SEFI, EDIS, DIS, Coil On Plug, and TFI with MS and Holley

clintonvillian

Famous Member
1. For starters, everyone agrees a DIS system is better than TFI. I am just not convinced that the extra headache and money is worth the effort. Both megasquirt and holley are easily adaptable to the tfi. (Holley even has a harness, plug and play). So is SEFI and DIS worth the hastle???

2. Fords EDIS system is great and as THESAMEGUY has shown it can be done cost friendly and aesthetically. With the new M/S and Holley HP I think using the EDIS adds some "junk" that doesn't need to be there and I would prefer to just allow the ECU to control the timing.

The rep at Holley said I should find some Ch#vy LS coils (one per cylinder) and use them. All I need is Positive and Negative from battery, and the ECU wires. No ignition box needed............is that how the COP systems work?


Having said that, what do you guys think is the proper route?
 
Nevermind, I think I found what I was looking for in another post...........


pmuller9":5f3y3zdm said:
carbureted":5f3y3zdm said:
Is there a good writeup somewhere of how to swap over to a COP setup?

I just want to take the time to thank you for all the help you've given me so far. It means a lot.
There are 3 basic coil arrangements for a distrbutorless ignition system and all 3 are supported by the Holley HP system.

The first would be 3 twin tower coil packs where each coil fires 2 plugs at a time, one plug at the start of the power stroke and the other cylinder 360* away during it's exhaust stroke or what is called the waste spark.
This arrangement doesn't need the cam sync signal to identify when cylinder#1 fires.
Dodge Hemi, Ford and others.

Then there is the near plug coil like on the GM LS engines that normally mount on the valve cover.
You would need 6 coils and a cam sync signal to identify which coil is cylinder#1.
The LS2 truck coils are more powerful and are identified by a visible heatsink for the driver transistors.

Last is the coil on plug that simply mounts on the spark plug connector. No plug wire.

In all 3 cases 12 volts is supplied to the coil driver which is part of the coils and the HP system simply supplies a 5 volt trigger pulse.

There are several ways to supply a spark trigger signal and a cam sync signal for sequential fuel and/or spark control.

The most accurate is to mount a 60-2 tooth wheel to the harmonic balancer and a sensor.
The cam sync signal is then generated by grinding off all but one of the reluctors in the distributor and timing it to 60 degrees before TDC for #1 cylinder.
 
Yep, that's the gist.

Waste-spark systems like EDIS (where there are half as many coils as cylinders) were an intermediate step, largely cost motivated. Back in the '80s and '90s, one coil per cylinder ignitions would have been expensive to design and build. Saab was very early to this game in 1988 (1990 in the US) whereas most systems stayed with waste-spark well into the '00s. By the '00s, when emissions requirements started really ramping up moving to coil per cylinder ignitions was a no brainer. This is commonly called coil-on-plug (COP). Even on GM's small block motors where the coil isn't physically on the plug, it's still COP. The reason the coil isn't on the plug is because o pushrod motors don't have the same packaging opportunities as on OHC motors. Same tech regardless. GM makes plenty of OHC motors with coils physically on the plug driven by the same electronics as the small blocks.

There isn't all that much functional difference between COP and waste-spark systems. There are some, but none you're going to realize with an old inline six. ;) COP needs more engine position information and twice as many coils. That's about it. :) It's possible on an old motor waste-spark might yield some slightly improved emissions. They are both driven in the same way - a computer tells the coil when to fire... same idea as Duraspark, just more coils. :)
 
So given what you just said, technically on 3 coil packs are needed.

Can a V6 FORD coil pack be used in conjunction with an aftermarket (Holley, MS) ECU? Without the need for the Ford EDIS module?

Might sound stupid, but I had hoped to have a 6 pack that I could mount on top of the old distributor (Cap stripped of course and modified) just to retain some of the older look and plug wire locations.........
 
For a waste-spark, yes, three coils are needed. The EDIS-6(cylinder) "coil pack" (like I have on my car) has three coils inside. One coil for each of two cylinders.

Nothing prevents a Ford coil pack from being used with any ECU you'd like. They are just ignition coils like you've got in any ancient car. In the factory configuration the EDIS module which manages when the coils fire, but nothing would prevent another system from doing it the same job.

However, the EDIS module has some brains in it and typically (such as with Megasquirt) interacts with the "main" computer to manage ignition timing. Without a computer telling it to do otherwise, the EDIS system is locked at one advance (I believe 14 degrees). It's a failsafe in case there is a problem. It's a very reasonable setup, and you can work with it or around it.

From a practical standpoint there probably isn't a major reason to choose DIS over a distributor. They both work. You'll never rev an old six high enough or make enough power where TFI can't keep up. A proper, modern, programmable FI system can do just about anything you'd need with TFI. For most old six apps, the sole reason to dump the distributor is to eliminate spark scatter that results from worn distributors & distributor drives. I think that's totally worth the price of admission, but it may not be enough for you.
 
The only other good reason to go COP over DIS or TFI that I can think of would be to enable cylinder-to-cylinder misfire detection, but that's more in the realm of maintenance than performance.
 
COIL PACKS and coil on plugs. Advantage is saturation time between firing. Also the ability to increase duration of spark. Ability to fire 1 cyl on ignition another on exhaust improves emmissions.
First 2 advantages mentioned are not all that necessary for more stokish motor build but would be an improvement but not realy worh the money it might take to convert. Now a more performance built engine such as my 430 HP 302 and high RPM would truely benifit. Benifit of coil on plug over coil packs is control over each spark as each cylinder is a bit different due to many reasons. I like the coil packs over the col on plug as they seem to have fewer issues.
 
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