Mowing, full throttle or half?

[MalMac 1,328]

Lot of ideas and opinions floating around here. One thing not really mention was not just the motor was design to run at Full Throttle but parts and attachments were design to run for the most part at that RPM to. There may be one or two attachments that might not work best at 3600 rpm but most of them were design to run there and they give there optimal performance there. Same goes for parts. Other than the motor the hydro was design to run at full throttle, anything less and your not getting the cooling and pressure it was design to run at.

I am not for or against Engineers here, They do their share of making mistakes. Guess I have to trust all the number crunching they do must be for something. Like most of the other post this is my opinion, but I based mine on what I have read from the people that built the thing. I figured they must know more than I do. It's thier baby they should know what makes it work best and what does not.

[Wade 9]

Good Morning

This is a good conversation. I work with a Project technician ,who worked for Kohler in there Engine Test and Development area. The comment made "ya know, these engines are only designed to spin around just so many times, so why subject them to higher speeds when you don't need to". He is right. when my co-worker was part of a development team John Deere wanted an Engine that would last X number of hour's. There deck was designed to last x hours. Well it turned out Deere wanted the Engine to fail approx.. half a year bore the deck's life was designed for. For obvious reason's negative public relation's Kohler s not going to be part of that. I have had three different brands. Kubota G3200 Diesel required full throttle when cutting lawn or it seemed to cause a weird harmonic's in the belt that drove the blades as well as the drive shaft to the mower ck. The Old C-120 8 speed was usually run at three quarter throttle for normal 1"-1.5" cut. This was a 36" three blade side discharge. I should mention I had the tractor in second /high gear That tractor is from 1978 or 79 and was used for the normal Central Wi. summers. for aprox.12 years with out ever having a Engine problem. I still have it today and use it for grading my 1/8" mile drive way. The 540X Deere water cooled 54" deck works best at full throttle or you ended up with a poor cut. How ever that engine when started gives you a nice puff of smoke when started cold. Oil Smoke. I have 430 hours on that and most were from the previous owner. I did some research and that smoke condition seems to be the norm for that engine even a very low hours./New. I will ,if time allow's doing some Temp testing on one of the other's 312-8's when I cut.

Have a good weekend !

[Mike 6]

also ran my splitter for 20 years fast idle 

[Catmanii 36]

Wow! I didn't mean to cause a big debate on this. Sorry guys.

Don't be sorry, this is a good post. Learning is what it is all about. I never run any of my equipment any harder then I need to. I mow the yard with a box store Cub Cadet at WOT because that is what it takes to cut the (hot and dry) tough grass in the yard. Because of the sand and high RPM's the blades only last 30 hrs before they have to be changed due to holes in the metal. The C-120 pulls a small Bush Hog for the outer yard (Stumps) at about 3/4 throttle in high first gear with the Honda on the Bush Hog at WOT spinning a single (Very heavy) 42" blade. The C-175 is the garden tractor and only runs at WOT when pulling the plow. For everything else it is run at 3/4 or a little less. Been working well for yaars with no problems.

[Geno 1,928]

Wow! I didn't mean to cause a big debate on this. Sorry guys.

 

We live for this stuff, thanks for starting it. 

[JC 1965 1,528]

I don't get not running at full speed for cutting grass. Here in GA, our grass gets dry and tough and even with sharp blades can be hard to cut unless you drive slow.  I wanted to be able to cut grass in high 3rd with my 160 so I upsized the pto pulley to spin the blades faster.  I set the high idle speed to 3600-3650 with a tach and keep it that way when mowing. For other lighter jobs, its set to give enough power for what I'm doing. As far as splash lubrication in these motors, I can promise that there is plenty of oil flying around inside at the 1200 rpm idle speed if the oil is full. Imagine dipping into the oil 20 times a second. Oil everywhere.

 

Could you give me more info on how you up sized the pto pulley ? What size did you up size to ? I assume you had to go to a longer belt, if so what size ? Any info you can give me would be appreciated. I would like to do this also if it isn't to complicated.     Thanks !!

[pacer 3,159]

Well! - this HAS turned into a quite lively and interesting post, thanks for starting it all off Jasen.

 

So, with there having been several mentions of "splash" lubrication reminded me of another application of this.

