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Tuning on VE instead of Pulse time

EFI Tuning Fundamentals

Discussion and questions related to the course EFI Tuning Fundamentals


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Is there a good resource for conceptual and mathematical conversion into a VE table based Standalone? I greatly enjoyed the class but do not have a 100% feeling as to how this part of the practical application works.

Can you elaborate?

VE is really simple to understand. It's a ratio based on basic data that you provide to the ECU.

On some ECU, you set your engine and injectors size and that give you a master pulse-with (I'm gonna call it MPW for sake of simplicity), on other you have to do the math yourself to get that value.

If you had absolutely no correction: 100% VE = MPW.

The big advantage is, if you change the injectors you don't have to redo your whole fuel table, you only have to change the values related to the injectors (so injector size or PW, and the dead time / small pulse table)

As for the mathematical conversion, it can be a little bit tricky depending of the data you have.

Let say you got a 5.7L V8 engine with 28.6lb/hr (300cc/min) injectors (<-LS1)

That give you a MPW of 15.8ms.

At that point, if you have 15.8ms in your fuel table you could think this is 100 VE, but like I said there is corrections.

The two most important would be the dead time, then the MAP pressure.

your PW = MPW x VE x MAP / Atmospheric Pressure + Dead Time

Now let say you have a 65 VE at 7psia (50kpa) and the injector dead time is 1ms:

15.8 x 0.65 x 50 / 100 +1 = 6.135ms

PS: the RPM isn't a part of the VE equation, but keep in mind it give you the duty.