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View Full Version : Do Yoy really need to run at full throttle?


Beckham
06-12-2007, 07:52 PM
First let me tell you I'm not in the business just enjoy reading the discussions about the machines. Keep up the good work! I come from the old school (read age here) where you use enough throttle to get through the grass you were cutting. Thus more throttle for higher grass and less for lower grass might even go down a gear (pre-hydro here) for the heavy stuff and stay at the same RPM. Thats the way we were taught, saving engines and fuel economy and such. I know they now say open her up......cut wide open, the engine cools better, you get a better cut etc. It just seems that you guys that have high HP machines or larger machines with the diesels would not need to run with the throttle wide open. Lots of those engines are water cooled so cooling shouldn't be an issue at most RPM's. Max torque is very seldom made a high RPM especially in those diesels! Do you guys with those engines peg them to the max and head out for a days work or is there a happy medium somewhere?:confused: :confused:

cantoo
06-12-2007, 08:03 PM
The pumps need to run at the correct speed and as far as I know this is usually full throttle. I know my Steiner whines if it is run below half throttle. We usually run them wide open to keep blade speed as fast as possible.

LindblomRJ
06-12-2007, 08:10 PM
Yes, blade speed for quality of cut and cooling on an aircooled machine is important. These engines are designed to run at high speeds. Both gasoline and diesel.

02DURAMAX
06-12-2007, 08:11 PM
Is this your first post since July 2004??

oh and yes they need to run at full RPM..

cantoo
06-12-2007, 08:29 PM
02DURAMAX Is this your first post since July 2004??

oh and yes they need to run at full RPM..

He didn't want to speak out of turn.

LindblomRJ
06-12-2007, 10:00 PM
LOL. At least its not a question that gets asked 50 times a day.

02DURAMAX
06-13-2007, 12:42 AM
02DURAMAX Is this your first post since July 2004??

oh and yes they need to run at full RPM..

He didn't want to speak out of turn.

well then i guess he won't be posting here again for another 3 years..:rolleyes:

tacoma200
06-13-2007, 12:55 AM
How many times have I heard that you need to idle the engine a while to "cool" it down before shutting it off. So that would seem to contradict the WOT is needed to cool an engine.

I personally don't know if idling cools one down but that's what I've always heard. Throttle down on the way back to the trailer and let it run a while a low rpm to cool the engine before shutting it off.

Just wondering why there are two schools of thought here. I run mine at lower than WOT at times such as when I'm not wanting to discharge as far (around beds) or in wet grass the lower blades speed seems to help. Exmark told me it wouldn't hurt them to run at less than WOT.

Can't say I'm sure.

KS_Grasscutter
06-13-2007, 01:03 AM
How many times have I heard that you need to idle the engine a while to "cool" it down before shutting it off. So that would seem to contradict the WOT is needed to cool an engine.

I personally don't know if idling cools one down but that's what I've always heard. Throttle down on the way back to the trailer and let it run a while a low rpm to cool the engine before shutting it off.

Just wondering why there are two schools of thought here. I run mine at lower than WOT at times such as when I'm not wanting to discharge as far (around beds) or in wet grass the lower blades speed seems to help. Exmark told me it wouldn't hurt them to run at less than WOT.

Can't say I'm sure.

An air cooled engine is going to have more air flow at WOT, thus helping it cool down better. Not sure on liquid cooled engines though.

topsites
06-13-2007, 01:31 AM
If I really open up my new 15hp engine, it literally turns the muffler red hot. And if I don't let the mowers idle for a good minute before shutting it down, they go Ka-BOOM as unburned fuel backfires out the exhaust. If I do it on the new engine, it shoots a flame out, kinda cool looking, like on a rice rocket, it's a short white burst.
But, should I let it do that?

I've ran machines both ways from new to crapped out... That is, either run it WOT the entire time from the day you get it until you throw it away, or do it the other way (just enough to do the job).

I personally see no difference in how long they last, I would think they last longer away from wot.

I usually run WOT when I've got the area to do it in, but if I'm not in that much of a rush, I like 90% throttle (which is, back it off full until the rpm's just want to drop, right before they drop, that I call 90%)... It seems to save fuel.

The Z has hydros, those need power.
But the gear drive fixed deck has plenty of rpm's, even at 1/2.

I turn down rpm's near the house and vehicles, also when the chute has to face the street or the house, around people and animals as well, and when I run in 4th gear instead of fifth, I use less throttle as well.

With the trimmers and blowers, same thing, just enough to do the job.
It saves considerable fuel, I get 4-5 lawns on a trimmer tank during spring, 8-10 in the summer... The blower lasts 2-3 days on one tank, sometimes 4.

Honestly, I think the thing about running it WOT is a saying because you can't go wrong telling Lco's to run Wot. Either way, running less than wot saves $ on fuel, I keep the Wot option open for hardcore work.

Beckham
06-13-2007, 07:06 AM
I guess this is my first post since July 04, I can't remember what that one was about. See ya in 2010! Just joking there as I said in my post I really enjoy reading this forum in season. I actually enjoy watching a good operator work when I see one out on the job. Thanks for all the responses!

MOW ED
06-13-2007, 07:10 AM
Interesting question Mr. Beckham. Why did you wait so long to ask?:waving:
As stated above, the air cooled engines on mowers that I own are all hydro drives. It is painfully obvious when they are not running at full throttle. I also notice a varation in the cut. I am used to moving at a certain speed and you are correct in the fact that if I was to slow down I can still cut grass because everything is moving slower. I just can't go slow and make money. If I half throttled my 26efi my 62 inch deck would also spin slower and my hydros would definately get into crawl mode. I could chug along at about 3 mph and cut grass. I could cut grass with a 4hp push mower comparatively cheaper with even less fuel usage and definately as fast as riding on a large mower but not covering as much ground.
I don't own a diesel mower but I do own a diesel tractor and I never run it up to max r's. Its a 15hp Mits diesel and she has plenty of snort in the low r range in all but the highest gears. But that is with a geared machine. I think most diesels produce their power in a much lower r' range to begin with but the variable to your question is the transmission type. I would agree that if you have a gear driven machine, you can get away with not running full throttle but the hydro systems of today almost demand it.
I am not blastin anyone here but this is a nice diversion from how much to cut or what z is the best. Thanks for posting and putting some rust dissolver in my head. Don't wait so long next time.:laugh:

MarcSmith
06-13-2007, 08:00 AM
i was alwasy taught to to throttle down for 10-15 seconds at idle before shutting off the engine. You never shut your car off while it running at WOT or you trimmer. Shut it off at idle and you'll have less unburned fuel dumped into the engine as its shuts off...

