Get a better experience by installing our free app!
Not now
Install
Get a better experience by installing our web app!
Hide
How to do it?
In Safari, tap on the menu bar. Scroll down the list of options, then tap Add to Home Screen.(If you don’t see Add to Home Screen, you can add it. Scroll down to the bottom of the list, tap Edit Actions, then tap Add to Home Screen.)
Here is a drawing showing how to drive the stock boost gauge with a 0 to 4.9v signal.
boost-gauge-schematic.gif (289.07 KiB) Viewed 970 times
To drive the gauge in the software, this formula is a basic approximation (which can be fine-tuned with a better 'best fit' function to each individual gauge if desired).
Absolute pressure reading on gauge is approximately this: APSI = Vdc*5.42 + 2.575. For example, when you want the gauge to read exactly 1 (i.e., 14.5 psi absolute), set the arduino output to 2.2 volts, since 2.2*5.42 + 2.575 ~ 14.5. With this basic formula, you can also 'remap' the boost gauge however you want. For example, one setting in the SpeedoBooster remaps the gauge to read in boost pressure from 0 to 2 bar of actual boost (or 0 to 20 psi if preferred).
Nice work done today. Was able to get the wiring for the cooling fan controller finished up and the controller unit installed. See below. Knocksense box arrived today so I can assemble the secondary engine control unit now that will house the Arduino, knock sense, CANBUS interface, electronics components with circuits for ICV and Boost gauge control and a 12v-5v step down adaptor. Coming together slowly but surely.
IMG_0632.jpeg (45.69 KiB) Viewed 926 times
Best location I can find. Not a lot of space in here to mount extra stuff!
IMG_0633.jpeg (44.71 KiB) Viewed 926 times
Closer look at location. I did verify that the headlight bucket will clear
IMG_0634.jpeg (52.42 KiB) Viewed 926 times
The new harness from the aux power box to the controller. +12v, PWM control wire, and ground
IMG_0635.jpeg (51.18 KiB) Viewed 926 times
New harness runs along firewall bulkhead from aux power box in front of HVAC blower, then through the firewall near the 14-pin. Harness routes along AC refrigerant lines along fender
IMG_0636.jpeg (42.01 KiB) Viewed 926 times
Completed tie in to Mazda plug
IMG_0637.jpeg (46.86 KiB) Viewed 926 times
Ground wire attaches through harness to bracket attachment for coolant crossover pipe
IMG_0638.jpeg (42.62 KiB) Viewed 926 times
Finished product. Have to run the individual fan motor wires through a new harness once I can set it in for measuring
Drscottsmith wrote: Fri Apr 28, 2023 5:20 am
Nice work done today. Was able to get the wiring for the cooling fan controller finished up and the controller unit installed. See below. Knocksense box arrived today so I can assemble the secondary engine control unit now that will house the Arduino, knock sense, CANBUS interface, electronics components with circuits for ICV and Boost gauge control and a 12v-5v step down adaptor. Coming together slowly but surely.
Tim Current: '26 911 Carrera S - PTS Verde British Racing Green
'24 Cayenne S - Algarve Blue Metallic
'21 718 Cayman GTS - Black
'22 911 Turbo S - Carmine Red
'21 718 Cayman GT4 - White
'11 GMC 1500 Quad Cab 4x4 - Black Musik-Stadt Region
Spent a little time on the car over the weekend - rain Saturday meant some inside work.
IMG_0641.jpeg (53.58 KiB) Viewed 866 times
Initial layout of the new "KLR" module. I have always thought of these cars as having a primary computer (the DME) and a secondary computer (the KLR). This version will also have two unique computers. The main will be the microsquirt, and the secondary is this little contraption.
Moving clockwise from the top right, we have (1) 12v to 5v step down converter; (2)Circuit board with circuit for ICV control using microsquirt; (3) Arduino Uno with input/output shield on top; (4)Knocksense module; and (5)CANBUS Shield for Arduino.
IMG_0648.jpeg (16.27 KiB) Viewed 866 times
All of the harness for the second unit will come out of the front. I will use locking connectors for these. My vision is to mount this unit into an old DME type box with the connectors simply available at the front. This will also allow access to the USB connection on the Arduino for programming. The input from the Knock Sensor on the engine will be direct wired to the module (not going through the multipin connector due to the shield). This will make it a little more tedious to take the module in and out, but hopefully once the car is running that will be minimized!
IMG_0650.jpeg (51.87 KiB) Viewed 866 times
Connectors attached. I will wrap these with cloth tape as I have the other harness legs in front. There is a 15 pin connector (still have three spots left for future expansion needs) for most everything (power and all signal connections) and a separate 4 pin harness for the Serial LCD Screen.
Looking good! Does the MS system not have an idle control valve function? Seems like that would be a must for any stand-alone? I wonder if the actual KLR could be used with the MicroSquirt system to get the benefit of the factory-tuned knock frequency signature? On the other hand, if banging on the engine with a wrench triggers the KLR, then maybe it's not as precise as it could be. Very much looking forward to hearing how this all comes together and works out. Keep the updates coming!
p.s., how confident are you that the motor itself is healthy?
Thanks for the encouragement! The Microsquirt does have an ICV control circuit, but it is only for a two wire ICV. Factory valve on the 944T is a three wire. That little electronic circuit basically pulls the valve closed (the third "wire") when the signal is not coming from the MS box. It is a little confusing but apparently works well.
