Hi all !
Little update on my build.
I recently decided to go Turbo instead of Supercharger, and bought a IS20 turbo from a Golf 7 GTI. It has electronic waste-gate (ETB style) and electronic bypass (solenoid).
I'm also running the car using Hellen72 (Rev. C) PnP board.
I decided to use the OEM "boost sensor" located in the engine bay and which is used on stock cars for EGR system. It's a 1 bar (approx) absolute pressure sensor and is thus suited for running speed-density on a naturally aspirated car. File used for calibration is available as attachment to this post.
I had to modify the H72 board and my harness slightly to make it fully functional.
First i cut the 4T wire on the OEM ECU plug and routed it to a 12V source (in my case CAM sensor supply), so that ECU gets a reading of battery voltage, even when alternator isn't running. H72 rev D should not need this mod because Vbatt sensing will be taken from 4AF ECU supply.
After that car was running ok-ish but tachometer and alternator charge control weren't working properly, as you can see in following video :
https://youtu.be/gXZ1wQmEwUI
Then I had to remove the 12V PROT circuit protection by removing Q313 transistor, R313 resistor and D304 diode, circled in red in the following image :
![117037781-db773900-acd4-11eb-9e23-73f0ad681494.png](./download/file.php?id=7565)
- 117037781-db773900-acd4-11eb-9e23-73f0ad681494.png (535.83 KiB) Viewed 13289 times
This mod made alternator and tacho working again, allowing me to drive the car to work to make some logs and assess how it was running.
https://youtu.be/Gs9rVYSrhH8
I felt the car less powerful in mid range, and had issues with it struggling to maintain idle when cold. Turned out VVT and IAC weren't properly working. This was due to the absence of fly back diodes on VVT and IAC. After bodging something i'm not too ashamed of (see following picture), I can now report the car as 100% functional. Pulls great, runs fine and is definitely daily driveable.
I had to add two 1N4007 diodes, between 2P and 2Q for IAC (stripe facing 2P), and between 4D and 4R (stripe facing 4D) for VVT.
![117421190-99d9ce80-af1e-11eb-9716-d07e980c73a6.jpg](./download/file.php?id=7567)
- 117421190-99d9ce80-af1e-11eb-9716-d07e980c73a6.jpg (4.43 MiB) Viewed 13289 times
![117421169-95151a80-af1e-11eb-893a-d9ea0109c26f.jpg](./download/file.php?id=7566)
- 117421169-95151a80-af1e-11eb-893a-d9ea0109c26f.jpg (4.2 MiB) Viewed 13289 times
Overall I can say H72 is a very potent board for miata NB2, allowing a fast and easy install. The minor issues should be corrected in future version.
You can see tunes and logs of the car running H72 here:
https://rusefi.com/online/index.php?vehicleName=H72_CS_NB2&user_id=853&sorts[uploadedMsq]=-1&sorts[uploadedLog]=-1