2X044

If we can get the PCM to respond quickly enough, it would be reasonably straight forward to compare the fuel pressure to the boost pressure (available on CAN) and create a simple calculation to determine if the fuel pressure is low.

This is the approach that I tested, unfortuneately the logged temperature took 5+ seconds to reach its new level, so even with an instantaneous change in resistance, it doesn't look like we will have a timely response. Kirby was going to check if there is a way to hasten the system. I will check if the PCM responds rapidly even if the log shows it changes slow, but I don't like my chances. I found that the PCM ignores a resistance that is too low (~below 100 Ohms), it also seems to ignore very high resistance. Everything in between seems to be accepted, when translated to the calculated "coolant temp" that value tops out at 122 deg C regardless of how high the CHT goes.

Thanks Kirby. Thankfully I have not had the occassion where I have lost fuel or oil pressure but I would think that a system would need to react in less than a second to reduce/eliminate damage. Speaking to racers, it seems the most effective way of getting the drivers attention is an annoying buzzer which is also an option. While I used the word damping, on further reflection a more accurate term would be low pass filtered, increasing the frequency of the filter cut-off will reduce the time to change but may cause noise issues. If hardware level filtering is being used (capacitor/resistor) there will be no way to practically change it. There are other ways to shut down an engine that I can think of, such as interrupting the CAS, though this has EMI/RFI noise management implications. The crudest may be to just cut the ignition/coil power using a solid state relay.

Got some testing done today and might have hit a snag. I can mimic any temperature I like for the CHT. A picture I never want to see for real. However there is monstrous amount of damping in the PCM responding to changes. Maybe 5s for it to go from 23 to 189 degrees where the change of input occurred instantaneously. Is the damping an editable field?

Thanks Bill, it's like you've been watching me. My car was originally HAANFHZ and HAANFG4 was one of the codes I tried as it was very close to the original without knowing if it was a T56 or T5 tune, I now have the HAAT3VC in the car and it appears to be pulling the pin low as it should. Although I have the "Professional" license for PCMtec, I have never seen the "Workshop/Professional Development Parameters". Might be "Workshop (not) Professional". Is this correct?

I've spent a ridiculous amount of time in trying to find the exact parts required to make a system plug and play and am now waiting on a slow UPS boat... Meanwhile I had the thought that the strategy that I used to convert my car to a t56 from btr may have been a t5 strategy so tried a couple of other strategies. It turns out that my hunch was correct and with the ba f6 strategy the pcm pulls the pin low and the original motivation for this thread was a mistake. No regrets I've learned heaps and have some spare parts for other things. Hopefully I'll have first testing of the cht spoofing done in a couple of weeks. Still need to fix my boost issue and now have a rattle that I've concluded is the flywheel coming loose... No rest for me.

I'm sure this would be possible, but not on my BA as BA's don't have a rear O2 sensor. Anyone want to set up a "go fund me" page to buy me a BF/FG xr6t?

Thanks for the input Kirby. I agree the feather is not the best choice but was a really easy choice to get started with. I've just got the first PCBs made that still use the feather but a chip shortage issue and a slight miss on geometry got through the design. This was still just a prototype but starting to put a few more parts in place, such as reverse polarity protection and diodes on digital channels. I've started working through a redesign using the ESP32 S3 and a CAN bus transceiver but I likely won't pull the trigger on this until I can get closer to the goal using the feather. Regarding CHT, I was planning to be lazier than your logic description, I was planning to leave the CHT attached to the PCM to read normally unless a "fault" state is detected, at this time, I would pull the output of the CHT down either directly to ground (and therefore straight to full scale (255 degrees?)) or to ground through a resistor (to some value lower than full scale). After reading through the details of the CHT sensor, I wasn't confident I could emulate it accurately enough. Progress is slow and my xr6t is having boost control issues presently (mechanical, not electrical) that will need to be solved before I can do any testing.

Doing skids in gravel car parks takes me back to my youth... Finally got the progressive shift light working though not installed properly, I've halved the rpm that the lights are coming on so I don't have to rev the berries out of the car for the demo. First light will come on at 3000rpm and they all go red at 6000. Interesting to see how much lag is in the tacho. https://vimeo.com/757148325

I've been doing some reading and making sure the next PCB can support this requirement. I found this information regarding the EOT sensor: Unless we can change the behaviour of the PCM on receiving an "out of range" or "abnormal" reading, the EOT will be ignored and the desired outcome of protecting the engine will not be achieved. Am I reading this correctly?

Better than my bodge splitter.

