No, what I want to do is find out if the 3.1ms is the correct dwell for the coil....

There are voltage compensation changes allowed in the software, but I don't want to fool with them until I understand a little more about the MS dwell circuit. What I read in the manual ain't exactly what I see it does (not unusual).

The coil seems fine - I'm just checkin' stuff and trying to learn as much as I can about the software controls.... mainly because I tend to be suspicious of anything I don't understand perfectly. I learn better thataway. <img src="/forums/images/graemlins/notooth.gif" alt="" />

You see, if I understand how it works, then I can figure out how to fool it. <img src="/forums/images/graemlins/wink.gif" alt="" />

Frank

Frank, I recant the avionics stuff. Johnboy says all the work is board plugins now, except on real old stuff.

Google "ham radio columbia sc" and you'll get contact info on a bunch of ham guys. Bet one of them has a decent LCR.

Yes, they use them quite often if they build their own stuff. There's a set of plans on-line to build an adapter to work with a VOM, but I have more to do right now than go on an electronic parts hunt. <img src="/forums/images/graemlins/wink.gif" alt="" />

Frank

I found about 5 of them in plan/kit form. One of the ham nuts probably lives within 5 miles of you. Just follow the static...

Here's you a couple of names one of which works in the county solicitor's office, or at least did in 2004...

There are some LC meters on ebay for less than $50.

I asked Matt at DIY AutoTune if MS has a sense circuit. His answer is "NO", but a little confusing:




Apparently, MS does use the battery voltage value before the alternator kicks in to raise dwell as a coil charge compensation. After it reads the alternator-supplied voltage, it reduces dwell to a compensated value. This amounts to the same thing that Charlie was saying..... so I need to find the coil inductance and adjust voltage compensation to make the dwell time match the coil requirement.

So, I just bought this LC meter for $35 (inc. S&H):



Who wants to bet that after I make the calculation I find that the present 3.1ms setting is correct? <img src="/forums/images/graemlins/lol.gif" alt="" />

Frank

We will know soon. I have not tried to get the minimum charge time with the setups I have done. Right or wrong when I get it running I leave it there. Part of this might be that with the Mitsu multi coil ignition that is in use by many manufactureres it is pretty well documented what works. Now with the single coil you are working with there is little to no documentation. But there will be soon.

I would have bet money that you had arrived at the 3.6ms by putting the car on a scope and reading the spark output. I'd have lost the bet, eh?

At 3.1ms, I don't have any ignition cutout that I can tell and the coil runs cool....... but - my curiosity is killing me..... as usual. <img src="/forums/images/graemlins/rolleyes.gif" alt="" />

I hope I can get an exhaust system installed before Tuesday, because I have an appointment at a Mustang eddy current dyno shop to tune it. It's a 1750 model with single eddy current controls - should be fine for what I need. It's a really weird 6 bay shop - way out in the country, owned by a young fella who built it behind his parents house after he found he wasn't happy working as a mechanic at a dealership because he liked to tune race cars. He's only tuned one MS car, but seems to at least understand the principles of MS and the fact that I don't want the tune on the edge. He has a lot of very, very fast and powerful Mustangs and such in the shop - 800-1200HP <img src="/forums/images/graemlins/scared.gif" alt="" /> <img src="/forums/images/graemlins/scared.gif" alt="" /> and his own blow-through carbureted Mustang with a Powerdyne blower running 35psi. <img src="/forums/images/graemlins/scared.gif" alt="" /> <img src="/forums/images/graemlins/scared.gif" alt="" /> <img src="/forums/images/graemlins/scared.gif" alt="" /> What I really like is the fact that he works alone, is willing to learn about MS and will let me tune it how I want it. <img src="/forums/images/graemlins/kewl.gif" alt="" /> For $200 or so, I'll get to play with the dyno and learn some more.

Here's his website:

Carolina Chassis Dyno

Frank

Now it sounds like you found the right guy to work with, nice.

I set the coils by overall feel and how the engine pulls. I have scoped the inputs but not the outputs of the coils. I used to have a big ole Sun 900 engine anylizer. Parts of it appear to not have liked the cold and started to fail. That big old scope gave real nice traces for the plugs. But now that a good portion of what I work on no longer has plug wires to hook a scope to, I guess I do not even know what to scope the spark with. Or at least be able to justify the cost of a tool to do so.

Long ago - in the days of points ignition - I would set the dwell for good ignition at WOT/redline and feel the coil at idle to make sure it didn't get too hot.... not very scientific, but it was all I knew to do. With today's stuff, the dwell is constant, so we don't know what the coil really needs without doing the calculation in the MS manual.... or trial and error for a best guess "feel" as you have done.

What started me down this road was the initial attempts to start the engine on the range 7 plugs and I said the plugs read like weak ignition. When it ran on range 5 & 6(but not on 7), I became more curious - and even more so when I swapped in the Diamante coil with a slightly lower secondary resistance and sensed a slight difference in ignition quality.

I guess that even knowing what the dwell "should" be will still leave room for "feel", but it seems to make sense to know where the "norm" is found before playing with it. I'd like to do that before I get on the dyno, but it's probably not necessary.

Generation One sent this webpage - you might find the coil information useful:

picotech

Frank