I put the new coil in the ignition, charged the battery, and drove the car to work today. It started right up,bang. It was warmish, at 62 degrees, so nothing proven yet. However, the Af ratio as read on the broad band meter now reads richer than it ever has, once it falls outside of the feedback range. Does ignition effect the apparent AF ratio? Does burning the mixture more completely do something to the exhaust that the O2 sensors sees as richer?

Sam

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Yes! A misfire will cause the "raw" oxygen, not used for combustion, to get into the exhaust. The O2 sensor will read this as lean.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Wow! Thanks. I am sure someone told me this before. So I now need to go retune the base fuel map. Maybe this car sill start getting decent fuel mileage. The difference was significant also. It was idling at about 13.8 or so, and this morning, after it had warmed up it was idling at 12.8 or even richer. At cruise the O2 snesor and feed back was keeping it around 14.8 just fine. I didn't check it out, but high map values probably will be too rich as well since this goes outside the parameter of the feedback control.

I changed the coil from an old fashioned stock coil to a Blaster. Not the canister style but the GM style square unit. It will be interesting if it turns out all the problems I have had with this EFI set up are just the most basic, low tech things. First the ignition switch, and now the coil.

Sam

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Will this 8207 coil work on mine? This is 1987 caravan 2.2L carb with computer-controlled spark and have no resistor like the slant six used.

Cheers, Wizard

I would be the wrong guy to answer that Wizard. Maybe one of our resident electronics guys could answer that. Or maybe the MSD web site could tell you.

I turned off the O2 feed back and went out tuning(solo) this evening, which was really hard to do, as I had to keep one eye on the road. It was far from perfect, but I was taking out 20% of fuel from the parts of the map I could get to in my local driving. I need to find a relative who owes me something, (I seem to recall putting brakes on my son in law's car recently), and go cruising and tuning again.

No wonder the gas mileage was so bad. And with a weak component in the ignition, it wasn't even running all that well. The thing is, that coil was almost new, and installed by a speed shop,(of all things). I just assumed it was fine. I know, assume makes a you-know-what out of you and me. Dan, thanks for insisting that I get rid of that old coil.

Sam

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What a relief! I bet the exhaust smells a lot nicer now that all the gas is actually getting burnt.

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1980 Aspen 225 super six

Absolutely. My daughter is expecting again, and she just had a fit last week at how smelly the exhaust was. She was concerned about the new baby inside her of course. And she was right, it was bad. Now, you can hardly smell it idling in the garage with the doors open.

As I think I said in an earlier thread, this coil is the only thing that really changed besides the ECU when I went to Accel. All sensors, wiring, injectors and fuel plumbing was essentially the same. I just never put those facts together. I was chasing phantoms in the ECU whle the big problems was my NEW coil. I did learn alot about the tuning process in my search for the "fix" in the ECU. It was good training, if somewhat discouraging at times. So, at this point, (I won;t hold my breath here), it seems all good, and a real relief.

So now back to the point of the thread. Any advice on target ratios to shoot for in tuning? I am told 14.8 should be the target for most of the NA range. Is there agreement on that? I know there are a couple of threads right here with AF target maps published.

Sam
Sam

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Sam,

I would shoot for nearly as lean as the engine will tolerate without misfiring under low load conditions. More of a weak (lean) mixture is more efficient than a less of a rich mixture as it reduces pumping losses. If you can run 16-18:1 under light load cruise I'd do it. The only reason to run 14.7:1 is to keep a catalyst happy. Catalytic converters do not like excess oxygen if you can believe it. Once you get below about 4" of Hg vacuum I would switch to a richer mixture just as a carburetor with a power valve does. You can have an intermediate step or taper up to say 13:1 at higher loads and go slightly richer from there as you get into boost. Believe it or not you can run lean under boost and have the engine live, but it has to be lean enough that it's also cool enough to not burn parts. I wouldn't try it in a passenger car application, but it was done reliably with supercharged piston aircraft engines.

The SDS EFI web site has lots of good info on tuning.

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Joshua

Thanks Joshua. I know you have as back ground in aviation. I have talked to a local here who is a helicpoter and aviation mechanic, and he has shed some light on the issue of running either 50 degrees lean, or 50 degrees rich of peak EGT. I wish there were an easy way to tweak this on the fly, without the lap top. I have asked about a PDA or pocket PC tuning program, and they don;t appear to have any plans to do this. I know some ECU systems have a small hand held tuning module, which would be nice. But it would be great if you could watch the EGT gauge, and turn a knob to fiddle with the AF ratio.