I would venture to say the air cooled engine running at idle will stay just as warm/cool as it does at WOT.....at Idle its not generating as much heat as it is at WOT so it needs less air to keep it cool. and remember like fluid dynamics, you can only push so much air through a system.

with a water cooled engine WOT or idle, the key to cooling is air and water moving through the radiator. lose one of those two movements and you'll get an overheat situation.

Brad Ent
06-13-2007, 08:28 AM
tacoma200,
The conflict (in my opinion) is between old school and new.
Old School says never run at full throttle, save the motor, conserve we need this thing to last a lifetime.
New school says run it wide open and throw it away in three to five years
If the machine is calibrated properly WOT is not necessarily full power/max RPM
WOT should provide optimal performance for all componants
You need to determine what works best for you and your operation
:)

puppypaws
06-13-2007, 10:14 AM
First let me tell you I'm not in the business just enjoy reading the discussions about the machines. Keep up the good work! I come from the old school (read age here) where you use enough throttle to get through the grass you were cutting. Thus more throttle for higher grass and less for lower grass might even go down a gear (pre-hydro here) for the heavy stuff and stay at the same RPM. Thats the way we were taught, saving engines and fuel economy and such. I know they now say open her up......cut wide open, the engine cools better, you get a better cut etc. It just seems that you guys that have high HP machines or larger machines with the diesels would not need to run with the throttle wide open. Lots of those engines are water cooled so cooling shouldn't be an issue at most RPM's. Max torque is very seldom made a high RPM especially in those diesels! Do you guys with those engines peg them to the max and head out for a days work or is there a happy medium somewhere?:confused: :confused:Never run at anything less than full throttle this is what keeps your hydraulic fluid cooler to keep you pumps and motors from going down prematurely. The air cooled engines cool better at full speed, why do you think they are called air cooled, a air cooled engine will get hotter at idle so that is a misconception.

Even a liquid cooled vehicle sitting at a stop light will heat a little more than one moving air through the radiator at 60 mph.

KTO Enterprises
06-13-2007, 10:31 AM
tacoma200,

If the machine is calibrated properly WOT is not necessarily full power/max RPM

:)

well if i throttle my scag down even the slightest bit the hydros sound like they are going to die trying to move the machine. air cooled engines do need to run faster to stay cooler.

And as for the dumping the fuel into the cylinder while shutting off at WOT, that what they invented the little thing on the bottom of the carb bowl for. Its a fuel shut off solenoid. As soon as there is no power it springs up and stops fuel. most carbureted engines will actually load up at low rpms. The carb is designed for the fuel mixture to be a little richer at an idle.

LindblomRJ
06-13-2007, 11:04 AM
I do let the engine idle down a bit before I shut it off.

cybervision
06-13-2007, 11:29 AM
I was told by a Hustler rep that you should cool down the engine and never shut it off at idle. He claims if you shut it of at idle that fuel can be pulled through the idle circuit and this causes the backfire. But if you shut it off at higher rpms the idle circuit is closed and then when you turn off the key the solenoid closes and all the fuel is shut off.

Eric D
06-13-2007, 12:27 PM
First off this is a great question and you will find many theories as to what is right and wrong. I would like to point out a few misconceptions. First, the lever we all use that most operation manuals call a throttle should really be called an engine speed control. On gasoline engines there is a throttle plate that controls engine power, but the lever we move has no direct connection to it. The governor controls the throttle and will open and close it based on the needed power to hold the rpm we set with the lever.

Why is this important? When you put the “throttle” to the highest rpm point there is very little load on the engine and the actual throttle will be just part way open. The only power the engine needs to produce is enough for the cooling fan, and generator. This low load but high fan air flow cools the engine best. When you have the “throttle” lever to high rpm, the actual throttle might not ever reach WOT because of the governor.

Fact of the matter, the engines we have these days are more durable then in years past. As long as the cooling fins are kept clear and the oil at its proper level any cool down technique will work. The fastest cool-down however is with the engine unloaded (PTO off, mower not moving) at maximum engine rpm. One to two minutes is all that is needed.

As far as cutting, I will run mine always at the highest engine rpm for maximum cooling and maximum lubrication while under load. Running less the maximum does your engine no favors.

Eric D

cybervision
06-13-2007, 12:42 PM
Eric D,
I agree with you on your running and cooling at full throttle. I am just curious as to what rpm you turn your engine off?

Thanks

KTO Enterprises
06-13-2007, 12:44 PM
I thought about what Eric just said after I left the house earlier. We do not run the engine wide open. The highest position on the throttle is the optimum working rpm. The engine has a governor to stop it from revving beyond optimum working rpm. Wideopen is when the motor can no longer achieve more rpm.

Basicaly in a nutshell, run your equip on the highest setting. It is good to let it warm up first thing in the morning on a lower rpm before you pull it off the trailer. But once you start working, it is necessary to run at the highest throttle setting.

cybervision
06-13-2007, 01:01 PM
Most engine governors are set to 3600 rpms at the factory for mowers. This is what is commonly referred to as full throttle, wide open, high idle or fast idle. No matter how hard you push the cable it still goes 3600 rpms.

69lt1bird
06-13-2007, 01:06 PM
These engines are designed and governed to run at full throttle. As long as the governor is set correctly it will not hurt anything. Like others have stated, you need the max RPM's for the blade speed and the hyro units so they do not become stressed by having the pumps operate a too low of speed which decreases fluid flow and pressure. In a nut shell, run it like you stole it and like the manufacturers designed them. Do not engage your decks a full throttle, throttle back a bit to add life to the electric clutches.

Eric D
06-13-2007, 01:11 PM
I agree with you on your running and cooling at full throttle. I am just curious as to what rpm you turn your engine off?
Cybervision,

When I'm done cutting I will stop the mower, bring the throttle lever down near idle, and disconnect the PTO, back to full rpm for one to two minutes, back to near idle to move mower onto my trailer or into my shop and shut it down. Is this the best way? I have no way of knowing if this will make my engine last longer then the person that just shuts it down when they are done, but at least I feel as though Iím doing the best I can to help it last.

As I pointed out in my earlier post, current engine designs are very forgiving on the abuse we put them through. The folks that just use their equipment and donít worry about how to best engage and disengage PTOís and how to shutdown their engine my have less stress then I do. In the over all picture of things their procedure might be the better choice then mine. I tend to think about this stuff more then maybe I should.

Regards,

Eric D

themowerman
06-13-2007, 01:27 PM
The main reason to run engines full throttle on hydro drive machines is to prevent premature wear. Inside these hydro pumps is a rotating group and a swash plate. As you move into forward or reverse the levers move the pump plate shaft which in turn rotates the swash plate inside the pump. The rotating group spins up against the swash plate and the hydro oil move through the ports in the rotating group. The angle of the swash plate dictates the speed and direction of the machine. There is more to it than that and I am not good at describing the whole process but the bottom line is you want the slippers of the rotating group to keep constant contact of the swash plate....if not the slippers will wobble around and cause premature wear on the system.

