Gas MPG on a mower?

esbwn · May 12, 2006

Just something I was thinking about on my drive home today. I hear about MPG on vehicles all day *I work at a GM service dept* and was wondering why lawn mowers do not get better "mileage." I have a LT 1050 now and get about 2.5-3hrs, which is about 1 round of mowing at my house, out of a tank. I regularly change the oil, air filter, and keep the blades sharpened to make it as easy as I can on my mower. Just wanted to know what everyone else thought.

JTKub · May 12, 2006

The kohler command 20 in my 2544 burns about 1gal/hr while mowing. I get about 2.5 mowings out of a tank.

Joel

Mrwurm · May 12, 2006

I gal/hr sounds about right. When I was using a Yardman with 18hp Briggs, I used about 3 gallons to mow 2.5 acres, which took me about 3 hours. When I switched to a ZTR with a 25hp Kohler, I decreased my mowing time to less than an hour, but I still use about 3 gallons per cut.

jmt1271 · May 12, 2006

( I gal/hr sounds about right. When I was using a Yardman with 18hp Briggs, I used about 3 gallons to mow 2.5 acres, which took me about 3 hours. When I switched to a ZTR with a 25hp Kohler, I decreased my mowing time to less than an hour, but I still use about 3 gallons per cut. )

the 25 hp command in mine does much better than that. if my math is right your burning a gallon in less than 20 minutes.

Fordlords · May 12, 2006

Lawn mower engines use significantly less gas than they did 15-20 years ago. My Honda GX610 18 HP V twin uses about half the amount of gas as the original 25 year old 17 HP Kohler KT17 did in the same tractor, and along with 1 additional HP the Honda produces about 5 more ft/lbs of torque than the Kohler did. Innovations in the mower engines mainly came from the automotive sector, including use of overhead valves, aluminum blocks and heads, hydraulic valve lifters, efficient head porting, shorter and cleaner intake runners, higher compression ratios, higher spark voltage on the ignition, better valve and ignition timing, less restrictive exhausts, etc.

I would say around 1 gal/hr on a 18-20 HP modern small engine sounds about right.

New innovations we are seeing on mowers are fuel injection and some rebirth with overhead cams and liquid cooling, although most mower owners don't like the extra maintenance expenses associated with these items. I expect to see air cooling and carburetors to be around on mower engines for a long time to come.

-Fordlords-

EuropaChris · May 13, 2006

I'd love a fuel injected, liquid cooled engine on my Cub! Kawasaki makes them already for John Deere.

I'll bet we'll see a lot more of them in the future as emissions regulations clamp down on lawnmowers. Going to FI and liquid cooling will allow tighter tolerances and better control of combustion, as well as the addition of catalytic converters and probably O2 sensors. Yes, gang, I'll bet we see lawn mowers with computer controlled engines in the next 10 years or less.

The downside will be cost and complexity, but the upside will be longevity and performance. Think about a modern Corvette. 20 mpg or better on the highway, and over 400hp. Power and efficiency that far eclipses any of the muscle cars of the 60's. How often does a modern engine break down? 100,000 miles? Piece of cake.

The problem then would be the engines will far outlast the rest of the tractor. Even today, with superior engines like the Kohler Commands, you'd be hard pressed to wear one out before the tractor itself.

Chris

JTKub · May 13, 2006

( I'd love a fuel injected, liquid cooled engine on my Cub! Kawasaki makes them already for John Deere.)

The problem with liquid cooled (gas or diesel) on the CC 2000/3000 series is the layout of the engine. They stick the radiator in the lower dash area, right where it sucks in all the dust/debris.

Joel

JSharp · May 13, 2006

My 2554 won't quite run 2 hours on a full tank, at least doing the heavy grass cutting I've been doing so far.

I notice a lot of push on the Kohler site for their fuel injected engines. They're claiming pay back of the additional engine cost in just a couple of years from fuel savings. Of course they use a lot of yearly hours to make the numbers work.

I expect we'll see carbs for many years to come unless the greens get some really tight emissions standards passed. At that point the small engine makers will be almost forced into EFI just like the auto makers were.

That's not really a far fetched possibility. I haven't looked at the numbers but it wouldn't surprise me if my 23hp Kohler pollutes as much or more as a modern small automobile...

EuropaChris · May 13, 2006

( I haven't looked at the numbers but it wouldn't surprise me if my 23hp Kohler pollutes as much or more as a modern small automobile... )

It probably pollutes more than a small fleet of modern 4 cylinder automobiles. These newer engines aren't NEARLY as bad as the old iron flathead engines (Kohler K-series, etc.), but they still blow out a pretty fair portion of pollution.

