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

_________________

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

_________________
Home of Slant6-powered fun machines since 1988

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

Sam

_________________

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

Sam

_________________

Well, as a point of reference, the standard practice for OEM multi-port systems (ever since the mid-80s) is to cut off the fuel injectors entirely during deceleration.

For example, my Ford EEC-IV cuts fuel when throttle is closed, coolant is >140*F, and RPM above 1500, as long as there is a VSS signal that the vehicle is in motion. Mazda chooses similarly, but uses 1900 rpm if the AC is on.

When I learned this, and began downshifting at every stoplight to take advantage of keeping the RPMs up (while double-clutching to save syncros), my tank fuel mileage jumped between 1 and 2 mpg in the city.

Haven't done any MegaSquirt programming yet, but it's on my to-do list for "Someday". I've been quite firmly planning on taking advantage of the fuel cut mode... it can be programmed as such, yes?

- Erik

_________________
Lots of early Valiants and Barracudas have crossed my path.
Also a handful of other toys for variety now and then.

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

_________________

Hmmm, underlying issues... one possible place to look is this: I would expect that during those moments where the computer is dictating fuel cut mode, it would also be ignoring the O2 reading.

I would not expect it to reacquaint itself with an O2 signal until some number of milliseconds after the fuel strategy is returned.

Wait, even better... assuming the TP sensor has an idle switch, make sure it's adjusted to signal the computer when the throttle is closed. If the 'puter thinks the throttle is open even 0.010", it will never allow cutoff strategy to happen even if you thought you programmed it.

- Erik

_________________
Lots of early Valiants and Barracudas have crossed my path.
Also a handful of other toys for variety now and then.

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.

_________________

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

_________________
Home of Slant6-powered fun machines since 1988

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

_________________

There's something called "Over Run Fuel Cutoff" listed in MS2-Extra. Might be an enhancement worth pursuing.
http://www.msextra.com/doc/ms2extra/MS2 ... ersion.htm

- Erik

_________________
Lots of early Valiants and Barracudas have crossed my path.
Also a handful of other toys for variety now and then.

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

_________________

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

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.
Also, the MS-II cannot "read" a misfire. It has no way of knowing a misfire happened. I daresay the misfires happen because the CPU is resetting. I'm speculating there.

Also, MS-I has fuel cut. I was using it on the Ramus. Works quite well. I believe it was a "decel fuel" setting in Megatune. We were running it in the Neon and it worked as advertised (on MS-II), and it gave me a start while I was looking at the logfile of a strip pass. Then I realized it was the fuel cut.

The car won't fire at all, because there is no fuel. You can specify an RPM to turn the fuel back on at. On ours, when the RPM came down to 1500, fuel came back on.

_________________
It's a Slant thing. Even I don't understand.

1974 Duster, EFI /6 soon to be turbo...

Get that Monkay! Get that nasty thing!!

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

_________________