Eric D
06-13-2007, 01:41 PM
TheMowerMan,

For Hydro-Gear units the manual states the minimum working rpm is 1,800 and the maximum is 3,600. From this I guess one could assume that operations of the hydraulics at less then 1,800 rpm would want to be kept to the shortest time possible.

Regards,

Eric D

cybervision
06-13-2007, 01:44 PM
Eric D,
I am with you. My wife bought me a shirt that says "NEVER LEAVE WELL ENOUGH ALONE". That is my motto. With owning a machine shop I am always trying to increase production. That is why when I hear guys complain about the price of blades I think they are crazy. We spend $500 - $800 a month on disposable tooling(IE. endmills, inserts, taps, drills). It is the same as cutting lawns you have to balance all the cost and the most expensive is time not the equipment. Speaking of over thinking, I have noticed on my Ramrod Mini Loader (23 HP KAW) that it back fires if I don't let it cool down. I will pay more attention to if it is speed related. I should also be running that at full throttle but it make to much noise and bugs my wife. I only run it high when I need full hydraulic pressure.

Cybervision

themowerman
06-13-2007, 01:49 PM
3/4 to full throttle at all times will keep you out of trouble. It is your equip and you can run it how you want. I have been repairing hydro pumps and motors for 25+ yrs now and have been to the service schools and you want to keep the rpms up. Cybervision.....keep an eye on the temps on that machine....those taskmasters run very hot!

Richard Martin
06-13-2007, 02:13 PM
I don't always run mine at full throttle by any means. Like topsites, I'll throttle down near cars, landscaping or anything else that I don't want to get grass on.

Also like topsites and Tacoma200 I'll throttle down in wet grass.

When conditions are dry and there's nothing nearby I run it just as fast as I have it set to which is around 3600 with the blades on.

puppypaws
06-13-2007, 02:22 PM
Eric D,
I agree with you on your running and cooling at full throttle. I am just curious as to what rpm you turn your engine off?

Thanks

I am speaking only for Kohler engines, you can shut them down anywhere from 1/2 throttle to full throttle on the carburetor engines. My 28 efi I pull back to the lowest rpm's for maybe 5 seconds and switch it off. I had one 27 hp Kohler that could only be switched off at the highest throttle setting to keep it from backfiring and the Kohler engineers recommend killing the engine from 1/2 to full throttle and they are correct with the exception of the efi.

cybervision
06-13-2007, 02:22 PM
Themowerman. Are you referring to the engine or hydraulics running hot?

tacoma200
06-13-2007, 04:33 PM
I don't always run mine at full throttle by any means. Like topsites, I'll throttle down near cars, landscaping or anything else that I don't want to get grass on.

Also like topsites and Tacoma200 I'll throttle down in wet grass.

When conditions are dry and there's nothing nearby I run it just as fast as I have it set to which is around 3600 with the blades on.

Yea, I think you and Topistes are thinking the same as I am. I mean there are just times when full throttle is just not feasible and sometimes dangerous around expensive items or dangerous places. I'm definitely not going to discharge full throttle toward a car, home, window, street with traffic, etc. But most of the time 3/4 to full.

puppypaws
06-13-2007, 06:23 PM
Yea, I think you and Topistes are thinking the same as I am. I mean there are just times when full throttle is just not feasible and sometimes dangerous around expensive items or dangerous places. I'm definitely not going to discharge full throttle toward a car, home, window, street with traffic, etc. But most of the time 3/4 to full.

You are right, 3/4 throttle occasionally want give you a problem but I have heard people say they just don't want to mow that fast so instead of using their hydraulics they pull the throttle back. That is a serious mistake, the longer you run at lower rpm's the harder it is on all components of the mower.

It is just a matter of using common sense.

logorhea
06-13-2007, 06:41 PM
To Cantoo (post #2) - if your Steiner whines at 1/2 speed, you need to tighten or replace the hydraulic filter. I've been running Steiners for almost 30 years, and the filter's always been the cause of a whine. They've had trouble the last few years with the seal on the filter not sealing properly so it sucks air, and that's a slightly different whine than when the filter's plugged and pushing (and overheating) the oil real hard through the bypass valve. I always travel at about 2400-2600 rpm. The new engines really backfire if shut off hot and that can blow a gasket.

sheshovel
06-13-2007, 07:15 PM
Never run at anything less than full throttle this is what keeps your hydraulic fluid cooler to keep you pumps and motors from going down prematurely. The air cooled engines cool better at full speed, why do you think they are called air cooled, a air cooled engine will get hotter at idle so that is a misconception.

Even a liquid cooled vehicle sitting at a stop light will heat a little more than one moving air through the radiator at 60 mph.

This is how I always understood it to be as well.

themowerman
06-14-2007, 10:24 AM
cybervision....both....everything is encased it a steel shell....We used to distribute those units and I took one home for two weeks for a home project...great maching but damn that thing got hot!!! A few times I had to stop as the fuel was boiling in the carb...LOL Customers always complained of how hot they got.

johnnywill08
06-14-2007, 11:58 AM
we talkin mowers??? WOT no doubt.

J.Gordon
06-14-2007, 12:33 PM
First let me tell you I'm not in the business just enjoy reading the discussions about the machines. Keep up the good work! I come from the old school (read age here) where you use enough throttle to get through the grass you were cutting. Thus more throttle for higher grass and less for lower grass might even go down a gear (pre-hydro here) for the heavy stuff and stay at the same RPM. Thats the way we were taught, saving engines and fuel economy and such. I know they now say open her up......cut wide open, the engine cools better, you get a better cut etc. It just seems that you guys that have high HP machines or larger machines with the diesels would not need to run with the throttle wide open. Lots of those engines are water cooled so cooling shouldn't be an issue at most RPM's. Max torque is very seldom made a high RPM especially in those diesels! Do you guys with those engines peg them to the max and head out for a days work or is there a happy medium somewhere?:confused: :confused:





If you run at a lower Rpm you will need to gear your blades and hydro pump for that rpm so you will have the speed/control (hydraulics) and cut (blade tip speed)


Generally I run my 25 hp Kawasaki at 2400-2800 rpm, I think this engine makes it peak torque around 2400 rpm at about 17 hp give or take.
Once you take your engine out of its peak torque your just using more fuel than is required imho.

I have my blades turning at the speed I want for that rpm, I am getting ready to gear my hydro pump for 2400 rpm though so I will have more pump flow (better control).

