Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

is it better to run the generator once a month or can it be stored until it is needed.I read it should be run monthly under load so the generator head stays magnetized.Is this true?

Real generators may lose their field strength over time. Self-exciting alternators do not have such problems. You may want to check you owners manual to see what you have....check to see if it refers to "flashing the field" or such. As far as cooling a generator/ alternator.. There should be no "hot spots" in the unit. Even a 240 v generator only running on one phase at full load should be able cool itself or disperse heat evenly, copper being the secound most wildly used thermal conductive metal after silver... My 2 cents Friiy

I'm thinking about converting my EU2000i's to a tri fuel option.

As far as running a generator with no load for a few minutes after use, that is something I have heard of all OPE or engines in general.

As far as a "Cool down Period".(no-load for X min after use)...  What is going to happen?  Is the engine going to get HOTTER than running under load?  Does anyone have a "cool-down period" for their car?

Just food for thought...

Friiy

friiy wrote:
Actually the engine will get hotter for a period of time after shutdown when running under a load.  When the engine is running air is being moved across the engine in large amounts to pull heat away from the engine.  In a water cooled engine the water is being circulated and cooled in the radiator to remove the heat.  When shut off both engines will heat soak.

The engine will cool down idling under a no load condition.  With an air cooled engine letting it run for a few minutes with no load will help it from heat soaking and possibly cooking the oil some.   A hard run water cooled engine should also be allowed to run at an idle for a bit before shutdown. 

Your car is not normally driven anywhere near its max load but a generator is.  If you take a car and run it hard under a load and shut it off I am certain it will puke water all over the place.  

I used to race both cars and motorcycles and we always allowed a idle cool down period after a hard run.  Drag race cars normally don't need an idle cool down because they normally don't get too hot in one pass, but  if you put a few passes on it in a row it will get quite hot and need to be cooled down by idling and blowing cold air, water, nitrogen  or nitrous through the radiator to help cool it down.


Carl

I disagree with the statement , not the proceedure. The engine will not get "physically hotter" if you shut it down, oil will not "bake". The worst condition that the engine or oil is under is full load, it gets no hotter. Anything that can't handle full operating temp. probly isn't worth having. I believe in a cool down period in my own person equipment. Not for the engine's (block) sake, but ease of putting the damn thing away or fueling it. Not trying to pick a fight I just think the idea is flawed as stated. We can all state "novelty engines" or special requirements, but as blanket statement I believe it's false. Especially in regards to OPE. Friiy

You're both right ... or you're both wrong, take your pick   It's a whole lot simpler if you just trace the heat path I'm not saying anything here you don't already know, just stating it differently.

In an air cooled engine the moving air extracts heat from the fins, which extract heat from the block [I'm including the more "solid", unfinned, parts such as the cylinder housing with the term block here]. The fins will be cooler than the block under normal conditions.
This is where the engineer who designed this engine has to know his stuff, and most of them do. Anyone who has had a mouse build a nest under the cooling fins and seen what happened to the engine can tell you that.  Sizing the fins and the fan (flywheel fins) and designing the tins is critical, but we don't have to worry about it since the engineer already did.
When the engine is shut off, there's no moving air and less heat will be absorbed by still air. If the fins are still cooler than the block, they'll continue to absorb heat while giving up less, so  their temp will climb until some sort of balance is reached with the block. (this can include the actual engine block absorbing heat from the heads or jugs depending on the configuration) The block can only cool down as:
(1) It is giving up heat to the air around it and to the fins.
(2) No new heat is being produced.

In a water cooled engine the radiator (appropriately named, isn't it!) gives off heat to the air; the same principle applies except for the extra step of transferring the heat to and from the water that connects (heat path, not physically) the radiator to the block. That has a fan also. Shut that fan off and the radiator/water temps climb for the same reason - the water is absorbing heat from the block but the radiator is no longer absorbing as much heat from the water as it did because it is no longer ... radiating. So the water can get hotter and start spitting out the pressure relief on the cap.

Update after reading this: Remember that the various parts of a running engine will be at different temperatures. Once that engine is turned off, the parts that are bolted together will tend to stabilize. Parts that were cooler become hotter, and other parts will cool down. Most likely the combustion chamber will be the hottest and the tips of the fins the coolest.

When I was tuning/testing my twin cylinder air cooled two stroke Yamaha motorcycles, I'd use an infrared thermometer to check the heat on each cylinder/head/exhaust pipe etc. to see if the readings on each side of the engine were reasonably close.  While the engine was running, the heat remained consistently higher than shortly after shutting it down. 

I've never seen an occasion when any part of the engine actually returned a higher temperature reading after shutting it down.   Finned parts of the engine cooled more rapidly than say, crankcase areas.  Exhaust pipes cooled the quickest due to having the highest temperatures vs. ambient temperatures. 

That makes sense. Totally finned jugs with no tins so you'd have direct convection. I'm sure you noticed that stopped at a light on a hot day! I know I did. Something like an Onan twin, even some B&S single cylinders, would surround those fins with tins that trap heat when there is no air being forced through them.

I stand by my assessment that it is best to idle down an engine that has been working hard for a few minutes before shutting it down. Exhaust valves and seats get very hot when the engine is run hard under a large load and if when you shut down the engine the exhaust valve is closed a lot of heat is trapped in the valve and seat. Idling down for a few minutes allows the exhaust valve and seat to cool a fair amount before stopping the engine.