I know the old formula to figure out psi,gpm, hp required.
There’s a place in florida claiming to sell an 8gpm @ 2500 PSI with a GX 390. There’s also video of it achieving 2500 psi. So if it’s an 8gpm pump and there’s videos of it at 2500 psi then what’s the argument it’s not true?
Now we’ve always been told that the gpm won’t be affected, but the psi will be when required hp isn’t there.
There claiming that with a 1750 rpm pump and certain pulley sizes is how they’ve achieved it.
This is what the owner said when someone was skeptical about the specs:
” on older model pumps that run at lower rpms, these specs cannot be achieved.
1750 rpm pump with correct pulley ratio and increased pump piston stroke and bore make this machine setup capable of producing these specs.”
That Comet pump is a 8035 model that does run at 1750rpm rather than 1450. If the gx390 is modified then it is possible. Not sure about reliability though.
If they are under-running the pump so it’s putting out around 5.5-6 gpm, it will easily hold 2500 psi with a 13hp engine.
My inner cynic is saying that’s what’s happening here, a bit of slight-of-hand. I’d like to see a bucket test, as well.
The bit about “selecting the proper pulleys” seems suspect. It’s an odd inclusion of superfluous information. Of course you have to select the proper pulleys to run it at the rated rpm. But if you select different pulleys to run it a little slower, you can manipulate your test results.
I thought I put it in my last response but guess I didn’t…I think to be legit he should do a bucket test like others have mentioned. If it’s 8gpm…good for him. Still, that gx390 has to be putting out 18+ hp to run that pump.
I still wouldn’t buy it. It’s like buying a modified Civic running 300 hp (back in the day)…as soon as you start modifying things…stuff goes wrong. I used to modify turbo cars 20 years ago…there were plenty of days where I wished I would just left it stock.
Hey @Patriotspwashing I saw this too. I’m thinking about going down there Monday and checking this dude out. He did post a bucket test video. I can figure out how to get the link copied but I took a screen shot. The big bucket he said is 6 gallon bucket and the small is 5 gallon. And I think they are using 10gpm tips, 10010 tips ! image|281x500 maybe?
I know it’s not the same numbers but I just put together a 5gpm 3500 Udor on a gx390. It actually puts out a solid 6gpm and when I put a psi gauge on the end of the ball valve it shows exactly 3000psi. I set the unloader so that when In use it just sprays out a little like ibs suggests. With the formula those numbers shouldn’t be possible either but that’s what it is. 200 ft of hose too.
I spoke to sales rep from Udor last week about putting an 8 gpm on a gx390. He said the pump will put out 8 gpm no matter what the engine horse power is but the psi will be significantly lower. He said it will put out 8 gpm on a gx390 but he didn’t know what how low the psi would be. I’ve seen posts and videos of guys getting 1800 psi.
Did he work for Udor or a vendor who sold udor? There are very few udor sales reps. It is a misnomer to think that a certain gpm pump will always flow it’s stated speed, and that only t hg e psi will change. Very few people have actually ever done a bucket test using both pressure and gpm. It almost had to be done into a bucket with a lid because of over spray or with a pitot gauge
This is my local dealer! I’m actually set my hand on that unit. Never seen it run. I’ve talked to him about it and it seems legit. However I must say it’s been there awhile so I think many are skeptical. I believe he told me they modified the engine. My fear would be the mower not holding up for a long time.
