After months on the bench, the Megasquirt ECU is now officially in use in the car. For ease of access and simplicity, I decided to mount both the computer and the relay board inside the glove compartment. I almost never wear gloves in my car anyway.
The Megasquirt II is capable of handling both fuel and spark. After reading about the Ford EDIS (Electronic Distributorless Ignition System) on the web sites of some BMW 2002 EFI pioneers like Tim Skwiot and on the Megasquirt site, I decided to go for it and ditch the distributor.
Most people seem to do the fuel injection first, then upgrade later to computerized ignition. I decided to do it the other way around, since I wanted to trigger the Megasquirt from a VR or Hall-effect sensor rather than a coil signal, and once I had the trigger wheel installed, it was a simple matter to install the rest of the EDIS. Once I have the EDIS/Megasquirt dialed in, I will move on to the fuel.
EDIS uses a toothed crank pulley trigger wheel and variable reluctor sensor to read engine position, which it passes on to the Megasquirt, where the ignition advance table is stored. The megasquirt then shouts back to the EDIS module how much to advance the spark for a given RPM/load/temperature, and the module fires off the coils accordingly.
I ditched my heavy, cast-iron smog pump crank pulley in favor of the Euro-spec stamped steel, single groove pulley, which I sent off to my old standby 2oo2 machinist Tom Rafalski over at 02Again. Tom machined up a steel shim to adapt the trigger wheel to my pulley. All I had to do was bake the trigger wheel in the oven and slip it onto the pulley. Shrink-to-fit!
Once I had the trigger-equipped crank pulley installed, I set the sensor gap to about .5 mm.
I slapped in the rest of the ignition components (module, coil, and wiring) and gave the old key a turn.
Much to my amazement, the car started right up on the first crank. Look Ma! No distributor! Even without a signal connection to the megasquirt, the EDIS will function in “Limp Home Mode” at a fixed advance of 10 deg. BTDC.
I installed Tim’s configuration file to get me started (my car reads XML, how cool is that?).
Now the tweaking can begin.
Update: No ignition table tweaking needed. Tim’s advance map is fantastic. I had a slight mis-understanding about where to set the baseline timing for “limp home mode”. I essentially had the VR sensor 1 tooth off. To correct this in software, I set the “Trigger Offset” parameter in MegaTune to -10. At some point, I need to physically reposition the VR sensor so that “limp home” will be optimal. Once that confusion was cleared up, I was off to the races.
So how do I like it?
It’s amazing .
I knew that ignition timing was an important variable in engine performance, but I honestly didn’t expect this much improvement. The motor runs so smoothly throughout the RPM range, it just climbs and climbs. I can’t keep my foot out of it. Totally programmable, solid-state ignition with vacuum (MAP sensor) advance works really well.
Distributors are kind of garbage.
I can’t wait to install the fuel injection.