Calculation Injector Pulse Width

Hi, How to deal with the pressure in the manifold?

Example: We need more fuel when the engine is at 6000 rpm in 5th gear compared to when the engine is accelerating in first gear.

Am I wrong?

What changes should I do in all the calculations respect to map pressure?

The "Differential Fuel Presssure" is the difference between manifold pressure and fuel rail pressure. If your fuel pressure regulator has a connection (hose) to the manifold then it should maintain constant differential pressure as the manifold pressure decreases (throttle not fully open), or the pressure increases (due to forced injections. You set the fuel pressure at the regulator when the engine is stopped, and this becomes your differential pressure.

The advantage to doing this even with normally aspirated engines is that a 10% change in fuel pulse width will result in a 10% change at all manifold pressures -- so compensations are much more predictable.

A simplified fueling model says that twice the air (manifold pressure) will require twice the fuel -- so if you're looking for something to calculate -- try that.

BTW - I don't agree with your assertion that the fueling will be different at 6000 RPM in two different gears. If the load is the same and the RPM is the same, the same amout of fuel will be required to deliver desired mixture.

Hi David, regarding the example of the 6000 rpm, I mean 6000 rpm at different loads, but I will follow the advice about double the load, double the fuel PWM