When I operate at 2400 instead of 3600 rpm I use about half the fuel that I would normally use. The fuel savings alone has made it worth it to me. And when I need rpm all I have to do is put more fuel in.

I havenít noticed any heat related problems doing this but it seems to run cooler by feel.
I am getting an infrared thermometer to verify the EGT though.

But of course everyone here is an expert and is always full of advise so use your own judgment.

cybervision
06-14-2007, 12:51 PM
If you gear you pumps to run at the proper speed when the engine is running at 2400 rpms then when you take the engine up to 3600 rpms, which is a 50% increase in rpms, your pumps will be going 50% faster than designed. Also, the same thing holds true for the blade speed if you have changed them. If you change your ratios you may not be able to ever run the engine above 2400 rpms without causing problems.

lawnmaniac883
06-14-2007, 01:13 PM
These machines are designed to be run a full throttle that is 3600rpm gas and whatever the governed speed on the diesels is. Cuts better, runs smoother and is at peak efficiency.

J.Gordon
06-14-2007, 01:30 PM
If you gear you pumps to run at the proper speed when the engine is running at 2400 rpms then when you take the engine up to 3600 rpms, which is a 50% increase in rpms, your pumps will be going 50% faster than designed. Also, the same thing holds true for the blade speed if you have changed them. If you change your ratios you may not be able to ever run the engine above 2400 rpms without causing problems.

Very true, so if you decide to do something like this you need to do your homework and know the operating limits of the components that this will affect. If you happen to smoke something when you make changes to any equipment itís on your dime (it will void your warranty.) So know the operating limits!

But if you like experimenting and reading you may or may not have great results.

puppypaws
06-14-2007, 02:19 PM
If you run at a lower Rpm you will need to gear your blades and hydro pump for that rpm so you will have the speed/control (hydraulics) and cut (blade tip speed)


Generally I run my 25 hp Kawasaki at 2400-2800 rpm, I think this engine makes it peak torque around 2400 rpm at about 17 hp give or take.
Once you take your engine out of its peak torque your just using more fuel than is required imho.

I have my blades turning at the speed I want for that rpm, I am getting ready to gear my hydro pump for 2400 rpm though so I will have more pump flow (better control).

When I operate at 2400 instead of 3600 rpm I use about half the fuel that I would normally use. The fuel savings alone has made it worth it to me. And when I need rpm all I have to do is put more fuel in.

I havenít noticed any heat related problems doing this but it seems to run cooler by feel.
I am getting an infrared thermometer to verify the EGT though.

But of course everyone here is an expert and is always full of advise so use your own judgment.

I would not say everybody on this site is an expert but I will say the engineer I just talked with at Kawasaki is.

He said your 25 hp. Kawisaki engine was designed to perform at it's peak efficiency running 3600 rpm's. He said your engine was not running clean and actually polluting the air more at 2400 rpm's. He also said, when I read him your post that was your opinion and it was totally wrong and he wondered if you had a clue as to how much productivity you were losing because of this.

So now let's hear some more about your argument since we do know what a real expert had to say about your opinion.

J.Gordon
06-14-2007, 02:49 PM
I would not say everybody on this site is an expert but I will say the engineer I just talked with at Kawasaki is.

He said your 25 hp. Kawisaki engine was designed to perform at it's peak efficiency running 3600 rpm's. He said your engine was not running clean and actually polluting the air more at 2400 rpm's. He also said, when I read him your post that was your opinion and it was totally wrong and he wondered if you had a clue as to how much productivity you were losing because of this.

So now let's hear some more about your argument since we do know what a real expert had to say about your opinion.

I did say everyone is an expert (that was supposed to be meant sarcastically.) Sorry for the communication flaw.
When did I say the engine is more efficient? What I did say was I thought the engine is at its peak torque at 2400rpms!!!! Big friggen difference dude! Have your engineer explain torque to you!

If you have your pumps and blades geared for 2400 RPM then you would loose no speed period! Tell that to your engineer!

No I do not know for a fact that this will harm my engine, thatís why my test is ongoing, will I need to rejet probably I will know that in time. I can change back anytime I desire if this doesnít work out.

But I can tell you and your engineer for a fact that my fuel consumption is a heck of a lot less than at 3600RPM.

By the way would you have your engineer friend pm me I have a lot of questions I would like to ask him?

puppypaws
06-14-2007, 03:00 PM
I did say everyone is an expert (that was supposed to be meant sarcastically.) Sorry for the communication flaw.
When did I say the engine is more efficient? What I did say was I thought the engine is at its peak torque at 2400rpms!!!! Big friggen difference dude! Have your engineer explain torque to you!

If you have your pumps and blades geared for 2400 RPM then you would loose no speed period! Tell that to your engineer!

No I do not know for a fact that this will harm my engine, thatís why my test is ongoing, will I need to rejet probably I will know that in time. I can change back anytime I desire if this doesnít work out.

But I can tell you and your engineer for a fact that my fuel consumption is a heck of a lot less than at 3600RPM.

By the way would you have your engineer friend pm me I have a lot of questions I would like to ask him?

He doesn't need to pm you, call up there just as I did they will all tell you the same thing.

I didn't think you were being sarcastic, I thought you were being stupid.

J.Gordon
06-14-2007, 03:18 PM
What’s the name of they guy and number ext ?

I will give you a PM so I don’t hijack this thread,
Sorry for the hijack Bedkham

cybervision
06-14-2007, 03:33 PM
As the rpms drop torque decreases and horsepower increases. The torque may be the highest at 2400 rpms but the HP is only around 19. The max HP of 25 is at 3600 rpms. That is the net power of the engine. If the engine put out more power at 2400 rpms than 3600 rpms then that is what they would be set-up for.

Also to achieve the same speed every thing would have to be geared up.

An example would be trying to get a car moving in an upper gear. Your rpms are much lower closer to where the highest torque is but you can't get the car moving as quickly as if you were in 1st gear with the rpms a lot higher and the torque lower.

Beckham
06-14-2007, 03:35 PM
I'm good with it as long as the moderators let her fly.:drinkup: I'm learing alot here. I want to Thank everyone who has some thoughts on the subject and is willing to share!

MOWALLTHETIME
06-14-2007, 03:40 PM
At a receent open house at my local equipment company they had both the Gravely and Kawasaki reps there to answer questions. both of them reccomended that running the machine at WOT is better and the machine will actually last longer. They explained it like this. With the machine at WOT and cutting normal grass the machine actually works less because the motor is at full hp and torgue and less load is applied to the motor. At half power the motor is working as hard or harder than it would work at WOT, I also asked them about shutting the mowers down and what they reccomend, They both told me once you have the mower on the trailer to throttle all the way down wait for the engine to slowdown about 10 seconds and turn it off. This will eliminate the backfire and the fouling of plugs.

themowerman
06-14-2007, 03:47 PM
I gotta go and grab some pop-corn for this one!!! LOL

kawasakitech
06-14-2007, 04:17 PM
I have noticed many bad ideas, misconceptions and we have been misquoted in this chain and we would like to clear a few things up:

The ďthrottleĒ on the control panel controls engine RPM. It does not directly control throttle position.

