Stiff Wastsgates, Preadator, and PCM Boost

[duster360]

There a lot of guys fiddling with different waste gates trying to get one or another to run like they want it to on PCM boost. I put together a short list of do's and don'ts and a short intro.

PCM Boost control what is it?

Think of it more as Torque control. The PCM is programmed to deliver a certain amount of Torque at specific times. The PCM measure TIP pressure and compares it to the MAP pressure, and uses the difference to calulated Mass Air Flow. It varies boost to match a preset Mass Air flow in able to reach this preset Torque value. The mechanics of moving boost, is that the PCM has a big table stating that if it applies X duty cycle to the wg solenoid then it “Should” deliver X manifold pressure. These tables are made for thier respective wg(Stock, S2, S3) There’s two key points here pertaining to swapping WG around.


1) The preset Torque goes up and down from its base value(aka Desired Torque, yes you can log this) Don't expect it to be the SAME EVERY TIME
-a. Engine temps under 176F REDUCES Boost. If you hop in the car and mash the gas, your boost will be lower than if you waited till the engine warms up. If you’re running a 160 stat your sol.
-b. Mph under ~30mph limits Boost—aka infamous “boost by gear”
-c. Cooler ACT lowers Boost—so if its cooler outside than the day before your boost will be lower.
-d. Knock, High CAT temps, high Engine temps, rev past limiter,,ect lowers boosts but not very often.


2) When you swap in a different WG, the WG duty cycle vs Torque tables don’t match up anymore. So the PCM gets a bit befuddled. BUT there’s a sneaky deal provided to the PCM.- Waste gate Adaptives. The PCM will “adjust” the WG duty cycles to get the manifold pressure it wants., but they have limits. If the PCM hits the Adaptive limits before it reaches the proper manifold pressure then you’re stuck. This is where MINDMELT has come in and “manually” adjusted the WG tables make up the gap. What does this all mean to the average guy

-a) DON’T make HASTY JUDGEMENTS. After a new wga install or rod adjustment, reset the battery to clear the old Wg Adaptives, then Drive it a while(at temp)!
-b) Let the PCM do its business to clean up the Wg DC table THEN decide if a change is needed. You might find that the PCM changed things for the better!


After discusions with Ds, I'm pretty sure, when you increase the boost in the Predator you're only upping the Desired Torque and not overwriting any of the WG dc table.

EDIT: DS has confirmed that the Wg DC table IS LOCKED w/ the 93tune. All the above will only apply if the WG DC learning is activated. SInce the Learnig is turned off in the 93tune, if the WG performs eracitally or overwise "poorly", the PCM CAN NOT adjust it. It will require a CMR tune to manually adjust the WG DC Table to better match the WGA being used.

Here's what the WG DC table looks like:




As you can see the table arranges the DC by RPM and by Mass Air FLow. Problems occur when the PCM tries to reach a certain Airflow at the proper RPM but the specified DC its forced to use doesn't get it there. This leads in inconsitant and erractic boost control. WG learning allows the PCM to "modify" the WG DC up or down so that the it can reach the proper Airlfow at the proper RPM.

What Mindmelt and other CMR tuners do is simply rewrite the DC values so that a stiffer sprung WG will deliver the AirFlow and the RPM the PCM is expecting.

[letxen3]

nice write up i thought i could add this here its from the dealers service manual on “operation” of the prowertrain control module.

Quote:

POWERTRAIN CONTROL MODULE
The PCM receives input signals from various switches and sensors that are referred to as PCM Inputs. Based on these inputs, the PCM adjusts various engine, transmission, and vehicle operations through devices that are referred to as PCM Outputs (PCM).

NOTE: PCM Inputs:

• Air Conditioning Controls
• Ambient Air temperature Sensor
• ASD Sense
• Baro/Tip (Turbo)
• Battery Voltage
• Battery Temperature Sensor
• Brake Switch
• Camshaft Position Sensor
• Clutch Upstop Switch
• Clutch Interlock
• Crankshaft Position Sensor
• Engine Coolant Temperature Sensor
• Fuel Level Sensor (Bus message)
• Ignition Switch
• Intake Air Temperature Sensor
• J1850
• Knock Sensor (2.0, 2.4L)
• Natural Vacuum Leak Detection (NVLD)
• Manifold Absolute Pressure (MAP) Sensor
• Oil Pressure Switch
• Oxygen Sensors
• Power Steering Pressure Switch
• SCI Receive
• Speed Control Switches
• Throttle Position Sensor
• Transmission Control Relay (Switched B+)
• Transmission Input Shaft Speed Sensor
• Transmission Output Shaft Speed Sensor
• Transmission Pressure Switches (L/R, 2/4, OD)
• Transmission Range Sensor (TRS)
• Transmission Oil Temperature Sensor (Integral to TRS)
• Vehicle Speed Sensor (MTX-equipped models)

NOTE: PCM Outputs:

• Air Conditioning Clutch Relay
• Auto Shutdown (ASD) Relay
• Charging Indicator Lamp (Bus Message)
• SCI Transmit
• Proportional Purge Solenoid
• EGR Solenoid
• Fuel Injectors
• Fuel Pump Relay
• Generator Field
• Idle Air Control Motor (2.0/2.4L)
• Ignition Coils
• J1850
• Malfunction Indicator (Check Engine) Lamp (Bus Message)
• Oxygen Sensors Heater Controls
• Radiator Fan Relays
• Speed Control Solenoids (2.0/2.4L)
• Transmission Control Relay
• Transmission Solenoids (LR/CC, 2/4, OD, and UD)
• Transmission PRNDL Position (to Cluster)
• Transmission Torque Reduction Request (Internal to PCM)
• Transmission Temperature (Internal to PCM and a Bus Message)
• Vehicle Speed (Manual Transmission)

Based on inputs it receives, the PCM adjusts fuel injector pulse width, idle speed, ignition spark advance, ignition coil dwell and EVAP canister purge operation. The PCM also determines the appropriate transmission shift schedule and shift points, depending on the present operating conditions and driver demand. The PCM regulates the cooling fan, air conditioning and speed control systems. The PCM changes generator charge rate by adjusting the generator field. The PCM also performs diagnostics.

The PCM adjusts injector pulse width (air-fuel ratio) based on the following inputs.

• Battery voltage
• Coolant temperature
• Exhaust gas content (oxygen sensor)
• Engine speed (crankshaft position sensor)
• Intake air temperature
• Manifold absolute pressure
• Throttle position

The PCM adjusts ignition timing based on the following inputs.

• Coolant temperature
• Engine speed (crankshaft position sensor)
• Knock sensor
• Manifold absolute pressure
• Throttle position
• Transmission gear selection (park/neutral switch)
• Intake air temperature

The PCM also adjusts engine idle speed through the idle air control motor based on the following inputs.

• Air conditioning sense
• Battery voltage
• Battery temperature
• Brake switch
• Coolant temperature
• Engine speed (crankshaft position sensor)
• Engine run time
• Manifold absolute pressure
• Power steering pressure switch
• Throttle position
• Transmission gear selection (park/neutral switch)
• Vehicle distance (speed)

The Auto Shutdown (ASD) and fuel pump relays are located in the Power Distribution Center (PDC).

The camshaft position sensor and crankshaft position sensor signals are sent to the PCM. If the PCM does not receive the signal within approximately 1 second of engine cranking, it deactivates the ASD relay and fuel pump relay. When these relays are deactivated, power is shut off from the fuel injectors, ignition coils, oxygen sensor heating elements and fuel pump.

The PCM contains a voltage converter that changes battery voltage to a regulated 5 volts direct current to power the camshaft position sensor, crankshaft position sensor, manifold absolute pressure sensor, throttle position sensor, A/C pressure switch, A/C pressure transducer, and vehicle speed sensor.

Powertrain Control Module Connectors

The PCM is an engine and transmission controller module all in one, if the vehicle is equipped with an automatic transmission. The PCM uses four wiring harness connectors to receive and send engine and transmission data. To ease assembly, the mating wiring harness connector is color-coded. Each module connector cavity has its own unique color identification stripe located on the outside of each connector cavity.

The PCM module utilizes four wiring harness connectors as described:

• Connector Cavity A is for Power & Ground (Black)
• Connector Cavity B is for Engine Side (Orange)
• Connector Cavity C is for Headlamp & Dash (White)
• Connector Cavity D is for Transmission (Green) If equipped

NOTE: Connector Cavities A, B, C, And D must be connected prior to battery connection and ignition key on to avoid setting erroneous controller fault codes. It is also recommended that cavity A connector is made prior to any other connectors.

[KBizzle]

i am going to sticky this guys, and then close it, if anyone needs to add to it just shoot me a pm!

[duster360]

edit^^