So, remember my cutout is CO2 powered. I have a MAC valve plumbed in, and that valve is controlled by a single PWM- output from the Holley. If I remember correctly, I have X axis as RPM and Y axis as speed. I don't know if there would be a way to do a PWM- output on an electric stepper motor to get it to open as a function of the TPS and speed, especially because the motor could lag behind throttle input.

 

This is what Chat GPT says:

Yes — but not directly. A typical electric stepper motor cannot be driven straight from a 12 V PWM output on an ECU like the Holley Terminator X. The PWM output on the Holley isn’t a stepper driver; it’s a simple switched 12 V signal (intended for things like fans, relays, or solenoids). A stepper motor needs a proper driver that provides controlled current to its coils in the right sequence.Here’s how you can make it work for your exhaust cutout control:🧱 What You Need1. A Stepper Motor with Enough TorqueChoose a motor that can physically move your exhaust cutout mechanism reliably.2. A Stepper Motor DriverPopular choices include:TB6600DM542A4988 / DRV8825 (for smaller steppers)These drivers take simple step and direction signals and handle all coil sequencing and current control.⚠️ Do not drive the stepper coils directly from the Holley output — there’s no current limiting or sequencing.📊 How It Works ConceptuallyHolley PWM output → controls a voltage-to-frequency converter (or microcontroller)↳ converts PWM into step pulses + direction signalThat step + direction goes into the stepper driverThe driver powers the stepper motorThe motor turns your cutout linkage🔌 Wiring OverviewHere’s a generic wiring flow:Copy code Holley PWM Output (12 V PWM) │ ▼ PWM → Step Converter / Microcontroller (e.g., Arduino, LM2907, or dedicated converter) │ ▼ Step Signal (Pulse) + Direction Signal │ ▼ Stepper Motor Driver ┌─────────────┐ │ Step Pulse │ │ Direction │ │ Ground │ │ (Driver Supply + Motor Power) │ └─────────────┘ │ ▼ Stepper Motor🧠 The Key Parts Explained🟡 1) Holley PWM OutputOutputs switched 12 V PWMYou’ll need this to tell something how fast or how far to move the cutout.You may configure PWM based on RPM and throttle position in Holley.🔵 2) PWM → Step Pulse ConverterThe Holley PWM output by itself doesn’t tell a driver how many steps or in which direction to move.You need to convertWM duty cycle → Step frequencyA threshold or signal → DirectionThis can be done with:Simple control moduleArduino/TeensyDedicated PWM-to-step converterExample logic:0–50% PWM → Close cutout (reverse direction)50% → Neutral (no movement)50–100% PWM → Open cutout (forward direction)Pulse frequency sets how fast it moves🟢 3) Stepper DriverAccepts step & directionProvides current to motor coilsMust match stepper voltage/current ratingsDriver connections:V+ / GND → motor power (12–36 V typical)STEP → pulse from converterDIR → direction signalENABLE → optional (can disable motor)Motor A+/A– B+/B– → to stepper coils🔴 4) Stepper MotorWired to driver coils:A+ → Coil A+A– → Coil A–B+ → Coil B+B– → Coil B–🛠 Example Wiring (Simplified)ComponentPinConnect ToHolley PWM outputPWM outPWM input on converterConverterPulse outputSTEP on driverConverterDirection outputDIR on driverDriverMotor +Stepper motor coilsDriver GND—System groundAlways common-ground the Holley, converter, driver, and motor power supply.⚙️ Configuring BehaviorIn your Holley software:Assign the PWM output to variables like RPM, TPS, Boost, etc.Map PWM duty cycle to desired cutout positionExample mapping:< 1500 RPM → 0% (closed)1500–3000 → 0–50% (opening)3000 → 50–100% (fully open)On the converter:Convert 0–100% PWM into step frequencySelect direction based on above thresholds🧰 AlternativesIf this seems too complex, consider: ✔️ A geared DC motor + H-bridge (simpler open/close control)✔️ An actuator with built-in position control✔️ 12 V linear actuator + limit switchesThese can often be run directly from Holley PWM or a relay output.🧩 Summary✅ You can control a stepper motor with Holley’s 12 V PWM❌ You cannot connect the stepper directly to PWM✔️ You need a step converter + proper stepper driverIf you tell me the stepper motor model and desired cutout travel, I can help size the driver and write a simple converter logic!

 

Ive already listened to chat gpt a few times on this and nothing it told me worked. It actually opens really fast with output on tps. I think I need to install a 6 wire double pole double throw switch. I have a spdt switch but its only 3 wire switch. I have a 6 wire 3 way switch today, if it works ill set the close on pwm- so I can control it not closing instantly. Opening i can keep ground.

 

Yeah, Chat GPT is only good occasionally, lol. That setup may work for you.

 

Im just going to leave it how it is, open & close with switch and open with holley. Chat gpt keeps telling me so many different ways and im tired of changing it with no results. Honestly it should work how I have it, if it opens with the output it should close but it doesn't. The last diagram it gave me is totally different from how I have it and now its telling me add diodes and its not that serious. Its easy to flip the switch and close it. I may try switch from ground to pwm- and see if that makes a difference but I think thats as far as ill take it.
I tried the 6 way double poll switch and it was worse, it didnt open or close with the switch and popped the fuse so i put it back like it was.

 

I think it's because it's a motor. You apply 12V and it opens fully, but cutting the voltage just leaves the motor static ( fully open ). You'd have to reverse the 12V in order to have it shut. I bet there's a way to do it using a relay.

 

that is why i used 2 relays, i was trying to reverse it with them. I have the output opening with boost 2 psi and I added the secondary closed at 1.8 on thag output and then the close output i put at 0 psi. When I go back to my tuners shop to weld the quick release clamps on the intercooler im going to ask him does he know a way to do it. He is pretty sharp.

 

 

thats only showing how to activate it by switch, ive already accomplished that part, its the adding the two holley outputs that ive struggle with, the open holley output works, the close does not. This is what I have,
Relay A
Pin 30 → Black motor wire
Pin 87 → +12v fused
Pin 87a → Ground
Pin 86 → Ignition 12v
Pin 85 → switch up and holley open output
Relay B
Pin 30 → Black/Blue motor wire
Pin 87 → +12v fused
Pin 87a → ground
Pin 86 → Ignition 12v
Pin 85 → switch down and holley close output
And the middle connections on thr 3 way switch is ground.

 

Have you tried to open and close it using the output test in holley?

 

no but I guess i could try that, I was thinking the opening output was maybe staying grounded once activated therefore it wouldn't reverse because if interference thats why i tried the secondary deactivated on the open output thinking as long as i had that higher then the close it should work but of course it didnt.