Thanks for cool info, thoughts! Will try this, if needed. I have used these on magnetic resonance equipment in my lab too...

Lou

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Home of Slant6-powered fun machines since 1988

Supton, The reason I applied a choke first to the alternator, was because Max reasoned that since the miss always happened at the same RPM, the interference was coming from some spinning device such as the alternator. The other major spinning device of course is the distributor, which brings us to the VR pick up, and consequently the ECU feed from the HEI.

Where along the VR/HEI to ECU line should I put one or more Ferrites chokes? If copying the laptop charger idea, it would go around all three of the twisted signal wires that enter the ECU, right at the entrance to the ECU. I could also put one around the VR pick up wires just before they plug into the HEI module. On the device charger module it clamps around both positive and negative leads, so I assume that is OK here. Any thoughts?

I still have one large one to apply somewhere, but can buy more easily enough. You say ham radio operators stick them all over the place with no harm, and hoping for some good. Are there other feeds that might be generating an unwanted signal in the line? If I were trying to simply improve the radio reception, where on the radio should I install one? Should this go on the antenna?

Resistance spark plug wires are still on the to-do list. In our initial attempts to cure this problem, one of the first things Peter had me do was close the spark plug gap down to .022. Does it not seem advisable to open that back up once I begin to get the miss eliminated? They were at .045" but closing them down seemed to do nothing towards eliminating the problem. We have always been led to believe the larger the spark gap, the better. Thoughts on that?

Last question for today: Do you think these little devices will stand up to underhood temperatures? Should I wrap them in electrical tape to keep them from falling off if the plastic latches should fail? There you go Lou, that one is a "worry/concern".

Thanks, Sam

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Putting a ferrite over the antenna would be fun to try. Due to the frequencies involved, it might not do anything... and it might just do a decent job of blocking radio stations. I'm talking over the arial. I wouldn't leave it there though. It'd be a fun experiment, to see if it'd block the AM signal...

IIRC, larger gaps try to get a bigger spark, to light off the mixture faster and/or to get a better burn of lean mixtures. Bigger gaps require higher voltage to get the arc started. However, the resistance--and therefore the current through the arc--might not change very much. Thus I could buy that RFI would change little in response to gap changes, since the interference is likely rising from the current waveform and not the voltage waveform.

Around both leads is good, in terms of installing the choke. You can experiment with opening up the choke (if it is a split type), wrapping two or three turns onto one half, and then installing the other half. The inductance goes up as turns squared; and this can also cut noise pickup.

In terms of placement, it depends upon what you are trying to accomplish. On computers, the computer itself can be a large maker of noise; so the choke tends to go next to it, to prevent the charger cable from radiating EMI. In your case, since the noise signal is being picked up on the VR line, putting the choke next to the ECU prevents any noise pickup on the VR wire from getting into the ECU. Putting a choke next to the VR signal likely won't have much impact, as the rest of the wire would still likely act as a noise pickup.

On a home setup, I would up using ferrites on some computer lines (mouse, keyboard) since my radio and my antenna were very close to the computer. The computer was radiating the noise, on any length of wire attached to it; installing some chokes got the noise to a bearable level. It was kinda hit or miss; but at the same time the noise was very easy to find (leave the radio on and listen!) and experimentation was fast.

I could be wrong, but I don't think you will get much out of putting ferrites onto the injector wiring. If you did, it likely would be best to have the choke again next to the ECU--but that would be because of the ECU itself radiating the noise. Which I don't think is the case. But it won't hurt, either; and I was wrong on the ferrite on the altenator. I don't think the engine sensors (MAP, TPS) need one. You might get something, though, out of putting a choke onto the +12 to the coil.

All excellent info. Thanks.

Can I assume that if the ECU is registering extra RPM counts it must be from a square wave generated by the HEI? If so, the a choke on the VR feeds might be the place to filter unwanted RPM counts, since an RPM count would start as sine waves in the VR feed pick-up wire. What I am gathering by now is that the VR pickup wire also acts as an antena and ends up with stray impulses on it.


Sam

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Lou do you have a source of a better quality part than Radio Shack is selling? Or is a magnet is a magnet is a magnet?

Sam

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You could try digikey.com or newark electronics, but I bet the radio shack ones are just fine.

Lou

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Home of Slant6-powered fun machines since 1988

The problem with Digikey for me is that you need to know more than I know to order something. There are lots of options that I have no idea how to chose from. Radio shack has at least three different sizes, and as near as I can tell the wire size is the main concern. The big ones go on big wires, etc. That much I can handle. Until I know more about this stuff, I am stuck with RS.

Sam

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Even though it is better, we are not there yet. I took it out and drove it hard today, and it missed, and broke down right around the same RPM. It does run much, much better. That is, it idles smoother, and starts quicker. In all light to medium load conditions under 3K rpm it is smooth, reponsive, and nimble feeling. Push it and it fails.

