Our commercial Gravelys at work, which we run full throttle, constanty get shut off by the thick wet grass that we cut. We just crank them right back up, with the lever on full throttle till it bogs down and gets shut off again. We pull them on the trailer after were done, sometimes we pull the throttle back to half and let them idle, other times we pull ti back to half and shut them off right away, never had a problem. I used to overthink it when it came to maintaining these Kohler engines, now I keep it simple. Napa 15W40, Baldwin BT223 filter every 60-100 hours, and let her rip. Off topic but I laugh at anyone who says it doesnt get hot in south Louisiana. Its the hottest month of the year right now and its been absolutely brutal. We weedeat in the morning and cut anytime after as its way too hot to weedeat any other time but the morning.
Idle to cool down, isn't full throtno load better?
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Originally Posted By: Cujet
Easy to answer. Engine temperature goes up as RPM increases, regardless of load. A simple infrared thermometer illustrates this.
But the engine is already hot! I don't think an idling fan speed cools an already hot engine.
Originally Posted By: Propflux01
Idling before shutdown cools the engine. Less RPM equals less heat. If you shutdown from full, many times it will backfire or pop afterwards. This is because exhaust valve is hot enough (probably glowing) to burn the raw fuel. Idle down, valve cools, no pop or backfire.
Less rpm is less heat. But the heat is already there from running. I dump my throttle to idle and immediately shut it off, i don't let it idle for any amount of time, as i feel the engine is already hot, the engine is still burning fuel and the fan is not moving much air, so the temps might go up idling.
Easy to answer. Engine temperature goes up as RPM increases, regardless of load. A simple infrared thermometer illustrates this.
But the engine is already hot! I don't think an idling fan speed cools an already hot engine.
Originally Posted By: Propflux01
Idling before shutdown cools the engine. Less RPM equals less heat. If you shutdown from full, many times it will backfire or pop afterwards. This is because exhaust valve is hot enough (probably glowing) to burn the raw fuel. Idle down, valve cools, no pop or backfire.
Less rpm is less heat. But the heat is already there from running. I dump my throttle to idle and immediately shut it off, i don't let it idle for any amount of time, as i feel the engine is already hot, the engine is still burning fuel and the fan is not moving much air, so the temps might go up idling.
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Cut some pretty deep grass (undeveloped land behind me) in the heat today - was thinking about this - so I kind of staged down the load, then speed - but also thinking if there were some big issues this mower might have a temperature gauge somewhere
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Owner's manual for my John Deere/Sable says to run engine a lower RPM
after use to reduce engine heat before shut down. I don't always listen.
My 2¢
after use to reduce engine heat before shut down. I don't always listen.
My 2¢
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Originally Posted By: mobilaltima
Our commercial Gravelys at work, which we run full throttle, constanty get shut off by the thick wet grass that we cut. We just crank them right back up, with the lever on full throttle till it bogs down and gets shut off again. We pull them on the trailer after were done, sometimes we pull the throttle back to half and let them idle, other times we pull ti back to half and shut them off right away, never had a problem. I used to overthink it when it came to maintaining these Kohler engines, now I keep it simple. Napa 15W40, Baldwin BT223 filter every 60-100 hours, and let her rip. Off topic but I laugh at anyone who says it doesnt get hot in south Louisiana. Its the hottest month of the year right now and its been absolutely brutal. We weedeat in the morning and cut anytime after as its way too hot to weedeat any other time but the morning.
Weed eating isn't bad, but walking behind a mower is imo. It's kind of funny when you're just sitting on a ztr mower I always seem to feel a nice cool breeze, not sure if it's because I'm always moving anywhere from 3-10mph or just not using much energy sitting still.
Our commercial Gravelys at work, which we run full throttle, constanty get shut off by the thick wet grass that we cut. We just crank them right back up, with the lever on full throttle till it bogs down and gets shut off again. We pull them on the trailer after were done, sometimes we pull the throttle back to half and let them idle, other times we pull ti back to half and shut them off right away, never had a problem. I used to overthink it when it came to maintaining these Kohler engines, now I keep it simple. Napa 15W40, Baldwin BT223 filter every 60-100 hours, and let her rip. Off topic but I laugh at anyone who says it doesnt get hot in south Louisiana. Its the hottest month of the year right now and its been absolutely brutal. We weedeat in the morning and cut anytime after as its way too hot to weedeat any other time but the morning.
Weed eating isn't bad, but walking behind a mower is imo. It's kind of funny when you're just sitting on a ztr mower I always seem to feel a nice cool breeze, not sure if it's because I'm always moving anywhere from 3-10mph or just not using much energy sitting still.
Originally Posted By: Odd_Ball
Instead of all this speculation, why doesn't someone collect some data. Get an IR probe and measure the cylinder head temperature under these various load/rpm conditions.
This is exactly what I was going to do after I cut the grass this weekend. I'm going to guess that the best cooling will be achieved somewhere above idle, maybe around 40 to 50% engine speed when the main circuit starts to add more fuel to the mixture. This is with no-load on the engine of course.
Instead of all this speculation, why doesn't someone collect some data. Get an IR probe and measure the cylinder head temperature under these various load/rpm conditions.
This is exactly what I was going to do after I cut the grass this weekend. I'm going to guess that the best cooling will be achieved somewhere above idle, maybe around 40 to 50% engine speed when the main circuit starts to add more fuel to the mixture. This is with no-load on the engine of course.
Thank you dwendt44. Owner's manual for my John Deere/Sable says to run engine at lower RPM
after use to reduce engine heat before shut down. Same information for my B&S Twin 20HP in my JD. Ed
after use to reduce engine heat before shut down. Same information for my B&S Twin 20HP in my JD. Ed
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My toro manual for my zero turn says to set throttle to fast then turn off. Since its carbed , i don't want that much fuel going in when i turn the key off. I pull the throttle to idle and shut off immediately.
