This needs to be a sticky. Just discovered this calculator. Takes the guesswork out of reading a nozzle chart and figuring what your actual pressure will be with flowrates not listed on the chart.
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I use this one
I feel like that one’s pretty limited in its application. Did you check out the one I linked? It lets you run the calculations the other ways around, so you can determine:
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What your psi will be at a given gpm and orifice size, which would be useful for determining psi through a surface cleaner at non-standard flow rates
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Or what gpm is needed to generate x psi through a particular orifice, which could be useful for determining how much flow will be bypassed using a smaller nozzle
The one you linked is definitely more informative. I can’t remember the last time I used it . I just keep it bookmarked in my phone
This is the best I’ve seen. But you still have to know what you’re doing. What will happen if I put a #3 nozzle on my 4/4000 machine?
You won’t flow 4 and you’ll just create a excessive load. With that size orifice you’d need to get up to 7k psi to flow 4gpm and I don’t think your lil 11.7hp engine would be up for the task.
If your unloader is doing its job properly, you’ll bypass 1gpm and have 3 gpm @ 4000psi
Use the 3rd calculator on the link to figure out how much you’ll bypass with undersized nozzles. For instance, the 6.5 nozzles they sold with my 5.6@2500 machine will cause nearly a half gallon to bypass. (5.6 - 5.14 = .46)
I think I finally understand what an unloader does LoL!
I’m surprised they didn’t send #7 nozzles with your machine. I have the same pump as you do on a gx390 just gear drive…got 7.0 nozzles and set the unloader so only a trickle is coming out bypass line with high pressure tip.
Thanks for the calculator. It gives me a headache reading those charts.
