I'm sure it's all about the $$$. Not enough return on investment in this small market. I know Whipple paid a large price to acquire the rights to it (Seems like I remember it being in the 6 figures). Mark Boos can program them. Not sure how he came up with the software. Also heard Raylar had somebody reverse engineer one several years ago. I'm not sure how that turned out. Maybe Larry can elaborate.

Seems there are lots of 525's and 496's out there that could benefit by an end user tuning solution, similar to MEFI burn.

As for ditching the 555, I have smartcraft gauges, I can't go to another ECM solution without changing all my gauges out, and I like the guardian safeguards as well.

I've done a couple where I piggybacked the ecu's to keep the pcm for the smartcraft function. Kind of a pain but it can be done.

I do not think it is just your opinion it is fact that combustion chamber burn rate is the primary if not the only factor that determines what the optimum timing is for an engine. That is my biggest unknown input parameter for modeling my engines in Performance Trends Engine Analyzer Pro engine dynamometer performance simulation software. 10 - 15 % difference in burn rate has a huge impact on best power timing required and detonation probability. I reverse engineered my burn rate using the Innovation Marine HP3 Gen 1 max timing spec but that is marginal because I do not have a dyno test on their engine to baseline model against nor detailed measurements of their intake manifold.

Tuning real time on a dyno is definitely the best but as you say the PCM555 fuel, volumetric efficiency and spark tables can not be accessed with out unlock key and Merc software to my knowledge. Also there apparently are a huge number of fuel tables if you could access them to tune.

Larry,

Always wanted to ask about that 600HO dyno test, isn't that AFR at the higher RPM's rather on the lean side or is that where that engine is the happiest?

One of the biggest drawbacks with the PCM555 is that there is no engine knock fault code or data output real time. It does attempt to control knock by retarding timing on the individual knocking cylinder similar to the J&S Safeguard system but that knock event timing retard is not available as data output either only the base timing is available.

How was your conclusion on the Innovate/Bosch versus the NTK AFR reading accuracy arrived at?

A lot of people, actually almost everyone I trust, are telling me to put a Holley EFI on the engine. Maybe I better listen.

I would like to get back to the initial question that started this thread.

Question. What is the leanest naturally aspirated engine AFR [ with GM Gen VII 8.1L, Merc 496HO heads] that is safe from detonation damage from idle to 2200 rpm? Plane out is ~2200 RPM. Significant MAP/engine load increase begins at ~4000 rpm. Knowledgeable responses only please.

Yep, but the stock computer becomes the limiting factor with "tuning" these engines in boat applications. 50-51psi seems to work pretty well, but the best fuel delivery solution is an aftermarket computer like SDFever has on his boat.

I was under the impression that it pull timing and dump fuel on either 1357 bank or 2468 bank due to one knock sensor per side?