Taking this topic back up: I hooked a 2200 uf capacitor between the black VR signal wire and ground. This wire is hooked up to the connection "N" on the 8 pin module. The pin not filtered is pin "P". I do not know if I filtered the ground pin or the non-goround pin, so do not know if I have it hooked up to the correct lead. It runs fine, but don't know if what I did is helping filter the signal. I do know if you place the capacitor across the two VR signal wires, it will not run at all. I was told one went right to ground, but it does not work to ground it AND the pin on the module. Does anybody know if "N" is the correct wire to filter?

IN the next week I am planning on putting a relay on the ECU to power it. I will also put a capacitor on the ECU feed at that point.

Sam

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Drove car to work today, and ignition pukes out under same conditions. It drives wonderfully till you nail it and climb into high boost areas. Still wonder if N or P should have cap filter.

Sam

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I just looked up the HEI MS conversion on DIY's web site. This shows the P pin as the positive pin. So I will transfer the cap lead to the feed and try it again.

Hey! What are the chances P stands for "Positive" and N stands for "Negative"? That seems too obvious to be obvious. As Lou always says, look for the most basic, underlying ideas. I never thought to try and guess what those letters stood for. I was making it more complicated than that.

Sam

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I hooked the capacitor up between the P feed, and ground and it would not start at all. Took off the capacitor, and it fired right up. So, a capacitor on the VR feed is not the answer.

AGain it is a 2200 uF @ 35 volts. Is it too big, or the wrong type?

Sam

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Since driving the car, or just thinking about it did not magically fix things, I decided further action really is needed. So, I have been sitting and studying, among other things, the replies so far on the earlier thread, trying to see what was the most logical thing to do next. I read the entirety of the slide show that George linked us too in that thread, which apparently was a talk someone gave at a convention for Megsquirt users in 2008. I wish I had been there. I have studied the Megamanual for insight, as well as the various manuals linked on the msextra forum.

Last night, I decided to take the capacitor that killed the engine when placed on the VR "P" signal wire, and placed it instead on the power feed for the relay box, which ultimately feeds the 12+ to the ECU. I don't have high hopes for this to be "the" fix, but have concluded from the reading I have done so far that: A. This is not easy to track down. and B. It is likely more than one thing. And, filtering the power for the MS box is not a bad idea.

Here is the current to-do list:

1. I would like to filter the alternator in some way if possible, but am not sure how to do that. I don't know if a capacitor is the thing here or not. I don't know if these Radio Shack 2200 capacitors are too small to amount to anything, or if they are just fine. I really am at the edge of my stupid border here. Although it is moving slowly.

2. Put shielded wire from the HEI to the ECU. These are twisted now, but unshielded. I noticed that the harness for the old Accel stuff had shielded wire for that application. If it is long enough I will use it. If not, I still have microphone cable left over, but may go to Capital Electronics and buy the stuff Pierre suggested earlier.I suspect the Accel stuff is what Pierre was recommending. I could not find it at Radio Shack.

3. Someone suggested isolating the HEI set up with a relay, (I think it was Olaf) which I have not done. The red wire to the coil (which feeds the HEI) is like number 10 or 8 which would suggest they thought it carried a lot of current. It is fused with a number 30 fuse, and it has not blown that, so suspect the wire is overkill, and I could use a standard 30 amp relay. So that is step three in this hunt and kill operation.

Any comments are welcome. I just wanted you to know I am grateful for all ideas so far, and your earlier comments did not fall on deaf ears. In time, I will get to them all. I do think it is important to make one change and then drive the car for awhile. JUst for the record, I did move the O2 sensor closer to the turbo outlet, so fuel tuning can now continue. And, just in case someone is still reading this, I will keep reporting.

Sam

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Sam - I just looked at the schematic... a cap that big isn't appropriate for the vr signal to module wiring. In fact no cap should be put here at all. If you have the shielding situation under control the rest of it is up to the module to filter. Without getting overly technical, a cap at this point will alter the frequency (and hence RPM) the module sees. If anything you'd use a really small cap, on the order of tenths of uf but again that should be built into the module itself.

Isolating with a relay while won't hurt anything probably isn't necessary as long as the wiring upstream is able to deliver the current. You could put the cap between the positive incoming power wire and ground if you'd like.

If I understood you right, per your #2, the wiring between ecu and hei module is NOT shielded yet? If I recall right your using the relay module box right? Stop putzing around with caps and other stuffs until the wire between box and hei is shielded. This really needs to be your mission before doing anything else. Seriously... I don't mean to be blunt but, there's reasons OEM's put shielded wire in these areas. It's expensive, if they could save a penny with unshielded wire they certainly would.

