Due to a number of discussions on internet forums regarding crank angle signal replication of the XEDE computer, a current model March production XEDE was tested by Dastek on the Falcon BA XR6. The following report details the results.

Report

Older vehicles with inductive sensors used a single signal system. Most modern vehicles have advanced to a double inverted signal. (technically called a differential signal system). The reason for the differential system is that it automatically cancels out electrical noise using special components. Electrical noise is one of the biggest problems in automotive electronics.

A highly advanced oscilloscope was used to monitor the crank angle signal wave form.

The standard crankshaft signals on the Ford are shown above. This clearly demonstrates the double inverted signal, one in green and the inverted in yellow.

The XEDE interceptor computer was installed and the signals again checked. When connected, the XEDE computer did away with the inverted signal and merely connected the inverted signal to ground. Whilst the engine continued to run, the signal system was no longer a differential system - and essentially took a step back in time and technology by returning to the old style system. This means that with the XEDE installed, the engine management system as a whole became highly susceptible to electrical noise.

Contrary to information presented on the internet that shows identical input and output on the XEDE, in practice the input to and the output from the XEDE are nothing like each other.

In fact it looks like the picture above. (Green in this case is the output from the XEDE and the yellow the input to the XEDE). The signals are so different that the voltage scales had to be changed between the signals to even fit them both on the same screen. This picture was taken at 5000 RPM. Careful scrutiny will show that the signals prior to the missing tooth line up with the output and after the missing tooth it doesn’t line up any more. Clearly this will cause ignition timing imbalance between cylinders and timing scatter.

Because of the lack of support for a differential system, the slightest electrical noise causes false teeth and scatter as shown on the picture above. The green is the output and the false tooth can be seen in the area of the missing tooth. Of particular concern is how greatly the output differs from one tooth to the next. The output very clearly scatters when compared to the input. The tooth right after the missing tooth lines up perfectly. The tooth prior to the missing tooth is retarded by about 4 degrees.

When the negative signal was monitored, it again demonstrated that the signals were significantly different.

For the sake of completeness, a Unichip computer was installed on the same Ford vehicle. Again, the signal looked different to that posted on the internet discussion group.

The standard ECU takes the crank angle signal and internally converts it into a digital signal that is of a square wave pattern in nature prior to processing. When the standard ECU sees a square wave pattern, it's internal conversion task becomes much easier and precise.

When the Unichip computer was installed, the output signal shown in yellow was the square wave pattern that the standard ECU uses internally. In fact, the Unichip computer performed much of the digital conversion processing for the standard ECU.

The Unichip sends the digital format, which the original ECU understands.

The most important part is the stability of the signals. The Unichip uses the modern differential inputs. As can be seen above, the Unichip output is uniform to the input. (The position of the output is changed via the maps).

We further invite anyone with an oscilloscope to verify the above statements for themselves.

Conclusion

On the BA Falcon XR6T, the XEDE computer degrades the quality of the crank angle sensor signal presented to the standard ECU. The degradation includes timing scatter, false tooth signals and missing tooth signals. With no support for Ford's differential signal, the entire engine management system became susceptible to problems caused by electrical noise.