The governor controls throttle plate position.

When the lever on the control panel is by the rabbit and the engine has no load the engine is at high idle not wide open throttle. The governor opens the throttle plate up only far enough to increase the RPM to the preset limit. As the load increases the governor opens the plate only enough to respond to the load.

In simple terms engines with governors consume only the amount of fuel needed to do the work. The most efficient way to use your machine is to operate it as designed. If the manual says run engine with lever on the rabbit, put the lever by the rabbit.

WOT (wide open throttle) can only occur when the engine is under full load in a governed engine (unless engine is shut off).

Why shut off after allowing engine to run at low idle? This is to cool the exhaust system not the engine (very important if engine has a turbo). Low idle in an air cooled engine can actually make the engine components (minus the muffler) hotter because of reduced airflow from the cooling fan.

cybervision
06-14-2007, 04:28 PM
Thanks Kawasakitech, Now that you are here can you elaborate on the best was to shut off the engine for cool down and reducing backfire. Thank may clear up a lot of speculation.

Thanks

puppypaws
06-14-2007, 04:37 PM
I have noticed many bad ideas, misconceptions and we have been misquoted in this chain and we would like to clear a few things up:

The “throttle” on the control panel controls engine RPM. It does not directly control throttle position.

The governor controls throttle plate position.

When the lever on the control panel is by the rabbit and the engine has no load the engine is at high idle not wide open throttle. The governor opens the throttle plate up only far enough to increase the RPM to the preset limit. As the load increases the governor opens the plate only enough to respond to the load.

In simple terms engines with governors consume only the amount of fuel needed to do the work. The most efficient way to use your machine is to operate it as designed. If the manual says run engine with lever on the rabbit, put the lever by the rabbit.

WOT (wide open throttle) can only occur when the engine is under full load in a governed engine (unless engine is shut off).

Why shut off after allowing engine to run at low idle? This is to cool the exhaust system not the engine (very important if engine has a turbo). Low idle in an air cooled engine can actually make the engine components (minus the muffler) hotter because of reduced airflow from the cooling fan.

This is exactly what I have been telling these people time and time again.

Why don't you state you credentials so people will understand your knowledge of these engines. Mine comes from common sense and research.

You shut them down at high rpm's anything half throttle and above should be adequate. I had one engine that would only switch off at full throttle, it would backfire at any other throttle setting, (and no it will not hurt one to switch it off at full throttle).

tacoma200
06-14-2007, 06:45 PM
Well all I'm stating is that there are times when running the engine at high rpm's is not in my best interest. Mainly when around dangerous area's as stated before. Or maybe in a very small area with flower beds, that sort of thing. If the engine last a few less hours because I slow it down around certain area's so be it. I'll take my chances. I can buy a lot for the price of a window, paint job, hole in some siding, etc. Seems like running an engine at full rpm's is the general consensus from the manufacturers. When it comes to trimmers I run it the way I want and what is safe. I feather the throttle around dangerous area's that I don't want to take chances. Compared to the price of damage a trimmer could do in certain area's and the liability I consider the actual trimmer disposable. Same for the ZTR. If I don't feel comfortable running at the highest rpm's I'll slow it down for a while. This thread is going a lot of different directions. But informative.

puppypaws
06-14-2007, 09:00 PM
Well all I'm stating is that there are times when running the engine at high rpm's is not in my best interest. Mainly when around dangerous area's as stated before. Or maybe in a very small area with flower beds, that sort of thing. If the engine last a few less hours because I slow it down around certain area's so be it. I'll take my chances. I can buy a lot for the price of a window, paint job, hole in some siding, etc. Seems like running an engine at full rpm's is the general consensus from the manufacturers. When it comes to trimmers I run it the way I want and what is safe. I feather the throttle around dangerous area's that I don't want to take chances. Compared to the price of damage a trimmer could do in certain area's and the liability I consider the actual trimmer disposable. Same for the ZTR. If I don't feel comfortable running at the highest rpm's I'll slow it down for a while. This thread is going a lot of different directions. But informative.

I don't know what different directions you are really talking about but Kawisakitech is 100% correct and you can basically forget about anything else you read.

Running you mower 1000 rpm's less for a few minutes is not going to take a certain amount from the mowers life, not one you would ever notice anyway.

You get out there and it is 90 degrees and you run long enough at low rpm's and it will kill the engine and all hydraulic components, the oil will burn inside just like an automatic transmission.

J.Gordon
06-14-2007, 09:01 PM
As the rpms drop torque decreases and horsepower increases. The torque may be the highest at 2400 rpms but the HP is only around 19. The max HP of 25 is at 3600 rpms. That is the net power of the engine. If the engine put out more power at 2400 rpms than 3600 rpms then that is what they would be set-up for.

Also to achieve the same speed every thing would have to be geared up.

An example would be trying to get a car moving in an upper gear. Your rpms are much lower closer to where the highest torque is but you can't get the car moving as quickly as if you were in 1st gear with the rpms a lot higher and the torque lower.


Youíre right again the engine has more hp at 3600 rpmís but the torque (what does the work has dropped off significantly) so why operate a 3600 rpmís if you are past your peak torque? Unless it would hurt the engine.

From the testing I have done, it uses a lot more fuel to run at 3600 rpm than at 2400 rpm.

What I am after is the best fuel economy for the amount of work Iím doing while hopefully lengthening the life of my engine by reducing the rpmís.
I understand the carb may have to be rejetted because I donít want to run the engine in a lean or rich condition.

Thatís why I want to measure the EGTís and oil temps, because it wouldnít be worth saving a hundred bucks in fuel and have to replace a $1500.00 engine.

The only drawbacks I can see with this would be overheating the engine and I have not seen or heard any scientific evidence of this happening just hearsay.
(I know a guy whose brother is an engineer that said it wouldnít work and kill your engine.)

Does anyone have proof of this other than hearsay?

It would save me a lot of time if you or someone could prove this.

Go ahead and call me stupid or crazy but itís kind of nice too do the same amount of work using 1/2-2/3 fuel for the same job.

Eric D
06-14-2007, 09:53 PM
From the testing I have done, it uses a lot more fuel to run at 3600 rpm than at 2400 rpm.

