Do gear reducers change the horsepower formula

[gear junkie]

So the formula......gpm x pressure divided by 1100 to get engine size. Do gear reducers and belt drives change that formula?

 

["Red"]

You'd think a "gear junkie" would be educating the rest of us. LOL

As for me, not a clue.

 

[tomtucson]

I say no, the formula was made for 3600 rpm small engines and won't change unless the engine speed changes. But remember the labeled engine hp is usually max hp, not continuous.

 

[Matty P]

So the formula......gpm x pressure divided by 1100 to get engine size. Do gear reducers and belt drives change that formula?

No.

I have a spare t9281 with a great drive on it, I've hooked it up to a 9hp and a 13hp, psi and volume was spot on with both.

 

[JDhomeservices]

I would think it would be a little different since belt drives turn at 1450 rpm and gear drives turn at 1750. Or so I've heard.

Sent from my DROID RAZR using Tapatalk

 

[Russ Johnson]

So the formula......gpm x pressure divided by 1100 to get engine size. Do gear reducers and belt drives change that formula?

First, forget that formula. That's unrealistic for a real world engine. A better formula is ([gpm X psi] / 1450) X 1.5.

Horsepower is horsepower. Belts, gears, and direct bolt ons won't change that.

 

[814jeffw]

Hey Russ,..with formula...[gpm X psi] / 1450) X 1.5,...does the 1450 part change if the pump being used is a 1750 RPM pump? Would it be: [gpm X psi] / 1750) X 1.5?

Jeff

 

[gear junkie]

First, forget that formula. That's unrealistic for a real world engine. A better formula is ([gpm X psi] / 1450) X 1.5.

Horsepower is horsepower. Belts, gears, and direct bolt ons won't change that.

why won't gears or pulleys change that? Riding a bike up the hill and you change gears? Is this right? What am I missing?

 

[gear junkie]

No.

I have a spare t9281 with a great drive on it, I've hooked it up to a 9hp and a 13hp, psi and volume was spot on with both.

Ok this one I can answer. The reason why is because pumps work off rpms to get the flow.....more rpms more flow. If both engines are running 3200 rpm, then the pump will produce the same flow as long as the engine is powerful enough to handle the pressure.

 

[Russ Johnson]

Hey Russ,..with formula...[gpm X psi] / 1450) X 1.5,...does the 1450 part change if the pump being used is a 1750 RPM pump? Would it be: [gpm X psi] / 1750) X 1.5?

Jeff

No, the constant divisor, 1450, doesn't relate to rpms at all.

why won't gears or pulleys change that? Riding a bike up the hill and you change gears? Is this right? What am I missing?

Same horsepower (legs), different gear ratios. You can change the rpms with different pulley ratios, but it won't effect the net horsepower output.

 

[WASH-IT H.B.]

do you need to factor in belt drive efficiency. www.gates.com/facts/documents/Gf000188.pdf‎

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[Ralph Q]

First, forget that formula. That's unrealistic for a real world engine. A better formula is ([gpm X psi] / 1450) X 1.5.

Horsepower is horsepower. Belts, gears, and direct bolt ons won't change that.

According to that formula a 3500 psi 4 gpm pump needs a 14.5HP engine. So should I be reducing my max pressure down to 3200?
And this 5gpm 3000 psi northstar pump I have, needs a 15.5 engine. I have been using it on a gx 390 and I had the unloader set for max 3000, though I rarely use 3000 psi, was I burning up the pump, or unloader? and what about my new 4.6 gpm 3000 psi pump ?
That formula says 14.27 hp ??? Should I adjust the unloader down? Russ if I get a few of those lifans 15 hp, is that a real 15 hp that will keep up with these pumps? I am thinking two lifan 15 hp and two ez3045g pumps will I get 9.2 gpm at 2800 psi at least?

 

[Russ Johnson]

Let's not forget, the pressure washer manufacturing industry has always adhered to a +/- 5% difference from advertised output.
95% of 3500 psi is 3325. 95% of 4 is 3.8. Plug these numbers in, and 13.07 is the magic number.
If you're running at 3,500 psi with a #4 nozzle, that is only 3.74 gpm.

 

[Ralph Q]

Let's not forget, the pressure washer manufacturing industry has always adhered to a +/- 5% difference from advertised output.
95% of 3500 psi is 3325. 95% of 4 is 3.8. Plug these numbers in, and 13.07 is the magic number.
If you're running at 3,500 psi with a #4 nozzle, that is only 3.74 gpm.

I dont even own a #4 nozzle, well I have some #4 megs for my surface cleaner. The most pressure I will ever need down here is 2800, if that.

I need maximum flow. What can I do to ensure that?

 

[Russ Johnson]

Any nozzle larger than a #45 will assure full flow.

 

[tomtucson]

First, forget that formula. That's unrealistic for a real world engine. A better formula is ([gpm X psi] / 1450) X 1.5.

Horsepower is horsepower. Belts, gears, and direct bolt ons won't change that.

I get the nod to electric motors, but why not just say divide by 967 instead of 1100?

 

[tomtucson]

GPM x PSI divide by 1450 for electric motor, 967 for gas engine - 850 for chinese engine? LOL. And what is the number for diesel? But then the engine labeled horsepower is not the actual running horsepower....

 

[Benjamin]

Yeah I was just going to say, that formula is good for gas engines, diesel and electric are different. Diesel and electric both have a way better torque to hp ratio.