(Old post copied over from the old forum)
You all may remember last year I converted my cobra from carbureted to fuel injection with the help of Brian (luce). Well, not being able to leave well enough alone, I decided to take it one step further and remove the distributor completely, in favor of a 4 coil wasted spark ignition system. The coils are now controlled directly by the megasquirt system. Now that it's all working, I thought I do a little show and tell in case anyone else wants to take the plunge.
Here's the engine as it was with fuel injection:
The wasted spark system uses 4 coils which are fired using 4 coil drivers added to the megasquirt controller.
Coil drivers in the megasquirt controller:
I added a separate connector here for higher current capacity to the coils as well as an extra relay powering the coil +12. This prevents the coils from passing current and heating up if the MS controller is not running.
In order to operate the coils with the correct timing, the MS controller needs to know where the engine is during rotation. A timing wheel has to be added for this. The wheel I used is a 36-1, which is 36 teeth with 1 missing. The missing tooth is an index which the controller uses to indicate tooth 1. I could not find an appropriate timing wheel for the ford small block, so I drew one up in CAD and made it on the CNC plasma table. Turned out pretty nice.
Since the timing of the wheel is critical with respect to TDC of cylinder 1, I made the wheel with 12 mounting holes. Only 4 of these are used, but it allows the wheel to be positioned at 30 degree intervals by selecting the right holes. The wheel could also be mounted to the rear of the balancer, but it was a lot easier to mount it at the front.
Since the alternator pulley also mounts here, the pulley had to be milled down the thickness of the timing wheel, which is 1/8". Here's the pulley being machined.
Once I could test fit these parts, I had to make a mount for the hall effect sensor. The sensor is magnetic, and senses the gear teeth as the wheel rotates. These sensors though have to remain within about 0.02 inches from the wheel teeth, so the sensor mount needs to be pretty rigid. I made it out of 1/4" 6062 aluminum. The sensor mount replaces the original timing tab so made new tab mounted to the same plate at the top of the balancer.
Test fitting the timing wheel
When it's all set up, tooth 1 of the wheel needs to be exactly 40 degrees in advance of cylinder 1 TDC. Having 30 degree adjustment on the wheel itself and another 30 degrees of slotted adjustment on the sensor mount gives me enough to place the sensor right on the money while holding it the right distance from the wheel.
Wheel, sensor, mount, and pulley all installed
Before buttoning everything up, I disabled the fuel pumps and cranked the car while double checking the timing with a light. Also checked all of the sensor signals with an oscilloscope to make sure there will be no noise issues. Everything checked out good. Tunerstudio is also very helpful here as you can watch all the gauges to make sure you've got all the signals you expect. That's the megasquirt controller on the floorboard.
Now that all of the senor inputs are tested and ready for the controller, I just needed to find a spot to mount the coil packs. I mounted the coil packs near the original distributor location so I didn't have to make custom length plug wires. I also used coil packs with the standard wire connector for the same reason.
Since the distributor was being removed, I used a cam sensor from a ford 5l explorer to turn the oil pump. All I really needed here was the mechanical shaft, the actual cam sensor is not being used. I did change the gear to a steel one to match the camshaft. Very important...
I used some plastic to rough out a mounting plate for the coil packs. Once I had the basic shape and mounting spot with the plastic, I drew it up in cad and cut one out of aluminum. Used the aluminum mig on the welds.
Drilled and tapped the coil mounting holes for #10 screws. The whole bracket mounts to the topmost unused bosses on the water pump. Here it is mounted on the engine.
Tidied up the wiring, mounted the coils, and trimmed the plug wires a bit, and voila, the finished product:
Now I can simply connect to the megasquirt controller with a laptop, and change any factor of the fuel injection or ignition with the push of a button. The tunerstudio software lets me set up a spark map, which controls the spark advance at all rpm ranges and MAP values. You can dial in as much or as little advance at any point to maximize your power and throttle response. I love it...
Oct 02, 2017#2
Update:
With the original trigger wheel, I was having missed triggers when the RPM was above 5000 rpm or so. I decided to remake the wheel with more metal for the sensor to sense. I redrew the wheel with longer fingers, then bent each finger over at the same point with pliers. I chucked it up in the lathe and used the tool holder to set the outside diameter of each tooth the same. Spun it on the lathe and used a grinding wheel to round off all the teeth at the outside.
The new wheel seems to have fixed the problem. Runs up to 6500rpm now without a hitch...
