What fuel to stop detonation with high compression help please

4 replies to this topic
  • AUSmoker

Posted April 24, 2015 - 01:49 AM


I am putting together a wr400, 444cc big bore with 13.5:1 hc piston.

I was hoping to run 98RON fuel.

How do i find out what fuel to run. I know if it pings to run higher octane, but how do i determine the correct fuel.

I can get higher octane but its expensive and not available at the pump.

Can i run 50/50 pump and race fuel? Can i use an octane booster? Is there any fuel i cannot run Eg. Methanol, ethanol etc.

There is a 10% ethanol mix available at some pumps thats called 100 octane.

I live in Australia so im talking RON ratings.

I want to know how to test my new engine safely to find the right fuel, and know what additives work.

Hopefully 98ron will be ok but if its not i can get up to 106ron for $$$.

Does any changes require jetting/fuel system changes.

Thanks for the help and only answer if you have credible knowledge.

  • Krannie McKranface

Posted April 24, 2015 - 04:50 AM


Race fuel mix is the most common solution

You mix to the minimum amount of race fuel to eliminate detonation

13:5 is a substantial increase, so 50/50 should be expected

Ocatne boosters are typically just Toluene: not a very good fuel source on it's own.

For more detailed info, you should contact the Piston company

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  • offrd beatr

Posted April 24, 2015 - 03:35 PM



  • patrick2wd

Posted April 24, 2015 - 10:40 PM


and I woundnt experiment with fuel/ combustion ratio's etc..

98 should/ could work fine,

but if not, use a booster, make sure "other" fuels dont "eat" rubber/ plastics...

  • grayracer513

Posted April 29, 2015 - 02:33 PM


98 RON should be more than enough.  In fact, the originally required 95 RON should be adequate.  Here in the states, gas pumps are all labeled with "AKI" ( anti-knock index), which is an average of RON and MON, and most pump premium is labeled 91-92.  This is roughly equivalent to 95-96 RON, and generally works out as being enough for most people running 13.5:1 with no other additives.  I wouldn't worry about it too much.


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