Go ahead and call me stupid or crazy but itís kind of nice too do the same amount of work using 1/2-2/3 fuel for the same job.

J. Gordon,

In your write up about running a 2400 to save fuel. If peak torque was at 2400 rpm you might save a measurable amount of fuel on a given cutting job. I wish I could find the power curve for a few of these engines. I think you would find the peak torque point is closer to 3600 then to 2400.

I wouldnít be using 2400 with my unit for a number of reasons. The main reason is cooling; we all know that one, less airflow less cooling. The one that I think is even more important is lubrication. Your engine is design to supply the right amount of lubrication at 3600 rpm. Unlike automotive lube systems, these small mower engines donít have over capacity oil pumps; car engines do to support low rpm operations.

No, I donít think you are stupid or crazy, but you might be misinformed, and I can understand that. There are as many opinions as there are people here. Asking the question no mater what it is means you are pretty smart.

Happy cutting,

Eric D
My earlier post (http://www.lawnsite.com/showpost.php?p=1862798&postcount=19)

J.Gordon
06-14-2007, 10:37 PM
Double post

J.Gordon
06-14-2007, 10:41 PM
J. Gordon,

In your write up about running a 2400 to save fuel. If peak torque was at 2400 rpm you might save a measurable amount of fuel on a given cutting job. I wish I could find the power curve for a few of these engines. I think you would find the peak torque point is closer to 3600 then to 2400.

I wouldnít be using 2400 with my unit for a number of reasons. The main reason is cooling; we all know that one, less airflow less cooling. The one that I think is even more important is lubrication. Your engine is design to supply the right amount of lubrication at 3600 rpm. Unlike automotive lube systems, these small mower engines donít have over capacity oil pumps; car engines do to support low rpm operations.

No, I donít think you are stupid or crazy, but you might be misinformed, and I can understand that. There are as many opinions as there are people here. Asking the question no mater what it is means you are pretty smart.

Happy cutting,

Eric D
My earlier post (http://www.lawnsite.com/showpost.php?p=1862798&postcount=19)



Thanks for the reply Eric but the peak torque for my engine is 41.2 ft-lb @ 2400 rpmís after that it falls drastically.
I had the torque cure once but cant find it, just the max torque/Horse power rating in my manual.

I have been using a tach on this mower for about 400 hours so I can verify the rpmís vs fuel.

Good point about oil starvation though! I will install an oil pressure gauge before I make the change complete or run it any longer.

Like I said earlier I still need to change my pump speed before I do this a lot.
My stock BTS is around 17,200 FPM and at 3600 rpm I believe there around 21,000 FPM and the cut is actually better while at full ground speed when I bumped the BTS up.

Iím still testing this now so I have only run my SWB about 10 hours at 2400 rpm and like I said the fuel consumption dropped dramatically.

Thanks for the feedback.

bsalter5
06-15-2007, 12:20 AM
Interesting thread. Good luck with your testing - not many good ideas came about without doubters. I'm not saying you are right - or wrong - just that I like the fact that you are thinking, and testing your theories.

There is a company (GAMI General Aviation Modifications Inc.) in Ada Oklahoma that has made a very good business of going against the grain, and has, IMHO disproved one of the longstanding cardinal rules of general aircraft engine operation. Conventional wisdom has long been that you should run engines rich to control heat and increase durability and safety. These are large air cooled engines... GAMI developed a system that purposely runs the engine lean of peak, but uses "relatively" high tech engine monitoring and accurate fuel injection systems to keep all cylinders operating evenly. From what I've heard and read, their system doesn't hurt engine longevity, and gives a significant boost in economy.

I can't pretend to be an expert regarding these small air-cooled engines, so won't comment on the cooling or lubrication issues. I will state that it is fairly unusual for gasoline engines to run at their peak torque. Diesels are a different story...

bes

J.Gordon
06-15-2007, 01:41 AM
bes Iím not an expert on small air-cooled engines either, but I havenít read or seen any viable data as to why they would operate beyond the engines peak torque. I did have one dealer tell me that one engine manufacture did because the mower co insisted they raise the rpmís for Blade tip speed. That was the easiest and cheapest way (at the cost of engine longevity.)

Hopefully when I confirm the engine temperature and oil flow pressure at the peak torque I will get the real world differences in fuel economy. If my test shows any significant heat or oil starvation issues I will just save for a 2V750 from Yanmar.

This will be my last post on Beckhamís thread but PM me if you want.

Again sorry for hijacking your thread Beckham!

Richard Martin
06-15-2007, 04:43 AM
In your write up about running a 2400 to save fuel. If peak torque was at 2400 rpm you might save a measurable amount of fuel on a given cutting job. I wish I could find the power curve for a few of these engines. I think you would find the peak torque point is closer to 3600 then to 2400.

Actually, on some engines peak torque occurs at a lower RPM than 2400. Here the graphs for the 17 Kawi...

jrc lawncare
06-15-2007, 06:23 AM
You get out there and it is 90 degrees and you run long enough at low rpm's and it will kill the engine and all hydraulic components, the oil will burn inside just like an automatic transmission. I hardly believe that. We been running tthps for 4-5 yrs at 3/4 maximum throttle with good results, that's the most rediculous thing I've ever heard. Whatever.

Eric D
06-15-2007, 06:41 AM
I have been using a tach on this mower for about 400 hours so I can verify the rpmís vs fuel.

Like I said earlier I still need to change my pump speed before I do this a lot.
My stock BTS is around 17,200 FPM and at 3600 rpm I believe there around 21,000 FPM and the cut is actually better while at full ground speed when I bumped the BTS up.
J. Gordon,

Let me start off, I would never try and discourage experimentation, it can be fun and you can learn a lot from it. However, I would like to make a few predictions on your project if you donít mind. I hope you will report back with your findings.

The rotation of the deck blades is one of the largest energy absorbers on your unit. Once you ratio this drive to bring the tip speed back to what it is at 3600 rpm I believe you will loose the fuel savings you might have seen at 2400.
Here again, upping the ratio on the hydraulic pumps will also suck your fuel savings away.
You will find that because of these ratio changes the operation temperature of your engine will become higher due to less cooling.

My point, everything is a balance and compromise. For the best operation of the engine compared to the loads it has to handle, I am sure the manufacturer of your unit took a lot of time and effort to come up with the 3600 rpm point. Fuel usage, cooling, lubrication, durability, vibration and noise are just some of the issues that have to be addressed. You most likely can improve one of them but at the expense of at least one or all of them.

Regards,

Eric D

puppypaws
06-15-2007, 07:17 AM
I hardly believe that. We been running tthps for 4-5 yrs at 3/4 maximum throttle with good results, that's the most rediculous thing I've ever heard. Whatever.

