Docwheelhorse 2,560 #26 Posted July 21, 2008 HI--I also notoced that there is a HUGE performance difference going from an 8--10 but not so much a 10--12, I couldn't really figure out why but then Sparky and I figured that the BigXHuge flywheel on the ten must help keep it going versus the little 8's unit. There just seems to be alot more torque in the 10.... Tony Share this post Link to post Share on other sites
WheelHorse_of_course 99 #27 Posted July 21, 2008 <_< Hey guys.... I just happen to have my K series manual in front of me so time for some real data.... K181 HP (@max RPM) 8.0 Displacement 18.6 CI Max torque 13.6 ft/Lbs RPM @ max torque 2200 Torque @ max RPM 11.7 ft/Lbs Max RPM 3600 K241 HP (@ max RPM) 10.0 Displacement 23.9 CI Max torque 16.7 ft/lbs RPM @ max torque 2220 Torque @ max RPM 14.5 ft/Lbs Max RPM 3600 K301 HP (@ max RPM) 12.0 Displacement 29.1 CI Max torque 22.2 ft/lbs RPM @ max torque x 2200 Torque @ max RPM 17.3 ft/Lbs Max RPM x 3600 K321 HP (@ max RPM) 14.0 Displacement 31.3 Max torque 23.5 ft/lbs RPM @ max torque 2000 Torque @ max RPM 20.5 ft/Lbs Max RPM 3600 If anyone asks nicely I could add additional models to the above chart. B) Share this post Link to post Share on other sites
Curmudgeon 28 #28 Posted July 21, 2008 Displacement is meaningless without compression. A large bore engine will not produce the same power as a smaller bore of the same stroke, head clearance, etc., because the larger bore yields less compression. 8 hp to 10 hp IS a 25% jump and 10hp to 12 hp IS only a 20% jump, no matter how you look at it. It may only be 2hp, but is a much larger PERCENTAGE of the original power. An increase of 2hp is not much when you get up into the larger engines, but in the small category 2hp can be significant. An increase of 25% will be felt more than one of 20% regardless of the other #s. And let's not forget GEAR RATIOS! 8:1 compression ratio is 8:1 compression ratio, no matter the bore/stroke ratio. You can also debate that the longer stroke engine will make more torque because of mechanical advantage. The other side can argue larger bore will provide more torque because of greater piston area exerting more down force. Rotating mass stores energy, rotating mass does not create energy. I'm pretty sure Einstein will back me up on that one! The variables are infinite. Compression ratio, displacement, valve size, valve lift, valve timing, size of carb, intake flow restrictions, exhaust flow restrictions, exhaust pulses and pressures, exact fuel mixture, intake port shape and size, exhaust port shape and size, completeness of atomization of fuel mixture, ignition timing, spark quality, to name a few. ANY general statement can be proven wrong just as much as it can be proven right when it comes to the internal combustion engine. 95% of the time, we are not using these engines to their capacity. Don't believe me, (and don't sue me when you fall off like an idiot) next time your working your beast to the max, flip up the hood and push the governor over. Most likely you'll find yourself at half throttle or less. I've run 48" decks on 10 horse models, 76" decks on 16 horse models, always had PLENTY of governor movement left. Blowing snow is the only time I ever lugged a tractor down enough to fully open the throttle. Share this post Link to post Share on other sites
