Wasted Spark

[cowlum]

Hi

Thought my pet project may be interesting to some of the people on this forum.

About 3 months ago I started coding a wasted spark ECU mostly to improve my coding skills. I was quite happy with the code so I bought a cheap Bosch imitation coil pack and bench tested. Again I surprised myself when the thing passed all my bench tests. I plugged a really rudimentary development setup into the engine expecting a poor result. Again the thing ran better than I had hoped.

So after some more refining my project now looks like this.

https://youtu.be/STVazpihkaw

The ECU has two cores, one runs the engine ignition, the other runs the wifi and a webpage to provide the data you see on the laptop. Any wifi capable device could display the data as the webpage is hosted in the ECU.

Obviously the wiring is very quickly 'hacked' into place, the coil is held in place with a piece of scrap metal, the crank pickup is mounted using a piece of coat hanger but it gives you an idea of where I'm headed. Ultimately the coil will be mounted behind the head where the original coil is.

My engine was running a distributor with electric ignition which ran very well. The new system runs at least as good using the 'ear' test. The spark is massive, the Atomic is so lowly strung compared to the vw group engines the coil was designed for I can run a huge dwell and the coil(s) never develop any heat. I can also start the engine at only 1 or 2 degress advance so it starts softly. There's also rev limiter.

Thought I'd share. I've been enjoying building this thing.

[Al Schober]

OK, you've got me dazzled. Not sure what I'm seeing but the idea of an RPM limiter sounds great!

[ndutton]

If I'm seeing this right, you're discharging all 4 coil outputs simultaneously yet not getting combustion at the bottom of the intake stroke, correct? Or maybe I'm missing something. Have you taken the system out for a sea trial?

We've talked about a wasted spark system before with the goal of eliminating the distributor but a mechanical advance mechanism on the crankshaft made the exercise more daunting than it seemed to be worth. Our scheme traded the complexity of the distributor for the complexity of the crank mechanism and we were looking at a twin double output coil system (necessitating two crank pickups 180° apart), wasting only the exhaust stroke spark in each cylinder. We limited ourselves by sticking with mechanical designs, the result of old school concerns of electronics in a marine environment over the long term.

Good on you for making a working prototype, I'm impressed.

[edwardc]

I'm guessing you used an ESP32 module for the MCU?

[cowlum]

OK, you've got me dazzled. Not sure what I'm seeing but the idea of an RPM limiter sounds great!

haha, thanks. I dazzled me.

The rev limiter is quite basic at the moment it simply doesn't instruct the coil to fire if the RPM goes over a set RPM. I've chosen 2800 as its higher than the engine could possibly require in my Ericson 27.

When it hits the rev-limiter the carb continues to flow gasoline which gets ignited in the exhaust so amusingly the Atomic pops like a supercar on launch control.

In future I'll retard the timing before it approaches the rev limit and maybe let it fire every second cycle as it gets close to slow the engines climb before it gets there. But low priority at the moment.

[cowlum]

If I'm seeing this right, you're discharging all 4 coil outputs simultaneously yet not getting combustion at the bottom of the intake stroke, correct? Or maybe I'm missing something. Have you taken the system out for a sea trial?

We've talked about a wasted spark system before with the goal of eliminating the distributor but a mechanical advance mechanism on the crankshaft made the exercise more daunting than it seemed to be worth. Our scheme traded the complexity of the distributor for the complexity of the crank mechanism and we were looking at a twin double output coil system (necessitating two crank pickups 180° apart), wasting only the exhaust stroke spark in each cylinder. We limited ourselves by sticking with mechanical designs, the result of old school concerns of electronics in a marine environment over the long term.

Good on you for making a working prototype, I'm impressed.

It basically has two coils. One each for the two banks of cylinders. Banks are one and four, two and three. When a cylinder is on the compression stroke its fired as well as the sister cylinder on the exhaust stroke. Firing on the exhaust stroke is wasted but likely cleans up any unburnt gasoline. I may have the most environmentally freindy Atomic around

I did take it out for a run with my partner and 10 week old baby onboard, so I trust it. I can also run the engine at the dock which I do most of the time Im testing.

The advance is in the code, I have a table that follows the rpm so the computer is advancing the engine as the rpms climb.

If its still without issues at the end of this coming season I'll likely remove the distributor mechanism entirely. As it is now all I need to do to revert to the original setup is move the plug wires back, add power to the indigo electric ignitoin and she's good.

[cowlum]

I'm guessing you used an ESP32 module for the MCU?

Thats exactly right! I've soldered a Wemos D1 Mini ESP32 to a pcb board of my own design. In future I'd like to surface mount just the esp32 to a board of surface mount components but I've little experience with that and will try it out when this one is in place and forgotten.

Originally I was using an ESP8266 but decided I'd like the ignition code to have its own core so the wifi has little chance of adversely effecting the running engine. Its only a few dollars more. Both MCUs have way more grunt that this project needs but horsepower is cheap.

[joe_db]

This is very cool
I have a project that has been on the backburner for a long time to make a dual coil ignition.
I have the combiner that connected two coils one distributor, but still need the 2 ignition systems. I was going to use 2 Indigos with 2 sensors.

[cowlum]

I was starting work on making a the crank pickup more permanent than the "made of things I found in around the house" setup I'm currently using. When taking measurements I noticed that one of the flywheel studs is off center.

I assume this is normal, am I correct?
Anyone know why this is?
Are all the studs exactly evenly spaced except for number 1 in the attached pic?

edit: upon thinking about it I am guessing this makes sure the crank and flywheel are always mated the same way preserving the balance.

[ronstory]

Correct on the alignment , but I don't remember the exact orientation of the of the pattern versus the roll-pin. It could be correct or 180 degs off.

[cowlum]

Mounted the coil pack where I had originally imagined it would go. Leads seem to be the perfect length.
Wiring is still messy.

[cowlum]

Put some time into boxing and wiring the thing more permanently into the engine bay.
I used PCB boards as the covers and crank components because they are cheap, cut my machine and quite tough.

https://www.youtube.com/watch?v=GZBaOKuiqLw

^^ with newer video of the engine running.

[cowlum]

Engine bay as it stands now.

Not entirely satisfied with my wiring efforts but that'll have to do for a while.

.

[cowlum]

I'm proud to say after an entire season including a two week cruise that the system ran without a single glitch. So much so I pretty much forgot about it and moved onto other things.
The only change I'll make is have the device connect to the boats access point and submit RPM nmea messages to the nmea data stream. This will replace the access point / webpage setup.
This is getting a bit off topic for Atomic 4s now but I just wanted to close this thread out.

[joe_db]

This is inspiring me to make my dual-ignition A4.