LML Will not build over ~22PSI of boost

[Mitco39]

Hey guys I am posting this here to get a little more exposure to my problem,

So I have gotten quite a few LMLs done to date and have been fighting them to build boost over stock values. I have noticed that it seems tired to a maximum MAF value that the truck will allow itself to run. The boost will come up to 21psi (35MAP) and then the vains will open up to keep the boost low. I have noticed that if I do not touch the tables in the misc folder under turbo boost the ECM will open up the vains completely (right to ~0%).

Now if I go in there and max out the turbo compressor map as well as the efficiency tables I can get the vains to sit right around ~30% and build the ~21PSI again keeping the MAF below 62lbs/min. I have noticed that B0173 only goes up to 473gram/s when infact the truck can easily support higher values than this. <-- I have seen higher values than this on larger tunes, but still boost is being limited in someway.

I had a H&S programmer that I logged and it did very much the same thing on the same truck. Today I also tuned a 15' Denali that acted in 100% the same way.



Here is a screenshot of the log, do not mind the TCDBPR values that are so high, I was doing some testing just trying to get the turbo to listen. You can see that the ECM is commanding a MAP of much much higher than its allowing the truck to run. All the boost tables are such that the truck is not hitting a wall (peak boost I set at 46PSI at B0734 and B0727. Either way the fact that the TCDBPR is calling this much means something else is holding back the turbo and I believe it is related to a maximum MAF value possibly.

The AIRFLOW tables have also been maxed out for these tests I been doing to ensure that they were not limiting the airflow.

[GMC-2002-Dmax]

I see its a 2012 OS, that particular OS is different in some way from the 2011 and 2012-2013 OS in the way it acts.

I have tried a 2011 OS in my 2012 and a 2013-2014, the 2011 OS is fine the 2013-2014 will do some weird stuff with vane going to 0% especially on the highway but I can still make 30+ psi of boost with all the OS's

[Mitco39]

I have tried a 4094 with the same results on this truck. I also confirmed that the 2015 is doing the exact same thing. I have had issues with the cruise when running the 2011 in the 2012 so I went right back to the 12OS.

So just to confirm your seeing a MAP of 46PSI? I have not been able to come close to that. On a built truck with a big tune you might get close, but thats only because your making a bunch more heat and even at 30% Vain position its able to build that boost which is what I saw on the 2015 I did yesterday.

[GMC-2002-Dmax]

From memory when I went to the track with mine about 3 weeks ago I was seeing 30-31 PSI at WOT with vane at between 0%-6% and Boost Pressure set for 48 in the boost tables and the boost limiter lifted to 50 in the limiter tables.

The only anomaly I have with the 2012 OS is that at around 150-160 degrees I lose the 20% Rumble vane position, when the engine is cold its fine and its hit or miss depending on the trucks, some guys have lost it at that temp transition while others have no issues with the target position staying at 20% at idle.

My own personal truck is set to factory target positions because it won't keep the rumble/20% in drive or park but it rumbles in reverse, quite strange for sure.

But I am making the target boost

[Chavez91]

The only anomaly I have with the 2012 OS is that at around 150-160 degrees I lose the 20% Rumble vane position, when the engine is cold its fine and its hit or miss depending on the trucks, some guys have lost it at that temp transition while others have no issues with the target position staying at 20% at idle.

My own personal truck is set to factory target positions because it won't keep the rumble/20% in drive or park but it rumbles in reverse, quite strange for sure.

But I am making the target boost

I can agree wit this as well... We have a 2011 and it will rumble and keep the 20% vane, but once it warms up it will loose it. Reflash it and it will hold rumble, then make a few changes non turbo related and reflash and may or may not loose rumble... its hit or miss... if I make a change and i loose rumble, i usually just reflash the same tune once or twice more and Ill have rumble again. Its weird.... but I always build desired boost. I can get it to hit 35 if i ask no problems at all. So idk about that part. But its always hitting the 30-31 psi mark i have set for it no problem. Usually maintains about 22-28% vane pos.

[Mitco39]

I can agree wit this as well... We have a 2011 and it will rumble and keep the 20% vane, but once it warms up it will loose it. Reflash it and it will hold rumble, then make a few changes non turbo related and reflash and may or may not loose rumble... its hit or miss... if I make a change and i loose rumble, i usually just reflash the same tune once or twice more and Ill have rumble again. Its weird.... but I always build desired boost. I can get it to hit 35 if i ask no problems at all. So idk about that part. But its always hitting the 30-31 psi mark i have set for it no problem. Usually maintains about 22-28% vane pos.

Could I ask to see just a screenshot of a log? Maybe its just the 12+ trucks that are doing this? I havent got my hands on a 11 since I decided to dig into this more.

[Mitco39]

On a truck you are pushing hard its no inconceivable that you could see that, what I am arguing is why are your vanes opening up before you reach your target? At 0 percent the truck is essentially trying to get rid of as much boost as possible for some unknown reason. The fact your seeing boost still is only because I would suspect you are generating alot of heat pre turbo and even fully open the turbo is pushing some air through. If I take what you said I would expect to see the vains riding a maximum vane table to try its best to meet your requirements (which you said is 48 to 50PSI). If the turbo cannot make that boost under conditions you set out for it it will throw a low boost code (unless its disabled of course) which would cause the truck to run exactly like it is. Technically its in a underboost condition even though you are seeing 30-31WOT.

Unless I am wrong? I am just explaining my understanding of the situation. I think there is a maximum vane position table missing, or some other hard limiter that we cannot see causing the turbo to ignore your boost tables after a certain threshold.

[GMC-2002-Dmax]

You have to add atmospheric to target boost for total boost, 48psi in the table - minus 15 psi at sea level leaves 33 psi commanded, and it makes that on the CTS 30-31 at wot.

I have no doubt the charger is screaming at that psi

I make that on the street as well easily just hitting the throttle.

Also the chargers changed for all 5 years, so the target tables are different based on the difference in the chargers

[Mitco39]

Right so your quoting both Absolute and gauge pressures. But the turbo maps are based solely off absolute pressure which means thats what its going to run to. So my argument is if the absolute pressure that the truck is seeing is below what your calling for in the table (whatever that may be) the truck should try and run a more aggressive vane position to meet those conditions.

I am seeing a command of 48PSI but im only making 38PSI (Absolute) yet the turbo is anywhere from 0-30 percent. On previous generations that turbo would ride any maximum vane position table to try and meet its requirements in closed loop mode.

[GMC-2002-Dmax]

We only have what we have, so if we need more then we need to ask Ross to look if you think its an issue