"will work the engine harder, it wont have much of a load on it" confuses me. If there is not much of a load, then I can decrease the engine rpm and decrease engine wear, right? I dont know hydraulics and dont want to be argumentative, but the way you and trip are explaining this is the opposite of how I imagine it to work.
Ok,on paper you are correct,you can decrease the RPM,which will quiet things down a little,and may even save a small amount of engine wear.The thing you are not factoring into this equation is time and productivity.They play a larger role than engine speed IMO.You theory about increasing engine life,here is my take on that subject. First off, lets start with the engine,since air cooled engines are built to run at a steady 3200-3600 usually,There cooling fan,and fins are designed to move the correct amount of air over the cooling fins at those engine speeds.They are also designed with respect to ignition timing,camshaft,compression,carburation and exhaust to deliver the most HP per pound of engine weight,and per gallon of fuel at those speeds.Now the 13GPM pump is only a 9 GPM,and its not running as fast as it could be,so it also is having to run longer times to split the same amount of wood,so it gets more time put on it.Like I said,you can run it slower,but you probably will not save any fuel or egnine wear when you factor in production.Instead of splitting 10 cord in 10 hrs for example,it now takes you 12.5 hours since you decided to run it at 2700RPM instead of 3600RPM.I hope your following this.In 12.5 hours at 2700 you will burn more fuel than 10 hours at 3600,and have more engine wear in 12.5 hrs than 10,the wear doesnt offset the time.
So what it going to happen if you buy the 13,you are goingto run the engine at the high end of the rpm range because it is slower with the 13gpm pump,OR run it slow,and take forever to split everything .With the 16GPM pump you will be done and inside by the fire,and you will not need to run the engine at the high end,you will be able to run it a little slower,and still have fast ram speed.In knots,it will work the engine a little harder than the 13GPM,but the load is within the designed limits of the engine,so it isn't going to add any appreciable wear for the few seconds it takes to go thru it,and shift back to the 2nd stage,and lower load.With 90% of your cutting,you will blow right thru the wood, with fast cycle time,and a nice engine speed.
One last comparison I can think of is a pickup truck. 2 of the same trucks,both 1 ton chassis cabs,both need to carry 3 tons of wood 100 miles back and forth.We needot move 30 cord this week. First truck has a 292 inline 6(this is actually my old dump truck a 65 C30,it has a 4 speed manual and 4.11 gears.It can run 60 mph all day,but at over 3300RPM.It has enough power to run the wood all day by using the mechanical advantage of 4.11 gearing.This gearing makes up for the small engine by spinning it faster at a given road speed,but not so high that its outside its designed rpm range.This truck is slow to accelerate,and works hard,but it gets the job done. truck #1 represents your typical 5-6hp splitter w 11/13GPM pump and 4" cyl.Say you are building truck #2,but you have a 454 under the hood of this truck. Using your theory,your going to save engine life on this truck by deciding to buy a 4.11 axle for it as well,and additionally you are going to reduce engine speed while running this wood every day.My theory says,since were buying a rear end anyway,lets go with a 3.42 or 3.73 and let the big engines torque do the work,so we can maintain road speed with a touch less engine speed and get done in less time,saving my valuable time, fuel,and wear.So if we have 30 cord to move,you will be still moving it on day 4,I'll be out tinkering with my saws in the garage,since i finished in 3 days.You think you are saving wear and fuel though.I burnt 2 gallons an hour,for 20 hrs,you are only burning 1.6 per hour,but you need to run 26 hours to do the same work.My engine MAY wear out in 3500 hours,and yours lasts 3800.
The point I was trying to make is the bigger pump will do more work in less time,and with less engine speed.That is why I would buy it.If you only had 5HP,then yes a 13GPM pump would be the one,as a 16GPM may overload it in knotty wood.You have 8HP,use it!:greenchainsaw:
