Boost timing compensation

Been tuning my truck since 2016 but have never dipped my toe into the boost timing correction. Never really felt the need to up until recently. I did some mods to my intake side pre-turbo and those mods have resulted in a faster spooling turbo under lighter throttle conditions with higher boost peaks on the typical commute drive. What it has done though is tanked my mpg's. Best resent tank was a 23.4 over ~250 miles in mild weather the week of Thanksgiving. I was shocked it was that high but, it was a steady state drive for most of the trip. Speeds were kept 60~64 & there were not much higher loads on the trip. Now in the middle of winter (typical weather pattern for my area) I'd expect 21~21.5 each tank but am lucky to get 20.5. I suspect the drop is related to the amount of timing correction related to boost, meaning I think there is not enough. I suspect the boost as when I slow the boost response down (undo the mods), mpg's go up.


Looking at the Boost Correction & Multiplier tables, it the correction is set to 0.74* across all engine speeds & fuel rates with a max correction of 1.25 @ 2100 rpms @ ~17 psi of boost. I typically see 12~15 max going up some of the grades to & from work. With timing in the main tables dialed in fairly well and for a cruising boost of 3~4 psi, I am thinking the advance is not enough for the amount of fuel being dumped after ~5-7 psi. The engine has 50 hp injectors so it is dumping more fuel than stock... (stock table config currently).

My thinking is the advance is not enough as boost builds based on the additional fuel from the 50 hp injectors and the LPP is moving towards TDC. I do not have any smoke that I can see unless the BPF is hit, which does not happen often with the current intake configuration.


Any input is appreciated...