 

Another of my hobbies is restoring metal machinery and in lathes many of the mid sized and up has splash oiling. I got a 13x36 South Bend lathe that went thru Katrina - I initially though it was a hopeless case! The gear box in it is splash and it had sat for months with who knows what kind of liquid concoction in it and this was a concern if it was damaged beyond use. On disassembling and replacing some 20 bearings and clean up, I needed to view the workings of the guts so I left the cover off and turned it on - luckily I had installed a VFD (variable speed) and had it set for about 100-150rpms --- :eek: oil vomiting out the top!! To view the operation I had to run it at around 20-30rpm.

 

So, to sum up this long winded, somewhat off topic post, I dont think low rpms - say typical idle in 800-1000rpms - would would be much of a factor in oiling.

 

Here in N La we have Bahia grass and it is horrible to get a clean cut - in the areas of my yard where this stuff is, yes, I do indeed run the horses at WFO!

Edited September 5, 2014 by pacer

[Theroundhousernr 589]

   My hydros get run at WOT to keep them cool . They tend to groan at anything less especially with my huge hill yard. That being said my 520h I run at 3000 to 3100. Seems to be just enough to keep the hydro quiet and the grass flying. Runs fine and takes no oil. Does not smoke either. Motor is approaching 1150 hours. Oil change every 25 hours and filter change every 50 hours.

 

  Gear drive tractors I just use as tugs around the yard. Pulling trailers, logs, etc..... They get run usually at half throttle. I usually only go small distances and if I am pulling hard enough to hear the motor lug, I might give a little more throttle. That's just me though.

 

  I look at it as , generally a motor has an average running temperature at said RPM with no load. If a load is added at a low RPM greater than the hp being made at said RPM , heat will rise. So a higher RPM is needed to force more air over the cylinder and produce more HP to lessen the load given. Also , I believe in the theory of bearing surfaces in the motor are only going to spin so many times before wear tolerances are met due to heat and friction.

 

  So if its a Hydro, you will be catering to its needs and WOT will be needed for pump pressure and cooling. Gear drive you have some flex to your RPM's. I say just give what your motor is asking for. I am by no means saying just idle around the yard all day either. Its good to open them up ,burn off carbon and not lug them like a diesel.

 

  Look at generators. Many of the generators where govern to run 2800 RPMs. Less fuel consumption , noise , wear , etc..... But how can they do that , its not 3600 RPMs !!! Well the motor was chosen by its HP rating at said RPM and was matched to the max generator load. Which goes right along with the way I treat my garden tractors. Some had larger cooling fins on the flywheel , but that was a double edge sword. To move more Air meant more HP= less for electricity. Most have standard flywheels.

 

   That's my story and I'm sticking to it! lol
 

Edited September 5, 2014 by Theroundhousernr

[546cowboy 301]

Another thing I didn't see anyone mention was that with a hydro you need to run WOT or risk damaging the pump. I see that was stated in the post above no that I looked again.

 

Another thing with a hydro you don't have to worry about what gear to put the tractor in since forward speed is controlled by the motion lever.

Edited September 5, 2014 by 546cowboy

[tbarnhart 240]

Could you give me more info on how you up sized the pto pulley ? What size did you up size to ? I assume you had to go to a longer belt, if so what size ? Any info you can give me would be appreciated. I would like to do this also if it isn't to complicated. Thanks !![/quote

I don't have any pictures with me now, but if you search for my thread on my 74 c-160 restore, there are a few pictures and a description. I've been using an original belt but the mule drive is pretty tight to the axle. So far it hasn't caused any problems but when it's replaced I'll get one a bit longer.

 

Here is the link to my earlier thread on the upgrades I did to my 160

Edited September 6, 2014 by tbarnhart

[boovuc 1,090]

I have always run wide open throttle. I will use three-quarters if I'm simply moving a tractor from point A to B. The loader on my 520-H requires 3600 RPM to do most anything. The snow blower C-175 is the same way. If not WOT, it won't work at it's top efficiency. My 310-8 Speed with the 37 inch deck will cut well at three-quarter throttle but honestly, none of my other tractors would cut worth a crap at anything other than WOT with the 42 and 48 inch decks running 2nd gear on the manuals.

Kohler says wide open/3600 RPM. Onan also states the same thing. I don't doubt others here have run at less without issues over many years but how often are they used? Do they do hard work consistently? (Not just blow snow in the winter then sit like my C-175 or like my loader, get used only hours a year).

