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From what I've seen, it sounds like no one has properly figured out how exactly the MAF mod should be preformed if you already have an aftermarket intake on the car. I figured I'd attempt to run some calculations and see if I could figure out a model that could be used to calculate spacer height as a function of the diameter of your intake at the location of the MAF sensor.
Based on the simplified calculations I did, I found that a 0.25" spacer increases the free area of the factory intake by ~5%. If I understand subsonic compressible fluid dynamics correctly, that should lead to an increase in airflow of 5%, assuming a constant velocity.
Here's my measurements and math:
This should mean that to maintain the same AFR, we need to increase the fuel flow by ~5%. In the MAF/Injector Mod, this is achieved by replacing the stock green injectors with yellow 2ZZ injectors after increasing the air flow.
The problem is, that I'm not sure I'm even on the right track here. I'm not an Engine Expert, or even a Mechanical Engineer, I'm just an Astronomer using his extremely basic understanding of engines and subsonic compressible fluid dynamics to make an estimate. I'm not sure that the readings on the MAF aren't changing due to it's relocation, on top of the increase in area for the air to pass through. The 5% number may be a red herring, and not applicable to a generalized model for the MAF mod. (If it is applicable though, then this mod may work on other cars as well. I could see the Miata crowd going nuts for this)
So, can anyone help me double check my theory?
If the theory isn't way out in the wrong direction, then I'll post the rest of my equations for calculating spacer thickness based on a few measurements taken of a generic intake.
By the way, if the theory is correct, then anyone who did the mod by tuning the ECU or using a piggy back ECU instead of the yellow injectors (or by adjusting the fuel pressure regulator) should have needed to increase the fuel flow by close to 5%. Though I'm not sure if that would be across the board, or if it would be only in the low-mid range.
Thanks,
~Catachan
Based on the simplified calculations I did, I found that a 0.25" spacer increases the free area of the factory intake by ~5%. If I understand subsonic compressible fluid dynamics correctly, that should lead to an increase in airflow of 5%, assuming a constant velocity.
Here's my measurements and math:
This should mean that to maintain the same AFR, we need to increase the fuel flow by ~5%. In the MAF/Injector Mod, this is achieved by replacing the stock green injectors with yellow 2ZZ injectors after increasing the air flow.
The problem is, that I'm not sure I'm even on the right track here. I'm not an Engine Expert, or even a Mechanical Engineer, I'm just an Astronomer using his extremely basic understanding of engines and subsonic compressible fluid dynamics to make an estimate. I'm not sure that the readings on the MAF aren't changing due to it's relocation, on top of the increase in area for the air to pass through. The 5% number may be a red herring, and not applicable to a generalized model for the MAF mod. (If it is applicable though, then this mod may work on other cars as well. I could see the Miata crowd going nuts for this)
So, can anyone help me double check my theory?
If the theory isn't way out in the wrong direction, then I'll post the rest of my equations for calculating spacer thickness based on a few measurements taken of a generic intake.
By the way, if the theory is correct, then anyone who did the mod by tuning the ECU or using a piggy back ECU instead of the yellow injectors (or by adjusting the fuel pressure regulator) should have needed to increase the fuel flow by close to 5%. Though I'm not sure if that would be across the board, or if it would be only in the low-mid range.
Thanks,
~Catachan