Nozzles and unloaders

Alright, so I understand that undersizing your tip when using a trapped pressure unloader is bad for the unloader because it never really gets to fully unseat, but about flow sensing?

Ok, so I have tips for running my machines at really low pressure for sensitive property when I am more or less soft washing with low enough chemical concentration that I don’t have to use the diaphram pump to put it on. I have nozzles for running my machines at around 1000 for stubborn wood, brick, ect…

But now it’s time to get some high pressure tips for cement work. I’m thinking around parking stops and curbs where a surface cleaner doesn’t get to. 8.5 gpm at 3500 puts me at a 9.09. A 9 would put me at 3567, just a scooch over what my pump is rated for, so with a trapped pressure unloader, I would definitely go with a 10. But will undertipping damage anythi g woth a flow sensing unloader?

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You are making it way more complicated than it needs to be. the bigger question here is, where did you get a custom machine that puts out 8.5/3500?

Flow unloaders are meant to bypass approximately 5% of the flow. Subtract 5% from 8.5 gpm and I bet that puts you right at 9.0 or a little smaller for full pressure tips.

But I’m also curious what you’re using to drive that 8.5@3500


Probably the Isuzu 4LE1 he mentioned in another thread.


Muscle’s got it right. It’s a 4 cyl industrial diesel. It’s paired with a tsf2021 that is also on the way.

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I’m leaving a few horses on the table, but not many if I’m running at the top of the torque curve for maximum longevity. Should be quite the efficient machine if i can ever get the dedgum suppliers to live up to the written quotes they gave me.

And yes, I over complicate things sometimes. I just like to know things I’m doing inside and out. An answer of, “this is one of those good-enough’s good enough situations” is entirely acceptable. I understand that reality and theory don’t always line up. It’s one of the advantages of being a mechanic/millwright as opposed to an engineer. For example: you learn when it’s best to just overbuild (increase service factor) as opposed to trying to save a nickle by going with the straight calculations.

(Though honestly, engineering still sounds like a ton of fun. Half the fun of a project is the design decisions)