stiff wastegates, predator, and PCM boost
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 calculated Mass Air Flow. It varies boost to match a preset Mass Air flow in order 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 waste gate solenoid then it “Should” deliver X amount of manifold pressure. These tables are made for their respective wg (Stock, S2, S3) There’s two key points here pertaining to swapping wastegate 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.
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.
Mph under ~30mph limits Boos - aka infamous “boost by gear”
Cooler ACT lowers Boost - so if its cooler outside than the day before your boost will be lower.
Knock, High CAT temps, high Engine temps, rev past limiter, etc. 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?
DON’T make HASTY JUDGEMENTS. After a new wg install or rod adjustment, reset the battery to clear the old Wg Adaptives, then drive it at temp for a while!
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
When you increase the boost in the Predator, you're only upping the Desired Torque and not overwriting any of the WG dc table.
All the above will only apply: if the WG DC learning is activated. Since the Learning is turned off in the 93tune, if the WG performs erratically or otherwise "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.