kpinnc 10,718 #29 Posted July 21, 2008 K181 HP (@max RPM) 8.0 Displacement 18.6 CI Max torque 13.6 ft/Lbs RPM @ max torque 2200 Torque @ max RPM 11.7 ft/Lbs Max RPM 3600 K241 HP (@ max RPM) 10.0 Displacement 23.9 CI Max torque 16.7 ft/lbs RPM @ max torque 2220 Torque @ max RPM 14.5 ft/Lbs Max RPM 3600 K301 HP (@ max RPM) 12.0 Displacement 29.1 CI Max torque 22.2 ft/lbs RPM @ max torque x 2200 Torque @ max RPM 17.3 ft/Lbs Max RPM x 3600 K321 HP (@ max RPM) 14.0 Displacement 31.3 Max torque 23.5 ft/lbs RPM @ max torque 2000 Torque @ max RPM 20.5 ft/Lbs Max RPM 3600 I would say if this tells anything, it is that the idea of going from 8 hp to 10 hp being be a "more noticable" leap, is questionable.... Difference in max torque between a 181 and a 241: 3.1 ft/lbs. Difference in max torque between a 241 and a 301: 5.5 ft/lbs. This also constitutes the largest gap in torque values of all the engines by far. Given max torque is accomplished at @ 2000 RPM, does this mean torque actually falls off somewhat at max RPM? Laws of inertia are screaming NO at me here, so I am a little confused... And yes, I do remember that we are talking horsepower, not torque. But the horsepower ratings are pretty linear (8-10-12-14), while the torque values are not... So the "mass" discussion is out. There is a much larger torque difference between two big blocks than the difference between a small and big block. I know the crank is different between the 241 and 301, but the flywheels are the same. That makes me think rotating mass is not affected much.... If someone brings a K341 into this, my head is gonna pop. This thread is giving me a headache.... Kevin Share this post Link to post Share on other sites
linen beige 14 #30 Posted July 21, 2008 The percentage increases are interesting. At 2200 rpm the K-181 to K-241 increase is 8.14%, the K-241 to K-301 is 7.52 %. But at max rpm the K-181 to K-241 increase is 8.06% and the K-241 to K-301 is 8.38%. That shows that one step up is greater at the mid range but the other step up is greater at full throttle. When you consider what Dale points out about seldom running them at full throttle, then the 8hp to 10hp jump seems to be the greater increase in usable power. Share this post Link to post Share on other sites
Curmudgeon 28 #31 Posted July 21, 2008 If MAX torque is at 2000 RPM, any speed above or below that there will be less torque. The big question is, and what comes into play with the new versus old engine debate, just how MUCH does it fall off? What's missing in those numbers is the speed at which MAX horsepower is made. Torque times speed. If it's falling off fast, the speed numbers will be close, but if the torque holds with little drop off, the numbers will be farther apart. Now how about a max torque number for a new engine? I wonder where that is? And is a flat curve, as I suspect the older K-Series are (I've seen a chart somewhere of it) or is there a narrow little peak? Narrow little peaks give big numbers, but in the real world often fall short of having that "feel" of usable power. Share this post Link to post Share on other sites
Curmudgeon 28 #32 Posted July 21, 2008 Still looking for that chart, but found this for you math freaks: CALCULATING USABLE HORSEPOWER Example: Application: Fan Load: 8HP @ 3600 RPM (Manufacturer's specs) Duty Cycle: Constant Altitude: Up to 4000' Temperature: (max) 100 degree F. Power transmission: V-belts. 1. Duty Cycle = use 80% factor (constant) 2. Altitude + 4000ft x 3.5% loss / 1000ft = 14% loss (or 86% available) 3. Temperature = (100 degree -60 degree) x 15/10 = 4% loss or 96% available) 4 Power Transmission = V-belt (97% efficient) The engine HP actually required for this application can now be determined from the following formula: Engine HP required (unknown) X duty cycle .80 X Altitude effect .86 X Temperature effect .96 X Transmission .97 = 8HP required to drive fan or 8HP required to drive fan _____________________ = Min. 12.4 HP engine actually required .80 X .86 X .96 X .97 Now wasn't that FUN!!!!!!!!!!!!!!!!!!!! Share this post Link to post Share on other sites
Curmudgeon 28 #33 Posted July 21, 2008 Found this one for the newer Command engines. Share this post Link to post Share on other sites
