2014 Chevy Cruze 1.4LT Changing Desired Boost?

[gtnawymrdr]

I am very new to tuning and this 2014 Cruze is my very first turbo car. According to research, these engines can hold 22psi pretty well. Naturally, this is the boost pressure I am looking for. On the VCM scanner, I have it logging Desired Boost, Actual Boost and Boost/Vacuum. The first two are absolute whereas the third seems to be reading in "gauge". After making changes to the torque limits and base DC table, I have been able to get the gauge pressure to read 21.6psi. However, the desired boost sits around 30.3psi, Actual Boost sits at 40.8psi. None of these numbers are matching up. Also, with this increase in boost, the throttle position now caps out around 48%-50% at WOT. My biggest question is, how do I increase my desired absolute pressure to about 37psi (22psig + 14.7psi atm). Also, which one of these numbers do I trust? Can the turbo boost sensor be maxed out at 21.6psi and I need to go off of actual boost reading 40.8psi which indicates I am overboosting to 26.1 psi? I got the tune to work, but I don't just want it to work, I want it to be right. Thank you for your time.

[Flyer]

http://www.sonicownersforum.com/foru...ing-1-4-a.html

Take a look at that. Stew went through a lot of effort to make a good post with a ton of info and pointers.

Without looking at your tune and logs it's hard to say for sure where YOUR problem is. I have a feeling it's in the 'Knock Airmass' table, but I'm not sure. There's a handfull of tables that play a LARGE role in boost control.

[nickalltogether]

I personally use manifold absolute pressure to get my actual boost reading, but I do compare that to desired boost and actual boost. It seems like you have a grasp of the gauge vs absolute difference, so I won't bother explaining that.

I recently had the same issue with throttle body closing. For me the boost was going higher than needed for the desired torque (DC of boost solenoid too high) and as a result the car was closing the throttle to keep the actual torque in line with the desired. So it was boosting 18-20psig with the throttle 50% open...

Definitely read the thread that Flyer posted.

[sprinto7]

I am very new to tuning and this 2014 Cruze is my very first turbo car. According to research, these engines can hold 22psi pretty well. Naturally, this is the boost pressure I am looking for. On the VCM scanner, I have it logging Desired Boost, Actual Boost and Boost/Vacuum. The first two are absolute whereas the third seems to be reading in "gauge". After making changes to the torque limits and base DC table, I have been able to get the gauge pressure to read 21.6psi. However, the desired boost sits around 30.3psi, Actual Boost sits at 40.8psi. None of these numbers are matching up. Also, with this increase in boost, the throttle position now caps out around 48%-50% at WOT. My biggest question is, how do I increase my desired absolute pressure to about 37psi (22psig + 14.7psi atm). Also, which one of these numbers do I trust? Can the turbo boost sensor be maxed out at 21.6psi and I need to go off of actual boost reading 40.8psi which indicates I am overboosting to 26.1 psi? I got the tune to work, but I don't just want it to work, I want it to be right. Thank you for your time.

Very glad to see more 1.4 T people on here. We are running one with a Trifecta tune (4 years now), one with a BNR/Me tune. Both run OK, but I'm sure there is plenlty of room for improvement. I'm starting from scratch on a 2015 Trax engine in standalone mode in a Lotus 7 autocross car..