i know a couple local guys that did a megasquirt setup in their cars and they say its a pain in the *** to get a clean signal from the cas

I have a Ford EDIS 4 module and vr sensor sitting here will it run the leading and trailing timing properly?

or can I just use the Vr sensor itself with a 36-1 wheel?

 

There should be no problem with the CAS if it is wired correctly, the shield is grounded at the ECU end, there is a 0.1uF capacitor accross the input at the LM1815 and the CAS wheel gaps aren't too wide.

No reason that 36-1 won't support trailing but you'd have to figure out the triggers yourself. The CAS is far easier.

 

Ford EDIS 4 post will not work as post 1-3 & 2-4 are set up as wasted spark, a EEC-IV 6post from a contour/mystique would work: use one post from 2nd and 3rd trigger wasted event as your trailing 1-2.

or go with some LS1 coils and call it a day. much less wiring in the end anyway.

 

"Will not work"? That's strong language. How do you reconcile that will the people who have used that setup?

 

It may work, but it's harder on the coils.

During normal operation on a wasted-spark coil, one post of the coil will have very high voltage (the piston/rotor that is currently on compression). That one is the one that actually sparks. The "wasted" spark may not even spark visibly at all. This is because the exhaust it's firing into is essentially an ionized gas. It's much easier for the electricity to pass through that.

Now if you fire both plugs on a compression stroke, both plugs will fire at high voltage, and I'm not sure that the effects are what you'll want, and I'm also fairly certain doing it this way is harder on the coil.

Aside from some very rare cases, it is better to use the stock system in my opinion.

Ken

 

Whew! If that is the only concern, I'm golden. Having the higher resistance of firing across two impeded plugs will actually be MUCH easier on the coils. The coil insulation will already handle all the voltage we can throw at it with our 12volt system. The danger to coils is heat build-up from environmental concerns, and (more importantly) CURRENT FLOW. Voltage doesn't cause heat. Current flow does.

The ground, plug-gap, coil, plug-gap, ground of the wasted spark system is a series circuit. Add extra resistance anywhere in the line and you have less current flow. Add TOO much resistance, and you have NO current flow. Then you don't have any ionization, which means you don't have a spark, which mean...your engine stays awful quiet. 8*) If it fires with the extra resistance, I'll be golden.

My eventual setup will feature dual EDIS-4 coil packs, one for the leading and another for the trailing. One end of each of the 4 coil sets will be grounded. Now, that WILL be harder on the coils. I have it setup to provide blast air to the coils to keep them cool.

 

I believe that on a real wasted-spark system, the current for the "wasted" spark actually flows the opposite direction to the non-wasted one.

I read a paper on it once, I'll have to see if I can find it, but the end result of the paper was that it's harder on the coils to do what you want to do.

Ken

 

Ken said,
In waste spark ignitions, current flows in the same direction all the time. Let's say from the center of the plug to the outer case for #1 rotor and outer case to center on #2 rotor. All the time. It could be the other way around. But it is always in the same direction whether during waste spark cycle or the ignition cycle. If you look closely to the center pin of used RX plugs, one will be rounded more than the other due to this continuous current flow direction. This unbalanced electrode wear is seen on traditional bent-ground electrodes in other waste spark applications too.

 

I think I'm saying what I'm trying to say incorrectly.

I believe these guys are saying it right though:

http://www.physicsforums.com/showthread.php?t=388053

The current in one plug flows the opposite direction to the other plug depending on which is the "wasted" spark.

At least that's the case looking at some of the diagrams there.

Actually, after remembering that, it seems like it shouldn't damage the wasted spark coil to fire both sides into a compressed mixture, but you will end up with half the spark energy on each coil, and a very weak spark all around, which is still a good reason not to do it that way.

I'd go with a good COP setup before doing an EDIS-based setup. Maybe some LS1 style coils and an e-shaft pulley mounted 36-1 (if you already have it there) or just the stock CAS.

Ken

 

Ken, you certainly understand the HV on the compression side and LV on the exhaust side. And thanks for the linky. I am trying to clarify your wording that direction of current flow being dependent of which is the wasted spark statement.

