Lower revs question

Hey all,

Not sure if anyone knows, but -

Will downstreaming at half the normal engine speed (GX390 in this case) impact the chemical draw rate negatively?

I have to clean some pensioner homes and would like to know if running the engine at half speed (noise purposes) would reduce the soap :slight_smile:

Not at all. Don’t run it too low, keep it in it’s torque band to protect engine. But 1/2-2/3 should be fine.

That’s great! Thanks @Racer

I’ll just get half the amount through at the same mix, right?

So at 1/2 throttle, I’ll get 2GPM at the same mix ratio at 4GPM. Might even help with this particular job, having less flow.

Thanks again!

Some claim it’ll help your mix be a little stronger but I’ve never tested that so can’t verify. Maybe someone else has. You could test it yourself.

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Lower gpm machines draw better with an xjet. Don’t know about injectors. If your machine is air cooled make sure you don’t run it long at low idle


I know your opinion on ball valves. But let me pick your brain on something anyway. If I restrict the flow at the gun with the ball valve(reducing gpm), shouldn’t the xjet draw more chemical:water?

I don’t know. A ball valve is made to be opened or closed. I can’t offer advice on unsafe practices

Lol, ok thanks anyway

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Sounds like you need to set up a roof pump or a small, portable chem pump, which you can do very inexpensively…That’s a much better option than endangering your machine and giving yourself headaches trying to get the x-jet to do more than it was designed to do.

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Yes, it will work. No, I don’t recommend it. William and Jesse are right. Better tools are available for the job.

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I have a 12v system. Just thinking theoriticals and regurgitating stuff I’ve heard elsewhere.

I’ve always wondered if rinsing flatwork with the ball valve causes too much restriction and bad for the machine. I use the ball valve to rinse 100% of the time. I have t found anything that comes close to being as efficient

That will create more back pressure and reduce the draw from your chemical injector. My Landa came with a valve that I can bypass water after the pump reducing the volume going through the coils so I can get the water even hotter for sticky situations.

Sorry I just went back and read that you were talking about an x jet


Harold rinsing with a ball valve won’t hurt ur equipment at all. Just the extra water gets bypass into the tank no different then using a 2.1 orfice extra water just gets bypassed. And since u use a K7 unloader u don’t get the jarring and pressure spikes. That’s what’s bad on equipment. Rinsing with the ball valve is the way to go munch more efficient :+1:

With a positive displacement pump, the ball valve won’t reduce the flow unless you reach the psi your unloader is set to, it will just increase the pressure, and it won’t draw chemical. The pump produces XX gpm @ XXXX RPM, no matter what. unless you exceeding the set psi, then it bypasses. Think about it, it pumps the same amount of water through that tiny hole in your tip and it does through an open hose.

Also, reducing the RPM is no problem at all at low pressures. But not good at all at high pressure. A gx390 produces 13hp at around 3200 rpm, at 1500 rpm is only produces about 7hp. The problem comes when you let off the trigger or close your valve at low rpm, the pressure tries to rise to the set psi, so it can bypass, the engine doesn’t have enough HP to make that much psi, and it stalls instantly. This is VERY BAD on your lil Honda!!!

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Wow. I was wrong, less than 5hp!!!

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Think Harold has the same pump as I do general 8.5 gpm. With a 2.1 orfice I am getting 7.5 gpm and with a 2.3 I am getting 8 gpm. If I don’t draw water through my injector. So if I installed the 2.1 mm orfice while running my burner it will get as hot as possible. Would be bypassing one gallon.

I think that makes sense. Lol! The slower the water flows through the coil the hotter it would get. Until it hits the high limit temperature. It just seems like it would create lots of extra wear on the unloader bypassing all the time. That’s just a guess on my part though.

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Yes sir it is bypassing the water before it enters the coil👍 will get about 7 more degrees.

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