Sulfur yellow 76: Megasquirted with tbi

[Toehead]

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Uh oh

[MegaDan]

Wonder how C5 would interfuse with Micro-Megasquirt or the like? I believe their trigger wheel is 90 teeth and optical reader.

You would want to call them and ask if it can decode a 90 tooth wheel with no missing "teeth" for reference. There is a cam position "tooth" as well on the C5 wheel. If you can get it to read the crank and cam signals, that would open up sequential fuel injection and coil per plug and ignition control options.

If you can find someone to make you a custom disc for the C5 module to include two missing holes (since it's cam driven) that would give you a missing tooth crank signal. I did something similar with a vehicle that had an optical wheel/sensor setup. One hole cam position and as 12-1 crank signal (24-1-1, 12 and a blank, 12 and blank)
Link: https://www.diyautotune.com/product/54- ... -or-vg30e/

The downside to this is that your crank position will not be 100% accurate thanks to things like belt stretch and torsion every so slightly misaligning while revving up. However, I never had an issue, and if you aren't going to be racing with an engine on the edge of destruction, it's not much of a concern.

[Toehead]

As far as I know, a single missing tooth wheel rotating at cam speed is enough to do sequential.

[MegaDan]

As far as I know, a single missing tooth wheel rotating at cam speed is enough to do sequential.

Sequential injection yes. Both signals are needed if you wanted to run coil per plug ignition and sequential fuel.

[Toehead]

Why? I am curious what an extra signal will give you.

[socrace]

The transformer looks good! What frequency will it use? Will the power supply be able to support 4 ignition channels?
Not sure about the benefits of 2 missing teeth on a cam wheel. Although, the signal from it could appear similar to a crank wheel, if the 2 missing teeth were 180 deg apart.

[MegaDan]

Why? I am curious what an extra signal will give you.

Having both cam and crank signal allows you to utilize sequential fuel injection and coil per plug/coil on plug instead of a wasted spark system. That's what it gives you. Necessary? no. That's what it's for though. If the ECU used has the ignition outputs and the coils have built in igniters (like an LS1 coil) then you have no need for a separate ignition control, and the ECU can direct fire the coils. It's how I ran on my last megasquirt 3 with MS3X setup.

Not sure about the benefits of 2 missing teeth on a cam wheel. Although, the signal from it could appear similar to a crank wheel, if the 2 missing teeth were 180 deg apart.

The two missing teeth on the cam wheel when trying to simulate a crank trigger wheel signal. Cam spins half the speed of the crank, needs twice as many teeth/holes for crank position.

[Toehead]

Dan,

Sorry, I should have been more specific. I'm curious as to why you need to simulate a crank signal to run coil on cap ignition and sequential injection? A single missing tooth wheel at cam speed should allow you to run without a crank signal. I am pretty sure that I read that on the MSextra manual, and it makes sense to me.

Edit:

about 3/4 of the way down: http://www.msextra.com/doc/general/sparkout-v30.html

to run sequential COP you MUST have a suitable cam signal:
* Missing tooth wheel at cam speed
* Missing tooth wheel at crank speed + single tooth at cam speed
* Non-missing tooth wheel at crank speed + single tooth at cam speed
* Non-missing tooth wheel at cam speed + single tooth at cam speed
The cam signal could be as simple as a magnet on the timing pulley and a hall sensor in proximity to it.

[MegaDan]

Dan,

Sorry, I should have been more specific. I'm curious as to why you need to simulate a crank signal to run coil on cap ignition and sequential injection? A single missing tooth wheel at cam speed should allow you to run without a cam signal. I am pretty sure that I read that on the MSextra manual, and it makes sense to me.

Edit:

about 3/4 of the way down: http://www.msextra.com/doc/general/sparkout-v30.html

to run sequential COP you MUST have a suitable cam signal:
* Missing tooth wheel at cam speed
* Missing tooth wheel at crank speed + single tooth at cam speed
* Non-missing tooth wheel at crank speed + single tooth at cam speed
* Non-missing tooth wheel at cam speed + single tooth at cam speed
The cam signal could be as simple as a magnet on the timing pulley and a hall sensor in proximity to it.

Ahh, you are right. I was confused by what you meant.

[Toehead]

It's all good!


I've got the high-voltage part of the circuit all set up. It'll run to a shade under 300 volts pretty quickly powered by just a 500 mA 12v AC adapter (seems to charge in about a 1/8 of a second just by ear). When I get a scope with probes that can read voltages that high I will know more. I would expect a more powerful supply would let it charge faster.
I've got 3 100-V zeners on the regulator circuit, so that's the expected voltage.

I'm pretty happy that everything seems to be working. These capacitors make some pretty nice sparks when I discharge them manually

The only casualty is one MOSFET that I cooked with a careless jumper.

Next up: I need to add the trigger circuits onto the SCR and the tach output. After that, it'll be ready to bench trial.

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Here is the driving signal for one of the MOSFETS on the primary side of the transformer.

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[Toehead]

Updates:

I had to ditch the SCRs as they kept latching on me. I replaced them with MOSFETs. I also had to try a few different primary side driver MOSFETS until I got some that seemed to work well with the overall system in the simulation.
I also had to add a small power resistor into the primary side. If there isn't any resistance there, I would sometimes drive the 12V rail too low, and the IC could get "stuck" with one MOSFET randomly powered. That's a quick way to cook components.

All MOSFETS have gate protection diodes, and I put shottkey diodes on the on the trigger inputs to prevent miswiring damage.

I changed from a direct trigger to a transistor-driven trigger to drive the discharge MOSFETS harder to get a better spark. I think I did alright

The circuit charges when the trigger wire is hooked to ground, and fires as soon as that connection is broken. It should be able to run off of both points or an electronic ignition. There are two independent coil channels and triggers.

Here's a link to the video:
https://youtu.be/I0JBG3I2GRQ

Here is the final diagram

CDI Final Design.png

The spark is a lot higher voltage than normal, but also a lot shorter. To take advantage i'll need to run copper plugs and open the gap way up.

If anybody makes this circuit do NOT connect the coils to +12V as it will fry the diodes on the output circuit. One side of the coil should go to ground and the other to the output circuit. It fires with a negative 400 volt pulse to the coil.

[sunnbobb]

wow

[ericheath]

Awesome, I think?? Yeah, it's way past me. Sometime when you're bored sitting out a blizzard, it would be nice to see how much you think your overall conversion costs in materials.

I keep thinking of different carburetion changes which are a black art, but EFI would be nicer. Unfortunately for me the electronics end is and even more black art than emulsion tubes and jets.

[Toehead]

I fixed the video link.

Thanks for the feedback guys! I will try to publish a BOM.. I don't expect it is more than about 20 bucks in components. I've spent a lot more since I bought a lot from the local electronics store to support a local business.

[ericheath]

I was looking for overall EFI conversion, megasquirt