Also if your base PSI is 43.5 is this with the vacuum line connected or disconnected
Quote from 034 Motorsports:
From the Sym Tech Lab site:MAIN FUNCTION
A FPR's main function is to maintain a consistent pressure differential across the injectors and the intake port pressure. What causes fuel to spray out of the injector and into the intake port is the fact that pressure is higher inside the injector than inside the intake port. For example, if base fuel pressure desired is 43.5 psi (a very standard 3BAR), then in order to deliver a consistent flow of fuel to the engine, a pressure differential of 43.5psi must always be maintained.
What this means is that during vacuum conditions, the manifold reference will actually lower fuel pressure as the intake is literally trying to suck the fuel out of the injectors. Under boost conditions, fuel pressure will be increased at a ration of 1:1, again, to maintain the reference, thus under 10psi boost, gauge pressure will be 53.5psi but the actual differential will still only be 43.5psi.
This is the most misunderstood function of the EFI bypass regulator, if you can wrap your head around this concept you'll understand the function of this part.
What kind of fuel pressure regulator should I use?
There are two main options, an adjustable 1:1 regulator and a standard static regulator.
The 1:1 regulator is the best choice for turbocharged vehicles as it increases the fuel pressure by 1psi for each 1psi of boost pressure. This feature balances manifold and fuel pressure which creates more headroom. You can also alter the base fuel pressure to perfectly dial in your fuel injectors. In other words, “you’ll get more out of your injectors.”
Adjustable fuel pressure regulators in other ratios (4:1, 10:1, 12:1, etc.) aren’t recommended.
Static regulators are best suited for naturally aspirated vehicles or turbocharged ones with low power goals (~300whp or less). Since they’re not adjustable and the base fuel pressure cannot be lowered, very large injectors are somewhat more difficult to control at idle. Also, since they don’t increase fuel pressure, less fuel will flow into the manifold for a given injection unit while in boost.