Digital/electronic N75 adapter

[lemoncurd]

Was just curious if there would be a market or interest for a electronic N75 adapter/translator/converter

The N75 valve is pretty simple from a electronics perspective, just a energized 12v coil which gets pulled to ground by a wire from the ECU.
It is pulled in accordance with a sine wave, though this wont matter much as in the digital adapter we can do whatever we want with whatever information. So this can change

I have some experience in designing embedded electronics aswell as coding them.

My idea is to have a small embedded device plug into the N75 valve connector, then connect to a digital VNT actuator seen on other vehicles aswell as the digital sensor connector which would normally plug into the vacuum actuator. The electronic actuator will be controlled by this embedded device through the ECU's N75 commands. In theory and done correctly this would allow for a plug and play swap from a vacuum actuator to a digital one. You could then do other fun stuff like add trim values to the digital actuator, add canbus so we can loop in vehicle parameters like speed / EGT / boost / etc.

Perhaps there is a way to simply add an electronic actuator without all this custom nonsense, i am unsure.

 

[dieseldonato]

Since I've started tuning my alh, I've wondered why they didn't use an electronic vgt actuator. The vacuum has such a lag in response imo. Besides that it had no clue as to vane position. Just seemed stupid since electronic vgt were available at the time those cars came out. Would be interesting to see what you could come up with, but I don't have the time or resources to start another experiment. I wish you the best of luck!

 

[TDIMeister]

YES!!!!1!!one!

Somebody PLEASE do a direct PWM turbo controller already!!!

With VK turbo swaps becoming more-and-more common, I cringe at being forced to remove the electric actuator and replace it with a vacuum can actuator to get the turbo to work with these engines. The signal from the ECU to the N75 is already PWM. The VK actuator is already PWM. How ridiculously...

forums.tdiclub.com

 

[lemoncurd]

reviewing a video in that thread, it looks like you can just fit a electronic mercedes actuator to the ECU and update the calibration settings in the ECU tune. says the VW electronic one is CAN?
hmm. using a stm32 chip would let us understand and graph the n75 pwm command from the ECU. then that could simply be translated to a new PWM signal for a PWM based electronic actuator, or into a canbus signal for a can based actuator

interesting.

i have a spare EDC17CP14 arriving soon, perhaps i can rope this project into my learning about diesel tuning!

 

[lemoncurd]

anyone have info on the CAN message used for the electronic actuator?
i have access to some vw CANbus datasheets..... been very helpful for my self driving stuff. if someone has a can ID i can look it up on the powertrain canbus

 

[BustedBolts]

I've done dozens of Hella actuators on edc15 and edc16 ecus. If you use the correct part number actuator it's a breeze, just add one wire and it's set, no need for an in-between interface, ecu software needs properly modified also.

 

[lemoncurd]

ah ok, nothing beats a simple solution. plus that solution is one which would continue to work even if i stopped making such an interface

the added 1 wire is for ground right? the N75 gets 12v, and PWM, so you'd just need ground on the electronic actuator for it to work.

then you account for the hardware change in software right?

 

[KERMA]

EDC15v in a tdi uses an analog output signal. I don't think there's any way to configure a digital output or canbus output. Though It's possible to use direct control on a servo actuator. EDC16 can also use analog PWM servo control.
EDC16 and newer (edit: software settings) are fairly straightforward to configure for digital or can-bus turbo actuator output. (edit: but physical configuration may be incompatible) There may be different pins on the ecu connector though. And depends whether H-bridge or PWM amp chips operate the turbo controller (CJ230 or TLE7209 etc)

 

[BustedBolts]

ah ok, nothing beats a simple solution. plus that solution is one which would continue to work even if i stopped making such an interface

the added 1 wire is for ground right? the N75 gets 12v, and PWM, so you'd just need ground on the electronic actuator for it to work.

then you account for the hardware change in software right?

Correct, sometimes the output frequency needs changed, also the output can be inverted if need be depending on how the actuator is mounted, and the n75 open circuit test needs adjusted for the lighter amperage of the actuator compared to the solenoid. Then mix/max positions, pid's and some other stuff related to turbo position needs adjusted. The vacuum control stuff is set to "overshoot" for a split second to deal with the mechanical lag of the system, with electric actuator that stuff needs to be set less sensitive because of how fast it reacts.

 

[lemoncurd]

ok, that sounds entirely doable in the calibration settings of the actuator, and in the PID controls scheme.
i'll keep this in mind while tinkering with my spare ECU. i might need to pickup an electronic actuator to play with lol. this paired with my spare cluster, canbusgateway, ABS, and steeringwheel basically means i have an entire mk6 golf on a bench LOL

 

[lemoncurd]

this project works kinda well with my other selfdriving project. the group i am involved with recently released their new canbus device, the "Ocelot Pro" which has canbus and a TON of IO for a STM32 exposed. i have already written somewhat sophisticated software for their ocelot, and built a shield for it for some other VW goodness. specifically on the fly bitflipping of a canbus signal, and an artificial ACC message to satisfy ECU and ABS until OpenPilot can send it's own radar commands to control gas and brake.

here is a link to the ocelot pro, and a couple photos of the shield i built for it.

Ocelot Pro Devkit - Retropilot Store

Universal CAN gateway and interceptor designed to make retrofitting of existing vehicle components like the iBooster or Corolla EPS easier. It is also firmware-compatible with Comma.ai Panda, allowing it to be used with tools like Cabana for CAN data visualization/analysis. It has 3x CAN buses...

shop.retropilot.org

i think i could pretty easily build another shield which would do PWM in sense, then PWM out. aswell as power regulation/control of the electronic actuator. the ocelot pro already has a built in 12v out which can be used to toggle a bigger mosfet to feed whatever we want. plus this has canbus, which would let us use a CAN based actuator or a PWM based one

the code i wrote for this special self driving related module:

https://raw.githubusercontent.com/actuallylemoncurd/panda/cc3e079a6cb6e3584142e6caa7bf26f360bd7665/board/ocelot_j533/main.c

as you can see, the firmware for such a module is pretty simplistic. i imagine the firmware for such a device to do what we want with an actuator would be very simple

 

[bn_]

EDC15 drives N75 via PWM. See "Funktionsbeschreibung" as reference.

To use an Hella actuator with it you need to limit the signal to 5 to 95% duty (actuator goes to fully open when out of boundaries), inverse it (to get the same behavior as the oeiginal vacuum actuator, but the hella actuator could alread be inversed by its firmware) and maybe change the PWM freq to whatever the actuator needs (~144 or ~300Hz iirc). EDC15 is fully capable of doing this "out of the box", you just need to find the right switches...

If you got this far, then you can also cut apart the old N75 (or the EGR valve) to use its connector for building a adapter cable. And as posted before, you need to run a extra ground wire to the actuator.

Here is an example of a GTD1752VRK converted to an PWM actuator, which works flawlessly with an ALH:

GTD1752VRK with PWM actuator

youtube.com

For more info on the actuator you can check this repo: https://github.com/djwlindenaar/Hella_Turbo_Controller