lookforjoe
True Classic
Aftermarket ECU question, for use with a turbo install.
Recently it seems there are several new options on the market for programmable ECU's. And they seem to be offering a lot more features for a lot less money than ever before. One thing I've been wondering has to do with the sensors most of these ECU's utilize. In addition to a crank position sensor for timing (fuel and spark), they also prefer a cam position sensor. The cam sensor is merely to tell the ECU which cycle the crank is on (as I understand). So it needs a signal every four rotations (hence the use of the cam) and is not as critical as the crank sensor as far as absolute accuracy (again, as I understand). I guess one question might be if all of this "as I understand" info is correct?
But my primary question has to do with utilizing such a ECU (requiring a cam sensor) on the X's SOHC. As far as I know there isn't a cam sensor for the SOHC that can easily be added. I did learn about one used on the Fiat Punto(???) that is essentially a replacement for the distributor. It is basically the lower half of a standard distributor with a wheel and sensor for the top half, no cap and high-tension wires, etc. By giving one signal per distributor rotation it is the input for the stock ECU on that engine. For use on the X's engine, replacing the distributor is not an issue as the aftermarket programmable ECU now controls all ignition functions with external coils. So this would work, unfortunately they are very difficult to get (in good working order) and very expensive if found.
But it has given me an idea. As an alternative could the standard X distributor be used as a cam position sensor by removing three of the four posts on the reluctor wheel? The distributor would now give one signal every four crank rotations (one distributor rotation), as needed. At least some (if not all) of the aftermarket ECU's are compatible with reluctor signals so I don't think that aspect would be an issue. The standard rotor would be left off and a replacement for the cap fabricated (basically a dust cover).
Any reason why this would not work?
On the Bosch systems I've worked with, the cam sensor is set to TDC on #1 as baseline. Any deviation created serious starting and/or drivability issues, as I discovered (after MUCH headache) when I addded aftermarket cams that had defective end cap slots. I'd get a cup & sensor from an existing (easy to locate) system & adapt them for your setup. Not hard to gut the dist & attach the cup & sensor cap. I'd lean toward modifiying a Cam end cap to house the sensor though, and have the cam drilled & tapped to retain the cup. Less work, IMO.