Purpose of WOT when GT has an electric PTO

[RMCIII 838]

Ok members, I am struggling here a bit. After putting about 38hrs of snow blowing on the xi, I am in a quandary, as to why the need for WOT....I have to admit, when I was cutting grass, if I hit a patch that was thick, I did hear the rpm's lower slightly. Not much though. This leads me to question the mfg. claim of needing to run WOT "AT ALL TIMES"...

Since most of us are probably "gear heads" of some sort, it leads me to say this, mfg. is not always the best for your application.. Example: I purchased a 2010 GT Mustang off the showroom floor. I am the original owner since mile 1. Now the mfg. claims to use only "unleaded" gasoline.. Since 2010 I have used a mixture of leaded and unleaded gasoline. The leaded, has always been a rating of, 105 plus. I can also, without question, say when I use the leaded gasoline mixed I see better gas mileage and less rpms. 300 less rpm's to be exact. I also see the mpg go from 25 to 29..... < The highway test has been done time and time again running 76mph....I can also say that when I changed the plugs at 50K miles, they were fire clean... When I use the word "fire" I am referring to sticking something into the fire and the fire burn off all contaminates that may be remaining. They were yellowish white in color and "0" build up or residue on them. Where is this going?

So I have been experimenting with the "xi". Here are my findings:

 

• At WOT I see a throw distance of 35' to almost 40' when I can keep the auger filled with snow
• AT WOT I see a throw distance of 25' to 30' when the auger is half full
• At 1/2 WOT I see a throw distance of 25' to 30' no matter how full the auger is.
• I see no RPM drop when it is operating at 1/2 throttle
• I see no temp. increase when only at 1/2 throttle
• Once PTO is engaged and I am operating at 1/2 throttle, I have yet to "bog" the engine down or see a reduction in performance of the blower as long as I am aware of the conditions of the snow.. Obvious I feather the hydro drive when approaching amounts of snow that exceed 6". Beside that, I can run the hydro as fast as I want without any type of power loss.

So why would I want to run WOT when 1/2 throttle seems to be 90% performance of WOT and I am not having to turn the RPM's? We all know that the amount of RPM's also has a direct affect in component life. I know these GT's are meant to last a life time, but we do need to do occasional repairs on the engines. So if I can use 1/2 the throttle, and still see 90% performance without having loss of power, as long as I am aware of the conditions, what is the point of WOT?

 

Rob

[HorseWhisperer 243]

Rob,I'm with you in your questioning of "The Authority".I never run mine wot.I adjust the throttle as needed per job,air temp and power needed.They claim the air cooled engines need that wot to ensure proper cooling through blower shroud is all I can assume and that recommendation is safe enough to keep the idiot out of trouble?I mean what does Kohler really care if you damage a ten year old engine,It just means you buy another sooner?I believe the man. Recommendation is put forth to make it dummies proof,to honor and protect a great product but common sense has to abide.I will continue to adjust the throttled as needed.

[shallowwatersailor 3,213]

Rob,

 

I think that it has more to do with keeping the engine cool while working and moving air from the fan across the cylinder heads. On my 520xi, the whole tractor was caked with dead grass from mowing. I cleaned the engine as much as I could without taking the shroud covers (tins) off and even used my HF inspection camera to look underneath. With the engine in the chassis there is not enough clearance to remove the covers. There is still a marked difference in the air moving at the top left side of the engine between my two 5xi. I haven't used the 520xi much because of this.

 

The previous snowfall two weeks ago I did use the 520xi for plowing. Even though the temperature was below freezing, it still came up on the temperature gauge. It rose slower but still like when the weather was warm. My 518xi never goes more than a needles width past half, even in summer. To be safe I went back to the 518xi for plowing the other day. Next weekend I plan on pulling the engine (when it warms up!) on the 520xi and clean it completely. I'm curious as to what I will still find in there.

 

In the winter it may or may not need the cooling. Don't forget that the transmission depends on air movement from the driveshaft fan as well.

 

John

[RMCIII 838]

John;

Ok. I think you have a point, but when the temp. gauge does not fluctuate when in WOT or 1/2 throttle, what is the answer then. Again we have a responsibility to do general up keep on these GT's. If we fail to do so, or do not know what the previous owners did, then we should default to mfg. recommendations. Beyond that, it seems like it becomes ""Common sense",

as stated, by Kevin.

[KC9KAS 4,741]

Running "WOT" is also to help the hydros run properly and cool properly.

[TT-(Moderator) 1,127]

They aren't necessarily at WOT as they are limited by being "against the governor" - where they have been designed and tested to make the most power.