For the guy that has ONE tractor.......you know, like normal people,   , where that tractor is used to mow in the Spring, Summer and Fall, then maybe plow or blow snow in the winter and till the garden in the early Spring over a period of 15 years, I truly wonder what side by side ccomparisons of two tractors subjected to this would fare if one is run per the manuals and the other run at less than WOT.

My C-175 was run at less than full throttle by the first owner. It was my only Wheel Horse for over 10 years and it worked hard year round. Some 8 to 10 years after I bought it, it needed a top-end rebuild BUT I mowed side hills with it and it did have and still does have the original Series I KT17 Kohler that has the lubrication issue when not on even ground. There is no way of knowing it the prior owner's use of it below WOT caused the overheating in the top end of that twin or if my running it WOT did it. No one can write on here one way or another with certainty. I'll just do what the manufacturer says to do. That way, I can't blame myself for the day when one of these motors takes the proverbial dump in my yard.

[wh500special 2,053]

I don't usually chime in on stuff like this since I have no expertise here, but I'll break precedent:

With respect to the cooling air issue, I wouldn't expect that the airflow through the engine rises linearly with flywheel speed. Granted the fins sweep a linearly higher volume of air as they increase speed, but the pressure drop through the engine probably increases via a different multiplier. So what actually gets shoved through the engine may or may not be directly proportional to engine speed.

Also, a faster running engine is burning more fuel necessitating more cooling. So even when run at lower speeds the airflow is probably more than adequate. In fact, I can see a possibility that the engine might actually over cool at lower speeds.

Running at low engine speeds and high loads promotes lugging which can cause a host of internal problems related to incomplete burning of fuel.

Power output will be linear over some ranges of speed, but often drops off faster at lower engine speeds. If you're mowing at half throttle with a ten hp engine and hit a tough spot, engine speed will drop and available power may drop precipitously. If uou have max power available and bit a tough spot, you might be on a more gentle slope of the power curve and be able to make it through.

I think it's beneficial to match engine speed to the load applied. Mowing is incredibly power intensive, blading snow isn't. On a gear drive tractor it's fine to slow down a bit for lighter loads.

Not so on a hydro. Run full blast if you're loading it up. And it's not really a cooling issue. The power transmitted through the transmission is proportional to the product of flow rate and pressure. If you decease the flow rate and demand lots of power transfer, the pressures must increase. Running at max pressure is tough on the equipment.

Back to the engine...a shaft spinning in a journal bearing with an oil film actually develops pressure that separates the metal parts from touching. It's a hydrostatic bearing. That pressure is a function of speed. I don't know when it happens, but allowing the speed to drop when significantly loaded can promote the film pressure from doing what it's supposed to do. This is why oil viscosity is such a big deal.

Or so I think.

For what it's worth, I run my engines at less than full throttle unless mowing, tilling, or blowing snow. If pulling a heavy load with a hydro, it's full throttle. Otherwise I match speed to whatever I'm doing.

On our older equipment we're mostly dealing with overbuilt, low precision stuff. I believe newer stuff manufactured with modern technology to tighter tolerances is less forgiving to improper use.

There is certainly some logic to the thought an engine will only last for some designed number of revolutions. Makes sense. But as load on the engines vary, so do the loads inside the engine. You can bet if you run your engine at full rated load it's not going to last the same number of hours it would if treated more lightly regardless of speed.

All opinion. Take it for what it's worth.

Steve

[tbarnhart 240]

Just to clear up what I said earlier about cutting speed. A clean cut seems to be directly related to blade tip speed. Like Pacer, I cut a lot of bahia grass and if you haven't cut it you probably don't know how difficult it is. Hence the larger pto pulley on my tractor and WOT when mowing. As far as the engine is concerned, I don't think lubrication is a big issue, but cooling could be. If there is one thing that an air-cooled engine will not tolerate, it would be lugging at higher load and lower speed. Combustion pressure, heat rejection, exhaust temps, etc. will be at high levels while cooling airflow will be reduced. Given that info, any high load application (heavy grass, snowblowing, tilling, heavily weighted ground-engaging implements) should be attacked at significant RPM. Light loads where heat rejection is not as much of an issue, adjust the speed to whatever works the best. I never had one, but I think VW recommended downshifting to keep the old beetles revved up to prevent heat failures. I agree that rpms will increase wear in a sense, and don't run my tractor faster than what I need to get the job done, but please don't stay in the governor very long at low to mid RPMs.

