by Tinker Engineering
As great as BMW's engines are, one thing that's always bothered me is how little information they give you about the vital statistics. All you get is a generic coolant temp gauge which leaves a lot to be desired. Sure you can add aftermarket 52mm gauges, but they're either an eyesore on top of your dash or completely out of your normal range of vision causing you to take your eyes off the road to glance down. So I decided to come up with something that was very functional, very informative, and last but not least didn't ruin the clean factory look of our cars. This is what I have come up with so far (sorry for the potato phone pic):
Now that I have a prototype working reliably, I wanted to start this thread to gauge interest and get the input of the community as to what features/information/capabilities you would like to see from the unit. I'll break down the basic components that are being used, as well as a few different configurations that I think would make sense to make available for purchase.
First off, the basic design of the unit consists of the Sensors, the Control Board and the Screen.
Sensors - The Sensors are the beginning of the system. Because most of BMW's engines didn't come with any sensors aside from coolant temp, we have to add new ones in order to get the valuable information we want. The setup I'm running right now utilizes a standard Thermistor type sending unit for the Coolant and Oil Temperature readings. For Oil Pressure I have a transducer that receives power from the Control Board and feeds a clean signal back as an input. The AFR is currently handled with an Innovate 02 Sensor/Reader combo, which also gives me a signal to read with the Control Board.
Control Board - The Control Board is the brains of the operations. All of the raw data from the sensors gets sent into the board. After some analog signal processing the data is read by an off the shelf microprocessor. This holds the program, as well as the logic for calculating the different variables depending on settings selected by the user. At the moment I have (3) 2 position switches for user input. This could be expanded if the need arises for more flexibility in the program itself. Once the microprocessor has computed the sensor data into usable information, it translates it into code that is send out to the Screen.
Screen - The Screen displays our helpful engine vitals in an easy to read format right there in the center of your gauge cluster. After some trial and error I was able to find a screen that 'fits' in the stock location for the water temp gauge. As you can see from the crude picture above, I currently have 4 different readouts showing on the screen. The color of the screen is also calibrated to match the stock amber coloring of the other lcd's in the car, as well as the stock gauge cluster backlights.
Important Things to Know:
1) As you might have already guessed, installing this in the gauge cluster does require modification to your stock cluster. I currently took my spare and literally cut off the coolant temperature gauge. This did not affect the operation of any of the other gauges, nor did it mean touching any of the circuit boards. I'll post a picture of what is required. With the stock coolant temp gauge out of the way, I was able to fit the screen in it's place.
2) Again, this was probably obvious, but depending on the level of integration you want with your vehicle you will need to splice into your stock wiring harness. I have a few ideas that would be very slick to integrate, but can't be done without some splicing. I would love to source a male/female connector that could be plugged inline to pull the needed power and signals from the car, but I have not been able to do so yet.
Current Specs
Right now I have (5) readings that can be shown on the display:
-Coolant Temp
-Oil Temp
-Oil Pressure
-Air/Fuel Ratio
-Volts
My initial though is to use one of the 2-position switches on the Control Board case to let the user select between Air/Fuel ratio and Volts. This is because the A/F setup is somewhat pricey to add. This would give you the option of buying the simplified system first while having the ability to add an AFR input down the road.
Another of the 2-position switches will allow the user to change between Imperial Units (degrees F, PSI) to Metric Units (degrees C, BAR). I feel like keeping the system more universal as opposed to Unit specific will make producing them easier, as well as give the end user more options. If you're feeling extra Euro that morning you can flip a switch and read BAR all day. There's no need for different sending units or transducers for the different units, the conversions are all handled within the software.
Future Additions
These are a few of the things that are not currently implemented but that I'm working on or plan to start soon.
- Dimming/Brightness control - Ties into your stock dimmer circuit to match the intensity of the dash lights during night driving.
- Warning LED's/Buzzer - Because the microprocessor is always reading the sensor values, it knows when something is too high or low. I've already tested the code and it work beautifully, I just need to finish installing the actual LED and Buzzer that will activate when a parameter is out of range. One thought is to use the stock Oil pressure light, or just add another one somewhere in the gauge cluster.
- Other vitals to monitor - I would like to add a Boost sensor/display option, though it would be difficult to choose what settings to replace. One thought is to give the screen a cycling display so that it reads certain parameters for a few seconds, then moves to new ones, then back and so forth.
- Headlight On Dummy Buzzer - Maybe it's just me, but I'm super forgetful about leaving my headlight switch in the on position as I get out of the car. I haven't drained the battery yet, but it's probably only a matter of time. I would like to take an input from the light switch that activates the buzzer, as well as prints a readout to the screen politely reminding the driver to the lights off if it detects the switch in the 'ON' position once the ignition is turned off.
- Expanding to Other Platforms - The Screen fits great inside the e28 gauge cluster, and would probably work in most e24's due to the similarity (I haven't been able to test this yet). That being said it would also be possible to mount the Screen inside a small enclosure, which would enable the system to be installed in just about any vehicle you can think of. While it wouldn't be the stealth install we get in the e28, it could still be done very cleanly and discretely. This is probably of less interest to the E28 community, but I thought I would put it out there anyway.
Moving Forward
1) First and foremost, I'd like to hear your thoughts and input. The main goal is to make something that is useful for as many people as possible.
2) Once I get the design a bit more finalized and neat, I would like to make a few units to send out as a beta test. It's one thing to have a unit working great in my car, but I would really like the real world feedback from a few other people. I would put the 'kits' together at a discount, and take requests once I have them ready to go out (no need to PM me about it right now lol). Also, anyone that does the beta tests will get free upgrades as the design progresses, so you wouldn't be stuck with an inferior unit once testing is done.
3) Once the circuitry is finalized and I'm content with the reliability I will get a batch of boards made up for a full public release. As I said before I see at least 2 levels for the system, one with AFR and one without. There may be more options depending on demand and feasibility.
With that I look forward to hearing from you guys.
Thanks!
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