damage, very expensive damage if no timing was pulled. In modern cars, they have a knock sensor which detects detonation and retards timing. For each pound of boost, the rule of thumb is usually near on 3 degrees of timing retardation. This high performance motor needs 105+ octane, some people run Methanol in this type of set up instead because it allows a degree of safety.

    On my old GSXR1000, I ran 98 plus octane booster because it was normally aspirated, but higher compression ratio to make more power. Same point, the correct octane for the correct compression ratio with the correct timing map.


    .
    "If you ran 105 octane, you'd essentially be wasting your time, there would be no using the extra "bang" in the fuel." Wrong. As you say right above that, it's a measure of it's ability to resist detonation. Octane is not a measure of energy value of the fuel. It just allows the engine and tuner/builder to do the things that create the power and not eat itself. Things can get funky above 100 octane. The original SAE testing only could test to 100. Once you start looking at specialist fuels the range is massive and fining the right one can be fun, just looking at the, Sunoco, VP or Elf range makes my head explode, let alone the wallet....there's a whole world out there. The good old regular Avgas works fine in a lot of older bike situations where they have been leaned upon, but it is set for low rpm engines at high altitude. Modern high rpm engines don't like it and I've heard of guys with R1's and the like thinking they'll get a bonus, but actually get less power than PULP and shittier running.

    Octane boosters.....hmmm, I've had a play with those, including one that is arguably the best. I've heard of independent testing that could not detect an effect. I used tetraboost out of the UK which gave good results in a 98 unleaded in the UK (specific dyno testing and real world results, better than Avgas for total performance due to good octane AND high burn speed, more like an ELF) and shit result for me here. I suspect the octane booster was okay, but the underlying fuel was the let down. Pre-ignition anyone.....that cost me a lot of money.

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