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Discussion Starter #1
Does anyone know if there is a direct relationship between MAF L/HR figures and horspower output?
In other words does the quoted OK 140 L/HR figure = 400 engine HP?
I know there are various corrections for altitude, pressure, temp etc but do lower and higher figures transfer direct to dyno results?

And as an aside what do the alpha-N tuned cars do down the track to check all is well? Same L/HR check?
 

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MAF readings only affect operation at partial throttle and idle. At wide open throttle (WOT), the computer can't react fast enough so the fuel injectors and timing are controlled by a state table in the ECU.
 

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someone told me once that the number in the MAF test is actually the fuel metered, not the amount of air. That sort of makes sense to me in terms of the order of magnitude of those numbers. 140lph of air isn't very much as all.
 

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I would have thought the figure from the MAF test was just that, a figure gained from the return signal of a sensor, with infinite other possibilities affecting actual output.
 

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Discussion Starter #6
I was hoping that a simple MAF fuel flow rate would equate to horspower, such as 100 L/HR = 300hp, 140 = 400hp, 150 = 420hp or whatever linear or non-linear relationship it is.
I know higher won't magically add more hp but lower certainly seems to kill it from all reports...
 

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Far too many other variables for me, I suppose if everything was running exactly as intended (like a brand new, properly run-in engine) then perhaps it could be 'assumed' that a low flow rate might lead to a loss of x BHP, but I don't think in the real world, it would work like that.

I think it was mentioned above, too, that the l/hr figure for the MAF test isn't necessarily fuel-flow rate, but air flow amount/rate (...?), as this would be what the MAF's are measuring.
 

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Discussion Starter #9
That's it I think, to get the quoted 400hp you need to pull 140+ and have everything else running sweet?
 

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That's it I think, to get the quoted 400hp you need to pull 140+ and have everything else running sweet?
Er...like running as it did from the factory...?

Many cars that are several years old are running lower than factory figures, due to wear, routine bits needing replaced etc. So, yes, MAF's running properly and everything else running sweet should in theory see the factory 400.
 

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If you have no restrictions to air flow (dirty filters, say) and the engine is mechanically sound and the Vanos equipment, including CPS's, is working perfectly to time the cams for maximum cylinder filling, the air flow into the engine at WOT/6600 rpm will be sufficient to make 394 HP if mixed with the optimimum amount of fuel.
And that is where the MAF's come in. If the MAF's are working and read this airflow correctly, the DME will take note (it ignores the O2 sensors at WOT and looks at the MAF readings and its internal fuel maps) and inject ~140 l/hr of fuel to give the best max-power air/fuel rato, probably around 12.5-13:1.
Seeing a fuel injection rate of 140 l/hr indicates mechanically the engine is good and the MAF's are reading the correct airflow, at least when bouncing off the rev limiter.
 
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