It is nice to have confirmation that 17to 18-1 is OK if it will run that way. Others have said this as well. Thanks again.

Sam

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You were running an MSD ignition?


How old was the bad coil?

and

What kind of coil was it?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Sam,

Actually my background is in reading too much about my mechanical interests. My Air Force training was in satellite and wideband communications. Before I enlisted in 1994 I did formally study automotive engine performance for a while.

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Joshua

Ems, I do have an MSD 6. It is at least 13-14 years old. It was one of the first modifictions I made to the car when I bought it in 1993. (The first was to replace the 13" wheels.

The coil is made by KEM, model U12L. It says use with external resistor on the can. It was installed by Total Performance in the Spring of 06 when I took the car to them for dyno tuning. The car started breaking down on the way way home from the shop. I would have taken it back, except I seriously lost confidence in them. The owner was busy having a heart attack,(for real), and the guy who did the tune up got fired shortly afterwards. The owner's son-in-law was trying to hold everything together through a tough time.

Their web site looked good, they were within 15 miles of home, and they sounded very positive that they could get it running when I called. I don't waste energy or time being angry. So I just set about trying to fix things myself. Which I was not really equiped to do, but at least I cared, and had time. Those struggles are well documented here on the forum.

The problems boiled down to borderlne primary ignition wiring, a bad ignition switch, and the wrong/bad/or inappropriate coil. The MSD module is still suspect, but at least it seems to work when the weather is warm. Oh yeah, because the car sits alot, and I was cranking on it to try and tune the start program, the battery was likely near the edge in terms of charge. This is why I want to get a battery tender. I just don;t drive the car enough to keep the battery up properly.

Through this, all the tuning with inadequate ignition created a situation where there was too much fuel, and not enough spark. I think this was true under all conditions. The thing is, the O2 gauge was misreading the situation and I THOUGHT the actual AF ratio was perfect. In fact it was at least 20% rich, based upon the numbers I have been changing in the VE table. It is possible to lean out the entire map, but I just started tuning the idle cells first, and took it for a ride and started reducing numbers where I could see what cells it was in when the gauge read rich. It was kind of nerve racking, and I came home feeling optimistic, but like a really need to enlist a buddy for this task.

Maryland Performance has said they could dyno tune the car for between $500-$1000 depending on the number of pulls. They are within a mile of work, and I could walk to work after dropping it off. The thing is, once burned, twice shy, and of course none of these places can guarantee anything since they are dealing with an owner assembled car. They know there could be problems built in that prevent them from getting excellent results.

So I will fool with it awhile longer. I am going to change the gas tank soon. It is probably best to get that done and stable before spending too much time tuning. One of the things I am finding out here is that there is alot of inter-depenedence in a system like this. Every single part in they system effects the final tune.

I ran into something last night after running it for awhile. It would not start right up after it became heat soaked from sitting 5 minutes after shut down. It fired on its third crank attempt, but not the first two. This is new, and I assume too much fuel. I need to go to the VE table and reduce the numbers in the cell for cranking which are the two cells at 90-100 KPA and 200 RPM. All start-up tuning starts with those numbers, and they affect all the other coefficients beyond that.

Life is so busy it is kind of hard to get the time to do this. We are having a big picnic here on June 1, so I really SHOULD be spending time on the yard. I feel a little guilty about car play still. Thanks for hanging in there with me, giving me a place to ruminate, asks questions, and journal this out. I must seem pretty dense at times. I know I feel it often. At the very least, I hope I am a good role model of what not to do.

I said earlier that with this car, I felt like I was dating Miss America with a chastity belt on. Well, it seems she has taken the belt off, but we are now just getting back together after a long seperation, and she is still a little cool and distant.

Sam[/u]

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I'd bet the coil was also your cold start problem and the MSD unit is fine...........

Although the MSD will work with any coil, the coil wasn't designed for CD igntions and I'd bet the MSD essentially took out the coil............

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Wouldn't you think a performance speed shop would know a standard coil was going to die with a CD ignition box? I guess with all the turmoil, there simply was not enough supervision of the jobs being done there at the time.

Sam

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who knows what they were thinking (or not thinking)

Another question, was this coil oil-filled or epoxy?

(I'm thinking epoxy,as there's no give internally, and that would explain the cold start, and other problems...... internal breakdown of continuity)

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes