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.
Stiff Wastsgates, Preadator, and PCM Boost
Linear Mode
