Lawn Care Forum banner
1 - 20 of 78 Posts

·
Registered
Joined
·
521 Posts
Discussion Starter · #1 ·
Anybody like to run mowers at about 2/3-3/4 throttle? I'm talking about on midsized lots, 5k-12k sqft.
I feel like the mower cuts just as well in most conditions and maybe stripes better too. Definitely makes controlling clippings easier. And I think it saves me time. I am not sure how that's possible but I feel it's true... maybe because the slightly slower speed makes me plan better and use more deck width??
 

·
Registered
Joined
·
526 Posts
Well, I'm not a seasoned or factory-trained mechanic, but if you are referring to a ZT they function better when run at full throttle. At least that is what I have always heard over the years, and the local Scag technician told me that also.

If you are talking about a lawn tractor that may be another thing altogether.
 

·
Registered
Joined
·
521 Posts
Discussion Starter · #4 ·
Power curve for hydro drive changes very little. So wide open going forward isn't as fast as it used to be. But mowing at full speed and full throttle doesn't always make grass look so great anyway. Depends, I guess.

I think you're not losing a lot of cooling power. Air movement is like a liquid. Like rowing a boat. There's diminishing returns. Just sayin' I wouldn't sweat the cooking thing. (Also RPMs are lower, so less heat is being created, right?)
 

·
Registered
Joined
·
2,886 Posts
Power curve for hydro drive changes very little. So wide open going forward isn't as fast as it used to be. But mowing at full speed and full throttle doesn't always make grass look so great anyway. Depends, I guess.

I think you're not losing a lot of cooling power. Air movement is like a liquid. Like rowing a boat. There's diminishing returns. Just sayin' I wouldn't sweat the cooking thing. (Also RPMs are lower, so less heat is being created, right?)
When running lower rpm's the hydros still work, but not nearly as responsive. Cant say I ever feel the grass looks better at lower rpm's either. The blades need to stand it up to give it a clean even cut, cant do that if your limiting their ability. The engines, and overall machine is designed for 3600 rpm on every mower Ive looked into.

The 1 time I do throttle down is when mulchin leaves in the fall. If I run full rpm I get more blowout, and leaves dont get sucked into the deck as well.
 

·
Registered
Joined
·
25,106 Posts
I generally recommend running the machine at WOT, but now and then I do lower the throttle and my cut looks just as good as at WOT, except when the grass is really long or lush. There, WOT makes a noticeable difference. For normal summer months though, 2/3's works fine if you choose to go that route, and in my case, my hydros are just as smooth and responsive at that speed as at wot. These are all things I have paid close attention to while running less than WOT just to see if I could detect any difference.

It's true these machines are designed to operate at peak performance at WOT, but backing off a little in most situations doesn't change a thing that I have ever been able to detect and in wet conditions, lowering the throttle can help a LOT.

Just my own personal experience. It's worth what you paid for it........................
 

·
Registered
Joined
·
7,826 Posts
Power curve for hydro drive changes very little. So wide open going forward isn't as fast as it used to be. But mowing at full speed and full throttle doesn't always make grass look so great anyway. Depends, I guess.

I think you're not losing a lot of cooling power. Air movement is like a liquid. Like rowing a boat. There's diminishing returns. Just sayin' I wouldn't sweat the cooking thing. (Also RPMs are lower, so less heat is being created, right?)
Winner winner. The only time I throttle down is in a few places with lots of bare spots that make tons of dust.
 

·
Registered
Joined
·
8,568 Posts
I feel like the mower cuts just as well in most conditions and maybe stripes better too. Definitely makes controlling clippings easier. And I think it saves me time. I am not sure how that's possible but I feel it's true
Sure is lots of emotions here. But no real facts.
If you FEEL it saves you time, but aren't sure, break out the stop watch and verify.
Reminds me of when my Daughter went to college. They were taught to say (I feel, I believe, I think).
In order to not (offend) what someone else may (feel, believe, think). Facts took second fiddle to feelings.
 

·
Registered
Joined
·
2,649 Posts
Sure is lots of emotions here. But no real facts.
If you FEEL it saves you time, but aren't sure, break out the stop watch and verify.
Reminds me of when my Daughter went to college. They were taught to say (I feel, I believe, I think).
In order to not (offend) what someone else may (feel, believe, think). Facts took second fiddle to feelings.
I think and feel you're correct!
 

·
Registered
Joined
·
662 Posts
I throttle down quite often actually. For starters, it saves fuel.

Our modern mowers decks move a ton of air - more than needed in many circumstances to lay down a clean cut. If you're not in heavy, thick, tall grass, and you're baldes are still sharp, you don't really need all 18,500 ft/min blade tip speed to cut the grass cleanly.

Chances are, you wouldn't be mowing full-sticks anyway. So if you lost a couple mph at full-stick, you'd never even notice.





Regarding the motor cooling, again - If you're not in thick, heavy, tall grass, or climbing an extremely tall hill - applications where the governor is truly at wide-open-throttle - then you don't need to worry about all of that cooling air.

I wonder sometimes if people don't understand how the governors work...

The governor steps in to CLOSE THE THROTTLE PLATE inside the carburetor/throttle body, to regulate the engines RPM. If the throttle plate is partially closed, then the engine is only consuming a fraction of it's maximum air & fuel - yes, even at the full 3,600rpm. If the engine is not at 100% load, it's not making 100% heat, and 100% cooling is not necessary...

It's only when you introduce a heavy load on the engine - tall, heavy, thick grass, or large inclines - where the motor begins to bog down, and thus the throttle plate is allowed to open fully, where the engine is under 100% load. Only when the throttle is truly fully open, is the engine under 100% load, which calls for 100% cooling - via engine/fan speed in this case.

