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MAF re-scaling

EFI Tuning Fundamentals

Discussion and questions related to the course EFI Tuning Fundamentals

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I was wondering the proper way to perform a MAF re-scaling. I understand this must be performed when you modify the diameter or the tube were the MAF sensor is positioned. What is the process, how to do it ???

If you alter the size of the MAF tube, you can calculate a correction factor that will get you close enough to be able to run the engine just by calculating the difference in cross sectional area between the original and new MAF tube. If you find the new MAF tube for example is 50% larger than the original one, simply multiply your entire MAF calibration by 1.5. This won't be perfect and you'll need to fine tune from there but it will get you close.

Once you're able to run the engine, you want to calculate the error between commanded air fuel ratio and measured air fuel ratio. If there is an error, it means the MAF cal is incorrect. It's a slow process of logging a lot of data and then applying a correction to the MAF curve before testing again. There are some excel based tools online that will correct your MAF curve based on logged data to simplify the task.

What ECU are you tuning?

OEM Subaru WRX STI with cobb accessport

Apologies for the late reply. I've linked to a thread on the romraider forum about the process. Despite using CObb, the logged parameters and the approach are the same. There is a link to a spreadsheet tool to help rescale the MAF too -

I´ll take a look!