Fuel injector sizing

[jazzyjay]

We all have seen the formulas that calculate the injector size based on crank horsepower. While looking into new injectors for a friend, I noticed the injector size is based on the base fuel pleasure at idle. That is good for NA car but we are boosted. Most people have 1 to 1 fuel pressure regulator, at 30 psi of boost you will have a fuel pressure of 73 psi if your base is 43 psi at idle. In turbo cars horsepower is in directly relation to boost. With that being said, why don't we put in our target boost plus base fuel pressure at idle, to get injector size or maybe it's just me I might be that football season is over and its sunday but this made me think

 

[steve]

With that being said, why don't we put in our target boost plus base fuel pressure at idle, to get injector size?

Because the base pressure never changes, it's the constant pressure difference between the fuel rail and the manifold. That pressure difference is what causes flow and since it doesn't change neither does the rate.

So you rate the HP your injectors can support at the base fuel pressure value (their effective flow rate).