Not hitting full boost under WOT

[milliardo]

hello! looking to get some clarity on a slightly confusing situation with my car. first off heres the engine details

rb25det s1
oem size upgraded turbo
rb26 itbs
256 poncam
boost target 16psi
3 port controller being controlled closed loop by g4+

 

so today i was street tuning the car under WOT and i noticed in the Log that it only hit the target boost pressure when i floored it in 5th gear at lower speed (9:52 in log). when i accelerated from 2nd up thru 4th at WOT the boost target was not met (12:47 in log). 

 

is this an ecu configuration issue, or a mechanical/engine issue?

Log 2024-05-25 5;02;27 pm WOT TUNE.llg

 

 

edit: it appears i cant upload both the log file and the tune due to size constraints. 🥴 here are some pictures of my CL boost settings. 

 

 

[jdniss]

There's a small IAT Wastegate trim occurring under 20° IAT, pulling 1% of WGate duty cycle - may be contributing to it.

The 9:52 run was about 22° IAT where the trim wasn't active,

The later 12:45 run at 19° IAT had a 1% WG active trim, boost never hits the 13.8psi MGP activation point to turn "CL-Stage 3 Active" on.

 

Maybe try uploading the tune file to Google Drive?

[milliardo]

https://drive.google.com/file/d/1zSkD5g8uiZsDpaEKsz6C647wVW1qyKgO/view?usp=sharing

heres that link. 

checking what you said, that does make sense to me. i will need to read up on exactly what these stages are and how they work. the boost pid wasnt set up by me so im honestly clueless as to how to tune this. but looking at the log i can see stage 3 activate once im in 4th gear and IAT raises above that threshold you mentioned. 

 

[Adamw]

The boost control set up is not even close to correct, you are probably better to put it back to open loop mode until you can get someone experienced to tune it. 

1. The smallest value in the target boost table should be no smaller than the lowest boost the system can make.  Having a target of zero in there means you are already above target as soon as boost control enables, you will get no stage 1, and often no stage 2. 
2. The wastegate DC table is a long way off.  For example in the first pull you needed 51%DC to get close to target boost at 5500RPM, but your wastegate DC table only has 36% DC in it for 5500RPM.  At 6500RPM it needed 42% to get close to target, yet DC table only has 24%. 

Not relevant to boost control, but be aware your lambda at high load is very lean, you will likely damage the engine if you continue to drive it like that.  

[milliardo]

6 hours ago, Adamw said:

The boost control set up is not even close to correct, you are probably better to put it back to open loop mode until you can get someone experienced to tune it. 

1. The smallest value in the target boost table should be no smaller than the lowest boost the system can make.  Having a target of zero in there means you are already above target as soon as boost control enables, you will get no stage 1, and often no stage 2. 
2. The wastegate DC table is a long way off.  For example in the first pull you needed 51%DC to get close to target boost at 5500RPM, but your wastegate DC table only has 36% DC in it for 5500RPM.  At 6500RPM it needed 42% to get close to target, yet DC table only has 24%. 

Not relevant to boost control, but be aware your lambda at high load is very lean, you will likely damage the engine if you continue to drive it like that.  

the worst part is the boost settings have been like this for years haha. 

but yeah, it doesnt surprise me that its set up wrong. appreciate the tips there, i will try to correct that or maybe look into changing it to open loop for now. 

 

also yes i am aware. the original purpose of those runs was to record the log data for mixture map tuning. the top end has been richened since then. 

[Adamw]

7 hours ago, milliardo said:

the worst part is the boost settings have been like this for years haha. 

Although this doesnt change my sentiment that the boost control set up is poor, with the newly added info that "it has worked for years like that" then I would now add this thought: If it now needs 20% more DC to reach target than it has needed in the past then I would be looking for a hardware issue.  A big leak etc. 

Why has the fuel tune changed so much if its been running for years?  

[milliardo]

2 hours ago, Adamw said:

Although this doesnt change my sentiment that the boost control set up is poor, with the newly added info that "it has worked for years like that" then I would now add this thought: If it now needs 20% more DC to reach target than it has needed in the past then I would be looking for a hardware issue.  A big leak etc. 

Why has the fuel tune changed so much if its been running for years?  

yeah thats a good point. ive reconfigured the entire boost control following the guide in the help file and the car is responding much better now. building boost very aggressively. havnt re-enabled pid yet so that will be the next step. but i will double check for leaks..

 

the fuel needs retuning because i installed a new intake manifold that positioned the injectors in a very different position. theyre firing more directly into the cylinders now so it was running more rich initially. 

sorry for the large picture lol.