I've always used 16-18 hp units with 48-50" mower decks. Unfortunately, new units in that hp. range come with 42" decks. To get a larger deck, I need to get units 23-27 hp.
Does a unit in 23-27 hp. range use appreciably more gas than a 18 hp. unit, assuming same driving speed and workload? Thx.
Even if you could arrange for the actual engine load to be the same (which it may approximate), the larger displacement/horsepower engine is still likely to use more fuel simply from the size difference. But, in general, if you can effectively use such a large deck, the actual _total_ fuel used can probably be kept to nearly the same by running at a higher ground speed so the extra power can be utilized to cover the same ground in less time negating the higher per hour fuel consumption. If, otoh, you have to run at a low speed to avoid obstacles or make many turns, back up, etc., and the time required is the same you'll undoubtedly find the fuel consumption noticeably higher.
The only consolation may be that the newer, larger engines may be slightly more efficient. If you're going that large though, I'd suggest at least consideration of diesel.
It's about the same amount of work, and should be pretty close. The blades use much more fuel than propulsion, especially in non-hydrostatic mowers, so with a larger deck there is a lot less maneuvering to hit the next row(many fewer rows).
Rob
Jack,
Don't worry about it. The 23-27HP units of today are the same 16-18HP units of days gone by.
The way the engine manufacturers rate their engines.... The size of the horse has gotten smaller.
What's about the same amount of work as what else? No clue what you're driving at unless you're thinking because two decks are the same size the cutting work is the same therefore the fuel consumption should be similar. There's a little truth in that, but it's also true that the engine needs to run at a fixed rpm to generate the blade tip speed and to do that will mean the larger engine will consume more fuel. Similar as to the relative fuel economy of a V8 vis a vis a V6 both running down the road at 65 mph--both needing about the same hp to keep then going, but the one is less fuel-efficient than the other. Larger engine-->larger carb jets-->higher fuel consumption. Didn't look to see, but manufacturers of commercial machines should provide fuel consumption numbers.
I don't know exact percentages, but I'd venture that a significant percentage of current mowers of 20+ hp and 48" or larger decks will have the hydrostatic transmission which is one prime reason they have the larger engines. That is, as I say, not a heavily researched fact but a hypothesis based on what have observed of machines I've recently looked at...
The lawn has to be entirely cut.
Each machine has to do the same amount of work for the same lawn.
The larger deck, though, will do it in fewer passes. This would likely be offset by the overhead of a slightly larger engine.
I use less gas with a 18hp lawn tractor than with a 5.5hp self-propelled mower for the same piece of lawn. It takes a lot less time too.
Don't forget the value of your time when considering a larger mower. You always come out ahead, even if you use more fuel.
Rob
Reference please?
Rob
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You're making the wrong comparison. OP was asking about the difference in fuel consumption between to mowers of the _SAME_ size deck, but one of significantly larger HP than the other. Therefore, the apt comparison is simply one of whether one can drive enough faster w/ the higher powered one to make up for the higher fuel consumption rate.
As noted, that may (or may not) be possible depending on the configuration of the area to be cut. If it's one big rectangular field w/ nothing in the way, got a chance. If it's full of flower beds and other obstacles or a very irregular area, not so much...
"To get a larger (48-50")deck, I need to get units 23-27 hp. Does a unit in 23-27 hp. range(48-50") use appreciably more gas than a 18 hp (42")unit"
Was the comparison I am making.
You guys must have smaller lawns than I do, I have hundreds of trees, & there is no way a smaller deck is better than a large one under any circumstances.
The OP is concerned over fuel usage, which really is moot when you consider acquisition costs & your time.
Rob
But the way you quoted it isn't exactly the way OP wrote it--
"I've always used 16-18 hp units with 48-50" mower decks. Unfortunately, new units in that hp. range come with 42" decks. To get a larger deck, I need to get units 23-27 hp.
Does a unit in 23-27 hp. range use appreciably more gas than a 18 hp."
Pretty clearly, he's asking in reference to his current machine which apparently is a 48" deck but at least the manufacturers he's looked at are now not providing that w/ as low as the 18 hp engine.
I guess that would obviously depend on how the trees are arranged and what portion is mowed... :)
No idea how big the mowed area is, OP didn't say. I've seen guys use things far bigger than the area would justify simply for the desire to have it. OTOH, I've seen other struggle along w/ a 20" pusher on areas that might take days to get over...
The size of lawn I have seems immaterial... :)
Guess that's in the eye of the asker, too...at pushing $4/gal it does begin to make a visible expense. Since it now takes over $200 to fill the tractor and during planting or other heavy use time periods that happens every day, I can certainly understand the desire to hold down fuel costs, even it if is just the yard... :)
BTW, if you're still around after the diversion into what OP really said ( :( ), I did a quick google to see what I could find...
I did discover that several of the lesser-known, more regional manufacturers do have what you're looking for in combination of deck size/horsepower, most often in commercial walk-behinds, but a couple of riders.
Did seem like the "name" guys are mostly in the bigger engine camp, you're right. But, you might want to do some more digging into what else is available at some of the smaller suppliers in your area. Around a lot of the commercial guys use Grasshopper stuff...
I hear the newer engines with pressure oiler systems are a LOT more efficient.
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