So, I did a datalog and studied it and it looks different than before. It seems the high AF ratio, that is below 11.0:1 precedes the extra rpm count. Unlike before,where a sudden high RPM count preceded the high fuel. It seems a miss from over rich fueling will cause a miss that then really sends out serious EMI confusion to the HEI and ECU. This happened readily before I enabled over run fuel cut off. It would go through the same song and dance when coasting down and there was too much fuel, but under very high vacuum conditions,(low map readings).

Here is what I observed in the data log.


RPM------2313----- 2817--------2859-------2920-------7900 (false)probably 3200-3400 in reality.
Map -----101.7------123.1------118.9------120---------145
AF ratio--11.6-------10.7--------10.5-------10.6------- 10.9

This all took about one second from the 2312 to the 7900 reading. I suppose it is possible that the higher boost created the false RPM reading somehow. They happened pretty much simultaneously.


It did not go into reset mode. It just missed, and stumbled badly. The plan is to reduce fuel in those cells, and data log again to see if keeping the AF ratio above the 11.5 range will eliminate the miss, and maybe thus eliminate the false RPM counts. I have ordered a set of stock spark plug cables which I will install time permitting. The Magnecor wires could be sending out enough EMI to be creating the extra RPM count, but only under load. They certainly interfere with the radio on AM.

I am wondering why the false high RPM reading did not make the fuel richer than it did. One possible explanation is that it this RPM number is not even in the fuel map. I guess under those circumstances it just would use the highest RPM count available. Since I have never operated up in that cell yet, the number there might actually be way too low for correct fueling. It could also go into a fuel cutoff when it misses. This is just speculation. I do not really know.


Any thoughts?

Sam

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Are you using resistor plugs?

If not, resistor plugs might damp down the interference (instead of resistor wires)

Also different manufactured resistor plugs will have different resistance. (I've usually found that champions have lots more than autolite......)

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

Eliminate the alternator totally for a test, and just run off the battery.

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

Sam,

This might sound silly, but don't forget to go back and look at some of the basics. I once had a car that would misfire and stumble terribly only under part throttle acceleration, such as maintaining highway speeds on a slight grade. Idled smooth as silk and wide-open throttle was fine. The problem turned out to be a bad distributor cap. Cylinder pressure was probably pretty high during these part throttle events making it harder to fire the plugs and the cap would break down. I wasted a lot of time refusing to look at the cap, because it was fairly new.

Your problem seems to happen when you start to develop some boost. In other words, when cylinder pressure starts to climb and it becomes more difficult to fire the plugs. I don't know for sure if a cap breaking down could induce erratic behavior in the VR circuit, but it sounds plausible, with several thousand volts on hand from the coil.

Good luck,

Scott.

That is great advice. Thanks. Dart 270 would absolutely agree with you. I think a basic tune up might be in order. I have stock wires to pick up today at NAPA. I could try to get the trick cap and rotor Dan is always touting.

The thing that makes this hard to get a handle on is that when I first put it all together with the new MSII, it missed and went into reset mode at high vacuum, because of excess fuel. That was just the opposite of high pressure. So, I have to be open to the likelihood there was more than one problem. I think the miss was too much fuel. The reset was from EMI caused by the miss somehow. The resets seem to be pretty much gone. Now it seems to be more just an ignition breakdown. with an associated RPM misread somehow.

I will say that the graphs in the current datalog look much smoother with the ferrite chokes in place. Everything is much more stable. That was not a waste of time or money. The long term plan has been to go to Ford EDIS ignition. However, I thought it would be best to get this figured out first, and drive it for at least a year and get a really stable tuning done. Maybe the EDIS would eliminate part of the problem. The thought of starting over kind of alarms me. I'll get into that later though.

Bottom line, I will do a basic tune up.

Sam

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I played around with NGKs for a long time trying to get rid of pre-ignition under boost. I may go with Champions later if the plug wires do not clear up the radio noise. There is a lot to play with here is there not. Cap, rotor, wires, plugs, and all combinations of the above.

Sam

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Data logged on the way to work after taking out fuel in offending cells. It still missed under hard throttle, but it did not show a single instance of extra RPM counts.

Something weird about this data log is that the TPS log indicated a max percentage of 23%. I am almost dead certain this is wrong. I would have thought I had the throttle close to WOT at least once or twice. Also, when the throttle was clear closed, at idle, it recorded an unsteady line that went from .1 to 0 and back with a regular pattern kind of like a square wave. The screen is not in expanded view, which will cause this appearance.

So, I am suspecting maybe a less than perfect TPS switch. I will check that out at NAPA when I am there to pick up the plug wires. And, I will do another datalog and this time be certain I do a few WOT moments.

Sam

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I am wondering if I do not understand what the numbers mean in the TP line of the datalog. On the datalog on the way home, I nailed the throttle hard several times and the highest number recorded is 46. I was assuming this is percent. Maybe not. Does anybody know? This is with tuner studio, if that makes a difference. If it means percent, then things are not registering correctly.

There are no false RPM counts in either of the latest logs, but there is still a serious miss under boost. So apparently I am past the false rpm counts problem at least for now.

Sam

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