I think that's what I miss from my childhood mowing experiences - that rich cloud of unburned hydrocarbons that mixed with the smell of fresh cut grass. That was heaven! These newer mowers just don't smell as good!

Chris

Gatorboy · May 13, 2006

( the 25 hp command in mine does much better than that. if my math is right your burning a gallon in less than 20 minutes. ) 

My pickup truck driving at 60 mph gives me about 14 mpg, so I burn a gallon every 14 minutes -- I would love to get 20 minutes per gallon (20 mpg) /forums/images/graemlins/blush.gif

Bob_Bainbridge · May 13, 2006

( I'd love a fuel injected, liquid cooled engine on my Cub! Kawasaki makes them already for John Deere.

I'll bet we'll see a lot more of them in the future as emissions regulations clamp down on lawnmowers. Going to FI and liquid cooling will allow tighter tolerances and better control of combustion, as well as the addition of catalytic converters and probably O2 sensors. Yes, gang, I'll bet we see lawn mowers with computer controlled engines in the next 10 years or less.

)

I just heard that California emmision regulations will probably cause catalytic convertors to be installed on all new mowers in 2007.

Bob B.

Bob_Bainbridge · May 13, 2006

(
My pickup truck driving at 60 mph gives me about 14 mpg, so I burn a gallon every 14 minutes -- I would love to get 20 minutes per gallon (20 mpg) /forums/images/graemlins/blush.gif )

I had a WWII airplane that burned 12-15 gph at 120-130 knots. It was only 220 HP although I think they rated those engines a little different than car and tractor engines since it was 7 cylinder 670 cubic inches. I sure wouldn't want to buy gas for it today. I paid 45 cents back then.

Bob B.

Fordlords · May 13, 2006

I transported around in my truck a JD 767 ZTR mower to trade shows last winter that had the liquid cooled EFI Kawasaki engine. You just start it by turning the key, no choke to mess with, and it would fire right up even in the bitter cold. It would however still bang out quite a bit of black smoke for the first few seconds just like a carb/choke engine will when cold. JD has been using these Kawi's for a while now in their top end tractors. I'm surprised I haven't seen Kohler's Aegis LC/EFI engines on anything except a few of the ZTR's, it looks like it would fit garden tractors fine. Kohler put that Triad OHC engine on one of the CC models before quickly discontinuing the engine for some reason. A lot of the early Honda L/G tractors had liquid cooled engines adapted from motorcycle designs, I think the air cooling just won out for sheer simplicity and lesser cost. The gov't has been pretty lax on lawn mower emissions requirements, so we gotta keep quiet if we still want some of that good unburned gas smell while mowing /forums/images/graemlins/grin.gif

-Fordlords-

EuropaChris · May 14, 2006

(

I had a WWII airplane that burned 12-15 gph at 120-130 knots. It was only 220 HP although I think they rated those engines a little different than car and tractor engines since it was 7 cylinder 670 cubic inches. I sure wouldn't want to buy gas for it today. I paid 45 cents back then.

Bob B. )

That's why I giggle every time I fill up our little 1946 Cessna 140. Average fuel burn is between 4 and 5 gal. an hour, and she'll cruise right at 100 mph. An average fillup is about 13 gallons.

Still, 100LL aviation gas is $3.70/gal. But, I do have the autofuel STC, so I can run 87 octane unleaded, as long as it doesn't have any alcohol in it. Autogas is good for the engine, as the little Continental C-85 series (actually all the small Continentals) were designed for 80 octane avgas, which had 25% of the lead content of 100LL. Running 100LL tends to foul plugs and is hard on the engine overall.

But, autogas STINKS compared to 100LL. If you get 100LL on your hands, it just evaporates and goes away. Autogas will stay with you all day long. Totally different fuel.

Anyway, enough OT rambling.....

Chris

rbodell · Jul 6, 2017

My life pretty well centers on small engine fuel consumption. I live off grid in Alaska. I live on 12 volts and recharge batteries with a 7 HP mower engine and an alternator. 12 volts and a 30 amp charge rate equals 360 watts, so it takes about 4 hours a day to charge batteries. These engines run about 1GPH or more. Simple math = 120 gallons a month

I said THESE engines, I did not say MY engine, I get 9 to 10 hours on a gallon. I said I live off grid, I didn't say it was my only option. There is power 50 feet from my house. I am off grid because I can make it cheaper than the power company. They charge $35 a month for the meter PLUS electricity. Nothing comes with the meter. Electricity is around double what it is in the lower 48. My fuel bill is a fairly consistent 12 gallons a month.

Sorry people, no big secret here, no conspiracy, hidden wires, hydrogen, no patents, NUTTEN. I even use regular gas.

