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Discussion Starter · #1 ·
what would you guess as a flywheel power number, with stock 72mm MAF, maxed out (reading 5.115volts). Assuming that the A/F is stoich or on the rich side, and knowing the total **mass** (not volume) of air, can one ballpark the bhp at the flywheel? I'm guessing that intake manifold pressure would be unnecessary to know because we'd know the total mass of air flowing into the engine.
 

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The question is, how far over maxed out did it go..?

Or are you just interested in what the power would be right at the point where they maxed out?

Rob
 

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Discussion Starter · #3 ·
I'm just interested in what the power might be at that maximum point - in other words, the maximum power stock AFMs can accurately measure before flatlining on the map.

just curiosity really, as I've got new Z32 AFMs going in.
 

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Pressure in the manifold is irrelevant as the MAF (MASS air flow) sensor directly measures mass flow (funnily enough!).

I`ve got a graph somewhere.......
 

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Discussion Starter · #5 ·
exactly...it's total air mass that's important. it's also why I am reluctant to consider D-jetro setups using MAP sensors. Plenty of people use them without issue, but I can't get my head around how you tune once you've reached max boost pressure.
 

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As well as mass air flow you need to have an estimate of brake specific fuel consumption. Typically it is at it's lowest at peak torque and rises towards peak power.

According to Nissan, the standard rb26 AFM saturates at approx 750 kg/hr mass air flow (55lb/min). This equates to around 460bhp max assuming an AFR of 12:1 and BSFC of 0.6.

To use a speed-density based ecu like d-jetro you need to know charge temp as well as pressure, as mass air flow is inversely related to temp when volume is constant. Anything that changes volume (read volumetric efficiency) then also affects mass airflow. Hence why just changing your airfilter can necessitate a remap with d-jetro.
 
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