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Old 01-13-2012, 05:35 PM   #51
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Originally Posted by Iceman00 View Post
She's swapping the block and using her existing ECU and sensors. Well see how it turns out.
From a programmable Bosch ECU guide:
The injection time depends mainly on throttle position, engine speed, fuel pressure and injection valve type. To get a first estimation, the following characteristics must be known:
displacement per cylinder VC (m3)
expected intake manifold pressure (after throttle) pi [Pa]
desired lambda value ***955;
operating fuel pressure pf [bar]
injection valve flow rate Qstat [g/min] at reference fuel pressure pfRef [bar]
intake air temperature Ti [K]
The fuel mass mf is calculated by: ...
The only difference with the E46 setup is in place of manifold pressure and intake air temperature there is a MAF. If you change the block, the displacement value goes wrong. The ECU will still calculate fuel, but it will have an incorrect value, and will inject incorrect amounts of fuel.

With a larger displacement, and no other changes I'd expect the mixture to run lean, misfires would occur, the engine would try some enrichment compensating, and then go into safe mode.

Maybe a ghetto fix would be just install an adjustable fuel pressure regulator, and slowly up the fuel pressure, until the engine compensation amounts were close to neutral. The mapping probably wouldn't be ideal though, as camshaft and intake properties would throw things off in a few areas.

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