You may be able to find shielded speaker wire at your hardware store electronics section - its used for longer in-wall runs. It is 20awg or so, plenty adequate for this scenario.

Still need to be shielded *twisted pair* cable. Yes that's right.

And this is silly to put a cap on a signal circuit with wrong values. The Megasquirt already have these filter circuitry for many inputs and outputs already designed in. If there were problems with noise, then you have installation issue not the megasquirt.

Remember, car makers had to take care of these many issues to construct functioning PCMs (engine computer in first place.) after testing for worst case issues.

Cheers, Wizard

Pierre: One should know if such conductors are rated for under hood temperatures; such as 90C or higher. Anything less will cause insulation to become brittle.

Bill

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

If you wanted to get that fancy lol... its running on opposite side of the exhaust so I don't imagine its gonna get much heat. Through it in a split loom if your that worried about it.

Thanks for the replies. The wiring for the HEI to ECU is direct to the ECU and does not go through the relay box. Peter said there are not enough wires in the standard MS cable, so we just ran them parallel to the cable.

I will heed your advice and get the shielded cable soon. Thanks again.

Sam

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Wires from dist to ECU shoud not be too long, I believe, or shielding is needed, as said above.

Also, I am still skeptical this is an ignition problem. Why would idle and part throttle be so smooth and good, and then all goes to crap under load? If the spark were weak or intermittent, that would affect cruisin' and idle too.

Lou

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Home of Slant6-powered fun machines since 1988

As boost builds more spark energy is required to jump the gap. In theory the increased output can cause interference on the input side of things if the shielding is weak. It's a stretch, but its possible. Or the module itself is tweaking... I'm assuming you've tried another module right?

Crawl before you can walk. The wires need to be shielded before anything else can be considered.

Peter thinks that the HEI and VR get to talking to each other under certain RPM's and under certain specific conditions. I think the certain specific condition is fuel mis fires. I say this because as I get the fuel tuned in, the miss goes higher in both rpm and boost range. But is still very predictable.

It is the predictability of things that makes the idea of outside interference less likely. But, I am working on that anyway.




Sam

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When this happen as Peter mentioned means VR is too close to the high voltage ignition or harness sharing two signal wires (VR and HEI) for too long length can do that. This is biggest reason need to separate and install shielded twisted pair cable for the VR signal and separate the HEI signal from that harness and routed separately. VR shielded twisted pair cable can be still routed in the harness.

Cheers, Wizard

I hope I have not bored you guys into complete indifference by now. You are one of my few links to sanity. I learned a long time ago not to talk about these things to my wife.

lI haven't shielded the HEI to ECU feed yet because I have too many options, and simply cannot decide which is best. I have three choices here.

It is important to know that one of the 3 wires has a disconnect in the middle to set the timing. Right now all three wires are twisted until you get to the disconnect. The twisting stops there for about 4 inches, and then things are twisted again. I think the other two wires are twisted beside the disconnect.

1. McMaster Carr sells a wrap-around grounded foil shield for about $6/foot that can be simply added to existing cable. It would not be possible to carry it through the firewall into the cabin. Maybe this is not important. It is the easiest option. The disconnect would still be unshielded. Total cost about $25 plus shipping. KNow and trust McMAster CArr, and their web security. Cost is not a concern here.

2. Microphone cable has 2@ # 24 conductors which are not twisted but are shielded with woven, grounded. Possible down side is wire size, and lack of shielding at disconnect. I own this already.

3. Option three is a foil shielded,grounded 3@20 inside the shielding cable. This would require that the disconnect be inside the cabin if I wanted to run the shielding through the firewall. This seems to be a minor inconvenience as you would only need to time it when making major changes to ignition set up. Total cost, about $6 plus shipping. I know nothing about the supplier or their web security.

I need someone to tell me if there is a problem with any of these. Is the wiring too small with #24 in the mic cable? Is it important to shield all three the entire way, or is the disconnect not carrying any count sensitive pulses? It seems the 3 conductor 20 is the best, but I have been told woven shielding is better than foil. True of false.? This came from an audio guy, who I think considers flexibility a primary concern. Option one is the easiest. Options 2 and 3 are about equal in difficulty.

As before, I hope the guys are not getting frustrated with my inaction here. You have all been very helpful, and I am still thinking on and working on this. As said many times, this may not be "THE" problem, but it is a good, basic start. Thanks again.

Sam

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