2012 Buick Regal Boost dropping

[fxracer20v]

Hey guys. We installed a FMI and ZFR 6758 on a 2012 Buick. This is the first time tuning the LHU and have ran into a snag. I am sure it is something simple that I have just overlooked, cant find, or just a table I didn't think was relevant and didn't modify. We are able to get the boost to hold 21.5psi or so all the way to 5k, but no matter what we do the ECU start commanding less boost after that all the way down to redline and ends up at 17psi. I was wondering if someone would take a look at the tune and point me in the direction of the mysterious table that is keeping us from holding 21.5 all the way to redline. The car is a rocket up till then but just falls off. The customer is bringing it back on Friday so I am hoping to have this figure out by then so we can finish the tune and so he leaves with an even bigger smile on his face. Any help is and will be greatly appreciated. And yes the throttle is staying open at 84%. It is just being commanded to a lower boost pressure. I don't have a log file cause my laptop took a crap, but I had him run the car over to pull the current tune. Thanks again in advance.

[Marc Town]

Are you keeping stock first cat ? Not related to your issue but we had an LHU with same upgrade but the extra boost made oil to leak into intake thru the pvc valve, we suspect that higher backpressure and first cat restriction aren't good friends. I suggest to delete first cat.

[fxracer20v]

Cats are removed. It smokes a bit during the initial tuning but seemed to clear up.

[T-Man]

Take a look under "Torque Management - General - Overboost Torque Limit"

Also, if it's catless, I'd suggest turning off COT under "Fuel - COT, Lean Cruise".

Any reason why you're running the car so rich(12.1x or .86 lambda) with so little boost and timing? Keeping things extremely conservative? More of a curiosity question than anything.

Edit - Also, why do you have it entering PE so late?

[cobaltssoverbooster]

.86 is 12.6 afr double check your math

[T-Man]

.86 is 12.6 afr double check your math

In a perfect world with 0% ethanol gasoline, sure? Stoich for E10 is 14.13. 14.13 x 0.86 = 12.1518 or 12.1x

You're a good guy and have gone above and beyond for the community but why not add something relevant to the topic at hand, rather than nitpicking my correct math?

[veee8]

Might want to up the bottom row of the driver demand tables, the max torque tables under torque management, up the pressure ratio max on the turbo overspeed table.
Also delete the cot as mentioned.
Try those changes and report back.
Post up the stock file when you can as well.

[fxracer20v]

Thank you to everyone so far. To answer some questions, the PE comes in later because it doesn't reach full boost till about 3500rpm. Little later than the stock turbo. As for COT, I have all the temps raised to max but I will turn it completely off. I have it a tad rich and lower timing to start because I was trying to get boost set first, then fuel, then timing. First time tuning the LHU or any GM boosted 4 cyl for that matter and like to take it slow. This ECU control strategy is similar to the Mazdaspeed, pertaining to Torque Demand instead of shooting for a specific boost pressure so this isn't a new concept for me. I think you may have hit the nail on the head in regards to the Overboost table and Max Torque Tables. I didn't think I was reaching the Max Boost threshold so it didn't strike me as being an over boost protection, but I may be walking the line of overboost. Like I said, it happens every time at the same RPM, the ECU just starts requesting less pressure. Pertaining to the Driver Demand Table, they seem to be very sensitive. The last row stock is 235, which gave me a consistent 17ish psi. Moving them to 245 raised it to the 21.5-22psi area. Just FYI for anyone else with the this type of combo. Not sure if it would be the same using a stock turbo. I did try raising the Demand tables in the upper range, as well as the Duty Cycle table but it didn't help, which is what led me to stop, and try figuring it out first Instead of wasting gas and time. He will be back Friday so I will start with adjusting the Overboost torque tables and see how it goes. Without having the car in front of me, I was just trying to get a head start before it came back.

[fxracer20v]

This may be a little off topic in regards to the turbo, but I noticed the Compressor Efficiency and Speed maps look like pretty relevant data in regards to most of the published compressor maps that are out there. I found the compressor map for the 6758 but haven't had time to see if I could modify those tables to match the new turbo. It seems like most of the data is there, just would take time populate the table. Has anyone ever played with the tables? Or is this still pretty new territory in regards to upgrading the LHU turbo? Thanks again guys.

[cobaltssoverbooster]

the ecu has a ethanol content table in it. you set the pe for the factory pump gas which if he measured it then we could get all nit picky and say it requires an offset. at that i wont argue, but with no information you have to resort to the lowest mixed ratio of gasoline on the table (14.7). I know he isnt watching the content sensor in his log but if he did then he could set a lambda offset based off the measured value. lambda is set to the lowest value when the mixture content is unknown and mixture table takes care of the rest.
the comment is appreciated and i'm sorry i shortened my response into an attack t-man. you seem to have a handle on this so keep going and i'll leave you alone.

