Hi from Colorado! BMW e30 with VGT Turbo, custom VGT controller + more

Been a member for a while, first post. My long-term project car, a 1987 BMW 325 (same as 325e), has gone through several iterations in the 13+ years of ownership. Started as a basket-case turbo project someone started and abandoned, required basically re-doing everything to get it up and running with the eta bottom end and 325i head ("budget stroker" in the e30 world, basically a 2.7L version of the 325i with lower compression ratio). Had an oiling issue early on, fixed it but the damage had been done. I ran the engine until it finally spun a bearing after a few years, eventually rebuilt it with a bigger cam (280/280), then sourced a VGT turbo (Holset HE351VE, electronic VGT actuator controlled via CAN). Car has always run a Megasquirt 2.

After many years, I built a manifold to get the giant turbo to fit, and over several iterations of code and electronics, got the VGT running pretty well! I designed a controller for the VGT, based on a Teensy 4.0. Latest iteration has a custom circuit board with Teensy 4.0, VR signal conditioner (turbo shaft speed), CAN transceiver, thermocouple amplifier (EGT), 3-axis accelerometer, and 14 MOSFET circuits for low-side switching. Over CAN, the controller communicates to the MS2 (both sending and receiving data), sends VGT commands to the turbo and reads data from it. It also feeds a touchscreen display for gauges and real-time VGT calibration changes.

I've got it set up with several analog sensor inputs (EGT, EMAP, wastegate dome pressure, fuel pressure, and oil pressure) and several output functions (fuel rate signal to the stock dashboard real-time fuel economy gauge, dual-solenoid wastegate dome pressure control, and control of the VGT actuator power relay). VGT control algorithm uses boost target (as generated by MS2 target table and received from MS2 over CAN) to control both wastegate and VGT actuator. Fairly complex algorithm based on mapping the VGT response to somewhat ride the surge and choke limits of the turbo.

There's not much info on VGT here on the forums and it seems to all be focused on diesel applications, but I'm pretty happy with the results I'm getting and hoping for some knowledge sharing. For my low compression ratio 2.7L 2-valve engine with 280deg cam, at 6000ft/1800m elevation, with a 60mm turbo, I can build to my full target boost (albeit slowly) at 3000rpm. I've got pretty tall gearing and with 180kPa MAP (~12psi boost at sea level), 2nd gear will quite aggressively spin the tires when the turbo spools (Direzza Star Specs, 2.93 diff gives 74mph at 7000rpm in 2nd gear).

Anyway, HPA was quite helpful in getting the latest iteration of the car up and running and providing inspiration to push my knowledge and skillset - glad to be here!

Welcome! I'm surprised I don't see more people playing with VGT stuff. Well done.

Thanks Mike! I’ll probably post more details on it in the near future, in a dedicated thread.