Engine Diagnostics
Discussion
You dont need to read the serial output from the ECU to get the sensor data, as a simple data logger can do it on the ECU input. Far as I can see the only extra useful data you cant get this way is the amount of long term and short term fuel trim the ECU is applying to keep the mixture correct. This would be very useful to establish a a particular map was suited to your engine. Other wise you have these inputs to the ECU:
Lambda 0 -1.2 volts x 2
AFM 0-5 volts
TP- 0-5 volts
Temp sensors x2 (these are supplied with 5 volts, so will be in the same range)
Speed sensor 12 volt square wave.
Engine RPM, approx 12 volts switched from the coil primary with about 200 volt spikes.
Velleman do a nice little 4 channel data logger that I think would do the job that interfaces to a PC, but the biggest issue would be how to splice it into the ECU loom. By using simple 2 way switches on each input you can grab all the data the ECU works with, or or course you could use two data loggers but that gets messy as you would have to run two sessions data reading app' on the PC at the same time. Like wise you could also use it to measure output voltages like fuel pump supply, and injector pulse widths to try and pin down elusive faults.
http://www.quasarelectronics.com/velleman/pcs10-4-...
Mark Adams did say to me that as the Engine gets near 6000 rpm, the CPU on the 14CUX cant actually send the sensor data out via its serial port, and process the engine data at the same time, its simply overloaded, so you loose the sensor data. There appears to be two 2 sets of data output from the ECU, on is purely for the fault code reader,(pins 30 and 38 and a diagnostic request Pin 31 ) and another a "diagnostic output" (Pin 9) , but unless I can get the format of the data Im flogging a dead horse trying to read it, even if I can work out the signal levels and baud rate.
More generally you can tell a huge amount about the state of the engine from the switching levels and frequencys from the lambda probe outputs, and I have built some simple 5 LED test boxes (plug and play) that are calibrated to show correct lambda switching, and open loop fueling, but due to the fact the probe voltages alter slightly with age they are not quite as acurate as I would have liked for the open loop mixture measurement across all probes (so I probibily wont make any more), but are spot on in closed loop. I have 5 of these units built if anyone is interested at around £50 each.
Mark T.
Lambda 0 -1.2 volts x 2
AFM 0-5 volts
TP- 0-5 volts
Temp sensors x2 (these are supplied with 5 volts, so will be in the same range)
Speed sensor 12 volt square wave.
Engine RPM, approx 12 volts switched from the coil primary with about 200 volt spikes.
Velleman do a nice little 4 channel data logger that I think would do the job that interfaces to a PC, but the biggest issue would be how to splice it into the ECU loom. By using simple 2 way switches on each input you can grab all the data the ECU works with, or or course you could use two data loggers but that gets messy as you would have to run two sessions data reading app' on the PC at the same time. Like wise you could also use it to measure output voltages like fuel pump supply, and injector pulse widths to try and pin down elusive faults.
http://www.quasarelectronics.com/velleman/pcs10-4-...
Mark Adams did say to me that as the Engine gets near 6000 rpm, the CPU on the 14CUX cant actually send the sensor data out via its serial port, and process the engine data at the same time, its simply overloaded, so you loose the sensor data. There appears to be two 2 sets of data output from the ECU, on is purely for the fault code reader,(pins 30 and 38 and a diagnostic request Pin 31 ) and another a "diagnostic output" (Pin 9) , but unless I can get the format of the data Im flogging a dead horse trying to read it, even if I can work out the signal levels and baud rate.
More generally you can tell a huge amount about the state of the engine from the switching levels and frequencys from the lambda probe outputs, and I have built some simple 5 LED test boxes (plug and play) that are calibrated to show correct lambda switching, and open loop fueling, but due to the fact the probe voltages alter slightly with age they are not quite as acurate as I would have liked for the open loop mixture measurement across all probes (so I probibily wont make any more), but are spot on in closed loop. I have 5 of these units built if anyone is interested at around £50 each.
Mark T.
Well here it is, full data logging for the 14CUX made in an old ECU case that sits in series with the stock ECU. This is a one off and took some time to make due due to the large amount of internal wiring, but proves it can be done. This measures 4 inputs simaltaniously, plus has LED displays for left and right injector banks, and fuel pump supply. On the input side it reads both lambda's, throttle pot, afm, primary ignition and road speed sensor. It requires a laptop to record and store data, and it does so as either a captured image of the waveform, or a text file of the voltages versus time at 1 second intervals. I did not think that the primary ignition wave form would be that good, as the logger can only read to 1/100 of a second, but lo and behold, I think I see a misfire on my car due to the extra high irregular primary spikes. I need to look at a stock Range Rover in comparason. Although this is a one off, I could see it being easier to run an 8 core audio cable from the ECU PCB (by soldering onto the back of the pin connections) to carry the signals out with a plug onto the end. You would then plug this into a logger box when needed. The only thing missing at the moment is a direct reading for RPM, but I could add this with a frequency to voltage convertor to give 1 volt per 1000 RPM. Hope these images are of interest all taken at idle (hence no road speed):
Ignition trace:
Throttle pot and AFM:
Both lambda, TP and AFM together:
Ignition trace:
Throttle pot and AFM:
Both lambda, TP and AFM together:
Hi,
can you tell the PW to the injectors or is it just an analogue input logger.
Out of interest is it possible to tell what rpm (at WOT) the AFM hits the 5V limit?
Would be good to know the resolution of the injector control of the Lucas, could have a good guess from the PW.
Also, any idea if the lucas is a 8bit processor?
Phil
can you tell the PW to the injectors or is it just an analogue input logger.
Out of interest is it possible to tell what rpm (at WOT) the AFM hits the 5V limit?
Would be good to know the resolution of the injector control of the Lucas, could have a good guess from the PW.
Also, any idea if the lucas is a 8bit processor?
Phil
I think the processor is a custom designed based around the z80 or like, but I will check this for you. As for the logger, its minimum resolution is 1 second per division, so it would be impossible to take an accurate reading for the PW for the injectors, all you could tell is they are firing. You could use a PC storage scope card, but the cost goes up very considerably over this set up. I will put an RPM display on the next one that I build, as this one was just to see if it works. Then all I need is a 5tr car flat out as I hold onto a laptop for dear life!
I now think a Motorola 8 bit custom chip based around the 6800 cpu, but I can find no info on it at all. As for why bother, something tells me there are more 14CUX's out there needing support than MS system. Having been made redundant from IT a few years back, and finding just how hard it was to get another job at a living wage (too many IT bods out there) this gives me a fairly unique string to my bow, all be it a niche market.
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