Ignition systems seem to be one of the most upgraded and least understood things on any vehicle. haha

The advantage of upgrading is NOT specific to forced induction applications. The biggest reason is so you can increase your plug gap for a more efficient ignition/burn of the air-fuel mixture.

I run a Jacobs ICM (on everything I own), a Jacobs Ultra Coil (square bodied style), duraspark replacement distributor with an MSD Cap-a-dapt large cap, quality 8mm wires (will be upgraded later but not required) and copper core plugs.

My plugs are currently gapped at 0.090" and I have tested gaps up to 0.115" but even though it runs great at that large of a gap the edges of the electrode wear off of the plug too fast for my liking being a Daily Driver. When I have the extra funds to run Iridium plugs I will run at maximum gap for my Ignition System and engine parameters.

In short, bigger gaps give faster engine response, shorter rev times, more power, better fuel mileage and cleaner emissions.

 

No, but not many people are trying to run lean burn or ultra-high EGR mixtures in these things, so forced induction is the most likely scenario where the mixture becomes difficult for a stock system to ignite.

A more energetic spark will help with early flame kernel formation; in situations where that's a limiting factor, it makes a difference. Provided a flame kernel is formed that reaches sufficient size not to quench, there's really not much effect on flame propagation rates after that. Differences in early flame kernel formation can largely be adjusted for by spark timing, provided ignition is possible at those conditions.

For naturally-aspirated, near-stoichiometric combustion, it's really not all that difficult to get good ignition. The resistivity of air (and of the fuel/air mixture) increases with pressure, so very high load operation can be a difficult situation; this can come into play even for naturally-aspirated engines at high-speed/high-load operation (e.g., WOT at 7000 rpm), but doesn't really enter the picture with the low-rpm operation that is more typical in trucks. Flame kernel quenching also becomes a problem for dilute mixtures, as does a low flame propagation rate, so a larger flame kernel is required to overcome this effect and achieve ignition in those situations.

But for a basically stock engine in a truck, neither of these scenarios is particularly relevant, and the Duraspark system is designed to work pretty well in the operating map that would be encountered for typical usage of these trucks. Upgraded systems don't hurt anything ... they just don't offer a huge benefit on otherwise-stock engines and are more an enabler of other upgrades.
Earlier combustion phasing does have many of those effects - but you could get many of the same effects by advancing your spark timing a bit at some conditions, and without reducing your spark plug life.

 

Timing and gapping do share similar properties/benifits but timing alone can't do what building an ignition system can.

For instance, the way my system is set up a Duraspark module can't handle the parameters and won't run the engine and an MSD 6AL can barely handle it and it runs like crap no matter where the timing is set.

An ignition is by all means a SYSTEM and must be treated as such.

I got a larher increase in MPG going from a Duraspark system comprised of all new parts to the full Jacobs setup I run now than I did swapping from a C6 to a ZF5.

A factory system in good condition/tune will do the job just fine but it leaves way too much on the table concerning performance, mileage and engine operating characteristics for myself to ever leave it in place and not upgrade.

 

I think my coil was original, but the Duraspark module was replaced about 4 years ago from a parts store. Maybe the coil was the difference, but the MSD resulted in a much smoother idle, allowed me to advance the timing a bit more, and lean the mixture further (my typical cruise is an AFR of ~17:1). I attribute some of this to the multi-spark nature of the MSD.

 

Oh, it would definitely allow you to lean the mixture further. That's exactly what you'd want to do it for. It just wouldn't do a whole lot for you at stoich, if you had it tuned to factory spec.

 

To clarify: I'm not saying it will do *nothing* - a higher-energy spark will create a larger initial flame kernel, which makes a big difference if you're running lean (due to the larger flame kernel) or if you're running with a lot of boost (so the spark can even happen), etc., because it can push it over the edge to where the flame kernel propagates rather than being quenched.


It's in other situations when you're running at a condition where the flame would propagate well even with the stock system that I don't think it's worth it: in that case, all it does is effectively advance your timing a tad, since you don't have to wait for the flame kernel to grow from the size it would start at with the stock system to the size it would be at with the more powerful system. In these conditions, it's not really buying you anything you couldn't get for free.


My point is that the bulk of the operation that most people will encounter on an unmodified engine will fall into the latter category, and thus the benefit gained from spending a bunch of money on these upgrades without doing anything else is pretty small. Now if you're doing something like NMFirst and wanting to run lean, that's an entirely different story (and a worthwhile endeavor, IMO - most of my research at work is focused on extending the dilute limit, and improved ignition systems are very impactful there!).

 

You just performed the classic "Magazine Test." That is where a magazine takes a vehicle with old, worn-out stock parts (38 year old ignition coil and an INFERIOR cheap Chinese knock-off ignition module) and replaces them with the latest, brand-new aftermarket parts (MSD ignition) and uses before/after tests to "prove" the aftermarket stuff is superior to the stock parts. But was it? Or was it just new?

For the record, I am running a MOTORCRAFT (no aftermarket Chinese garbage!) Duraspark ignition with a re-calibrated advance curve in the distributor. My timing is set to 14 BTDC and my spark plugs are gapped to 0.050. My idle is smooth as silk at only 500 RPM and this truck actually starts up faster than any fuel-injected vehicle I have ever owned.

 

I usually end up with GM modules on Duraspark vehicles simply because I can get them anywhere.

I haven't had any luck with parts store Duraspark, and around me, these trucks have been melted into toasters

 

The Duraspark system is really a better design; it just suffers from poor quality aftermarket replacement ignition modules. With an actual Motorcraft module, they're reliable as all get out.

 

I agree wholeheartedly, but I can walk into any yard and walk out with a 4 pin HEI module lol. It's really the only reason for me.

 

Fair enough.