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PostPosted: Tue 28 Jun 2005, 11:35 pm 
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Location: Melburn
AA/AB GSR Turbo: 97+ RON i.e Leaded/Lead Replacement fuel
AC GSR Turbo: 91+ RON i.e Unleaded fuel
All Cordia engines were built exactly the same, they all have hardened heads/valves/seats/seals etc. so you don't need to ad an additive to unleaded fuel in an AA/AB.
In short, the higher the octane, the less likely the engine will ping. Here is an explination of pinging...
Quote:
Detonation
Detonation also known as pinging or engine knock occurs simply when fuel pre-ignites before the piston reaches top dead center. This means that a powerful explosion is trying to expand a cylinder chamber that is shrinking in size, attempting to reverse the direction of the piston and the engine. When detonation occurs, the internal forces can actually exceed 10x the normal forces acting upon a properly operating high performance engine. Detonation is generally caused by excessive heat, excessive boost pressure, improper ignition timing, inadequate fuel octane, too lean of an air/fuel ratio, or a combination of these. Usually excessive boost and/or too lean of an air/fuel mixture is usually the culprit.


So, now that you know what the minimum octane rating you can use, here are all the fuel brands and their ratings...

BP http://www.bp.com.au/
BP Ultimate: 98 RON
LRP: 96 RON
PULP: 95 RON
ULP: 91 RON

Shell http://www.shell.com.au/
Optimax: 98 RON
PULP: 95 RON
ULP: 91 RON
LRP: 96.3 RON

Caltex http://www.caltex.com.au/
Vortex: 95 RON
Vortex 98: 98 RON
LRP: 96 RON
ULP: 91 RON

Mobil http://www.mobil.com.au/
Synergy 8000: 98 RON
Synergy 2000: 91/92 RON
LRP: 96 RON

Other fuel companies:
Generally if they sell Premium Unleaded it will be 95/96 RON

About 12 months when I was doing a bit of my own research I found that BP had the lowest sulphur and ethanol concentrate, therefore I always fill up with BP Ultimate, it works for me. Other people use different brands such as Shell or Mobil, thats fine, if it works best for their car, thats great! So basically you have to experiment, find which fue works best for your car.

Octane boost additives:
Most will raise you RON rating to race fuel standards (100 RON), this does vary among different brands, some will raise it to 102, 104 etc. Again, do your own research with this. I only ad this if I'm going drag racing and want to run a few extra pounds of boost, it works well for this purpose.
On that note, here is an (sort of) interesting read about the legislation concerning BP Racing 100 (Avgas) http://www.bp.com.au/fuelnews/PET2501.pdf

At the end of the day, unless you are running rediculous boost, and generating mass power you don't need 100 RON fuels. Infact, you are meant to use the lowest possible octane rating without causing the engine to ping, why? Because high octane slows the burning rate, and actually causes less of an explosion in the chamber, therefore less power. It acts in a kind of similar way as retarding the ignition timing.

I hope all this makes sense. If I've missed something or got something wrong, feel free to correct me.

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~8v 4G63 AC GSR
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110.6wkw @ 13.3psi

~1999 Honda VFR800


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PostPosted: Wed 29 Jun 2005, 1:51 pm 
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Location: Canberra
Trimmed and moved to FAQ. Octane boost question has been split to a new topic.

Thanks nash.

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