So you are telling us you know more about what you are doing than the people that design and manufacture these engines, this is very interesting.

The way you spell I'm not sure you even know where 3/4 throttle is unless you have a tach and know how to read it.

puppypaws
06-15-2007, 08:20 AM
Youíre right again the engine has more hp at 3600 rpmís but the torque (what does the work has dropped off significantly) so why operate a 3600 rpmís if you are past your peak torque? Unless it would hurt the engine.

From the testing I have done, it uses a lot more fuel to run at 3600 rpm than at 2400 rpm.

What I am after is the best fuel economy for the amount of work Iím doing while hopefully lengthening the life of my engine by reducing the rpmís.
I understand the carb may have to be rejetted because I donít want to run the engine in a lean or rich condition.

Thatís why I want to measure the EGTís and oil temps, because it wouldnít be worth saving a hundred bucks in fuel and have to replace a $1500.00 engine.

The only drawbacks I can see with this would be overheating the engine and I have not seen or heard any scientific evidence of this happening just hearsay.
(I know a guy whose brother is an engineer that said it wouldnít work and kill your engine.)

Does anyone have proof of this other than hearsay?

It would save me a lot of time if you or someone could prove this.

Go ahead and call me stupid or crazy but itís kind of nice too do the same amount of work using 1/2-2/3 fuel for the same job.

I think I may have figured out your thought process. I have owned and operated large hp John Deere diesel engines for many years but this is a totally different concept.

A 150 hp JD tractor will have a 2300 rpm engine rating but reaches it's maximum torque at 1600. I may be in the field pulling a piece of equipment that does not require the full 150 hp so I am able to go with the next higher gear at a lower rpm setting (maybe 1800). This allows me to do more work with this piece of equipment (because of the faster speed) but also save a considerable amount of fuel.

Now on the other side of the coin if I had a 6 shank parabolic subsoiler behind the tractor you would have to be in the correct gear at 2300 rpm's because you need all the torque (which is reached at 1600 rpm's) plus the maximum hp reached only at the top engine rpm rating of 2300.

This appears to be some of your train of thought. The difference is the JD diesel (or any diesel) is a totally different concept than a small hp air cooled engine. The manufacture thinks when a man buys a 25 hp air cooled engine he wants and needs a full 25 hp. This has never crossed their mind that a man wants to buy a 25 hp air cooled engine and run it at 2400 rpm's to achieve only 18 hp. Saving a small amount of fuel by lowering your rpm's is not something they have ever considered, this is why they designed and specified a engine to be run at their recommended rpm's.

The mower manufacture's know the specifications of engine rpm's required by the engine manufacture's so their components are designed for maximum efficiency coincided with the engine rpm's.

Does this help clear up any of your questions? You can possibly achieve you goal but only through certain engineering changes.

Richard Martin
06-15-2007, 08:42 AM
The way you spell I'm not sure you even know where 3/4 throttle is unless you have a tach and know how to read it.

Actually I only see where he spelled one word wrong. :nono:
Ridiculous.:)

puppypaws
06-15-2007, 09:40 AM
Actually I only see where he spelled one word wrong. :nono:
Ridiculous.:)

Well your no spring chicken so tell me what tthps means, that must be before my time. I don't understand some of this younger generations slang and abbreviations.

You will also notice I said low rpm's not 3/4 throttle, 3/4 throttle on his machine may be within 2 or 3 hundred rpm's, depending on the machine and the throttle linkage.

You do agree these engines were designed to be run at a specific rpm setting for a reason?

Richard Martin
06-15-2007, 11:28 AM
Well your no spring chicken so tell me what tthps means, that must be before my time. I don't understand some of this younger generations slang and abbreviations.

You do agree these engines were designed to be run at a specific rpm setting for a reason?

tthps stands for Exmark's Turf Tracer HP and he has more than one of them.

kawasakitech
06-15-2007, 11:42 AM
Engine manufactures can design an engine to work best under many conditions and RPM ranges. Most general purpose engines are designed to run at a given RPM because of the standards for blade tip speed.

If you want to lessen drag from the blades and increase fuel economy you could reduce the speed of the blades or put low lift blades on the machine. Most would agree lower blade speed would reduce quality of cut. Blade lift could be an opportunity to save fuel. If you have bagging blades on a machine without a bagger you could save fuel by changing to a lower lift (you may reduce the quality of cut because grass doesn’t stand up as well but this is a much better thing to try then changing pulleys).

If you changed pulleys to reduce engine speed but maintain blade tip speed you would need the same amount of energy. Again, engines with governors consume only the amount of fuel needed to do the work.

Cutting machines work best when they run above the torque curve. When the engine incurs a load, engine RPMs drop into the maximum torque area to handle the work load. If an engine was right on the torque curve the engine would be outside of the maximum torque when load is applied and may not have the necessary torque to return engine to maximum range (engine fall on it’s face).

Some OEM request special engines from engine manufactures to run at different RPM ranges and many times they require significant changes to carburetion and sometimes ignition to meet customer’s expectations.

69lt1bird
06-15-2007, 11:53 AM
This is pretty humorus reading how people think they can figure out things in the field on a lawn mower that the engineers/lab techs etc. spend their time doing every day. These are 4 stroke engines, they are designed to run at X rpm's and are tuned and governed to do so. The other components that depend on the engine operating at its specified RPM's are designed and engineered to perform at the optimum efficiency for the mower design, ie. pump style, tire size, vehicle weight, ground speed etc.. These 4 stroke engine, as long as they are not some low end knock off, are not like pulling the trigger on a high revving 2 stroke. The commercial grade engines are designed to run for 1500 plus hours without a rebuild while operating at the maximum governed RPM.

puppypaws
06-15-2007, 01:01 PM
This is pretty humorus reading how people think they can figure out things in the field on a lawn mower that the engineers/lab techs etc. spend their time doing every day. These are 4 stroke engines, they are designed to run at X rpm's and are tuned and governed to do so. The other components that depend on the engine operating at its specified RPM's are designed and engineered to perform at the optimum efficiency for the mower design, ie. pump style, tire size, vehicle weight, ground speed etc.. These 4 stroke engine, as long as they are not some low end knock off, are not like pulling the trigger on a high revving 2 stroke. The commercial grade engines are designed to run for 1500 plus hours without a rebuild while operating at the maximum governed RPM.

tthps stands for Exmark's Turf Tracer HP and he has more than one of them.

Thank you for explaining this abbreviation but I will never remember because it is of no interest to me.

You evidently know this gentleman, have him call Exmark and ask them if they designed his mowers to be operated at anything less than full throttle.