[fxracer20v]

Just to comment on the above posts about AFR, even though I know its off topic, is that .86 Lambda is still .86 Lambda regardless of the fuel being used. I agree with both. But to comment on T-Man's comment, yes you are right. .86 Lambda with a Stoich ratio of 14.13 is 12.15. But it is still a Lambda of .86. But using your thought process, if I were to use an "AFR" of 12.6 on a fuel that has a Stoich of 14.13, that means I would be running a Lambda of roughly .9, which in my opinion is to lean, but that's just me. Not trying to "fuel" the fire, just hoping anyone else that runs across this that hasn't already read the millions of threads regarding AFR and Lambda that are out there. Just wanted to point out that .86 is 14% richer than Stoich regardless of the fuel you run, and that's what's important. Yes, the "AFR" gauge may read 12.6, but in the real world it reads Lambda and converts it for you. So fuel that has a Stoich of 14.13 and is running at 12.1 "AFR" is still .86 Lambda, just as 14.7 fuel will be at 12.6 "AFR". I know I am new here but hopefully someone will read this and get something out of it. I started tuning using Lambda quite a few years ago and haven't gone back. Tuning pump gas to race gas to E85, the Lambda number is always right regardless of fuel, and not having to remember any conversion charts saves a lot of headaches, lol.

[fxracer20v]

If anyone has any more ideas, I am all ears. But I will post up the results after Friday for everyone to see. Thanks again guys.

[T-Man]

the ecu has a ethanol content table in it. you set the pe for the factory pump gas which if he measured it then we could get all nit picky and say it requires an offset. at that i wont argue, but with no information you have to resort to the lowest mixed ratio of gasoline on the table (14.7). I know he isnt watching the content sensor in his log but if he did then he could set a lambda offset based off the measured value. lambda is set to the lowest value when the mixture content is unknown and mixture table takes care of the rest.
the comment is appreciated and i'm sorry i shortened my response into an attack t-man. you seem to have a handle on this so keep going and i'll leave you alone.

Yeah, saw that but I made the same assumption, that it wasn't being monitored and utilized. All good my friend!

Just to comment on the above posts about AFR, even though I know its off topic, is that .86 Lambda is still .86 Lambda regardless of the fuel being used. I agree with both. But to comment on T-Man's comment, yes you are right. .86 Lambda with a Stoich ratio of 14.13 is 12.15. But it is still a Lambda of .86. But using your thought process, if I were to use an "AFR" of 12.6 on a fuel that has a Stoich of 14.13, that means I would be running a Lambda of roughly .9, which in my opinion is to lean, but that's just me. Not trying to "fuel" the fire, just hoping anyone else that runs across this that hasn't already read the millions of threads regarding AFR and Lambda that are out there. Just wanted to point out that .86 is 14% richer than Stoich regardless of the fuel you run, and that's what's important. Yes, the "AFR" gauge may read 12.6, but in the real world it reads Lambda and converts it for you. So fuel that has a Stoich of 14.13 and is running at 12.1 "AFR" is still .86 Lambda, just as 14.7 fuel will be at 12.6 "AFR". I know I am new here but hopefully someone will read this and get something out of it. I started tuning using Lambda quite a few years ago and haven't gone back. Tuning pump gas to race gas to E85, the Lambda number is always right regardless of fuel, and not having to remember any conversion charts saves a lot of headaches, lol.

Nah man, no argument from me here regarding lambda = lambda = lambda. Was just curious as to what your strategy was with this cal. Sounds like to me it's easy as she goes until you're more comfortable with it and I commend you for that! I just prefer to run things a bit leaner than what you're targeting. Just a simple curious question

Hope what was offered up helps with what you're experiencing!

[fxracer20v]

No sweat! I appreciate the help. Yesterday was a success! I think it was the over boost tables. Just raised those up a bit and lowered boost a hair. Boost kicks is at about 3500 at about 21psi, slightly raises to 22 and back down to about 20.5-21 by 6300. Put down 305hp and 315tq on our Mustang dyno. It baselines at 295tq and 275hp with a tune from another popular online company which everyone has heard of. I know it doesn't sound like much but the area under and after the curve is the most impressive to me. For some reason the other tune didn't have boost coming in till after 4k. We picked up 110tq at 3500, and over 70hp at 6300, with more power everywhere. This thing pulls to redline now and customer is happy. Now he wants more lol. I'm thinking 3bar sensor and Water/meth and more boost. I would rather push for E85 but its his DD and E85 stations are far and few between around here. One of my employees drive 20 miles each way to get it for his 300zx and my Acura. So last question, what's average maximum boost for these engines on 91? They seem to have a very efficient combustion chamber and the DI helps so I'm guessing the map sensor limit of 22psi is the only thing keeping it at that level at the moment. Thanks again for everyone's input. I'm looking forward to doing more.