Yes please, I'll PM you. I can think of two (maybe three) ways of doing this, not sure which would be best but all would be "invasive" to the wiring of the car and not a 20 min job. The challenge is that with the ABS controller connected it will be publishing the wheel speed data on the CAN bus. You either need to trick it to broadcast the "normal" info or disconnect it and then pretend to be it (with potential for all sorts of issues). I've ordered one of these from Aliexpress... Way too big for a final system but should be good for a plug and play prototype while leaving an OBD2 port available for ForScan/PCMtec.

That design looks good, I think I'm independently keeping several Aliexpress stores afloat and have a number of "automotive" enclosures and connectors. I bought the enclosure that I'm using from Altronics as I wanted to be able to see the LEDs inside. How do you cut the holes in the sliding lid?

@hjtrboI am using KiCAD for the pcb design. Thanks for the tips regarding connectors. The proto boards are using phoenix contact screw connectors which are still available on digikey (for now).

You've got my mind churning now! Some interesting "wishes" there. I'd been thinking about how to trip "limp home" mode through spoofing a sensor but hadn't thought of the oil temp. I'd been thinking about intercepting throttle position signals but if the PCM will respond to a change in the oil temp that would no doubt be easier. If anyone has a surplus oil temp sensor (BA if there are differences) kicking around send it my way and I'll work out how to intercept and mimic it. I suspect either the analog voltage outputs or the variable resistor that I've included on the PCB will do the trick I just need to work out ranges, slopes and offsets. The closed loop boost control is an interesting challenge, including making it fail to safe should anything happen to the micro-controller. I'll probably need to talk to you about how it is implemented by the factory PCM to try to match it and make sure I have all the inputs needed. Other sensors should be straight forward, again ranges, slopes and offsets will be needed to ensure the PCB is designed correctly as the micro-controller analog inputs are natively only 3.3V tolerant. I've got a SAAS oil pressure sensor and an autometer fuel pressure sensor kicking around so can start with them. By far the hardest part will be the packaging, QC, etc. to make it a commercial offering. I'm sure there will be some special "gotcha's" in the implementation, but that is half the fun. I'd given a little thought to how configuration could be made easy but hadn't got to simple dials. Depending on what is possible with the Tactrix, my first thought was that the configuration could be sent over the CAN bus via unused identifiers (extended?). It may even be possible to make it seamless for PCMtec users. This is only a hobby for me, I'll keep you informed of progress but it may be slow. My turbocharger is fubar at the moment so that will need my immediate attention.

Sharing this semi-complete project now that it is up and running. Before getting into it, I owe thanks to @Lukeyson and @jakka351, they don't know me but I relied heavily on the information they shared and to the team at ForScan it would have been a lot harder/impossible without there work! Beers are on me. I completed a manual conversion on my BA Mk2 XR6T, for some reason, the PCM would not ground the reverse lockout wire. I understand that the PCM is supposed to ground the pin when the car is travelling less than 7km/h and the clutch is depressed. I read that most people use the brake light circuit to ground the wire but I didn't like this idea. The data I required is available via the CAN bus so I bought a micro-controller with a native CAN bus interface and put together a prototype board that does the following: Listens on the CAN bus for the vehicle speed. When the vehicle speed is below 5km/h, once per second, sends a query to the PCM asking the status of the clutch pedal. When the vehicle speed and clutch status are correct, pulls the reverse lockout wire to ground using a MOSFET (and turn on an LED to show me it's working). Here is the proto-board: Here it is hidden in the console with all the wires coming in the back: Now that it is all working, my mind is running on all the possibilities having a programmable micro-controller hooked into the cars CAN-bus with a bunch of analog and digital ins/outs so I am currently designing a PCB that breaks out a lot more of the micro-controllers pins. My design brings out the following: 3x digital outputs via MOSFETs that will ground up to 2A each 1x 0-12V analog output (op-amp) 1x 0-10k variable resistance (to ground) 5x analog inputs (with voltage dividers so that it is 12V tolerant). More inputs/outputs are possible in the future but I would change to surface-mount components. My ideas on things that I can do with it are: Progressive shift-light using a string of 8xWS2812 LEDs Slow down the fuel-pump via PWM and a solid state relay when off-boost Spoof the F6 oil pressure sensor signal to the PCM (don't think this one is needed with PCMtec) Factor style PID boost control (for the NA + T crowd) Yaw control using the input from an IMU (needs a lot more thought and big cajones while tuning) I'll post up code and designs on github shortly and update this with a link then. I hope this inspires someone, I will try to answer any questions however this isn't a beginners project.