Anybody have a way to quickly gauge airmass/airflow/performance increase from mods?

I have spent hours trying to zoom into small sections of the log file then exporting to a CSV, then going through excel and making a query import. By the time you deal with Excel and text to number conversion and all these other stupid things you've spent 4 hours trying to compare airmass from a "before" run where you say had a stock piece on, and a "after" run where you put a ported piece or some aftermarket bolt on or something. We also have the added problem that we need a common RPM or other value to gauge from, which requires making up a pseudo new RPM, then pulling data points from both before and after run files that most closely match this new pseudo RPM you created. This way you can graph say airmass (which basically models torque and should be proportional to it) from both runs all on one x-axis of psuedo RPM. I've been doing this using VLOOKUP with an "approximate" match, but who knows how Excel is internally choosing which vlookup it choses.

Anyone else doing anything like this? I feel like the accuracy is there given modern MAFs and systems, and I would personally trust it way more than some "tuners" dyno who applies who knows what kind of corrections and tricks to make it look like their parts increased airflow and made more power.

One of the ways I would approach this is by using cylinder air mass (Cyl/air) is grams per cylinder and comparing that to the theoretical cylinder airmass in grams at STP.

VCM scanner provides you with that math channel already based upon your cylinder count. Depending on the year of the controller, you may have absolute load to monitor as well. This number should closely correlate to the VE% you see when comparing your cylinder air over theoretical.

Hope this helps.

Isn't the absolute load a EPA/SAE required ODB output? and therefore GM would just put it in to meet spec and may not be accurate?

I kind of overlooked comparing APC/Dyn Cyl Air/Airmass/whatever else GM calls it to the actual atmospheric conditions, which I think I could just compare this number to weather station data online or somewhere that gives you DA info? The VE% should be 100% independent of atmospheric conditions right?

Thanks for the help

Depending on the MY, you’ll have Calculated Load or Absolute Load. Absolute is found on later vehicles and goes from 0-400% and is likely more accurate. This load factor is cylinder fill which should provide the data you’re looking for. You could also log the dynamic PID Cyl/air and create a math pid using the proper formula.

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Originally Posted by Techsb

Depending on the MY, you’ll have Calculated Load or Absolute Load. Absolute is found on later vehicles and goes from 0-400% and is likely more accurate. This load factor is cylinder fill which should provide the data you’re looking for. You could also log the dynamic PID Cyl/air and create a math pid using the proper formula.

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Have you ever used the PID "Air Density Torque Multiplier"? What I have been doing is just comparing Cylinder Airmass between runs, but before I compare the numbers I multiply them both by their respected "Air Density Torque Multiplier". You have to be careful though since the air density torque multiplier depends on barometric pressure and baro is artificially inflated during WOT runs. I have no idea why GM would take the time to program this PID in because I don't see why a technician would ever need it.

You still have the problem that you have to find a common RPM to compare the air masses between runs, and of course it is a real pita to extract csv data from hp tuners and open excel files and reimport data and copy and paste and make formulas to transform and fix data and all that.