Hey guys,

I learned a lot in the recent thread involving double platinum plugs and why they are so important to an EDIS ignition system like in the 3.0L Vulcan.

Now I notice that the 3.0L Duretec uses a "coil-on-plug" style ignition which is a bit different than the Vulcan. But, as I underestand it, it is still an EDIS ignition like the Vulcan. Is that correct?

Also, Ford requires different plugs in the Vulcan (MC# AWSF-32PP) verses the Durectec (MC# AWSF-32F) and also different gaps for them, as well.

I could be wrong, but I don't think the MC# AWSF-32F plug is double platinum. If I am not wrong, then wouldn't that mean that the Duretec does not need DPs because it has a different ignition? Or is it the same ignition, just re-configured a little bit?

Any thoughts or comments on this would be appreciated. Thanks!

 

Hi Rock,

No, the Duratec does not need double platinum plugs because
each plug has it's own coil, and all the plugs get the same polarity
spark. The coil pack on the Vulcan produces opposite polarity
sparks for the plugs in each back...

 

Duratec ignition is hte same as an outboard engine. You do not need DP. However, it had been my experience with boat engines that the plugs tend to foul at an alarming rate on these ignition systems. It is also important to check each plug periodically. Since the ignition is governed differently for each cylinder, the plugs can wear at very different rates. Provided you keep the plugs in good order, these ignitoin systems are VERY dependable.

 

Thanks for the feedback.

Getting back to the Vulcan ignition system for a moment ....so in addition to the 'primary' spark firing the cylinder at TDC on the compression stroke for power, you have this 'secondary' spark that's firing a cylinder at TDC on an exhaust stroke......but for what purpose? What does this 'secondary' firing accomplish? Burn more exhaust fumes up? Is it an emissions thing?

 

You got it rock. It burns up unused gas for emissions. It also helps to fire the cylinder down on the exhaust stroke.

 

Joe, it's primarily a by-product of having one coil fire two plugs at the same time, since they're in series electrically -- in other words, with this system, you can't avoid firing them together. Stated another way, the current flow is INTO the top of first plug and OUT the top the second: a big loop.

I would doubt if any benefit is to be had by firing during the exhaust stroke; rather, it's more of a "no harm, no foul" than anything else. Since the exhaust valve is probably open to some degree at this time, you'll get no power benefit. As for emissions, you may trade some unburnt fuel for burnt, but I don't know the impact of that emissions-wise, or if it's even significant in the grand scheme of things.

(Bob, since I know you're reading this as well: Pulled the plastic cover on the A4's 2.8. Guess what? 3 coil packs. My plugs are non-platinum NGKs that have two opposing ground electrodes, which I assume is to extend the life of plug to hit the schedule, which is every 30k. Haven't confirmed that this ignition system performs exactly like EDIS, but my guess is "yes". Since this stock NGK plug is $5 discounted (!), think I'm gonna switch to DPs. How much more could they be, right? )

 

Mickeyp,

Motorcraft DPs are $3.99 at Autozone, I don't know if they would
have them for your Audi or not........Advance Auto carries
Autolite......Good luck!!!

AN update, I just checked the Autolite website, and it called out
APP3923, as the DP P/N for your Audi......

 

Thanks, Bob. I, for one, have no problem with Autolite, since they were the first replacement set I put into the Ranger at 40k (a bit premature, admittedly). So, at 90k (last week) I put in a set of the OEM Motorcrafts (6W10 / ASWF32P) which I picked-up from Autozone for a buck eighty nine each (we're talking single platinums here since my '94 is distributor-based).

Anyway, the Autolites I pulled out -- all six -- were positively beautiful. Nice, uniform white coat on all, still maintaining their .044 gaps after 50k. I was tempted to put them back in! You'd never know that I regularly burn a quart of oil every 1500 miles (since day one), something I attribute to engine braking for the most part.

So, this set will go probably 70 or 80k, or every other distributor cap/rotor change. (Wish THEY would last longer than 30-40k!)

 

Mike, thanks for the feeback. That helps explain the "waste" spark, as I guess they call it in the trade. An interesting design.

As is often the case, one question leads to another, and here it is:

Why close the loop that way (two plugs in series)? Couldn't it have been accomplished without involving the firing of another cylinder?

 

Hi Rock,

No, the easiest way to fire 2 plugs in series is to fire 2 cylinders
that are 360 degrees out of "phase"....That way everything is
"timed" right when they fire on every revolution of the crank....

 

Hi Bob,

I understand from your schematic that the EDIS ignition for the 3.0L vulcan fires the 1 and 5 cylinders at the same time, and that the same thing also happens with cylinders 2-6 and 3-4. I also understand the reason for this is because the 1-5 plugs are in series, as are the 2-6 plugs and the 3-4 plugs, respectively. I also understand that each pair of plugs that are in series sit in cylinders that are "360 degrees out of phase" because of (or as a result of) the engine timing.

I guess my real question is this: Why not close the loop(s) another way? Why do the loop(s) have to be run through 2 plugs? If there were another way to close each loop then you would only have to fire the one cylinder on its compression stroke, and there would be no waste spark at any other cylinder. I am assuming that you can program a computer to fire a single plug at the proper time, so why not do it that way instead?

P.S. Hope you don't mind if I post your schematic here so that everyone else can reference it a little easier:

 

(You slipped that last one in on me, Joe, while I was composing this. Let me add one thing: You've got only 3 "fire" lines for a computer to hit. Anyway, I'll let Bob do Electric Circuits 101 now. I'm going out for a beer! )

Bob, although you're correct in adding that point, I think you missed his question.

Joe, to do what you propose would require six coils (one per plug). They are doing that now on many engines, but it's more costly. Three coils is cheaper and still gets rid of the distributor, but the drawback is the connection of two plugs to each coil. Every "fire" pulse to each coil affects both plugs, but due to the phasing stated by Bob, the unintended firing occurs during a non-crucial time.

If you're thinking that you could somehow tell that one coil to alternate which plug it fires (I think this is your question), then your getting into very high-voltage post-coil switching circuits ($$$), or a conventional distributor again. That's why it's done the way it is -- a compromise between evolution and cost.

Hope that helps.

 

Another relevant thread regarding spark plugs here: Debunking the Myths of Bosch Platinum Plugs

 

Hey everybody, I have been wondering how the whole ditributorless ignition worked on my truck. Thanks to you guys I get whats going on now. I'm not sure if you will have any info for me or not, but you seem like a smart bunch. I am kind of a performance junkie, so I am always on the quest for more power. I was wondering if you guys know of any upgrades for the ignition on my '98 3.0? I have heard a few rumors that this system is a little weak. I have made a giant leap forward in tecnology with this truck, so I am a little out of my element. I mean this is the first fuel injected vehicle I've ever had. Yeah I am not a typical 20 year old. While my friends were out buying civics and 5.0s I went out and got a '73 Dodge Dart. But I figured it was time to get a newer vehicle now that my Dart is getting a little too wild to be driven every day, and my old jeep pickup started breaking down on a daily basis. I thank you in advance for any help you might be able to offer.