That also gives a smaller engine a quicker recovery time if the load increases suddenly.

A fellow member here at RedSquare pulls with a Command engine and leaves the line @ 9500rpm. That being said, you're only running at 1/3 throttle.

 

Yes, a 20 - 22hp engine can be operated at a lower throttle position compared to an 8 or 10hp engine, but I'd still stay at or above 3/4 throttle to keep the hydro happy. An engine that's lugged will suffer more wear / damage than one that's operated in the upper rpm range. Lower flow and pressure in a hydro unit can cause more heat and "jerky" operation.

 

P.S.> leaded gasoline plugs up catalytic converters.

[Hydro 130]

I run my tractor where I think the engine generates the most torque.  I think for my M16 that's somewhere around 26-2800 rpm.  WOT for me is supposed to be 3600 rpm.  I've noticed the engine rpm does not fall off as much at 3/4 throttle as compared to WOT which makes me think I'm where I should be  .  My Hydro works fine.  I've run 5W40 now for 3 years, year round.

Cooling in winter has never been an issue for me.  There isn't a place on the engine I can't touch with bare skin including the muffler when the temps get below freezing.    I'm amazed at how cold this engine runs in the winter. 

[JimD 3,345]

The title of the thread says when an "electric pto" is used. I would use WOT to engage that pto to prevent damage to the engine over time engaging it at a low rpm. That's another area where the  common sense portion of the debate comes into play. There is no gradual engagement with electric pto's.

[RMCIII 838]

They aren't necessarily at WOT as they are limited by being "against the governor" - where they have been designed and tested to make the most power.

That also gives a smaller engine a quicker recovery time if the load increases suddenly.

A fellow member here at RedSquare pulls with a Command engine and leaves the line @ 9500rpm. That being said, you're only running at 1/3 throttle.

 

Yes, a 20 - 22hp engine can be operated at a lower throttle position compared to an 8 or 10hp engine, but I'd still stay at or above 3/4 throttle to keep the hydro happy. An engine that's lugged will suffer more wear / damage than one that's operated in the upper rpm range. Lower flow and pressure in a hydro unit can cause more heat and "jerky" operation.

 

P.S.> leaded gasoline plugs up catalytic converters.

 

 

Terry;

 

I completely understand the need for WOT on the models that may operate with a "manual" PTO, but the electric "PTO" does not run off the engine directly... The rpm's, from what I have expierenced, have bvery little to do with the overall performance of the attachment. That being said.. You do have a very solid point of the Hyrdo cooling... Does that really come into play when temps are 20 degrees? I have not had an issue with the hydro or lift capacity operating at 1/2 throttle...

 

BTW... I knew someone would mention the cats..... Here is the catch... The cats are designed to capture "unclean" contaminates left from the combustion of the cylinders. These contaminate are left behind when "unleaded" fuels don't burn completely... SO>>>>> What does a "higher octane rated fuel do?" Leaded or unleaded within the chambers of the cylinders? It allows the fuel to burn longer to ensure the contaminates are expelled completely before they enter the "cats". Hence a cleaner cat and less contaminate. The mfg. do their test on 88 - 91 to 93 octane ratings..... Lead does leave behind more deposits at those levels. However, above those levels, the mfg. does not test because the "normal" consumer is not willing to spend $7.00 plus for a gallon of fuel...The end result is a much cleaner burn throughout the process. I have yet to be proven wrong on this. I have checked cats at 100k. The insides look like they may have 20k on them... Just saying.... We all have done our experiments with "stuff". Since leaving the Air Force my "stuff" has been engines.... Diesel, gas, jets, afterburning engines, ect.... Anything that has the ability to be "boosted" by fuels, turbo, superchargers, nitro, ect... I have played with. I am NO EXPERT.... But I have some compelling results from my experiments...We all have the capacity to learn from other's.. I learn from actual knowledge of "experience"//// I think most of us may agree to that comment... left side vs. right side of the brain.. I have been running the GT since Feb. 2010, it has 63K miles on it. The Cats show little, if any, build up... This is due to the constant heat of the supplied fuel.. I could really care less about a "advanced spark or timing" technology. I know they do not test with octane that is above the "pump" grade.... Put an oz. of 93 octane on a plate, and an oz of 105 octane leaded, let both burn out. Once done look under a microscope of what is left. I promise the 93 will have almost twice as much debris left on the plate... Again, experience. Getting a little passionate here. Sorry... Getting back to reality.... Why the WOT if the engine, trans. and attachment does not suffer performance?

