I wish I could find the article posted here written by a GM engineer that worked on the northstar.

Summary, detonation must be avoided in all instances to prevent premature engine wear. It's impossible for fuel systems to react quickly enough to instantaneous changes in load conditions or fuel distribution issues. Therefor under wot and wot transitions stock calibrations will be in this range.

No disrespect to all the garage engine building gurus but there's a reason they are the engine calibration experts at the #1 powertrain company in the world and you are a plumber. They've got millions of dollars and instrumentation you could only dream of.

Do you really want to go on the expert opinion of an internet guru and risk your engines at 13 to 1 when engine failures could cause you major economical hardship? No thanks

I agree hogey .

While I know there are a million variables, I think somewhere along the lines guys assume that anything richer than 11.5 you are blowing raw fuel out the pipes, washing cylinder walls, and diluting oil.

On some of these setups a simple change of 2 or 4 jet sizes will put you from "ideal" to "overly rich" on paper. How many guys have been a couple jet sizes to high over the years from their fastest mph? Did going 2 jet sizes higher blow gas out your tailpipe ? Did the boat lose 10mph?

Well my lm2 has tuned many of high hp boat engines and race cars.what I saw,,is what I saw.and if you don't believe me,give Marc at prescion a call and he'll verify what I saw.
I gave you the info,,do with it what you want.

I remember seeing a dyno sheet from a 1075 mark did. I was shocked to see the air fuel around 12.0. But if it works it works !

And that's after he adjusted it.

This is a very open-ended argument some motors are built to withstand more heat some aren't. I think the right afr's is a very application specific number. Some forms of endurance racing run as high as 20. Yes 20. The motor has to be built and tuned for it. 12 may work for one motor and not another.

You're comparing the reliability of a 1075 with a 50hr service interval to an LS9? Not even in the same ballpark. A 1075 will never accumulate enough hours on a set of pistons to see the effects of wear due to small and persistent amounts of knock. Whereas the LS9 could potentially see up to 200k miles, granted not at the same loads.

Well when your watching the sensor and in particular the knock sensors and you see them quiet.it's a good thing,even as lean as I've seen it.and a few others who were sitting in the back seat with me.
These to motors are both over a 150 hrs of run time,with a lot of it in the 5000-6200 rpm range.it's the running joke that they've run the equivalent of the eastern sea coast at 5000+ rpms,in one season.

The new direct injected motors are set up to be very resistant to detention.

:rolleyes::rolleyes::rolleyes:
Well there you have it. Everyone should target 12.7 then because anecdotal evidence :rolleyes: