Today's newbie question - Horsepower

[Anonymous Poster]

Today\'s newbie question - Horsepower

I have learned so much here. Much more to learn. The wife actually gave permission today to look at something new. I'm still recovering from the shock. I guess she's tired of hearing me curse at the 55 year old tractor I'm using now.

Question - Are horsepower ratings the same when comparing gas to diesel? For example, is Tractor A listed 20HP gas the same as Tractor B listed at 20HP diesel, as for horsepower? If I userstand things though, the difference comes in the torque ratings. A diesel engine rated at the same hp as a gas engine should have more torque than the gas, and thus be more 'powerful.'

So, I guess that's why most CUT's are diesel. More power (torque) in a small package.

I don't mean to get all theoretical here but I like to understand the basics before the sales guy starts showing me the 'really cool cupholder.'

Thanks,

wickman

 

[rockyridgefarm]

Re: Today\'s newbie question - Horsepower

Hi, welcome aboard!

Yes! and No! Just like in any area, specs can be tweaked. At what rpm is the HP acheived, can it be maintained throughout the useful life. Most small gas engines won't hold up well at the point that their advertised Hp is achieved. Most CUTs will. In Subcompacts, things get a little hairier. Often times the rated Hp is at a Rpm that is higher than the setting where the PTO operates. So the HP is slightly lower at the point they will be used. Probably just fine in most applications, better than gas.

 

[chrisjbell]

Re: Today\'s newbie question - Horsepower

Welcome to the forum! You're right - there is a lot to be learned here. I just wish I'd found it sooner...

HP ratings between deisel and gas don't really match well because, as you point out, the deisels produce so much more torque. My Kubota and JD lawn tractor have about the same HP ratings, but there's no question that the Kubota will kick the JD's butt when it comes to power.

(OK, so the Kubota has 4WD, R4's and is much bigger, but still, the engine is much more than the JD.)

But the other post was also right - HP ratings are done by manufacturers without much oversight. I'd say that my JD 18 HP lawn tractor is more powerful than my neighbor's Sears 25 HP tractor. I can cut deeper, heavier grass than he can (we did a side by side comparison just to see), with less bogging of the motor. It might not be pure HP - perhaps there is some other difference, but my JD has hydro, his is geared, and I can cut him "under the table".

You can get cupholders as aftermarket accessories - I think they cost about eight bucks /forums/images/graemlins/laugh.gif. Don't worry about that garbage - look at the basics.

 

[Bird]

Re: Today\'s newbie question - Horsepower

And then besides horsepower, torque, and rpms, you also have to consider weight and gearing ratios. /forums/images/graemlins/laugh.gif 20hp is 20hp whether you're talking gas or diesel . . ., but the end result (performance) is another matter. /forums/images/graemlins/grin.gif

 

[SteveM]

Re: Today\'s newbie question - Horsepower

I think weight is an underrated issue on TBN, at least if you are planning to move some dirt with your tractor. With the exception of finish mowing, a heavier tractor is always my preference, since most CUTs run out of traction far before power. The only power consideration I am aware of is the size mower you can run...everything else comes down to sturdy, heavy engineering. Have fun test driving!

 

[buzst]

Re: Today\'s newbie question - Horsepower

wickman,
1 hp is 1hp regardless of the engine type. However HP is really a meaningless method of comparison because of the variations in how it is achieved and the the impact these varaitions create on torque(which is what we are looking for on a tractor). For your initial screening compare displacement of the various engines, then take a look at the power curves to make your final choice.

 

[chrisjbell]

Re: Today\'s newbie question - Horsepower

<font color="blue"> 1 hp is 1hp regardless of the engine type </font>

True - as long as it is measured accurately and consistently from manufacturer to manufacturer. I don't think that it always is - I believe that some manufacturers inflate their HP numbers, especially in the lawn tractor size area.

 

[Anonymous Poster]

Re: Today\'s newbie question - Horsepower

Well,as far as that riding mower comparasion,what kinda engine does that johndeer of yours have on it?I mean a kohler is a kohler,wether on a sears or a john deere,a briggs is a briggs,etc,so when you compare power, you got to compare apples to apples,my sears has a kohler,my lowes speical also has a kohler,you knew that johndeere didn,t make the engine right? richard gauthier[or at least I didn't think they did].

 

[SteveM]

Re: Today\'s newbie question - Horsepower

I think the aforementioned issue of the 18hp Deere vs the 25hp Sears could have as much to do with effective deck design as raw power. That aside, I think most folks realize that all lawn and garden makers use the same engine suppliers, albeit with seriously massaged hp numbers accross the board....

 

[chrisjbell]

Re: Today\'s newbie question - Horsepower

Mine's got a Kohler engine in it.

But I think SteveM probably got it right - it may not be so much a question of raw HP as to how it is utilized, as far as mower deck design, power train, etc.

So I guess (to try and get back on topic) that a simple measure of HP won't determine the best tractor for a given task. You'd have to try out different combos, probably from different manufacturers, in order to determine what the best balance of HP, attachments, application, etc. will work the best.