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2005 Cobalt SS LSJ (turbo) Issue with MAF Pegging Under Initial Throttle

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Good Morning everyone I hope you are doing well today.

I have been having an issue with my cobalt SS since I have changed the Supercharged LSJ to Turbo LSJ. I essentially put my own turbo kit together and it is having some issues. I will break it down though for those to help.

The car is having an issue where the Mass Airflow Sensor is reading its highest reading on the scale and getting pegged under initial throttle blip, or tip in. It also happens if I let go of the throttle and then get back into it while the car is moving.

I am not sure what the issue with this could be, but it could be a number of factors since it only happened when I did specific modification changes after I initial turboed the car.

When I initially turboed the car I left the injectors and tune that came with the car in it and it ran fine, I even had the blow off valve in the wrong location past the MAF letting air escape and dump fuel under deceleration but it still ran fine.

I then in one sitting changed the Fuel pump, the injectors with some used siemens deka 80lbs and changed the BOV location as well as started using e85. We began to tune from there, and that is where we started seeing this maf pegging right away.

Please keep in mind this car is not meant to have a blow through mass airflow sensor either and that is what is running now. But either way I am not sure what is causing this issue, it could be that I messed up the wiring to the fuel pump causing an internal electrical issue where the maf is pegging due to incorrect readings under initial throttle. Or the injectors having an issue, or even something else. Other then that the car runs fine, AFR's are where they need to be and im unsure as to what is going on.

Any thoughts are appreciated and im here to help with any questions regarding my issue or providing any additional information.

Thanks again,

It could be turbulence to the MAF on that first throttle opening.

As in, the MAF only samples the air from a single point usually centrally in the pipe.

So if there's some turbulence or swirl etc which biases flow towards the centre of the pipe at that moment then it'll give you a big spike in readings.

Is your MAF located just after or just before a bend now? Generally they want to have a decently straight length of pipe either side.

I guess you can maybe look at datalogs and see what the voltage spike actually looks like, if it looks like a fairly organic ramping up then it might be the situation above, if it just has an instantaneous transition to 5V then maybe it's something else.

Issues like this are why I switched to map sensor haha.

it is an instantaneous transition to 5v and then it has to be an issue with turbulence at that time. I just cant understand why it would be doing that because before I switched the blow off valve location it ran fine. But maybe that was because it was still allowing air to pass by the MAF at idle and letting the turbulence go. Maybe I should change the whole intercooler set up at that point. I am just surprised though because I had used this same setup back in the day (and its on a straight section) and I didn't have any issues. I will see If I can change this all though.

Thanks again everyone so far!

wanted to bump this up since I havent really figured out what is wrong with the initial throttle. please see the attached video of my log that i had taken a couple of months back and let me know your thoughts.

https://www.youtube.com/watch?v=KEi4F1zxIjM

also please see the attached screenshot of my MAF calibration among other things. Any help is appreciated.

Attached Files
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One more bump for good luck

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