?My invention: Best boost/CAN gauge ever on the OEM red LCD display.

pieter3d · 2010-04-15 03:45:15

UPDATE: The GOODbox is now for sale in the group buy thread (https://www.rx8club.com/showthread.php?p=3629344) So while I wait for all my turbo parts to arrive, the one thing that has been bugging me is the fact that I need an AFR and Boost gauge, but there is just no good looking way to mount them. So I decided the best looking solution would be for the gauges to be on the pretty red LCD right above the head unit. Of course when I called mazda & their suppliers, no one would give me the signaling spec for the display, so I had to reverse-engineer it. Using a logic analyzer I figured it all out. Here are some pics of this process: https://i.imgur.com/YBhi8.jpg https://i.imgur.com/hQGSm.jpg Step 2 was to design a circuit board that could fit in a small enclosure. I decided the best place was the ashtray. I figured since the CAN bus isn't too far from there, there is nothing preventing me from querying the car's computer for sensor data as well. Here is the final product, I am calling it the GOODbox (Gauges On the OEM Display): 290170 290171 290172 290173 When on, it overrides the data coming from the head unit and shows you live gauge data. I can even override the fonts and make custom patterns & symbols. There is also a buzzer/beeper to warn about overboost, and while I was at it I added a feature that lets you choose custom startup text instead of the stock "mazda rx-8" It can display 2 different screens, A or B. Each screen can show either 1 or 2 gauges. This way you can quickly switch around up to4 different gauges. It has a menu system that lets you choose gauges, calibrate the boost gauge and edit the custom startup text. Since the display is 12 characters, each gauge gets 6 characters in dual mode. Sometimes that is kind of cramped, but oh well. There is probably some improvements I could make with the formatting of dual gauge mode. The harness just connects to tap splice connectors on the LCD's cable, a 12V power source and the CAN bus which is closest just above the head unit by the Tire Pressure Sensor Module. List of currently supported sensor data: Boost pressure Coolant Temp Air/fuel ratio Intake Air temp Short term fuel trim Long term fuel trim Throttle position Engine load (in %) Speed (mph) Engine RPM I can add anything to this list that the RX8's computer supports, just have to know the right ID. A couple of features I would like to add soon: When I designed the board, I added an additional analog pad that you could solder your own custom sensor to (for example EGT), but I haven't yet added that feature in the firmware. The idea is that you would use the menu to give it a name, and set calibration multiplier, divisor and offset. So displayed value would be data*multiplier/divisor+offset. Check Engine Light code reading & clearing. Here are some videos of it in action: http://www.youtube.com/watch?v=XSPWBuyuuLc http://www.youtube.com/watch?v=NXTIb2aJJqA http://www.youtube.com/watch?v=pA2Pt6ZCJow http://www.youtube.com/watch?v=FfoIZJvrJ6E http://www.youtube.com/watch?v=DICK5M4Ovug The display for the Mazda3 and Mazda6 is the same as the one in the RX8, so there is no reason it wouldn't work for those cars too. The MS3 definitely needs a nice boost gauge like this. Well, what do you think? I am thinking about selling these. I would love to hear some feedback, and refine it a bit more. Soldering on all the small parts is kind of a pain, so I might have to find some kind of manufacturer to assemble the PCB for me.