I have run 11.5:1 and things get very hot, even with 103 octane. I would never do it again on a car that I need to run on the street (especially in traffic). If you pull timimng and run rich of course you can get away wilth it but there are other better ways to make power.

 

Always good to have someone with experience respond.

 

I would suggest that it's all in the tuning. The stock ECU isn't made to handle the increased detonation that can easily occur in high compression/forced induction engines. While WildRice's experience is certainly important I wouldn't consider it the be all, end all. If properly tuned this mod could make a lot of power, and with what would probably be an impressively linear power band.

 

you could always go water injection to combat the detonation. Not sure what your petrol is rated by over there but can run 11:1 stock 4g92 on 96 or 98 ( ron+mon/2) and 12:1 on 98 only. Im planning on going 12:1 with water injection to be on the safe side. You just have to make sure you dont run out of water.

 

As helpful as that is, we don't get that high in the USA. Pump gas usually tops out at 91, or 94 if you're lucky. For 96 or 98, we would need race gas, which is far too expensive for daily driving.

 

No, they have a different octane rating in New Zealand. His 96/98 is roughly equivalent to our premiums. I forget whether they use RON or MON, but we use PON. I don't know about the mid-west, but I know 93 is standard premium fuel in every part of the east coast I can name, and the only places I know 91 is tops (for certain) is Cali.

 

Oh. I thought I just read last week that we use the average of RON and MON. And since he put in (ron+mon/2), I figured it was roughly the same idea.

 

The formula is correct, but the numbers look much different. I was trying to find a link before, but I got lazy. Sorry, bud.

 

I woudl suggest for most users to stick with our 10.5 : 1 pistons. For prices on these we have an online price list now on our website.

10.5 : 1 will handle a combined (ROn+MON/2) rating of around 93 rating.
This woudl be used very nicely with a stage 1 camshaft and piggy back tuing

You could go to the 11.5 : 1 pistons but only if you also used a stage 2 or larger camshaft, and some aggressive tuning with a true greddy unit etc. The larger camshaft wuodl bleed off some compression at low rpm's due to its larger profile and reduce likliehood of detonation at low rpms.

But be warned you wuodl need very good extractors, air intake system to make this work properly but it woudl work on the same 93 pump gas.