Curmudgeon 28 #34 Posted July 21, 2008 Fun formulas for those of us who are not mathematically challenged. Share this post Link to post Share on other sites
Curmudgeon 28 #35 Posted July 21, 2008 Horsepower EXPLAINED!!!!!!!!!!!!!!!!!!!!!!!!! Share this post Link to post Share on other sites
Curmudgeon 28 #36 Posted July 21, 2008 Any OTHER questions? B) Share this post Link to post Share on other sites
BPjunk 184 #37 Posted July 21, 2008 Well OKkkkkkk, Ya'll made me go into my chart files and dig out THIS CHART on usable horse power. .... Or what we call mathmatics down south. 7HP x 3 Speeds x Wild Driver :horseplay: = 4,ooo LBS Mass Moved <_< So in conclusion we know that 7HP = gettin' the job done! Wild Bill in Richmond, Va. Attached Image Share this post Link to post Share on other sites
Curmudgeon 28 #38 Posted July 21, 2008 Nothing better than theories proven!!!!!!!!!!!!! Share this post Link to post Share on other sites
oldandred 15 #39 Posted July 21, 2008 Nothing better than theories proven!!!!!!!!!!!!! O well there goes my story so much info Im getting a big head like Dale is it spelled right ?? B) Share this post Link to post Share on other sites
Curmudgeon 28 #40 Posted July 21, 2008 When I'm on a mission!!!!!!!!!!!!!!!!!! I copied these from original Koher K-90 and K-91 operating manuals. Share this post Link to post Share on other sites
Curmudgeon 28 #41 Posted July 21, 2008 Check this out boys and girls!!!!!!!!!!!!! Yes, it's a Briggs, a big ass Briggs, but check out exactly what this graph says: Do you see a difference between RATED and NET horsepower numbers?????????? Share this post Link to post Share on other sites
bluetuna08 0 #42 Posted July 21, 2008 B) but I do love the porn for engineers!!! Share this post Link to post Share on other sites
Curmudgeon 28 #43 Posted July 21, 2008 Oh my dear Tuna, if you think the horsepower issue is a dead one, just check back at how many times it's come up. It'll be a never ending topic. :horseplay: Ya'll have to admit one thing, all those formulas and graphs are more informative than drivel!!!!!!!! B) Share this post Link to post Share on other sites
Nick 13 #44 Posted July 21, 2008 Might as well throw one more chart into it. Numbers from the 857 manual. Share this post Link to post Share on other sites
Docwheelhorse 2,560 #45 Posted July 22, 2008 All this is irrevalant.... Wild Bill told me to simply pour Cox Model Airplane Fuel in and even the lowly 8 will swing a 60" deck :banana: Share this post Link to post Share on other sites
Curmudgeon 28 #46 Posted July 22, 2008 Ah, a little nitro....................... B) Share this post Link to post Share on other sites
kpinnc 10,718 #47 Posted July 22, 2008 All this is irrevalant.... Wild Bill told me to simply pour Cox Model Airplane Fuel in and even the lowly 8 will swing a 60" deck Just don't forget your seatbelts, crash helmet (with built in camera), and Redsquare banner.... Also, SWAT body armor might not be a bad idea. Kevin Share this post Link to post Share on other sites
TT-(Moderator) 1,127 #48 Posted July 22, 2008 HEY! --- I know a guy that runs airplane fuel in a WH too. B) Share this post Link to post Share on other sites
linen beige 14 #49 Posted July 22, 2008 HEY! --- I know a guy that runs airplane fuel in a WH too. Hunert oktain avgas'll get the job done! Ever have anybody try to tell you how much better it'll run on jet fuel (kerosene)? B) Share this post Link to post Share on other sites
WheelHorse_of_course 99 #50 Posted July 22, 2008 Any OTHER questions? Yes It seems to me that to increase HP at maximum RPM the easiest way to do that is increase maximum RPM. Most of the old Kohlers have a max of 3600 though ISTR there is one model at 3200. What is the max RPM for the typical modern engine? B) Share this post Link to post Share on other sites
