REV2 Board: Boost Control - Pneumatic Wastegate (Mac Solenoid) Support through REV2 Board - bootmod3 CustomROM V2

Overview

To avoid duplication, please see documentation described in the following document Boost Control Updates - EWG (Electronic Wastegate), Boost By Gear, Pressure Limiter Adjustment - bootmod3 CustomROM V2Preview. Everything there applies to tuning a conventional pneumatic style wastegate with a Mac Solenoid as well with additional tables that are used to set up boost control for a Pneumatic Valve such as a Mac Solenoid.

CustomROM V2 logic in the DME controls a Mac Solenoid through the REV2 Board in 2 possible ways:

1. FlexRay message

   1. Sent from DME to REV2 on FlexRay’s static segment.

   2. As opposed to CANBUS which can drop messages due to what is called arbitration, FlexRay’s static segment guarantees delivery within a time constrained window with much higher throughput and additional fault tolerance which is what CustomROM V2 and REV2 utilize.

   3. For reference and comparisons see 3rd party sources quoted in this document: Overview of bootmod3 CustomROM V2 featuring REV2 Board integration using FlexRay™ and DirectPWM | References on Vehicle Communication ProtocolsPreview

2. Direct PWM of the EWG connector pin (provided EWG is not used on the car) which is connected to REV2 through the EWG connector on the REV2 harness, and REV2 being connected to the Mac Solenoid

For output control where DirectPWM is available, such as in this case, we recommend using it instead of FlexRay but choice will depend on tuner preference. Both approaches work exceptionally well.

For details on configuration see this section: Boost Control Updates - EWG (Electronic Wastegate), Boost By Gear, Pressure Limiter Adjustment - bootmod3 CustomROM V2 | OEM EWG or Mac Solenoid control SwitchPreview

In addition, when the OEM Electronic Wastegate (EWG) Controllers/Turbos are removed from the vehicle, tuner should set the Map Configuration setting for EWG Disable to YES. Otherwise the vehicle will be in limp mode due to DME’s expectation that the electronic wastegate controller is there.

Boost Control (Mac Solenoid) Tables including PID Based Control

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Boost control of a Mac Solenoid with CustomROM V2 and REV2 allows for setting up the WGDC (Wastegate/Mac Solenoid duty cycle) using Manifold Boost Target vs Engine RPM tables as shown in the first pic above and its possible to do so across 4 separate map slots switchable using the steering wheel controls, along with a separate table for flex fuel blending.

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In the above pic we’ve set up Map Slot 1 (0% ethanol map for example) to run 0% duty cycle on the mac solenoid. No pulse to the mac solenoid represents the minimum amount of boost the setup can run which is wastegate spring pressure. If you’ve set up your wastegate with a 14psi spring, 0% duty cycle will run around 14psi of boost for this example.

WGDC Flex Fuel table shows a value of 60% duty cycle across which, given the Blend Factor (WGDC) table will be the duty cycle sent to the Mac Solenoid for 100% ethanol, provided that’s how your Blend Factor (WGDC) table is set up.

WGDC Trim By Gear and Engine RPM

When PID control is not set up in the tune, tuner has the ability to apply a fixed WGDC trim to the base MAP Target vs. Engine RPM tables based on Gear vs Engine RPM to correct for any overshoot or undershoot in boost as gear and RPM change and load on the motor changes. One table for each of the 4 map slots is available.

WGDC Trim By Vehicle Speed and Engine RPM

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When PID control is not set up in the tune, tuner has the ability to apply a fixed WGDC trim to the base MAP Target vs. Engine RPM tables based on Vehicle Speed vs Engine RPM to correct for any overshoot or undershoot in boost as vehicle speed and Engine RPM change and load on the motor changes. One table for each of the 4 map slots is available.

hPa (Metric) and PSI (Imperial) units version of WGDC Tables

When editing these tables you’ll notice tables in both hPa and PSI units. DME always works in metric and absolute pressure units. We simply created the PSI version of the tables for convenience. Tuner should use only one set of tables when editing and ignore changes in the other tables with converted units.

Example: If you’re used to working with boost in PSI, stick to editing the tables with PSI units and leave hPa versions of the tables alone. They point to the same address location in the map and editing both is not required or recommended.