SHHHHHH here is my secret ............ While there is a bit more involved with the alternator to make it work, the only thing I did was to set it up to run at an idle. People use a 3 hp engine running wide open under a strain to tun an alternator that takes 5 HP. What do you think fuel consumption would be. By using a couple extra HP I can run lower RPM. Here it running, you can hear it idling.
Gasoline generator ruing on propane w/o propane carburetor - YouTube

NOTE: This was an experiment running it on propane. I will get to that in a minute.

That may not help your riding mower much, but if you are thinking of building something or buying a new engine for something, Keep it in mind. Lowering the engine RPM has a HUGE amount to do with fuel consumption.

Now then for the riding mowers and propane, I played around injecting propane into the air cleaner and running the engine on solely propane. Propane mower with stock carburetor (large file) - YouTube In this situation I got about three times the running time/dollar in fuel savings and I didn't even have a propane carburetor. The difference is that it was running faster. At an idle, I actually get better fuel consumption on gasoline. AT AN IDLE, I got about 25% less running time on propane over gasoline (ON MY GENERATOR).

Hope this helps on fuel consumption

patrick_g · Jul 6, 2017

Some of the larger Cub Cadets at the big box stores have EFI and improved fuel economy. I don't recall the brand but there are riding mowers now that are fueled with propane. There are even small outboard motors fueled by propane. We are on our second propane powered automatic standby generator. New one is called 22KW but is derated to 20KW on propane.

I have had a propane only pickup back when propane was a bargain. Clean burning propane never turns the engine oil into black muck. In fact the instructions from Petrolane, the conversion folks, was to not change the oil, just change the filter and top off the oil. You were instructed to add some light weight oil to control the viscosity. Otherwise over time the lighter fractions in the oil would be depleted increasing the SAE rating too much. This was back in the days of 3000 mile spark plug changing schedule but on propane you could go 100,000 miles on a set of plugs.

Patrick

patrick_g · Jul 6, 2017

I forgot to mention in previous post that you need to do something about the heat of vaporization, especially in a cold climate. My propane pickup had a heat exchanger that had hot engine coolant flowing through it and to which liquid propane was introduced. So the heat of vaporization for the propane was supplied by engine heat. One time before going on an extended vacation camping out in the bed of the pickup I was concerned with the accuracy of the propane gage. So, I decided to run it till it ran dry and note the gage reading and then when filling the tank note the amount of fuel put in and how that registered on the gage at various levels. So as to not be stranded when I ran out of propane while conducting the test I carried a 20 lb propane tank and the adaptive fittings needed to use it. Eventually I started getting symptoms of fuel starvation, having to ease up on the throttle to avoid too lean of a mixture. Finally... I installed the 20 pounder and was good to go. I headed for the propane supplier to fill my 84 gallon (water capacity) tank to the 80% mark. All was good for a few miles and then I started getting fuel starvation, overly lean mixture necessitating a reduction in throttle position to keep the mixture rich enough to keep the engine running.

I had to get off the interstate (California Freeway) as I could not maintain the min permitted speed of 40MPH. Things continued to deteriorate and I was doing about 5-7 MPH max when I pulled in to the propane supplier. What was my problem? I had plenty of propane. I immediately knew the problem (my mistake) as soon as I went to swap the hoses back from the 20 pound propane tank to the truck's tank. I had set the 20 pound propane tank right side up just like when I used it to fuel a two burner Coleman camp stove and mantle lantern. The propane is supposed to be in a vapor state, not liquid, when introduced to the propane carb. My 20 pounder put out vapor. The heat of vaporization came from the tank, actually the surface of the liquid propane. So the more fuel that vaporized the colder the propane and tank got.

The vapor pressure of propane goes to 0 PSI down about 40 below zero (F or C, doesn't matter -40 F is -40 C) The propane got so cold it didn't have any vapor pressure to push the vapor through the hoses to the engine. There was over an inch of ice on the outside of the 20 lb propane tank at the level of the liquid. Had I been as smart as my mom always wished I would be (and considering I was a physicist before finding true religion, i.e. computer science) I should have inverted the 20 pounder and sent liquid through the hoses to the engine. The vaporization would have taken place with all heat supplied by the engine and you wouldn't be reading about my fun experience.

When I was stationed at a SAC base north of Minot, ND I witnesses farm folks starting wood fires under their propane tanks to get enough vapor pressure to get enough vapor to the kitchen to fry eggs.

If I were experimenting with running a gas engine with a gasoline carb on propane vapor (especially in a cool climate), I would give some consideration as to from whence cometh the heat of vaporization. My experiment was in San Diego, CA.

Patrick

rbodell · Jul 6, 2017

I can see having to run liquid. It is pretty hard getting it out through the really small orifices in the regulator. I never ran into that problem, because the engine was just a lawn mower engine and it didn't take as much fuel.