Detonation Issues - "Why is the Gen 7 496 such a bad platform to build"
11-14-2015, 10:26 AM
#71
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I prefer being referred to as the white elephants lol.
This 555 ECM is really a killer. It has some really nice capabilities, but it is either uncrackable or nobody is willing to do it. Nothing against Whipple, but it is pretty impractical to try to dyno tune a motor by shipping off an ECM for each adjustment.
I am just an idiot with a toolbox, but is there really no way to crack the programming on this thing so changes can be made by the end user? I would love to hear what you guys who have spent years massaging these motors have learned about this obstacle of an ECM.
This 555 ECM is really a killer. It has some really nice capabilities, but it is either uncrackable or nobody is willing to do it. Nothing against Whipple, but it is pretty impractical to try to dyno tune a motor by shipping off an ECM for each adjustment.
I am just an idiot with a toolbox, but is there really no way to crack the programming on this thing so changes can be made by the end user? I would love to hear what you guys who have spent years massaging these motors have learned about this obstacle of an ECM.
11-14-2015, 04:45 PM
#72
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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.
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.
11-14-2015, 11:25 PM
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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.
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.
11-20-2015, 02:58 AM
#74
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Could very well be. That is one of the big advantages of tuning an engine on the dyno. You can find the best timing for a particular combination I'll generally chase the HP until it shows no gains, then back up from there. Of course with the PCM you don't really have that option since you have to ship it off for tuning. My personal opinion(for whatever that's worth) is that combustion chamber design impacts timing requirements more than any other element in a build. Compression will affect the octane requirements but timing required for peak HP would not change significantly with changes in compression or camshaft.
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.
Last edited by Rage; 11-20-2015 at 03:42 AM.
11-20-2015, 03:03 AM
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AFR map from our tuner on a stage 1 540 build. If possible, you should be somewhere in the 12.2-12.7 range at WOT. In street vehicles, we've found that a lean cruise is fine at 14.0-14.5, but as soon as you dip into the throttle, power enrichment or the tuning should add more fuel to prevent a lean condition.
Here's a dyno from one of our old 600s which should be a pretty similar setup to yours:
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?
11-20-2015, 03:11 AM
#76
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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.
11-20-2015, 03:20 AM
#77
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There's a difference in AFR sensors, equip etc. IOE, if you are using a bosch type sensor with the Innovate hand-held then i'd recomend setting it almost one point richer compared to say an NTK in a nice, dry envirionment.
If you stay at Larry's 600hp level kit, then his instructions and stuff works really nice. If you use that same product and go further, it becomes a slide ruler on steriods. You really need an open EFI system that you can learn and tune. ...And it starts all over..
If you stay at Larry's 600hp level kit, then his instructions and stuff works really nice. If you use that same product and go further, it becomes a slide ruler on steriods. You really need an open EFI system that you can learn and tune. ...And it starts all over..
A lot of people, actually almost everyone I trust, are telling me to put a Holley EFI on the engine. Maybe I better listen.
11-20-2015, 03:39 AM
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OSO Thread Realignment
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.
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.
11-20-2015, 02:15 PM
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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.
11-20-2015, 05:06 PM
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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.
