Piston moves up and down more times in one minute at 3600 RPM than it does at 3000 RPM therefore it travels farther in one minute.Double the stroke and multiply by RPM and you have the distance the piston traveled.Multiply that number by the hours in use at 3000 or 3600 RPM continuous and you will see a significant difference in piston travel.
Running engines at half throttle??
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ckr74
ArboristSite Operative
Dalmatian90
Addicted to ArboristSite
Skipping pages 2, 3, 4 after comments on the first reminded me of this:
RTFM
Was recently reading a lot on riding mowers, and more than one thread mentioned "Kohler engines habit of backfiring when you shutdown"
I'm rolling my eyes because if you read the Kohler manual, if you have a fuel shutoff solenoid, you leave them at full throttle when you shut them off or, as the manual warns you, they backfire.
Had a semi-portable pump at the firehouse that we were taught by one of the old timers "Always let engines like this idle down for a few minutes before shutting if off." Off course it would backfire, and eat about three belts a year. Until I Read The Fracking Manual which first the Kohler manual warned you full idle or it backfires, and the Pump manufacturer's manual that warned if it backfires often it'll eat belts.
Change to what the manual said, no more belts being eaten.
So either find the manual for the model engine you have, or at least narrow down the question to a specific make and model of engine because I really doubt every single one cylinder gasoline engine was designed to either be run WOT all the time, or variable throttle all the time.
RTFM
Was recently reading a lot on riding mowers, and more than one thread mentioned "Kohler engines habit of backfiring when you shutdown"
I'm rolling my eyes because if you read the Kohler manual, if you have a fuel shutoff solenoid, you leave them at full throttle when you shut them off or, as the manual warns you, they backfire.
Had a semi-portable pump at the firehouse that we were taught by one of the old timers "Always let engines like this idle down for a few minutes before shutting if off." Off course it would backfire, and eat about three belts a year. Until I Read The Fracking Manual which first the Kohler manual warned you full idle or it backfires, and the Pump manufacturer's manual that warned if it backfires often it'll eat belts.
Change to what the manual said, no more belts being eaten.
So either find the manual for the model engine you have, or at least narrow down the question to a specific make and model of engine because I really doubt every single one cylinder gasoline engine was designed to either be run WOT all the time, or variable throttle all the time.
You guys can't actually believe it's that simple?? That would only be true if all else remains equal.
If you have a piece of equipment that requires an 8 HP engine, which engine will wear out first... a 10 HP engine running at half throttle (translates to about 7 HP output)... or, a 8 HP engine running full throttle?? I'll give you the answer... the 10 HP running at half throttle will take a crap well before 8 HP running full throttle.
Wear is much more effected by load (or the ratio of load to output power), heat, lubrication, and the amount of fuel being delivered to the engine.
I guarantee if you take two identical small 4-cycle engines, run one at 3000 RPMs, the other at 3600 RPMs, and apply the same identical load to both of them... the engine running at 3600 RPMs will outlast the engine running 3000 RPMs. That's because the ratio of load to output power causes the slower running engine to work harder to maintain RPMs (the governor is opening the throttle more often and for longer periods), and the slower RPMs are delivering less cooling air and lubrication.
And if you ran them both with zero load on them... someone would likely be digging your grave before either of them wore out
Heck... I replaced the head gasket on my 35-year-old splitter engine a couple years back and you could still see the crosshatch marks on the cylinder wall.
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4-cycle engines do not run at "WOT"... the governor opens and closes the throttle as needed to maintain RPMs.
The only time the throttle goes "wide open" is when RPMs drop below the governor set point, and only stays there long enough to recover the RPMs... and it don't matter if the throttle (governor control) is set for half throttle or full throttle, the actual throttle still goes "wide open" to recover RPMs.
The manual for the Kohler engine on my grass cutter says to run the engine at off-load full throttle for a couple of minutes to cool the engine before shutting it down.
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Hey... how 'bout we get back to the OP??
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Yes... what you've "always been told by small engine mechanics" is true... always run your small 4-cycle engines at full throttle when on-load.
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Sawyer Rob
Addicted to ArboristSite
AND your answer to post #70 is?????
AND you can replace WOT with, wide open "governed" MAX rpm...
SR
ChoppyChoppy
Tree Freak
I have a Kawaski on my ZTR that backfires no rhyme or reason. Loud enough to have people walk outside to see what guns are getting shot (to compare to what they own of course).
I shut it off with an idle down. It's SOP for every engine I've run aside from gen sets.
I shut it off with an idle down. It's SOP for every engine I've run aside from gen sets.
How would things change if the govenor system was to be removed? My honda push mower has a govenor, and I run it at various throttle settings according to how much load the grass is creating. I do use full throttle when grass is thick and high but that is not always normal conditions. Model is HRU196.
