Correct me if im wrong here regarding un loader spike setting. If a machine is billed as a 4400 psi unit, then when a gage is on it and the trigger is not pulled, is there supposed to be a 300 pound spike where it would read 4700 PSI at that time?
The good / bad news: you’re probably not pushing 4400 psi. Vendors would rather make a sale than provide you with accurate numbers.
GPM x PSI / 1100 = HP
HP x 1100 / GPM = PSI
HP x 1100 / PSI = GPM
Your rig is basically an engine & a pump. What are the model numbers on those components? It doesn’t matter at all what logos or numbers are on the ‘frame’. If you’re lucky, you have a Honda GX390 floating around in there somewhere.
There are solid methods out here for properly setting an unloader if you bypass to a buffer tank. If you don’t bypass to a tank, you are stuck with a gauge (like me). My hoses are rated for 4k psi, so I make sure the gauge never exceeds that just to play it safe & also, never reduce pressure by adjusting the unloader. Set it & forget it. Definitely not gospel, but just my 2 cents.
I have mine set by gage to where when I release the trigger, it returns to 4400 psi. When i got the machine, it would return to about 4700 psi. I tweaked it down just a little bit so it returns to 4400 psi, and everything feels more manageable. I reduce pressure via tip size and plan to leave the unloader alone. Right now I am struggling with SC tips as the 4GPM machine with 25025 tips is still reading about 3300 psi and etching concrete. Not related to the unloader post, just a comment.