Rick (Cobrapilot)
You all may remember last year I converted my cobra from carbureted to fuel injection with the help of Brian (luce). Well, not being able to leave well enough alone, I decided to take it one step further and remove the distributor completely, in favor of a 4 coil wasted spark ignition system. The coils are now controlled directly by the megasquirt system. Now that it's all working, I thought I do a little show and tell in case anyone else wants to take the plunge.
Here's the engine as it was with fuel injection:
The wasted spark system uses 4 coils which are fired using 4 coil drivers added to the megasquirt controller.
Coil drivers in the megasquirt controller:
I added a separate connector here for higher current capacity to the coils as well as an extra relay powering the coil +12. This prevents the coils from passing current and heating up if the MS controller is not running.
In order to operate the coils with the correct timing, the MS controller needs to know where the engine is during rotation. A timing wheel has to be added for this. The wheel I used is a 36-1, which is 36 teeth with 1 missing. The missing tooth is an index which the controller uses to indicate tooth 1. I could not find an appropriate timing wheel for the ford small block, so I drew one up in CAD and made it on the CNC plasma table. Turned out pretty nice.
Since the timing of the wheel is critical with respect to TDC of cylinder 1, I made the wheel with 12 mounting holes. Only 4 of these are used, but it allows the wheel to be positioned at 30 degree intervals by selecting the right holes. The wheel could also be mounted to the rear of the balancer, but it was a lot easier to mount it at the front.
Since the alternator pulley also mounts here, the pulley had to be milled down the thickness of the timing wheel, which is 1/8". Here's the pulley being machined.
Once I could test fit these parts, I had to make a mount for the hall effect sensor. The sensor is magnetic, and senses the gear teeth as the wheel rotates. These sensors though have to remain within about 0.02 inches from the wheel teeth, so the sensor mount needs to be pretty rigid. I made it out of 1/4" 6062 aluminum. The sensor mount replaces the original timing tab so made new tab mounted to the same plate at the top of the balancer.
Test fitting the timing wheel
When it's all set up, tooth 1 of the wheel needs to be exactly 40 degrees in advance of cylinder 1 TDC. Having 30 degree adjustment on the wheel itself and another 30 degrees of slotted adjustment on the sensor mount gives me enough to place the sensor right on the money while holding it the right distance from the wheel.
Wheel, sensor, mount, and pulley all installed
Before buttoning everything up, I disabled the fuel pumps and cranked the car while double checking the timing with a light. Also checked all of the sensor signals with an oscilloscope to make sure there will be no noise issues. Everything checked out good. Tunerstudio is also very helpful here as you can watch all the gauges to make sure you've got all the signals you expect. That's the megasquirt controller on the floorboard.
Now that all of the senor inputs are tested and ready for the controller, I just needed to find a spot to mount the coil packs. I mounted the coil packs near the original distributor location so I didn't have to make custom length plug wires. I also used coil packs with the standard wire connector for the same reason.
Since the distributor was being removed, I used a cam sensor from a ford 5l explorer to turn the oil pump. All I really needed here was the mechanical shaft, the actual cam sensor is not being used. I did change the gear to a steel one to match the camshaft. Very important...
I used some plastic to rough out a mounting plate for the coil packs. Once I had the basic shape and mounting spot with the plastic, I drew it up in cad and cut one out of aluminum. Used the aluminum mig on the welds.
Drilled and tapped the coil mounting holes for #10 screws. The whole bracket mounts to the topmost unused bosses on the water pump. Here it is mounted on the engine.
Tidied up the wiring, mounted the coils, and trimmed the plug wires a bit, and voila, the finished product:
Now I can simply connect to the megasquirt controller with a laptop, and change any factor of the fuel injection or ignition with the push of a button. The tunerstudio software lets me set up a spark map, which controls the spark advance at all rpm ranges and MAP values. You can dial in as much or as little advance at any point to maximize your power and throttle response. I love it...
Oct 02, 2017#2
Update:
With the original trigger wheel, I was having missed triggers when the RPM was above 5000 rpm or so. I decided to remake the wheel with more metal for the sensor to sense. I redrew the wheel with longer fingers, then bent each finger over at the same point with pliers. I chucked it up in the lathe and used the tool holder to set the outside diameter of each tooth the same. Spun it on the lathe and used a grinding wheel to round off all the teeth at the outside.
The new wheel seems to have fixed the problem. Runs up to 6500rpm now without a hitch...
Rick (Cobrapilot)