gemellocattivo.com

That's pretty much it... one has bosses to bolt coils down and one has only ribs so I can't bolt anything down
For the forward bank, I'm pretty limited in what I can do. The original system used a waste spark coil pack bolted to the baseplate on the rear cam cover as shown above... half the plug wires went straight down, while half the plug wires went across the engine. With no way to bolt coils to the front valve cover, I need to run plug wires to that bank.

The question I still have is whether I can use the '06 NorthStar pencil coils on the rear bank with a custom baseplate, while using a 4 pack of LS coils + wires on the front OR if I want to use LS coils for all 8 cylinders, and mount them all to the old style baseplate.

The part of me that wants to watch the world burn says to use pencil coils on the rear bank and LS coils + wires on the front bank, but the most straightforward way to do things will probably be with 8 LS coils and custom plug wires.

In theory you should be able to mix and match coils, but I've never seen it done. Most ECUs don't allow different dwell times which different coils normally require so that is generally a deal breaker right there. Then different coils will have different firing properties so the firing signal timing will probably want to be a little different bank to bank...this idea just seems like potential problems you don't need to create, plus the coil brackets come in sets

but I still can't believe you're going with mismatched valve covers so that shows what I know

If I send you a drawing, can you mill out a die set so we can melt some magnesium and cast an appropriate valve cover so they match?

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I realized that I can use 4x D580's and 4x D514A's and likely fit them all on the baseplate shown above. That would line up all the electrical connectors, while having half the high voltage terminals on one side and half on the other. That would greatly simplify plug wire routing. Interdasting.

I strongly suspect that pretty much all GM coils are going to have the same dwell requirements, as that simplifies their control design. Although since it's in software, the dwell time could easily be the thing that changes.

For certain the 585 coils I have use a different dwell than the 580 and suspect they are all a bit different. As you say dwell is a table in the software so easy for them to match to whatever coil is on the engine. You can no doubt find settings that are acceptable for both coils as they are probably pretty close, but understand that you will have different spark characteristics and therefore timing in the 2 banks....whether it would be enough to notice I don't know....the closer to the limits the engine is the bigger the issue it would cause though.

Interdasting. GM specs the coils from scratch, so I don't know why they'd make them different. Of course GM does a lot of things that don't make any damned sense, so why wouldn't they have different dwell on different coils?

Well, anything you do different on 1 coil vs another changes its dwell...size or shape of the core, number of winding, the length and gouge of the wire used to make the windings. They are trying to design coils that meet the needs of the particular engine while costing and weighing the least possible, and no 1 answer fits every application. what you're talking about is the equivalent of using different style and size fuel injectors in 1 bank vs the other....it can be done but its sure to cause issues that did not need to exist

Are you sure it's not that they design to minimize cost & weight, while hitting threshold spark energy and the dwell ends up where it ends up because they can deal with it in software?

Wouldn't be a big deal to use 8x D580s... either the plug wire routing or control wire routing would just end up less elegant. I asked the tuner who's setting up the ECM what he thinks. He can pull down the .bin files and check on applications that used each coil to see what the dwell & coil-related settings are.

How would you know the difference?

The standard practice these days is there is some kind of product spec document created that lists all the design requirements (I'm putting the finishing touches on one of these right now) and the engineers work to hit them all . The specs for weight and cost would probably be one sided do not exceed numbers, the spec for delivered energy 2 sided (fire the engine while not burning up plugs), and life expectancy one-sided minimum. There is probably a dwell spec, a max time probably for rpm requirements and max current draw for wire sizing I'd guess. After that its up the engineers to strike a balance...bonuses are usually tied to profit so low cost is often high on the list of spec you try your best to on....but in my industry (medical) its usually some performance metric that is most important and the max cost "requirement" is more a suggestion or aspirational goal because performance sells the product not the price so much but we'll always take production cost reductions as a win.

Anyway, swap out that valve cover and set up the new one for the same coils the other one uses and you'll be good!

....and I may still have a chance of catching up

I think the difference would be that a target dwell is on the spec sheet vs. a NTE dwell...



There literally are no other valve cover options.

Well... there is this extremely rare rear valve cover (I think this is the only one I've ever seen) from a mid-'90's Seville... Otherwise, let's get started milling out a die and melting some magnesium!
Not my project, but someone else on the Fiero Forum.

I can not imagine why there being a target dwell on the the basic coil requirements document...its possible, the replacement coil people probably measure and try to hit it, but on a factory coil that seems like a low priority floater....which is why I keep saying its probably not a great idea to try to mix and match coil types.

The discharge curve would also need a spec to make the coils interchangeable....even with matching or close enough dwells the discharge profiles could be quite different.




No way to cut/weld to make one fit the other bank? Or new covers of some kind over both so they look like a set and hide the coils maybe? I don't know why, but I always think anything on the top of the engine deserves a little attention to detail....you made some beautiful fittings and clutch parts no one will ever see, i think you sure give the visible parts the same love......but my engine doesn't run after 14 years so