[wh500special 2,053]

Edit to my previous post: replace "hydrostatic bearing" with "hydrodynamic bearing." Got my terms mixed up.

[Save Old Iron 1,563]

I don't usually chime in on stuff like this since I have no expertise here, but I'll break precedent:

With respect to the cooling air issue, I wouldn't expect that the airflow through the engine rises linearly with flywheel speed. Granted the fins sweep a linearly higher volume of air as they increase speed, but the pressure drop through the engine probably increases via a different multiplier. So what actually gets shoved through the engine may or may not be directly proportional to engine speed.

 

You should break precedent more often Steve. Your multisyllabic musings are food for thought.

 

I would imagine if more exact airflow / cylinder temps were needed, some sort of thermostatically controlled air vane would have been incorporated into the skins of the Kohler engines.

[clem 28]

Anyone ever have an internal cumbustion engine fail from TOO MUCH cooling or lubrication?

[Jasen 10]

Too much cooling no, too much lubrication yes! The only reason it failed though was because the oil level was too high.

[clem 28]

So yes to human error & no to mechanical ability to over lubricate

[Trouty56 565]

I think most tractor duties do need the engine running at a high speed....but I don't bury the throttle when I am pulling the tractor out of the garage,,,or when I stop mowing to move an object.....or taking the garbage to the end of the driveway....etc....if they weren't meant to idle then why would we need a throttle??  As far as lubrication.....that paddle hitting the oil at 1000 rpm is displacing most of the oil in its path.....leaving a trough that probably doesn't fill completely before the next revolution.....might even get more splash than at 3600......run your hand through the water in your pool and watch how water fills in behind it....doesn't fill in right away....

 

Good thread though....reminds me of the old saying about opinions and their likeness to a particular area of the body.......

[Challenger 27]

Not to highjack this thread, but upon first start of the day how long and at what throttle setting do you "warm-up" the engine before moving to WOT for lawn cutting, snow blowing etc?

 

I have a neighbor that upon start-up advances the throttle IMMEDIATELY to WOT.  He believes that proper lubrication and cooling must be facilitated immediately.  No warm-up needed. ! ? 

[Red-Bovine 289]

Since the engines are governed at 3600 rpm, placing the "throttle" to the fully forward position does not necessarily mean the butterfly on the carb is fully open at all times. The governor opens and closes the butterfly to regulate the rpm and the power demand at any given time. As power demands are increased, the governor will open the throttle to meat these demands. So you are not always running at WOT but allowing the governor to control power as needed. That is why you should be advancing the throttle lever to allow the governor to control engine speed. Timing is set on these motors to work best at 3600 rpm. Efficiency is not compromised and the notion of using excessive fuel is erroneous.

 

Red

[clem 28]

I agree with Trouty56 that opinions & individul experiences will vary on this subject or any other for that matter. I also realize this thread originally referred to a single cylinder engine. All that being said, I will stray slightly for my example. Of all the kt twins out there with a dead rear hole, how many got that way from excessive cooling or lubrication volume (not pressure)?

[km3h 543]

Since the engines are governed at 3600 rpm, placing the "throttle" to the fully forward position does not necessarily mean the butterfly on the carb is fully open at all times. The governor opens and closes the butterfly to regulate the rpm and the power demand at any given time. As power demands are increased, the governor will open the throttle to meat these demands. So you are not always running at WOT but allowing the governor to control power as needed. That is why you should be advancing the throttle lever to allow the governor to control engine speed. Timing is set on these motors to work best at 3600 rpm. Efficiency is not compromised and the notion of using excessive fuel is erroneous.

 

Red

I suggest you set your governed tractor to half throttle and then put a big load on the engine, such as cutting afield with about a one foot height of grass and see if the engine bogs down or the governor increases the RPM's. Won't happen. What will happen is the engine will remain static and if you don't either cut a small path or turn off the pto, the engine will stall. The governor on these engines is there to prevent RPM's from rising above a set level. Even if you don't have a tach, you can hear the difference, when an engine changes RPM's. The only time I have heard a governor change RPM's on it's own, is when the engine is running lean and it surges looking for more air.

[Red Horse 32]

Hey Jasen if you really want to stir up a hornet's nest ask' what kind of oil do you use' ? Never fails.

[Geno 1,928]

Oh no.     

 

I'll just watch that one.