Megasquirt Ignition

[bobcowan]

My Megasquirt project continues.

After months of work and lots of hair pulling, I finally got the EFI system installed and working. I had a few significant problems; some I created and some were the vendor's. I finally got those worked out and the engine running.

Over the last week or so I worked on the fuel tables and fuel enrichment maps. I haven't got much road time yet - tough to do in the winter.

Since Monday was a holiday(and it snowed) I decided to hook up the ignition portion, and get rid of the distributor.

I'm using an EDIS8 style coil pack in wasted spark mode. The Megasquirt ECU controls the spark directly. That gives me complete control of the spark, including dwell, spark duration, advance, etc. I can even use a secondary spark table for vacuum or low load advance.

I built the wiring into the harness, and installed the harness a month ago. For wiring, it was simply a matter of plugging it in.

I had to build a rack to hold the coils. It went into the same area as the oil:water seperater, so I incorporated that into the bracket. One of my goals is to make this easy to tear down.







I made new cables, using a MSD 8.8mm universal kit. I've been using those for years with good results. I don't like using a ready made set, I like to run them my way.

Then it was time for the moment of truth. Based on past experiences, I was actually kind of dreading this. I figured it would take me at least a week just to get the engine running. I left the distributor in place, and only unplugged it. I even kept the old cables.

I plugged in the lap top, primed the pump, and turned the key. It fired right up! I was shocked; well not really shocked. But certainly surprised. The idle's a smidgen rough, and there's an intermittent miss I need to work on. But it actually runs pretty good. I'm pretty impressed.

I have a bare distributer in the basement. I'm going to cut the top off and put it back in to drive the oil pump.

[bobcowan]

Got some good garage time today, and did some fine tuning. he engine starts, warms up, idles, and revs up just like it's supposed to. It runs smooth, and sounds mean. I can't wait to drive it.

The timing was off by 3*. A simple software setting change fixed that. Now I have complete control of the ignition system. Advance based on rpm, tps, and vacuum are easily adjustable with a few key strokes.

It's a wasted spark set up, with 4 coils feeding 8 cylinders. Each coil will fire two plugs at a time - one plug on the power stroke, and the other on the exhaust stroke. With a distributer and single coil, the coil fires a spark every 90*- 8 times for every full engine cycle of 720*. At full speed we're talking more than 400 times per second.

These coils will fire every 360* - 2 times for every cycle; about 100 times per second. That will allow more dwell time at high rpm's, and provide a much hotter and longer spark without a CDI box.

A side benefit is that the exhaust sounds a little different with a spark being delivered on the exhaust stroke. Not louder, just different. I'll be interested to see what it sounds like at speed.

If the weather clears up, I'll get some road time tomorrow evening. And we're supposed to have good weather on Saturday, too.

[Caprimaniac]

Great work