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Originally Posted By: John_VT
Originally Posted By: RedOakRanch
My experience on low speed, steep grade mountain roads is that you turn it off or downshift and keep going. I've had better luck pulling grades at 3500rpm vs 2000rpm in regards to over heating. None of my overheating was due to vehicle issues just large loads at low speed, 10-30mph. My lumberyard forklifts will over heat on 115° days. They will over heat at idle but will cool down if held at a mid range rpm for a few minutes. I guess I'm not a fan of the idle cool down.
It's been awhile but aren't forklifts liquid cooled. If they will overheat idling they probably have a problems
A forklift engine is just a little 4 cylinder engine like in a Toyota or Nissan car with a big fan and radiator on it.
Originally Posted By: RedOakRanch
My experience on low speed, steep grade mountain roads is that you turn it off or downshift and keep going. I've had better luck pulling grades at 3500rpm vs 2000rpm in regards to over heating. None of my overheating was due to vehicle issues just large loads at low speed, 10-30mph. My lumberyard forklifts will over heat on 115° days. They will over heat at idle but will cool down if held at a mid range rpm for a few minutes. I guess I'm not a fan of the idle cool down.
It's been awhile but aren't forklifts liquid cooled. If they will overheat idling they probably have a problems
A forklift engine is just a little 4 cylinder engine like in a Toyota or Nissan car with a big fan and radiator on it.
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Some mowers are bad about backfire. This can unroll the seams of the muffler and cause failure.
Idle lets the muffler insides cool below the auto ignition temperature.
There is a fuel shutoff solenoid, BUT that only works on the main circuit, not idle.
You declutch blades, low rpm to parking spot, then advance throttle to mid and shut off. With the butterfly open too far to feed off the idle circuit, there is only clean air in the muffler, and no pop.
Any other method and there is a LOUD pop
The engine it's self really does not care
Rod
Idle lets the muffler insides cool below the auto ignition temperature.
There is a fuel shutoff solenoid, BUT that only works on the main circuit, not idle.
You declutch blades, low rpm to parking spot, then advance throttle to mid and shut off. With the butterfly open too far to feed off the idle circuit, there is only clean air in the muffler, and no pop.
Any other method and there is a LOUD pop
The engine it's self really does not care
Rod
Don't over think it. If you shut it down under fill load the hottest parts of the engine (cyl head) will immediately cool down by conduction to the other parts of the engine. Its a tempest in a teapot. Life is to short.
For what it's worth, I always idle down the engine in my rider. Briggs 24hp V twin.
When mowing is complete, I park it at idle, and blow off the deck and everywhere else with a leaf blower, then park in the garage and shut off.
When mowing is complete, I park it at idle, and blow off the deck and everywhere else with a leaf blower, then park in the garage and shut off.
Originally Posted By: Fastzntn
For what it's worth, I always idle down the engine in my rider. Briggs 24hp V twin.
When mowing is complete, I park it at idle, and blow off the deck and everywhere else with a leaf blower, then park in the garage and shut off.
Yes, I always blow off the deck every time time. My good friend lost his mower and damaged his house when the grass on the deck caught on fire after the mower was parked. Insurance adjuster told him, we see this a few times a year. But you never hear of it do you.
Rod
For what it's worth, I always idle down the engine in my rider. Briggs 24hp V twin.
When mowing is complete, I park it at idle, and blow off the deck and everywhere else with a leaf blower, then park in the garage and shut off.
Yes, I always blow off the deck every time time. My good friend lost his mower and damaged his house when the grass on the deck caught on fire after the mower was parked. Insurance adjuster told him, we see this a few times a year. But you never hear of it do you.
Rod
Okay, I cut the yard today and here's some data from my Kohler 22 HP twin. I took temp readings in 15 minute cutting intervals, allowing 10 minutes of cooling (unloaded) before checking the drop in temp. I used a thermocouple for checking the oil temp and an IR gun to check the case temps between the cylinders. Ambient temp was 90F. You can see there's a negligible difference in cooling from idle to 1/3 throttle and cooling efficiency starts decrease as RPM increases after that. Temps held steady or increased above 1/2 throttle.
Idle-
oil temp decreased 6.25%
case temp decreased 5.35%
1/3 throttle-
oil temp decreased 7.73%
case temp decreased 6.47%
1/2 throttle-
oil temp decreased 2.48%
case temp decreased 3.2%
Idle-
oil temp decreased 6.25%
case temp decreased 5.35%
1/3 throttle-
oil temp decreased 7.73%
case temp decreased 6.47%
1/2 throttle-
oil temp decreased 2.48%
case temp decreased 3.2%
Thank you for the "real"data funflyer. From your data, one wants to keep the unloaded engine at less than 1/3 throttle for cooling down. Ed
You waited 10 minutes? I'd want to know the temp at wide open right after a load , then immediately idle down and check temps for the next minute.
Originally Posted By: spasm3
You waited 10 minutes? I'd want to know the temp at wide open right after a load , then immediately idle down and check temps for the next minute.
Initial temps were taken right after cutting at WOT then the throttle was reduced for the ten minutes before taking the final temp reading. I chose ten minutes because temps stabilized around the six to eight minute mark.
You waited 10 minutes? I'd want to know the temp at wide open right after a load , then immediately idle down and check temps for the next minute.
Initial temps were taken right after cutting at WOT then the throttle was reduced for the ten minutes before taking the final temp reading. I chose ten minutes because temps stabilized around the six to eight minute mark.
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