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Fuel Pressure Vs. Injector Pulsewidth

Practical Diesel Tuning

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So in the videos before the LLY walk though Nick talks about raising the fuel pressure and not touching the injector pulse width unless the truck had bigger injectors. Yet in the walk though he doesn't tuck the fuel pressure and changes the pulse width.

These lines are taken from the Fuel Quty video.

"03:00 Ideally the only time we touch this table is when we make changes to the injectors.

03:04 If we've actually fitted a new larger set of injectors to the engine then we'd want to change the table vales to reflect those, the actual fuel flow of those injectors."

In the walk though

"25:02 OK next is fuel pressure and this is really for show on a stock truck, I don't usually make adjustments to these on stock injector, stock pump trucks."

I'm not sure if I am missing something or...I guess what I am asking is would you adjust fuel pressure or injector on time first?

Good catch Matrix,

The operative word is 'Ideally'. In the later trucks it's much easier follow my advice, pre-2006 may require some more cowboy-esq adjustments.

Normally I'd prefer to adjust the pulsewidth table so that the pw values correspond correctly to the mm3 injection amount. This usually involves rescaling the mm3 axis of the table out past the desired mm3 fuel rate. On an LLY this table is factory scaled to 120mm3 (if memory serves). I'd love to rescale the mm3 axis out to 200mm3. IF you're tuning with HPTuners or a hex editor you can rescale the table, but EFILive does not allow rescaling of the axis on these older trucks. For this reason, if you're tuning with EFILive on an LLY you will be forced to manipulate the pulsewidth table using the less desirable method.

Does that answer your question?

Sorry for the late reply. Yes that answers my question.

How do you what is your math for extending the mm3 axis? I mainly use EFI Live but I have been using a hex editor as of lately due to EFI Live limits such as axis.

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