I am just going to put the resistor~capacitor~resistor assembly for the boost gauge in line with the output from the Arduino in heat shrink (rather than add that to the circuit board as well).
Apparently there are ways to maintain the use of the factory KLR box in tandem with the MS, but both my original DME and KLR tested bad, so that is what started this entire journey. Figured a modern, tunable update, brand new wiring, improved cooling, etc. would be a fair trade off to having to purchase two rebuilt ecu's.
Engine is fresh rebuild. New bottom end and head re-work. I purchased the car with the engine already out from a friend. That is one slightly unnerving issue though - trying to balance a fresh engine startup with a new management system that is likely to have a few bugs to work out. I hope the first time it fires it does not rev to 6500 because something in the programming is amiss and cause a problem!
Drscottsmith wrote: Mon May 01, 2023 11:38 am
Hey Tom -
Thanks for the encouragement! The Microsquirt does have an ICV control circuit, but it is only for a two wire ICV. Factory valve on the 944T is a three wire. That little electronic circuit basically pulls the valve closed (the third "wire") when the signal is not coming from the MS box. It is a little confusing but apparently works well.
I am just going to put the resistor~capacitor~resistor assembly for the boost gauge in line with the output from the Arduino in heat shrink (rather than add that to the circuit board as well).
Apparently there are ways to maintain the use of the factory KLR box in tandem with the MS, but both my original DME and KLR tested bad, so that is what started this entire journey. Figured a modern, tunable update, brand new wiring, improved cooling, etc. would be a fair trade off to having to purchase two rebuilt ecu's.
Engine is fresh rebuild. New bottom end and head re-work. I purchased the car with the engine already out from a friend. That is one slightly unnerving issue though - trying to balance a fresh engine startup with a new management system that is likely to have a few bugs to work out. I hope the first time it fires it does not rev to 6500 because something in the programming is amiss and cause a problem!
Gotcha on the ISV. If others have done that with success, no reason to reinvent the wheel. I've done a tiny amount of work on the ISV in the past, so if you need to get creative I'm happy to help.
Heat shrink should be fine for the resistors and capacitors, just remember the cap needs to be grounded on one end, so you'll have one wire going into the heat shrink and two coming out.
Yeah, that's why I asked about the motor. There's enough moving pieces just trying to get a stand-alone working, then add to that potential motor issues to work out, the need for break in, etc. Would be nice if you could dial the engine management in on another motor, but that's probably not realistic...
Got some great work accomplished this weekend. Some pics below but also did some other work:
IMG_0681.jpeg (56.96 KiB) Viewed 792 times
Incoming wiring harness from engine cleaned up and sorted. Plan is to mount the MS box and the secondary computer box to the back of the factory panel as original. I believe there is enough space back there for the plug. Have to put the multiline connector on the batch of wires that feed into the secondary box (that is most of the bundle headed back toward the pass seat area). In the pic left-to-right: gray wires going hard left are extra MS harness wires that are unused. Coming back towards seat by MS plug are connections either inside the cabin or to the secondary computer. Gray and Red wires next are 12V power to interior components and secondary computer (fused and relayed on ignition). Big black coil is from Wideband O2 sensor to gauge. There is also a 12V yellow wire for amp power and a speaker wire that will go back to spare tire well in there somewhere.
IMG_0679.jpeg (55.6 KiB) Viewed 792 times
New AN6 fuel lines built and installed. Extended them so they will route by firewall and not crossover header heat area. Need a firesleeve for these.
IMG_0678.jpeg (49.51 KiB) Viewed 792 times
Vacuum lines run for Wastegate and got that reinstalled. What a pain and I took the exhaust lines off. Hopefully new hardware will make reassembly a bit easier. Clarks mentions studs on one side of the WG for the connecting pipe and bolts on the other. PET shows bolts all around. Mine had a combination of studs and bolts. Need to figure out what is correct. If anyone knows for sure...
IMG_0677.jpeg (48.87 KiB) Viewed 792 times
MAC valve mounted over by cruise module. Out of the way. Little bit far in terms of vacuum, but since both lines are dedicated I believe it will be fine.
IMG_0676.jpeg (41.8 KiB) Viewed 792 times
Rear speakers mounted. Not doing anything extravagant with the audio in the car other than a spare tire subwoofer. Had these JBLs leftover from another project so made a little trim and they fit just fine. Ready for panel reinstallation.
IMG_0675.jpeg (48.58 KiB) Viewed 792 times
IMG_0674.jpeg (23.2 KiB) Viewed 792 times
J-boot repaired. Unfortunately won't be able to replace this - no muffler shop in my area has the right kind of jig to make that tight of a bend in 3" pipe. So - using the factory J-boot but still deleting the AFM and replacing with a piece of straight pipe from airbag to j boot.
IMG_0672.jpeg (22.4 KiB) Viewed 792 times
Wastegate before reinstall - note bolts/studs here. Have to figure out what is actually correct and/or most useable. Open to suggestions!
IMG_0682.jpeg (56 KiB) Viewed 792 times
Blower motor fully reinstalled. As soon as my new ignition switch comes in I will be able to start electrical testing of all of the car's systems. I have no idea what does or does not work at this point, and want to test all of the factory systems as well as the new harness electronics before the dash goes in.
Very much looking forward to hearing how this all comes together and works out. Keep the updates coming!