I think most of us know the answer to this, old tbird up above you there definitely does.

topsites
08-09-2007, 12:47 PM
So you are telling us you know more about what you are doing than the people that design and manufacture these engines, this is very interesting.

No, maybe we don't, but the one thing I always keep in mind is the folks who design the engines also sell them, and first and foremost from their side of things, they need to sell MORE engines always. So, how far can I trust their advice? In my own business my advice isn't always 100% FOR the customer, meaning it suits my own purposes as well, wrong it isn't and nobody is accusing anyone of treachery or outright deceit but for making the point we at least try not to stab ourselves in the foot, right?

Because if I were an engine salesman would I purposefully give you wrongful advice?
No, the simple answer is the truth works best, nobody is saying we give bad advice, do so and you will pay for it in the long run. But at the same rate less-than-Wot is not for everybody, you can't give this advice when WOT is such a no brainer...
Thus it is a choice, between one that will work for some, and another that works no matter what...
Just so happens, it could be that WOT also suits the purpose of the manufacturer, such is life and this is business.
So you either experiment and take your chances until you find those sweet spots, or you recommend WOT at all times because you can't go wrong.

That's the thing here, you can't go wrong with always WOT, but that's not saying than less-than-wot doesn't have its merits, it just involves more thought and possibly one could burn or foul up a component.

In business, to save money we take chances, we do what others say shouldn't be done, if for no other reason because I find the challenge excites me, but also so I know why... Many times have I lost time and money by not following what others say is so, but more than a few times have I come out ahead by trying the unproven route, it is in these gambles that over the years we learn how to squeeze the max out of our operation, and it really is and remains to each their own.

You are correct however, less-than-wot you take your chances.
I am correct in saying you save fuel and if done within reason, the machine lasts as long and maybe longer.
btw, hydros wot is good, I do agree but to a point.
On a Bobcat you start at Wot and you're likely to mess things up.
You start at low rpm until you get the feel of things, all that happens is the machine moves slower, lalala...
Then again it's a diesel, but it doesn't appear to affect the pumps.

For gears we may well have to agree to disagree :laugh:

puppypaws
08-09-2007, 02:42 PM
No, maybe we don't, but the one thing I always keep in mind is the folks who design the engines also sell them, and first and foremost from their side of things, they need to sell MORE engines always. So, how far can I trust their advice? In my own business my advice isn't always 100% FOR the customer, meaning it suits my own purposes as well, wrong it isn't and nobody is accusing anyone of treachery or outright deceit but for making the point we at least try not to stab ourselves in the foot, right?

Because if I were an engine salesman would I purposefully give you wrongful advice?
No, the simple answer is the truth works best, nobody is saying we give bad advice, do so and you will pay for it in the long run. But at the same rate less-than-Wot is not for everybody, you can't give this advice when WOT is such a no brainer...
Thus it is a choice, between one that will work for some, and another that works no matter what...
Just so happens, it could be that WOT also suits the purpose of the manufacturer, such is life and this is business.
So you either experiment and take your chances until you find those sweet spots, or you recommend WOT at all times because you can't go wrong.

That's the thing here, you can't go wrong with always WOT, but that's not saying than less-than-wot doesn't have its merits, it just involves more thought and possibly one could burn or foul up a component.

In business, to save money we take chances, we do what others say shouldn't be done, if for no other reason because I find the challenge excites me, but also so I know why... Many times have I lost time and money by not following what others say is so, but more than a few times have I come out ahead by trying the unproven route, it is in these gambles that over the years we learn how to squeeze the max out of our operation, and it really is and remains to each their own.

You are correct however, less-than-wot you take your chances.
I am correct in saying you save fuel and if done within reason, the machine lasts as long and maybe longer.
btw, hydros wot is good, I do agree but to a point.
On a Bobcat you start at Wot and you're likely to mess things up.
You start at low rpm until you get the feel of things, all that happens is the machine moves slower, lalala...
Then again it's a diesel, but it doesn't appear to affect the pumps.

For gears we may well have to agree to disagree :laugh:

Glad to hear from you my friend, I thought you may have melted up in Richmond like we have here. Today they are saying 103 degrees with a heat index of 115.

Eric D
08-09-2007, 03:00 PM
You are correct however, less-than-wot you take your chances.
I am correct in saying you save fuel and if done within reason, the machine lasts as long and maybe longer.
btw, hydros wot is good, I do agree but to a point.
On a Bobcat you start at Wot and you're likely to mess things up.
You start at low rpm until you get the feel of things, all that happens is the machine moves slower, lalala...
Then again it's a diesel, but it doesn't appear to affect the pumps.

For gears we may well have to agree to disagree :laugh:

Topsites,

Your comments are misleading and very ambiguous when it comes to your use of the term WOT. It stands for WIDE OPEN THORTTLE. On any of our lawn cutting equipment with a governor, when the engine speed control is in the full position this is called the HIGH SPEED IDLE. It has nothing to do with WOT. In fact the throttle is open just enough to keep the engine running at the high idle speed. If you wish to run your equipment at something less then this then go for it. It is your equipment. To suggest to others to run at an rpm less the high speed idle is bad advice for many reasons.

You also imply that the engine manufactures would tell us something that is ďgood for them but not the end consumerĒ is nothing short of hog-wash. Picking a set rpm to run an engine allows the engine designer to optimize every aspect of the engine. When you run an engine out of these parameters bad things can happen that you may not have any clue of until itís too late. Picking your own personal rpm point that you feel is better, might in fact find it right on top of a crankshaft torsional mode that will cause it to fail prematurely. Running at the manufactureís recommend rpm insures you are not in any of these danger zones.

Hey! just my two cents worth,:waving:

Eric D

KTO Enterprises
08-09-2007, 03:47 PM
I will say this about engines.

Using higher rpm to provide steady power is a lot less hard on an engine than a lower RPM and using torque to gain power.

Low rpm torque loads are harder on internal parts than higher rpms with a lower torque load. Engines run cooler, and friction surfaces stay cooler. I.E. crankshaft rod journals and piston wrist pins.

GreenT
08-09-2007, 08:50 PM
Wow!

75 posts on what rpms to run an engine. :dizzy: :dizzy: :dizzy: You guys have too much time on your hands. :laugh:

Now, are we done with this?

:waving:

cgaengineer
08-09-2007, 10:23 PM
Engine has more inertia at higher RPM's as well.

Richard Martin
08-10-2007, 04:57 AM
Wow!

75 posts on what rpms to run an engine. :dizzy: :dizzy: :dizzy: You guys have too much time on your hands. :laugh:

Now, are we done with this?

:waving:

Probably not and we will discuss this again in the future. As we get closer to Fall we will discuss blowers until the blue sky turns green. It's just the way it is here at Lawnsite. :)