ALL THAT TO SAY.... If you're not lugging the engine in overgrown grass, you don't truly need the full 3,600rpm to keep the engine cool... This is simply thermodynamics & heat exchange...




And perhaps, one last example before people combat this argument with their feelings & what some dealer told them. - IF this is such a big deal, somebody needs to call eXmark & Kohler, and let them know that their RedTech throttle control is doing it wrong...
 

·
Registered
Joined
·
2,649 Posts
If all our mowers were nuclear powered...... just sayin'. 😟😟😟
 

·
Registered
Joined
·
521 Posts
Discussion Starter · #13 ·
Sure is lots of emotions here. But no real facts.
If you FEEL it saves you time, but aren't sure, break out the stop watch and verify.
Reminds me of when my Daughter went to college. They were taught to say (I feel, I believe, I think).
In order to not (offend) what someone else may (feel, believe, think). Facts took second fiddle to feelings.
Fine point. I wrote "I feel" because I didn't have exact numbers yet. But based on minutes on each site there's a chance I'm losing very little time. I'll consider tracking time for several and compare them week to week.

The "I feel" statements are not a current trend at colleges, except when discussing sensitive personal or cultural topics. But when writing research essays students are sometimes encouraged to note their personal bias or interests in the topic, usually in their conclusion or their abstract. Even before the days of Jane Goodall's chimps, academic writing has struggled with how to approach this. The answer is different for different disciplines, but they all have trouble with responsibly identifying bias. Long ago I worked as a research assistant for a medical school prof at a top tier college, doing economics/med research looking at pay-for-performance to increase effectiveness of doctors. And that person definitely had a bias in what she hoped the results would show. There was also a rush to publish to avoid getting "scooped" by someone at Harvard or wherever.

Anyway, blade speed is not the same across mower brands, and also changes based on blade length... AND changes based in blade lift. Right?
So running wide open probably can make a difference for lifting grass, but so can about 3-5 other things.
 

·
Registered
Joined
·
662 Posts
Anyway, blade speed is not the same across mower brands, and also changes based on blade length... AND changes based in blade lift. Right?
So running wide open probably can make a difference for lifting grass, but so can about 3-5 other things.
Blade speed is fairly close among the major commercial brands. Between 18,000 - 19,000 ft/min seems to be the range most shoot for. They change pulley diameters for the blade spindles based on blade length, to achieve the necessary blade RPM to hit that 18-19k ft/min tip speed.

Blade lift/sail height does not = tip speed. Blade length x RPM does. Sail height changes the "lift" & airflow through the deck at speed.




Bottom line...

Anyone running a commercial mower 15 years old or newer, can safely throttle down to 3/4" throttle in light cutting conditions, and likely lose nothing in terms of cut quality. Only if your mower has a very slow ground speed, would you notice any loss in "performance."
 

·
Registered
Joined
·
624 Posts
First off, we are saying throttle, but what we are really changing is the governed RPM. The governor controls the actual throttle to keep the engine at the desired rpm.

I have thought about this. First off, the manufacture is going say run it at full RPM. But I feel the there may be some benefit running it at lower RPM when under light load.

The main concern is cooling on air cooled engines, because the flywheel fan turns at engine rpm (of course).

So if it's a light load, I feel like you can run at less than full throttle to save fuel, but under heavy load, your going to need the increase fan speed to keep it cool..

What's needed is a head temperature gauge, so if the motor runs hot, you can increase the engine RPM.

On a water cooled engine, I don't see why you couldn't safely run at the lowest RPM that produces the power needed to cut the grass.
 

·
Banned
Joined
·
1,290 Posts
First off, we are saying throttle, but what we are really changing is the governed RPM. The governor controls the actual throttle to keep the engine at the desired rpm.

I have thought about this. First off, the manufacture is going say run it at full RPM. But I feel the there may be some benefit running it at lower RPM when under light load.

The main concern is cooling on air cooled engines, because the flywheel fan turns at engine rpm (of course).

So if it's a light load, I feel like you can run at less than full throttle to save fuel, but under heavy load, your going to need the increase fan speed to keep it cool..

What's needed is a head temperature gauge, so if the motor runs hot, you can increase the engine RPM.

On a water cooled engine, I don't see why you couldn't safely run at the lowest RPM that produces the power needed to cut the grass.
You do understand don’t you that until recently, most all engine fans were motor driven. A lot still are. The ones that aren’t are typically thermostatically controlled to only kick on at certain engine temps. Your fan statement is null. Air cooled or not, the fan is only going to run to match the engine speed and load.
 

·
Registered
Joined
·
2,649 Posts
If guys paid as much attention to their books....
 
  • Love
Reactions: JawT

·
Registered
Joined
·
624 Posts
You do understand don’t you that until recently, most all engine fans were motor driven. A lot still are. The ones that aren’t are typically thermostatically controlled to only kick on at certain engine temps. Your fan statement is null. Air cooled or not, the fan is only going to run to match the engine speed and load.
.

1.The fan on a typical small air-cooled engine is on the flywheel, runs at engine speed.

2. The faster the engine turns, the faster the fan turns.

3. Typically, the more RPM a fan turns, the more air it moves.

4. The more air the fan moves, the more cooling it can provide.

5. There is a point where the engine is at it's torque max, where it can produce more heat at open throttle ( not governor, but the actual throttle) than the fan running at that RPM can dissipate.

6. It's for that reason, among others, that the manufacture recommends you to run the engine at full RPM

7. The fan does not "automatically" match the cooling load.
 
1 - 20 of 78 Posts
Top