I’m not an not an engineer in fluid dynamics and certainly not an expert on RZR fuel systems.
But I tend to think that a regulator, whether gas, liquid, or voltage, is supposed to regulate!
I would expect a regulator set at 39 psi would have a supply of greater than 39 psi.
The regulator would then allow pressures of 39 lbs of less to go to the injectors. Any pressure over 39 would open the internal valve and allow the excess to be bled off back to the tank through the fuel return line.
To maintain pressures of 39 psi during full throttle, the pump would have to be capable of higher pressures. I would expect a flow of fuel returning to the tank with engine off or at idle, meaning that you would have a minimum of 39 psi and the regulator is regulating!
If you have a weak pump as the injectors open, the pressure would drop.
Trying to reason through this.
My 08. 800 Boggs down at about 30 mph up hill and is getting worse. Just replaced tank and pump with aftermarket parts about 300 miles ago.
I’m going to build an inline gauge set up to monitor the pressure under load. I will let you know what I find out.
Any thoughts on my analysis, let know.
Clint