The con: At the risk of boring some folks, I guess it goes back to the basic reason of running a rising rate in the first place. If you are running say 40 psi fuel pressure, the injector flows fuel as sized...... Now you add say 10 psi of boost inside the throttle body pushing back against the fuel coming through the injector, the net result is only 30 psi (40-10) of fuel equivalent is getting through. To get more fuel flow into the TB now, the injector has to be open much longer each cycle. It could be easy to run out of time if the injector is stock.
One pro to NOT running rising rate would be in the fuel pump supply curve. I've done some simple, cheesy bench tests of the stock fuel pump and a battery. When I set the regulator to 45psi the stock cat pump(M7 or M8) would flow approximately 30 gal per hr. When I set the regulator at 55+psi the same pump would only flow about 20-25 gal per hour and it took about 25-40% more amperage to do it. 30 gph of fuel is good for approx 300hp, but 22gph is only good for a little over 200(approx.)
So if you don't do rising rate you have more fuel available, but the injector may not be able to flow enough at the effectively lower pressure it sees.
If you have rising rate.... the injector can flow more fuel, but the well might run dry either because of fuel flow drop or/and voltage drop due to high current needs.
Now enter aftermarket fuel pumps and 4 injector systems....virtually no worries about fuel starvation......and the addiction grows and grows :face-icon-small-win
That would be a 1:1 fuel pressure regulator, which is standard on most return EFI systems to keep constant base fuel pressure at all times, whether under vacuum, atmospheric pressure, or boost. 5 psi boost=5 psi increase in fuel pressure to compensate.
A rising rate FPR, will have a ratio of say 10:1. Out of boost it will act like a normal FPR to maintain base pressure. In boost, it will increase fuel pressure 10 psi, for every 1 psi of boost, which is a very crude way of increasing fuel flow for boost. So 5 psi boost= 50 psi increase in fuel pressure. So running 43.5 psi (3 bar) base pressure, and 5 psi boost on a 10:1 FPR, will result in 93.5 psi when under boost, for your fuel system designed to run on 43.5.
Increasing fuel pressure only increases flow by the square root of the difference. So although you over doubled the fuel pressure (93.5/43.5=2.15), you are only flowing sqrt(2.15)=1.466x as much as you were at 43.5 psi.
This also puts your fuel system under tremendous strain as it wasn't designed for this, and if you get too high of fuel pressure, it can hold the injectors shut.
