N54 BMW DI injector size / secondary inj ratio?

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beetos
Posts: 31
Joined: Thu Sep 22, 2022 7:41 am

N54 BMW DI injector size / secondary inj ratio?

Post by beetos »

Hi,
does anyone have an idea what the stock DI injector sizes are on a BMW N54? I want to try a decent number for scaling my secondary port injectors and to do this you need an idea of the primaries.
Cheers.
beetos
Posts: 31
Joined: Thu Sep 22, 2022 7:41 am

Re: N54 BMW DI injector size / secondary inj ratio?

Post by beetos »

Well I'm running 700cc deutschwerks secondary port injectors and they require a 2.7 multipler to get a seamless transition from DI to 50% port at mild to moderate load ~2-3000 rpm. Very unexpected number but it is what it is! Means the theoretical capacity of the DI injectors are quite large, which they are I guess because of the massive DI pressure used to cram a shed load of fuel into a partial inlet stroke at high RPM on the 'right' side of cam timing and overlap.....

Testing under load pending flex map implementation.

Anyone have thoughts on secondary port injector ATDC timing as a starting point? seems to like about 520 ATDC or bottom on inlet stroke at light loads. Surprising as typically I'd find on the back of the inlet valve just before opening would work good (~350 ATDC / 450 BTC). Mind you the injectors are in plate between the head and inlet manifold so perpendicular to the port which is hardly ideal but underload probably won't matter too much.
stevieturbo
Posts: 1321
Joined: Sun Dec 07, 2008 2:04 pm

Re: N54 BMW DI injector size / secondary inj ratio?

Post by stevieturbo »

simple way to test.

Run the engine til warm on DI, blend map 0%

Then when warm, switch the blend map to 100% so it can only run on the port injectors, then play with the ratio until it is running pretty much the same as it was when on DI.

That will give some sort of starting point

50% should then share load equally between injectors if that's what you want at higher loads
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