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Colorado 2.8 turbo diesel boost issue

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Hi guy, wondering if anyone here tunes or has tuned the new Colorado 2.8 diesel? Using hp tuners to edit and snap on scan tool for data logging (hp haven't got this sorted yet) I have an issue with the maf hitting 217g/sec at 2700rpm and not reading higher. As I increase revs, boost drops, maf reading doesn't change no matter what I do for boost control doesn't change. Not sure what's causing the issue I'm thinking maf maxed out and not sure if scaling the maff will help? All fuel tables and boost tables are mm3 and pressure related so not sure if scaling maf will help? Wondering where to go from here and what the maf has to do with the boost control? I have lifted all torque limits and would have thought if maxed out 100% load would keep boosting as per map .I'll check and see what voltage the maf is at when reading 217g/sec see if it's full voltage. Any help or insite greatly appreciated

We don't deal with diesel tuning at all so I can't help on a diesel related matter. It's not uncommon for an OE ECU to have a hard coded MAF limit which sounds like what you may be hitting. Often this is adjustable in the reflash software and needs to be increased if you're expecting significant increases in airflow. It really depends from there how the ECU calculates load to control aspects such as boost and it may well be that the MAF limit is affecting the boost control too.

Whether you can remedy this will depend on how complete the definitions are in HP Tuners for the Colorado. My experience with a lot of the fringe vehicles that HP Tuners support is that the definitions were incredibly basic to the point of almost being useless in some applications. I can't personally speak for the Colorado though as I have never tuned one.

Thanks for the reply, I have spoken to hp about the problem and they are trying to extend the sites for increased airflow. There are plenty of sites available but unable to change. I have since tuned a slightly older Colorado and maf site is voltage reference not freq and for the same airflow only using half of the table so no issues with boost dropping. I'll let you know how I go and if I get an answer back from hp.

Just an update, with hp tuners if the axis heading is underlined it is able to be changed. The maf freq axis is able to be modified so can extend the table quite easy. The next challange is to calibrate the g/sec to the new freq.

Ah yes, I now understand the problem you were having. As stated, I haven't personally had much to do with diesel tuning however I understand the basics. The process of scaling the MAF sensor is normally accomplished by looking at the error between commanded lambda and measured lambda - Any time there is an error it means the ECU is measuring too much or too little airflow and this can be corrected in the MAF scaling table. I'm unsure how well this technique would convert to the diesel world where EGT is probably more relevant under high load/boost than lambda. I'd start by extending the MAF curve into the higher frequency areas you've created and following the same exponential shape. This should at least get you started and you can recalibrate from there.

Let me know how you get on. I'm led to believe the potential gains in the 2.8 Colorado is impressive.

Should be getting this vehicle back in and on the Dyno in the next week.

im not 100% sure how to calibrate maf correctly as the afr sensor from what I can see is used with maf to work out egr flow.

Fuel mm3 table doesn't reference airflow at all. but there is a smoke limit table that has values in lambda. I'll have a play and see what happens when I extend the freq axis and maybe to start with run 512g in the highest cell and interpolate back to the last calibrated freq cell.

I'll post up a file for you to suss out when I'm done.

I think logic is simmilar to BOSCH ECU. And lambda table is limiting injection (smoke limiter).

If You have access to lambda tabe make new axis bigger than you see now - just last numbers of ariflow,

set lambda from 2000 - 4500 values for max airflow - 1.00. (don't know what original is, but think aproq 1.30..)

Sometimes is possible to switch off air mass meter and run just with MAP.

Hey Bogga

I've got one of these to do on Friday. How did you get on with it?

We usually reply within 12hrs (often sooner)

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