 

Rob

Edited January 5, 2014 by RMCIII

[RMCIII 838]

Jim.. Ok, but once engaged, why operate WOT if there is little difference seen in engine temp. hydro performance, attachment performance? I agree. If the rpm's are not at a respectable level, at PTO engagement, it will kill, the engine. Once running though, the RPM's truly have little to do, as long as the engine is above 1/2 throttle, with performance....

 

Rob

[JimD 3,345]

Rob, I get caught up in the thinking of the average guy. I'm no scientist, nor am I ever going to be inclined to get so deeply into the subject of WOT and experimenting the way you do. Hat's off to you on that count.    However, I don't have a twin cylinder hydro GT either, so I tend to think more in terms of the single cylinder Kohler operated tractor group to which I belong. As you and others here have said, winter weather isn't as much of a concern for air cooling of even an 8hp Kohler. However WOT on these engines provides optimal oil slinging lubrication, which is another reason to open her up. So I suppose the thing to do is for you to run yours at half throttle and I'll run at full throttle and while I predict no significant harm will come to either of our tractors in the short term, I will definitely use less gas then you.

 

Jim

[RMCIII 838]

^Terry;

 

^{Also.. a puller leaving the line at 9300rpm's is a completely different application than blowing snow... A puller is trying to attain a certain "lift" of a sled and tire spin off the line... If that is not obtained, off the line, then the overall performance, or distance the puller goes, will be limited// of course there are other factors in a pull. track condition, tire grip, weight transfer, ect... But I have yet to see a tuck, tractor, GT come off the line, at a low RPM and do a full pull.....}    

[TT-(Moderator) 1,127]

Terry;

 

I completely understand the need for WOT on the models that may operate with a "manual" PTO, but the electric "PTO" does not run off the engine directly... The rpm's, from what I have expierenced, have bvery little to do with the overall performance of the attachment. That being said.. You do have a very solid point of the Hyrdo cooling... Does that really come into play when temps are 20 degrees? I have not had an issue with the hydro or lift capacity operating at 1/2 throttle.....................................

Rob

The "electric" part of the PTO clutch is the method of engagement. It's an electromagnetic clutch - and once power is applied to the coil, it is (supposed to be) locked at the same speed as the engine crankshaft. Engine rpm is directly relevant to the attachment rpm. The only exception to that would be if the air gap is too wide or the clutch is just worn out - then it will slip. An out-of-spec air gap can also cause failure of the coil.

 

I doubt you see unacceptable heat in the hydro - even in the summer - unless you are really working the tractor.

 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I won't pursue the lead topic.....  I have a 7.3 IDI diesel and can burn almost anything except water. 

[RMCIII 838]

Jim.... I think that many GT's will burn less fuel, weather I run 1/2 or WOT, due to the dual cylinder vs. single...  

 

I have been trying to figure that our also. Best, or least fuel consumption, while obtaining optimum performance... No luck yet... I can tell you all this. the twin kohler drinks fuel like a thirsty camel on a hot desert night... Regardless of WOT or 1/2 throttle... I am open to "experience" here...

[RMCIII 838]

Terry, I promise, you can burn water through that diesel..... You just have to know the right mixture... Unless you have a "super sanative" fuel delivery system, water will allow some "cleaning" purpose... But that comes in moderation with a diesel.... But then again, water in any fuel delivery system, above moderation, is a very dangerous mixture. In my teen's, I actually steam cleaned, my heads by adding water directly into the carb... Yep... You have to adjust for the right flow, but, it works. I saw all kinds of junk being spewed out the exhaust pipes of my 71 SS Nova... But then again, those engines were built to take on slightly more, than what current engines are today...

[Rick_in_CT 156]

I have always run my Kohler K301 at WOT, and do the same with my 5xi twin cylinder, and yes the 5xi can drink the K301 under the table.  I am a believer in the WOT principle when operating attachments for the reason that these attachments are designed to be run at a particular RPM for peak performance.  The cutting deck was designed for a certain blade tip speed, to lift the grass before cutting, and to properly discharge the clippings.  The snow blower or thrower is designed to throw snow of varying density.  Someone ran the calculations of what would be the optimum auger and fan speed, figured out the needed gear ratio to get this from the engine, and they did this using WOT rpm's as the basis of their calculations. 