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Closed Loop Boost Control of Mac Solenoid

PID Boost control is activated by setting a value of 1 in the PID Boost Control Activation table. It should only be done once the WGDC tables are set up to hit near the desired boost target while slighly undershooting it by a few PSI and allowing the PID to close the loop (pun intended! ).

PID Activation Delay After Gearshift allows for setting a small delay before PID becomes active after a gearshift which can reduce unnecessary PID corrections due to load changes on the motor through gear shifts.

PID Boost Control Activation by Pedal Input (MIN) provides for a way to not have PID control always active and add to Boost Error calculations when the engine is outside of WOT.

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Closed loop boost control enables the tuner to set the WGDC tables with base values that work for their setup and get the actual boost values to be close to target boost. Instead of using the WGDC Trim tables to account for changes in load on the motor and turbo based on gear and vehicle speed, PID based boost control can optimize that in realtime.

PID-based boost control refers to the use of a Proportional-Integral-Derivative (PID) control algorithm to regulate the turbocharger’s boost pressure in an engine. This control method ensures the turbo produces the desired level of boost pressure by continuously adjusting the wastegate or other control mechanisms based on real-time feedback.

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Overview of PID Control in Boost Control

1. Setpoint (Boost Pressure (MAP) Target for PID) :

• This is the target boost pressure (e.g., 30 PSI) that the engine controller or tuner specifies for optimal performance.

2. Measured Value (Boost Pressure (Act)):

• This is the actual boost pressure measured in real-time by a sensor (typically a manifold absolute pressure (MAP) sensor).

3. Error Calculation (P-term, I-term, D-term):

• The controller calculates the difference between the setpoint (desired boost) and the measured value (actual boost).

4. PID Algorithm:

• The PID controller processes this error using three components to determine the appropriate actuator output (e.g., adjusting the wastegate):

• Proportional (P): Responds to the magnitude of the error. Larger errors result in stronger corrections.

• Integral (I): Accumulates past errors to address any consistent offset from the setpoint (removing steady-state error).

• Derivative (D): Predicts future error trends by evaluating the rate of change of the error, helping to prevent overshooting.

The control output is calculated as:

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Where Kp, Ki, and Kd are the tuning constants for proportional, integral, and derivative components, respectively. WGDC is adjusted accordingly in closed loop to modulate pressure in the wastegate actuator and thereby reduce Error and bring Boost Pressure towards Boost Target.

Here are some sample values for PID we’ve used with a 3-port Mac Solenoid:

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Discussion on Boost Pressure and Boost Target

Boost Target on these DMEs in reality is sort of a limiter or a ‘ceiling’ and if actual boost ever reaches the target the DME reacts to it by closing the throttle to manage boost the engine sees (Manifold Boost Pressure). This poses great difficulties in tuning with PID and we’ve come up with our own custom approach to PID Boost control that works really well on these DMEs and minimizes chance of throttle closure while still being able to have an appropriate boost target value.

Boost Pressure (MAP) Target for PID is a custom boost target made for CustomROM V2 that is offset from the Boost Pressure (MAP) Target to address the above issue. The offset is set up in the following table:

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In this case 140 hPa (2psi) is used as the offset. Therefore, for this example, if we’re looking to target 30psi using PID Boost control, we’d set up the tune to target 2psi higher than our desired target of 30, so 32psi. Once this is set up the PID based boost control has slight room for overshoot and management of the actual boost pressure without heavy throttle closure imposed by the DME that happens without this functionality.

As with any automated control system, we added additional safeties.

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Boost Error Setpoint table sets how much overshoot is allowed when PID Boost control is active. Boost Error timer sets up a delay of how long the overshoot is allowed to happen before the AB0101 custom DTC code for Overboost safety is triggered which triggers corresponding functions (FIDs) set up on that code for safety (in the above example 1 is set to cut boost on EWG and WGDC, and cut nitrous). In addition the DME will override the torque to 300Nm and load target limiter to 150 which will instantly impose a heavy throttle closure in the instant the AB0101 code is triggered.

For further discussion on Custom DTC codes, their setup and handling refer to: Integrated Safeties and Custom DTC codes - bootmod3 CustomROM V2Preview

REV2 Board: Wiring Instructions for EBCS Output (Mac Solenoid)

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