bigBADbenny wrote:So I guess I’d have to ask a tune pro:
Kimmo’s LV has stock rpm ranges in the fine learning table.
But it has a pw tmic, 50/50 bov and three port...
Fuel learning ranges C & D were less than 5% eg outside the comfort zone but with no significant boost leaks...
Would the car “have” to have been tuned to run the three port at all?
IMO 2 port (Subaru Bleed off method with restrictor pill) switching to 3 port boost control (Mac valve) definitely requires a retune.
Differences:2 port method/implementation:
- 2 Port BCS Setup
- 2 port BCS.JPG (96.41 KiB) Viewed 7323 times
3 port implementation:
- 3 Port BCS
- 3 port BCS.JPG (40.49 KiB) Viewed 7323 times
3 port essentially effects a couple of main area's:
1) Turbo Spool Up - Without adjusting the WG duty tables there is a potential to overshoot the target boost and as such pop the head gasket's with too much cylinder pressure.
2) Target boost stability - i.e. once spool up to target boost occurs the 3 port allows for greater control of boost up to redline, without adjusting and tuning for the 3 port all sorts of surging and spiking can occur.
Target boost is a PID controlled feedback loop all of this needs to be adjusted within the tune to ensure that the turbo is being controlled safely.
AFR learning values will show minimal adjustments after the 3 port has been fitted without a tune because the target boost level has not been raised therefore the OL fueling table will be relatively close. Generally when switching to a 3 port the main reason is to have better control of the wastegate to then increase peak boost level's. Stock wastegate spring is 9psi in a Gen4 Lib so we can increase to roughly 17psi while keeping decent control over the turbo with only having changed to a 3 port BCS method.
I mentioned to Kimmo at the health check day that its worth logging target boost in I / S / S# as this will be a better indication as to whether or not the car is tuned, if it's tuned it will most likely be targeting higher boost than the stock level of 14.5psi in S#.
Happy Logging