 

Can you run at less than WOT and still get "good" performance, yes, but I'm going to guess that you are not getting the optimum performance that was intended.  I would also think that the added rpm's add a "reserve" that the designer calculated for, so when you hit that thick clump of grass or snow drift, you don't burry the engine.  My machines have always been happy to run at WOT all day long when running attachments.  If I'm moving dirt, then I am all over the throttle all day long.  I would also venture to speculate that from the designers point of view, it is easier to design the implements to run at WOT, because they can then specify in the manual to operate at WOT to the consumer, rather than say to operate the blades at 2/3 throttle, the tiller at 3/4 throttle, and the snow blower at full throttle.  The WOT specification takes away some of the judgment call that you would be leaving with the consumer, who would then be calling the factory to complain that at 2/3 throttle the deck is not cutting the grass well, when in reality they are operating at 1/2 throttle but it looks like 2/3 to them.  Ask me how I know this would happen.  When building equipment that is a "consumer product" you have to make it easy and simple for the average person to operate.  You take away as much of the variable in operation as possible.  Hence you specify WOT in the manual.  For many on this site, you understand the inner workings of the hardware better than an "average consumer", and can be free to make you own judgments as to what rpm you want to operate your attachments, and make your own decision if you are degrading performance or not.  It is no longer black and white, we are now thinking in color!! 

 

I think that these engines are going to provide adequate cooling and lubrication at a wide range of rpm's, and that WOT is not required to for these reasons in most lawn tractor applications.  If you consider a snow plowing application, you really don't need WOT to plow a small snowfall of powder, so why run at WOT if you don't need to.  The engine will be happy at 1/2 throttle, and it won't overheat and it won't starve for fuel or lubrication.

 

That's my take on the WOT principle.

 

Rick

[RMCIII 838]

Rick;

 

So the bottom line it is more for the mfg. than the consumer.. Meaning, they wanted to "shield" themselves from owners that may not have the ability to "understand" what is happening or why it is not performing the way it should. So use a blanket mfg. claim and let the one's that do understand figure out what works best.......

 

Rob

[Kai Thomsen 17]

Sorry if i misunderstand the topic (I'm not that good with English) 

 

I have an electric clutch/pto on mine, and unless i run it somewhere near full throttle when the clutch/pto is in use + lights is on..it slowly discharges the battery.
The pto/clutch draws about 5-6Amp and the lights takes another 3-4Amps.  The engines charging system is good for 10A, but only when running at or close to WOT or the voltage across the battery will drop to much.

[Anglo Traction 759]

Kai, your spot on. The old Amp meter will be flickering around the - line with Lights n Clutch if it's only running at 1/2 - 2/3.

3/4+ throttle may be ok which is where you get max amp output and the best power.....At least that's where my 12hps show it to be.

Should also just about be ok for Implement speeds. 

 

I still feel for an engine running at WOT in a concerned hard working sort of way and just have to peg it back a tad. 

 

Good topic

edit - Use of LED Lights cut the leccy demand down drastically

Edited January 6, 2014 by Anglo Traction

[leeave96 487]

I run my engines at WOT for the following reasons:

 

1.  Maximum PTO speed

2.  Maximum battery charging

3.  Maximum cooling at I understand it.

 

Some of my Berthern with the IH Cub Cadets question this and run at lower RPMs while other do not.  I'd say run the tractor as you see fit...

 

Bill

[Machria 77]

Regarding unleaded / leaded.   Leaded gasoline can kill the CAT.  The lead leftover in the exhaust can make the platinum (active ingredient) on the surface of the CAT inactive and ruin the CAT.  It can also overheat the CAT and cause a fire, very dangerous.

[RMCIII 838]

The lead, is actually burned off, at higher octane levels. 88-93 I do agree. In the 100 plus range, the fire is not as "fast" or should I say, burns much longer with a high octane fuel vs. a low to high pump grade.

[RMCIII 838]

Kai - you make a good point. I do not have a volt. gauge on mine. It does have a battery light that will light up if the voltage is not sufficent... I have a volt meter, I think I will check it.

 

Rob

[Machria 77]

The lead, is actually burned off, at higher octane levels. 88-93 I do agree. In the 100 plus range, the fire is not as "fast" or should I say, burns much longer with a high octane fuel vs. a low to high pump grade.

 

Yea, but where would one get a 100+ octane?      As a NASCAR track?

[RMCIII 838]

 

The lead, is actually burned off, at higher octane levels. 88-93 I do agree. In the 100 plus range, the fire is not as "fast" or should I say, burns much longer with a high octane fuel vs. a low to high pump grade.

 

Yea, but where would one get a 100+ octane?      As a NASCAR track?

 

 

Almost any city has at least 1 gas station that sells racing gasoline. I have a Marathon by me. Cost $7.99/gal, and is 112 Octane... You just have to ask the right people. Most individuals will not even know about. Usually it is a pump that sits off to the side by itself or in the back of the station that looks like it may not eve work any longer.