It would over rev and explode.
This post??
First of all... no... you cannot replace WOT with wide open "governed" MAX rpm.
WOT means "wide open throttle"... maximum governed RPM (full throttle) can be just slightly off idle position if there's no load on the engine, or something more than that if the engine is on-load. The truth is... the throttle position is continuously being varied by the governor slightly... small 4-cycle engines are controlled by variable throttle position.
Now... about those inverter gen sets... and I didn't address it before because it gets highly technical, but I'll keep it basic.
First question for ya'... have you put a tachometer on your generator engine when you believe it's running at ½ throttle or less??
Inverter gen sets use a high efficiency alternator (rather than a generator) to produce a high frequency alternating current (much higher than 60HZ), which is then run through a diode bridge to convert it into D/C, which is then run through the inverter to convert it back into low frequency A/C (normally, very clean, 60HZ A/C). Those high efficiency alternators use magnets, rather than brushes... meaning very little resistance (very little load on the engine). The "load" (what you're powering) is placed on the inverter... only if the inverter needs more input to keep up with demand is load placed on the alternator. For all practical purpose, the engine is running off-load unless you place a very high demand on the inverter. The difference is off-load or on-load... there ain't a problem running less than full throttle when off-load... as I've said.
Not all inverter gen sets adjust the engine RPMs down during low load... many run at a steady RPM (whatever the specs call for, it ain't necessary for it to be 3600 RPMs because the alternator is high frequency, it ain't a 60HZ generator). However, those that use electronic modules (i.e. small computers) to control current and conversions will often also adjust the engine RPMs for low/no load conditions. Typically these RPM adjusting will be more expensive and often also use "special purpose" commercial engines designed to run in an operating range of 2000-3600 RPMs... or 2500-3600 RPMs... or even 2800-3060 RPMs (3060 is not a typo... 2800-3060 is a common "special purpose"). This is why you normally cannot go get parts for small engines using just the model number... you also need the spec number, or serial number, or whatever depending on manufacturer. The model number basically is the block/frame... it's the other numbers that determine what the engine is, and what its specs are.
As I posted earlier...
Dad's old pressure washer has a "special purpose" 3.5 HP Briggs on it... designed to run and produce peak power at 3000 RPMs per specifications.
The reason is the water pump bolted to it is rated for a maximum RPM of 3000.
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Sawyer Rob
Addicted to ArboristSite
I know how they work... and yes on the tach...
Point being, it doesn't need to be run fast to run cool OR last a long time (or use less fuel) WHICH is counter to what you've been preaching here! lol
SR
Point being, it doesn't need to be run fast to run cool OR last a long time (or use less fuel) WHICH is counter to what you've been preaching here! lol
SR
Glad Im not the only one.
What is it you don't understand about off-load and on-load??
Your engine throttles back because it's off-load... which is exactly what I've be "preaching".
Do you see the governor opening the throttle to maintain the throttled back RPM?? No, you don't‼ Because the damn thing is off-load‼
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NSMaple1
Addicted to ArboristSite
Loads aren't on or off like a light switch - they are variable. My genny throttles back with less load, throttles up with more. It doesn't wait until there is no load to throttle back.
If it's making HZ it's an alternator.Doesen't make any difference weather 50,60 or 400 HZ.
Unless it's an inverter generator, it's running at approximately 3600 RPMs all the time.
The governor opens and closes the throttle plate to maintain RPMs according to load... it may be "throttling back" under lighter load, but it's still running at maximum RPMs. The higher the load, the more fuel required to carry it... if there's no load the throttle barely opens past idle to maintain 3600 RPMs. That's why I asked @Sawyer Rob if he'd put a tachometer on his engine when he believes it's running at ½ throttle or less... a throttle plate half open on an off-load engine will cause the engine to over rev. Throttle plate position is relative to engine load, not so much engine RPM.
Not an exact comparison... but if you're driving your truck down hill (off-load) at 60 MPH you barely press on the throttle peddle compared to driving up hill (on-load) at 60 MPH. If the hill is steep enough you need no throttle to maintain 60 MPH on the way down (might even need brakes), and going up hill may require you to floor it (and you may still lose speed). On a small engine the governor takes care of the throttle position for you... kind'a like setting the cruise control.
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That's false.
An alternator produces electricity by spinning a magnetic field inside a stator winding.
A generator produces electricity by spinning an armature winding inside a magnetic field.
Alternators produce electricity on demand (they can put the driving engine off-load).
Generators produce electricity continuously (the driving engine is always on-load).
Generators need to be polarized... alternators do not.
Alternators are capable of higher output than generators.
And there's more...
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ckr74
ArboristSite Operative
The throttle plate is directly related to engine RPM. The purpose of the governor is to keep a constant RPM under a said load.
