P0234 overboost problem - Buick Regal LDK / A20NHT 26 psi

[Pmj-07]

I have recently installed a hybrid turbo & 3" ZZP DP w. sports-cat in my 2010 Opel Insignia 2.0 Turbo with the A20NHT engine, also called LDK , similar as in 2011 Buick Regal cxl.
When using my latest tune I have a problem with power cut and an overboost error (P0234) when (intentionally) boosting approx 1,8 bar (26 psi overboost) for a second or so.

I was hoping someone could advice on how to best get around that problem. I have been told about lowering/limiting the MAP signal with a resistor/voltage devider, zener diode or just install a 4 bar map sensor, but am afraid that will affect the performance/af-ratio etc in a negative way ? or is that all handled by the Mass Air Flow input?

From what I have noted after reading some forums, the signal reaches FF/255 = max at 2,54bar absolute. (Approx 4 volts, is that really max of what the MAP input can read, or is it "only" a matter of re-scaling? ECU = MED9.6.1) Using the VCM Scanner the boost reading stops at 255 which makes sense. Stock 3 bar map-sensor. Approx 1.8 bar is measured by manual gauge.

Not being very familiar with how these ecu's work I am grateful for any advice.

Attached is a VCM scan-file.
A short -not wot- pull on 2. went fine (Driving time 1:50) , however during the following pull on 3rd it cuts after 2:09:684 minutes driving time. (It cuts regardless of gear)

Lowering the boost is not an option. Having the 4x4 Sports Tourer w. 6 sp manual gearbox its quite fun to drive as it is right now

[MarkTucker]

Disable the Overboost/Underboost tab.
Overboost , Underboost Master Enable , Disable.png
Engine Diag>Airflow>Overboost/Underboost>Overboost/Underboost

[Pmj-07]

Thanks for quick reply, Mark.
I am however for some reason only able to read DTC's listing in my file, not the tab you are refering to.
Is there some setting in the Editor I am missing.

Attachment 65532

[cobaltssoverbooster]

you need to switch from standard view to advance view

if you already are in advanced view then you need to either update your software which would possibly move the tables around as they re-organized everything from v2.xx to v3.xx
also your tables may not show there. they were originally listed under the engine tab, not engine diagnostics.

[Pmj-07]

Advanced view helped a lot, thanks.

I do however not have the "enable/disable" option for o/u-boost, rather an "enable rpm"-table, see attachment. Will raising the rpm-value to max (eg 7000) give the same result?
Will I then disable all supervision on overboost or is there still some safety left? Could changing "overboost allowed error" (see other attachment)to higher values be an option?

It would be great if someone could shed some light on the relation between the p0234 error and the MAP sensor vs boost sensor?, as changing configuration on both of them seems to be possible. ( Anyone having a link to a Bosch's ECU manual...?)

[Flyer]

I think I turned the code off in my tune. Set the DTC to 'No Error Reported'.

[Pmj-07]

I think I turned the code off in my tune. Set the DTC to 'No Error Reported'.

I tried to "disable" the DTC code 0234, however it only turned the error message off, not the trottle cut/power loss.

[KLUG'S SS]

Many times what is happening that I have personally seen on several turbo cars now such as Cruzes, Sonics, Regals, Malibus, ATSs etc... is they will encounter throttle cut when the actual boost number exceeds the target boost number. The fix for This can be addressed in a few different ways such as lowering wgdc.

[Pmj-07]

Many times what is happening that I have personally seen on several turbo cars now such as Cruzes, Sonics, Regals, Malibus, ATSs etc... is they will encounter throttle cut when the actual boost number exceeds the target boost number. The fix for This can be addressed in a few different ways such as lowering wgdc.

Thank you for your reply. WGDC has been raised in my tune, thats right. Compared to stock WGDC it is however in an rpm range above where the trottle cut may appear, i.e mainly raised from 5000 rpm. See pink area in attachment.

I was about to try to get around it by increasing allowed Overboost Error - if that makes sense...?

[Flyer]

The knock airmass being exceeded will cause throttle cut too.

As far as the code .. you can't 'disable' the SES, you have to change where it says 'Error on 1st or 2nd' (or something like that) to No Error reported. I'm not sitting in front of my laptop at the moment, otherwise I'd tell you what it says. But if you set it to No Error Reported, you shouldn't have that problem anymore.

[Pmj-07]

Problem solved Increasing the Allowed Overboost Error fixed the problem with trottle cut & P0234 during (over-) boost above 24-25 psi. Now running fine at approx 26-27psi.
I have no idea about hp figures, however measuring afr above 270g/s during wot around 6000rpm. Any indication?

[lt1z350]

On my ats with a big turbo I was logging maf and stock was 32 38 gps I believe (grams) and with big turbo was seeing 42-44 and car was making 400 or so whp when it broke a rod.

[Pmj-07]

On my ats with a big turbo I was logging maf and stock was 32 38 gps I believe (grams) and with big turbo was seeing 42-44 and car was making 400 or so whp when it broke a rod.

Thanks. Seems to be a mix of units between our readings,though, or have you left out a "0"? My MAF (Mass Airflow Sensor) was Reading 288 g/s (grams/second) on my last try. (VCM Scanner)

[lt1z350]

Look at mass airflow sae it is lb/min that is showing how much air it is actually pulling in so the more air more power I use that as a judge if doing wot cam timing if it goes up then it is getting more in is how I see it and in the end delivered torque goes up which I use too

[Pmj-07]

Look at mass airflow sae it is lb/min that is showing how much air it is actually pulling in so the more air more power I use that as a judge if doing wot cam timing if it goes up then it is getting more in is how I see it and in the end delivered torque goes up which I use too

OK, lb/min makes sense. 44 lb/min x 7,56 converts to approx 332 g/s. Using roughly 1.25 to hp gives 415 hp. I was assuming approx 360 in mine.

What did you boost in order to get these figures?

[cobaltssoverbooster]

the estimate is 10 hp per lb/hr at the crank. so 440 hp times roughly 15% powertrain loss gives you 374 some setups report back a better drivetrain loss which could net at most i would bet from this guessing math to 8-10% loss in fwd which would show 404 or 396.