View Full Version : wasted spark vs. sequential ignition systems

01-04-2018, 07:55 AM

Can someone refer to some scientific research or, at least, some dyno measurements, that shows if there´s engine efficiency variation between wasted spark and sequential ignition systems? I´m focusing specifically in results related to these two firing configurations, supposing the same other parameters (ignition discharge energy, output voltage, spark plug electrodes gap, compression ratio, A/F ratio and so on).

01-07-2018, 05:58 AM
The only thing I have seen that makes sequential ignition is being able to cut cylinders individually. Power wise there is no real power advantage. bUT ideally if you loose a coil in say a cop system you read misfire(knowing firing order) swap coil to different cylinder(and in my diag experience swap affected plug to another cyl ) this allows you to "follow" a dead coil or plug to different cylinder.
Now a cute senario, had guy who was told to use dielectric grease in plug boots, was told it was vaseline LOOKING stuff that came with boots kits.
He starts having misfires. move coils, no miss, drive get warm, misfires.
Dummy used actual vaseline on boots and it has NO dielectric properties. So after swapping all 8 plugs and coils around for few weeks he had to bu new boots and plugs as all the plugs had arc over burns down sides.
I have been working on way to use northstar dual crank sensor/cam sensor setup with DIS(then module sends respective ignition/cam sequence signals to computer.
POwer wisw it makes little difference in the scheme of things but as in LSx it packages better, Ford Mod motors dont have bundle of snakes all over.
Oh and DIS helps a bit in emissions. So much many COP systems are passively firingd]g at a lower dwell in lower rpm range companion cop cylinders to help keep converters lit off. Found that the other day in diagnosing a COP system. Though computer was bad. turns out irs emissions tuning.
Packaging wise COPS work better. DIS need less computer outputs.
COP ignition calls for MORE wiring but also in specific systems allow the ecm to kill ignition to a missing cylinder in conjunction with killing injector. THUS making it a dead hole but not allowing the affected cylinder to either pump raw fuel into exhaust or run it down into crankcase and also washing down cylinder.
Had a guy bring in older Crown Vic and it had dead cylinder. Injectors was shorted open and washed down cylinder, diluted oil and trashed bearings and cylinder.
SO he goes and buys newer one with COPS, but bad engine. so we rebuilt that engine, had to dry sleeve that cylinder. So down road new car developed misfire out of town he drove it on home and when I diagnosed it as a dead injector he was worried about new short block (during rebuild we swapped on 4 valve Cobra Heads!). BUT I showed him how it killed injector and cylinder on newer car.

NOW I guess wiring up my engine to run sequential COP ignition might be easier but I was hoping at onetime to build DIS ignition kits for people to eliminate distributors(my plan as I am planning to run /dis on my 283 with LT1 fuel injection intake I was given for free).
Delteq (sp) was selling a DIS conversion for old optispark equipped LT1 engines with failed caaps and such.
DYNO wise little to no difference power wise. Certainly no advantage to swapping from stock ignition unless parts are considerably more money, like certain european supercars with $1000 COPs.
Guy in Oregon , I think, had hd 3d printer figured out how to meld some computer diagrams of connectors and built adapters to swap in specific LSx COPs and a bracket to mount. Italian engineers used $1000(aftermarket cost ,dealers got near $2000) for those garbage coils. LSx coils held up better, can be had at any corner parts store at worst in couple days. Fella I knew found adapters, 3d printed on varying colors with resistor built in and coils in box for like $700-$800 with mounting bracket. As he was looking at $3000 plus shipping plus wait time. They redynoed car and it made better power and actually passed Cali emissions first time!

01-07-2018, 06:06 AM
Oh yeah and all the parameters you asked about change with different coils. A COP fires one direction on plug from center to ground. In DIS one cylinder fires center electrode to ground the paired cylinder fires from ground to center electrode. Dwell times are longer on COP as it has bit more time to saturate but this difference is moot as the internal resistance can be adjusted to allow faster saturation ( we are talking microseconds at high rpm) but the difference with quality ignition parts are negligible. Also chain store coils tend to be spotty in quality if you race a lot. For DD they work fine.
Push a LSx to 8000 RPM and local duralast coil may not keep up with AC Delco/Delphi replacement.
Nissan is so picky about COPS I have yet to find aftermarket COPS to run and not set codes in early 2000 Nissan v6 engines. They keep setting coil codes as computer monitors them somehow.

01-07-2018, 06:24 AM
Lee Abel/MonzaRacer,

Thanks a lot for long time you´ve spent writing a so comprehensive post.
Several of what you mentioned is true, but I´m focusing on engine efficiency, strictly.

There are some specific scenarios that require or strongly recommend sequential ignition approach, but I won´t mention them here, since I am focusing on some hypothetical engine efficiency difference related to wasted spark and sequential ignition usage. If someone is interested on such scenarios, feel free to ask me.

As we all know, car makers apply effort to save production cost, even on high end cars. So, they won´t let cost raise regarding ignition subsystem for nothing, and sequential ignition system is more expensive then wasted spark one. Again, if someone is interested to know why, I can explain. Thus, I suppose that, except for those specific scenarios I mentioned above, makers will always opt for wasted spark configuration IF NO BENEFIT exist with sequential ignition approach.

Regarding turning distributor-equipped engines to DIS, there´s a company that have been producing several devices to do this since 2007, among several other ignition devices, that may remap ignition, deliver multiple sparks, provider higher voltage output etc: Motor Spice( http://www.motorspice.com.br)

I look forward and I will appreciate comments.

F-Body International
01-08-2018, 05:22 PM
Wasted spark fires on the exhaust and compression stroke. The additional spark on exhaust exit does give a slight extra burn to the exhaust gas for more friendly emissions.

Wasted spark is cheaper as it only requires the crank sensor for timing. A cam and crank sensor is needed for sequential ignition/fuel injection.

01-08-2018, 10:11 PM
Hi, F-Body International.

The aspects you mentioned were already known, besides other ones that makes wasted spark configuration cheaper than sequential one.

The focus of this thread is on engine efficiency, specific power (HP/liter), torque, power, fuel consumption difference between wasted spark approach and sequential one, being kept all other engine parameters (ignition discharge energy, output voltage, spark plug electrodes gap, compression ratio, A/F ratio and so on).

Anyway, thanks for your reply! :)

01-01-2021, 05:19 AM
Again, DIS only makes things simpler. COP sequential coils only added benefit is allowing for closer control of individual cylinder timing and ign event control.

01-01-2021, 01:23 PM
The OP hasn't been here in almost 3 years.