AF question for Dart 270

[Sam Powell]

Hi Lou, I read with interest your comments in the Turbo Duster thread about your cruise AF ratio. Can you talk a little bit more about that? Is 15-1 up a slight grade, and 17-1 light throttle, level ground? What KPA numbers equate with which ratios? I appreciate any insights you can share.

With my no available "dial a ratio" pots, I can easily play around with various numbers. With the planned road trip I will be able to experiment, but it would be helpful to know what you have learned about this ahead of time.

Thanks, Sam

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[Dart270]

Things jump around a lot when you are running open loop MSI as I am. I shoot for 15.5-16.5:1 on part throttle cruise on flat ground. Mid throttle or hills around 14-14.5:1, WOT 12.5-13:1 (nat asp).

I have not found a significant difference between running open loop and closed loop on mileage, but you sometimes need to tweak the map if the weather or altitude changes a lot. MS1 does not make altitude changes well, AFAIK. I have seen that open loop gives better mileage since you cannot change the O2 sensor feedback point for different parts of the fuel table. MSII or MSIII should take care of this with WB O2 feedback.

Light throttle is around 45-60 kPa on my engine at ~2500 RPM, mid throttle is around 60-80 kPa, and hard is 85 and up. Of course, these change with RPM. At low RPM, kPa numbers will be higher for a given throttle opening.

If it gets too lean, then I believe both smoothness AND mileage suffer. I tried really lean stuff early on when I got the MS-EFI on there, and mileage seemed worse by my testing, and certainly no better. 17:1 is about the limit and then things get rough and inefficient.

Lou

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Balancing out the driver's weight for more than 50 yrs

[Sam Powell]

Thanks for the feedback. Other's with experience are urged to add to the data base here.

Sam

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[Sam Powell]

What is your AF ratio during engine braking conditions with high Vacuum, of say 20 KPA?

Sam

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[mpgFanatic]

[Sam Powell]

Yes it can. The issue confronting me now is the fact that when the AF ratio goes somewhere above 17 (uknown precisely because of limits of AEM gauge) under engine braking high vacuum conditions, the computer scrambles. It reads a misfire, and then takes a moment to reset, so it feels like the engine is going to die. Programing in more fuel fixes this, but we (Peter and I) are looking for the underlying issue here. It might be that it does not cut fuel off entirely, and thus just misfires a lean misfire and thus sends the computer into a momentary frenzy. Fuel can be cut off entirely within the program just as you suspected. It is the same kind of miss that happens when you burn a setting to the flash memory.

So, Peter wants me to make a data log in its current state of tune, and not fix it with fuel, so he can study what is happening now. Another theory at this time is that there is noise in the VR line. So the plan is to make a shielded cable from the dizzy to the HEI module.

I still would like to know what Lou's AF gauge is showing under engine braking. There is much tuning and tweaking to do now.

Sam

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A REAL professional is someone who knows when to hit it with a bigger hammer.

[mpgFanatic]

[Sam Powell]

Peter read this post, and e-mailed me a configuration for over run fuel cutoff. I will get back to you on this. Thanks for thinking about it. Don't hesitate to forward any more ideas you have.

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[Dart270]

I am not aware that MSI has fuel cut available. I lean out the bottom of the table and it sits somewhere between 14-17 under full decel. I would love this feature.

I figure there's no load, so fuel use is minimal here anyway.

Lou

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Balancing out the driver's weight for more than 50 yrs

[Sam Powell]

I think you are right. With MSI my lowest cell was actually fairly rich, but had no computer scramble issues. Now with MSII things are not as happy, and I need to get them worked out. Thanks for replying.

Sam

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A REAL professional is someone who knows when to hit it with a bigger hammer.

[mpgFanatic]

[Sam Powell]

Thanks Erik. That is the feature Peter suggested I turn on, and he gave me values to try. I have filled them in, but it is raining hard here now, and will for maybe the next week from one of the hurricanes. It will be maybe a week before I can go out and try it. So, for now, things are on hold. I'll let you know what effect this has.

I appreciate your thinking about this.

Sam

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[Wizard]

MSII resets should not happen. This tells you there is electrical power bugs to work out.

Very important for MSII box being fed directly from the battery's positive (stout relay) and heavy grounding.

Cheers, Wizard

[GunPilot]

I agree. The MS should not reset, no matter what the AF ratio is and no matter whether it misfires or not. The most common problem I have read about is the crank signal input wire getting noise. (I have not had any reset problems, knock on wood). But regardless, the misfires are not causing the reset. They may be causing something that is causing the reset, if you know what I mean.

[Sam Powell]

I have read about the reset problem on the MSextra forum, but did not know what they were talking about, so paid little attention. Now I do know. I should go back and reread some of those threads. So, this should be maybe a wiring fix with an electronics twist.

So should I put a shield on the VR pick up wires? They run past the coil,the spark plug wires, and the alternator. It seems odd that this noise, if that is causing the problem, happens primarily at the engine braking section of the map. Peter was suggesting maybe getting the capacitor that Ford uses on their EDIS (is that the acronym) and put that across the pick wires. But I am not sure how to wire this, or what to ask for at a dealer. Could I use the same capacitors I was trying to filter noise out of the old Innovate AF ratio gauge? Wired the same way? I have hit my stupid border here on this one.

While driving home from VA Beach, I could keep the resets from happening by either turning the IAT pot up to enrichen the fuel, or pushing in the clutch and coasting. Once in a while, maybe 3 or four times, it hiccuped and reset at a low RPM accelerating mode in second gear. Push in the clutch and let it return to idle to keep going. This made the trip more exciting.

ONe of the things Peter has had me do in the last 24 hours is run a #12 ground wire from the engine block to the ground point on the fender. But as I said earlier, bad weather and lack of time will prevent me from testing this out until the week end.

Just for the record, the engine breaks down in the boost sections of the map, and I am pretty sure this is all fuel tuning. I am pretty sure it goes into reset mode at that point as well. The AF ratio drops to 10 at that point. I cannot tell which happens first, the 10 AF ratio, or the misfire. A data log would clear this up. I have had other EFI setups behave similarly with that low an AF ratio, and I have been able to cure the problem by taking fuel out of that section of the map. However Peter says a misfire can cause a sudden drop in AF ratio numbers because fuel goes unburned.

Thanks for all the pondering and offered thoughts. I am sure "WE" can fix this.

Sam

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