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Thread: AV Gas vs. Petrol

  1. #1
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    11th October 2005 - 12:11
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    AV Gas vs. Petrol

    I live in CHCH and the only place I know to get AV is the waimac. So instead of making the out of the way trip to get some there what difference would petrol really make? Some say the plug will blow constantly while others will say you just dont get any power. i am new to most of this, so would like some opinions. Anyone have some wisdom into this?

    I currently run AV with motul premix - but want to change...

  2. #2
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    10th December 2005 - 12:19
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    Quote Originally Posted by Disciple
    I live in CHCH and the only place I know to get AV is the waimac. So instead of making the out of the way trip to get some there what difference would petrol really make? Some say the plug will blow constantly while others will say you just dont get any power. i am new to most of this, so would like some opinions. Anyone have some wisdom into this?

    I currently run AV with motul premix - but want to change...
    Twostrokes dont need high octain gas what do you think happens when you add oil to gas it lowers the octain 95 or 98 will do but if you still want to raise the octain get some Tolulene dont mix to much in advance though as Tolulene evaporates more rapidly than gas
    Cheers
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  3. #3
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    11th July 2003 - 20:31
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    AV gas V petrol,no contest,petrol wins hands down.
    Why,you may ask well just look at it this way, planes are low revving, constant speed motors,and your bike is high revving,hi compression non constant speed motor,AV gas will burn too fast and hot causing detonation with some bad things going on inside your engine if you run it hard for a long time.

  4. #4
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    avgas is avgas is avgas. Buy some today, buy some tomorrow, buy some next month, it's all the same. Pump gas, , , welllllllllllllll, maybe not, in fact definitely not. Unless modified however your bike won't notice any differance. There's threads here already on this topic.

  5. #5
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    Quote Originally Posted by digsaw
    AV gas will burn too fast and hot causing detonation with some bad things going on inside your engine if you run it hard for a long time.
    No, you got it all back-to-front..............:slap:
    Drew for Prime Minister!

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  6. #6
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    2nd October 2005 - 00:47
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    Well, I ran 96 or higher in my bike and it ate plugs like crazy (one every ride!) and that started to really piss me off. So I got some 100 octane fuel and no probs now. Also "AV gas" is leaded (well mine is) which I've found runs better in my bike. Also starting is easy too.

    But then again, I've got local places for the race fuel, and it ranges from $1.90 - $2.50

    If you find it makes it run better, use it, otherwise go for 96 octane +

    I think it's more important to make sure you use good oils.

  7. #7
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    Av Gas is slower burning, high octane, making it more suitable for high compression low reving motors. This is exactly the opposite to what your engine needs. If you have a high compression V8 in you bike then certainly use Av Gas. Otherwise forget it. The only reason some people reccommend Av Gas is a throw back to the days of leaded fuel, and some engines do still need lead. However lead is a killer to spark plugs in a two stroke.
    Time to ride

  8. #8
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    5th January 2006 - 16:36
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    I agree with Jantar.

    Avgas has octane rating of 100/110 which is slower burning (more detonation resistance) so it will reduce the chance of detonation.

    However on an engine which is not tuned for avgas, it will tend to burn too cold and the lead in the fuel will be likely to cause plug fouling. (The reason why we try not to idle the engines in our aircraft for long - to prevent plug fouling) If you have a automotive engine which is not specifically tuned for avgas, run normal petrol.
    I have deep pockets. It's just that it's a deep empty pocket...........

  9. #9
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    Oh death,in away you are right as i was thinking methanol which will burn slower still,after using av gas and having big problems i wouldnt use it again,but proper race gas should be better than av gas

  10. #10
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    i ran 50/50 avgas in all my two strokes,
    both sides of this argument are correct, avgas is slow burning, misng this with 95 helps this, also avgsa is very stable and will store better than pump gas

  11. #11
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    We run AV Gas in the Honda RS125's and it is perfect I premix it with Spectro Marine PWC 2 Stroke Oil it burns perfect no crap no damage my piston was in mint condition
    Blindspott are back as Blacklist check them out
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  12. #12
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    8th November 2005 - 12:25
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    Av gas has a slow burn time, and as a consequence, using it at 100% you lose bottom end power.
    91 has a very fast burn time, so by running a brew ratio of 70% av gas and 30% 91 you do not lose any power down low and still gain the benifits of running the avgas. (being cooler running and allowing one to run higher compression)

  13. #13
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    Quote Originally Posted by digsaw
    Oh death,in away you are right as i was thinking methanol which will burn slower still,after using av gas and having big problems i wouldnt use it again,but proper race gas should be better than av gas
    no...death is completly right.....the higher the octane the slower the burn....does not alter explosive force of the reaction at all though.....91 and 95 have the same energy output when burnt...just different rates of burn...
    Quote Originally Posted by Drew View Post
    Given the short comings of my riding style, it doesn't matter what I'm riding till I've got my shit in one sock.

  14. #14
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    Quote Originally Posted by sugilite
    Av gas has a slow burn time, and as a consequence, using it at 100% you lose bottom end power.
    91 has a very fast burn time, so by running a brew ratio of 70% av gas and 30% 91 you do not lose any power down low and still gain the benifits of running the avgas. (being cooler running and allowing one to run higher compression)
    so u reckon run about 98-101 octane then?

    most those bike just need normal pump gas...best run 95 in the summer...and up to u in the winter really....as bike will run cooler anyway...
    Quote Originally Posted by Drew View Post
    Given the short comings of my riding style, it doesn't matter what I'm riding till I've got my shit in one sock.

  15. #15
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    Interesting comments chaps,

    When we run Stroudys bikes they run on 91. Why? Well it burns faster and easier than 96 or avgas or 100 octane (which is just old derated av gas anyway).
    You only need to up the octane rating if you increase the compression ratio or it is detonating on the gas you are using.
    If you run 91 it burns completely at high revs (fast flame spread).
    If you run 96/98 it burns slower and may not burn all fuel before the valves open at high revs
    100 octane is worse you, will definitly not get complete burnoff at high revs.
    Av gas is worse still.

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