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How to compare hp diesel v. gas


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#46 kubotakid OFFLINE  

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Posted September 22, 2011 - 12:18 AM

In a nutshell it's basically what DH1 said about peak ratings. This is from another site that (I think) descibes it well:

You have to consider how horsepower is rated in order to compare diesel engines to gasoline engines in a typical garden tractor. The horsepower ratings that you see are peak horsepower ratings. Gasoline powered engines in garden tractors typically have peak horsepower at about 3000 rpm and horsepower falls off quickly below that . Diesel engines in compact tractors typically have their peak horsepower at about 1000-1500 rpm and horsepower stays up throughout most of the rpm range. How does that make a difference? A gasoline powered garden tractor has to be at full throttle to achieve its rated horsepower. When the tractor has a load put on it by a mower or going up a hill, for example, the rpm will fall from, let's say, around 3000 rpm down to 2500 rpm. At 2500 rpm a gasoline engine will have significantly less horsepower than at 3000 rpm. At 2500 rpm, with much less horsepower, the load will pull the engine down even further until the rpm and horsepower are so low that either the engine stalls or you release the load (by shutting off the mower or pushing in on the clutch) A diesel engine, however, has a much broader power band. Using the same example, the diesel powered tractor running at full throttle encounters the same load as the garden tractor did. The engine rpm will fall from, let's say, 2000 RPM to 1500 rpm. At 1500 rpm the diesel engine will have roughly the same power as it did at 3000 RPM and will continue to pull the load. The horsepower and rpm will not continue to fall because the diesel engines power is not as dependant on the engine's rpm.


Actually,.If you look at kubota engine specs, They have there highest hp rating @ there highest rpm, The 482 peak is 3600 rpm, the highest torque peak @ 2600 rpm Eric
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#47 Boss 448 OFFLINE  

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Posted September 22, 2011 - 07:39 AM

Until recently one of the challenges of deploying diesel power in GT's has been the availability and affordability of small diesel engines. I know that there are a good number of water cooled Yanmars, Kobotas, etc shown in some very impressive adaptions on this forum. But the water-cooled approach depends on someone having availability to a source for these engines and above average fabrication skills and facilities. For simple mortals like myself I think tackling the installation of a water-cooled engine is above my pay grade.

The growing availability of Chinese air-cooled diesel engines expands possibilities for many of us. They provide a profile similar to many of the gasoline engines we are replacing, they are reasonably priced, and they are available new making them both accessible and at a known new condition. But even at a 'reasonable' price the cheapster side of me still had not made the plunge - until the other evening.....

I found a 10 HP China diesel in new condition advertised on CL for less than half of the going new prices. It was time. So now I hope to be able to embark on a diesel re-power project of my own. Along the way I hope to be able to illustrate the relative ease of adapting an air-cooled diesel. No disrespect to you guys taking the water-cooled route - it's just that you play in a higher league. :worshippy2:

JN
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#48 skyrydr2 OFFLINE  

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Posted September 22, 2011 - 10:55 AM

Boss, I have to disagree with you on this one, I put the engine in my Ford In a canvas shed using basic hand and power tools! Only fancy parts on it are the pto adapter and the custom made powersteering pump pulley added to the crank, if you didn't have powersteering you don't need it. The driveshaft to the transmission still needs to be connected, so some sort of flywheel adapter still needs to be had, weather fan or water cooled . Only difference would be room for a radiator, this can pose the single most difficult obstacle to overcome. Don't be afraid , just study your problem and do the homework, and if all else fails ask for help.
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#49 Boss 448 OFFLINE  

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Posted September 22, 2011 - 04:06 PM

One issue I had with going with a water-cooled engine is availability. It appears that some of the people on this forum have better luck finding a good deal on one than I have. My wife and I own and operate our own business which severely limits my ability to browse around locally for good deals on engines, tractors and parts. My searches are limited to what I can do from my desk on CL and E-Bay where the Yanmar and Kobota engines seem to carry high prices and are long distances from here. And then I would be purchasing used in unknown condition. There actually was one very good opportunity (didn't last long) I saw on a surplus website about a year ago offering brand new Yanmar 2 cyl water-cooled diesel engines for around $675.00. That would have been a tremendous deal but they were already 'out of stock' when I found it.

Until just the last couple of weeks I had neither the tractor or engine to attempt anything. Then within one week's time I acquired both. I was watching for either water or air cooled diesel engines and the air-cooled China diesel was the first really good local deal I came across. Perhaps once I get my first re-power project operational I will entertain one using a water-cooled engine. I will continue to watch for good deals on one whether for myself or just to alert others here if one appears. Then again I am very interested in seeing how the new v-twin air cooled China diesel engines work out since they are very similar in design to the v-twin Kohler and Briggs gasoline engines.

Either way I think this forum and the projects that everyone contribute are all great. I look forward to seeing all of the different ways people find to get it done. :smile1:

JN
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#50 middleageddeere OFFLINE  

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Posted May 29, 2012 - 01:58 PM

Wow, I had lost track of this one for a long time...Had no idea what I had started great conversation and great knowledge here guys.

#51 Cvans ONLINE  

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Posted May 29, 2012 - 10:01 PM

Wow, I had lost track of this one for a long time...Had no idea what I had started great conversation and great knowledge here guys.

I'll bet that everyone that read or added to this string enjoyed it.So thank you for getting the ball rolling! :thumbs:
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