Yes. I agree. This is each and every time the coil fires; x2 per eccentric revolution.

Not really.
The current runs from the one HV terminal on the coil, thru the wire the the center terminal on the plug. There, it sparks across the gap to the ground terminal and to ground. At the same time, on the other plug the same current runs from the ground, jumps the gap (may not spark) to the center terminal, out the wire and to the opposite HV terminal on the coil completing the circuit. This is all one event. Current flows in both plugs but opposite each other.

The next ignition event, the current flows the same same direction, only it is the opposite rotor ignites the fuel. Regardless of whether any given plug is "wasted" or is "ignition" during any given ignition event, the current direction in that given plug flows the same. The two plugs constantly alternate being "wasted" or "ignition" but the current always flows in the same direction.

 

That is an excellent link with REAL information. I consider myself schooled today, Ken.

I considered the COP solution. Still considering it in fact, as it would significantly reduce bulk, weight, and wiring complexity under my cowl. The problem with it is matching the coil properties (resistance and inductance) to what the EDIS modules expects. This will have a direct effect on the required dwell time, and I have no way of changing the dwell time in the EDIS module. I'm trying to pick the simultaneous unknowns I'm dealing with carefully.

For now, either it will or will not work as wasted spark going into the same cylinder. Some have actually done it, so I'm going to cross my fingers and hope for the former. Once I get the low load, low rpm running of the engine sorted out, I will add in the second EDIS module and coil pack, and ground one end of every coil. This will effectively double (give or take) the energy across each plug.

I also have a "pencil test" to perform now 8*)

BTW, off topic, but you're so helpful and I can't find the information anywhere. Do you have a link or reference to adding an oil temp sensor to MegaTune? I have the hardware installed. I have my sensor characterised. I have the circuit connected to JS4. All the references I've found discuss how to install a pressure sender and say to modify the adc7 entries in megasquirt-ii.ini. I don't have any adc7 entries in my megasquirt-ii.ini, or anywhere else I could find.

 

Which firmware are you running?

Ken

 

Sure, so I was a little off there, but I was remembering it off the top of my head. It doesn't really change the point I was trying to make though.

The main point I was trying to make is that by firing both ends of a wasted spark coil into a compressed air/fuel mixture is not ideal.
I was wrong on it hurting the coil. I don't think it'll hurt the coil, it'll just hurt the way the engine runs.

In any case, unless you have a very good reason for going with EDIS (like running it in an airplane), on a vehicle that keeps all wheels firmly planted on the ground, I'd go with the stock ignition system. The noise issues are not that difficult to fix (to get back to the original poster's question).

Ken

 

B&G MSnExtra 2.88. I think. I'm at work now, so I'm trying to remember it off the top of my head.

 

Haha, yeah, you should probably check again, that firmware doesn't exist!

The ADC7 issue is probably because you are running the B&G firmware. You want ms2/extra 2.1.0 or 3.1.0, those are both stable versions of the firmware that James (jsmcortina on msextra.com) and I wrote.

Ken

 

Did some more research. It appears the only difference that will affect me is:

"If you are building an ECU from scratch then you will find the MS2 official build manual (V2.2 / V3) tells you to install a wire for the ignition output (pad JS10 on a V3.0 and pin 17 on a V2.2 board), this is only required for MS2-Extra code if you are going to use EDIS. "

I don't have the computer apart, but I would assume that it is installed in my build, since I'm running EDIS. I'm not using the Stepper Idle valve output or the programmable outputs IAC1 and IAC2, so that is immaterial.

Is there anything else I should consider before switching the firmware? Now would be a good time for me to make a decision.

 

If you're planning on doing anything like staged injection for example, the extra firmware supports that as well.

For your use, I'm not sure if there's much other than that to consider.

Ken

 

This has been a while, but just a quick update....I have this engine running pretty good. I do have some tuning left to do (I'm waiting until I get my final propeller built), but the EDIS is working well.

Watch it fullscreen:

http://www.youtube.com/watch?v=F3pYW1lOcTo