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Discussion Starter #1
I know this is a long shot but does anyone know what was done to the engine to raise the HP from 18 to 20? The GX355 uses the exact engine as the 355D and got an extra 2 HP....Im looking to get 20HP from my 355D. I know the Rev limit went from 3K to 3600 so maybe that is it? Anyone have any thoughts or ideas for me? The extra RPM / HP would be nice when blowing snow or mulching leaves /wet grass.
 

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Where are you seeing the difference in specifications? TractorData shows both the GX355 and GX355D has having 18HP with a Yanmar 2V78 engine. Both are shown with the same bore & stroke (3.07x3.09) but the GX355 is shown as having a compression ratio of 22:1 and the GX355D as 23:1.
 

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Where are you seeing the difference in specifications? TractorData shows both the GX355 and GX355D has having 18HP with a Yanmar 2V78 engine. Both are shown with the same bore & stroke (3.07x3.09) but the GX355 is shown as having a compression ratio of 22:1 and the GX355D as 23:1.
I was mistaken, I was referencing the Yanmar spec sheet... Was wondering what was different other than a bump in RPM.

Spec Sheet

Yanmar 2V78 Diesel Engine

Rated Speed Output Hp Output kW

2800 rpm 16.1 12
3000 rpm 17.2 12.8
3200 rpm 18.1 13.5
3400 rpm 19 14.2
3600 rpm 20 14.9
 

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I was mistaken, I was referencing the Yanmar spec sheet... Was wondering what was different other than a bump in RPM.
I'm not a diesel expert but there are all kinds of things manufacturers can tweak on diesel engines to adjust the HP but I suspect the 2HP difference is RPM. Check out the Yanmar website and compare small engines of the same displacement. You can find HP ranges from 11 to 22 HP from the same engine running at different RPMs.
 

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I would look at JDparts to see if the rods, pistons, heads, valves, cam or injectors have different part numbers. If they all match up you might be able to just adjust your max rpm. If there are different parts I’d investigate further to see if the 18hp isn’t built to handle 3600 rpm.
 

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I would look at JDparts to see if the rods, pistons, heads, valves, cam or injectors have different part numbers. If they all match up you might be able to just adjust your max rpm. If there are different parts I’d investigate further to see if the 18hp isn’t built to handle 3600 rpm.
A Google search turned up a snippet from back when Yanmar first introduced the 2V78 engine.

Yanmar has developed a new twin-cylinder diesel engine. The 2V78V vertical shaft engine was introduced to North America at the recent OPEI Lawn & Garden Expo '97 in Louisville, Ky., by Yanmar Diesel America Corp. and is available in ratings from 16.1 to 20 hp at operating speeds from 2800 to 3600 rpm

 

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If I am not mistaken,, a snow blower needs torque,, not horsepower,

and,,,

max torque is usually at a MUCH lower than maximum RPM,, for either engine.

Compare the torque specs,,

Kohler offered a 16HP and 18HP engine for garden tractors back when,,

The difference was the 16HP did not have an oil filter, the 18HP had a screw on oil filter,, :laugh:
literally, that was the only difference,

I think they can make the engines spec to whatever brings in the most $$$$$$
 

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Discussion Starter #8
Ill keep digging. Its an older somewhat uncommon engine so info is sometimes difficult to get. I called Yanmar and they wouldn't talk to me and told me to call Deere.
 

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Kohler offered a 16HP and 18HP engine for garden tractors back when,,

The difference was the 16HP did not have an oil filter, the 18HP had a screw on oil filter,, :laugh:
literally, that was the only difference,

I think they can make the engines spec to whatever brings in the most $$$$$$
I think you are right. Did you ever take note of the low-end gear driven riding mowers? They are made by MTD and sold under a dozen different brands and usually differ only in color. They all typically have oil filter-less B&S engines that look identical with stickers that read 14.5, 15.5, 17.5 and 19HP. I find it hard to believe that B&S actually produced that many different identical engines which were 1HP apart. :)
 

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Ill keep digging. Its an older somewhat uncommon engine so info is sometimes difficult to get. I called Yanmar and they wouldn't talk to me and told me to call Deere.
Not surprising, a search of 2V78 on the Yanmar website returns nothing.

You can review the exploded parts illustrations on the JD website.

Just for kicks I looked up JD part number for the head assys for the engines in the GX355 and 355D and the engines use the same pair of heads (AM880598 & AM880599).
 

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Yanmar isn’t Briggs.

Besides that if you have the buying power of Deere and want 10,000 widgets the manufacturer will make them custom to your spec.

Another thing is having identical castings with different machining specs is common and has been since the 60’s. A k181 and k241 share bock, head and shroud dimensions, same with som k301, k321 and k341. The power outputs are not the same because almost every single part you don’t see is different.
 

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I think you are right. Did you ever take note of the low-end gear driven riding mowers? They are made by MTD and sold under a dozen different brands and usually differ only in color. They all typically have oil filter-less B&S engines that look identical with stickers that read 14.5, 15.5, 17.5 and 19HP. I find it hard to believe that B&S actually produced that many different identical engines which were 1HP apart. :)
To some extent you have hit the nail on the head. Not in all cases but in a lot of them.

The rating of engines is not just a simple HP and torque number. The oft forgotten and very important duty cycle rating has a huge impact on the durability of the engine. Electric motor have an equivalent rating which is called service factor (SF).

The duty rating of an engine speaks to how long any particular engine can run at a given output before failure is expected. So the same exact engine could be rated for multiple different HP outputs at different duty ratings. Sometimes the same exact engine can have it's duty rating increased by added extra cooling. The addition of an external oil filter can add significant cooling to an air cooled engine.

As people have known for a while now HP ratings of an engine can be vastly misleading. Buyer beware and take the whole package into account before passing judgement based on HP claims.
 

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Reasons for Deere to derate the engine to 18 hp and a lower RPM would be noise level and thrown objects certification. Most small engines are designed for and rated at 3600 RPM.
 

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Discussion Starter #14
Reasons for Deere to de-rate the engine to 18 hp and a lower RPM would be noise level and thrown objects certification. Most small engines are designed for and rated at 3600 RPM.
My research is pointing me in this direction as well. I have found guys going to 4K on this engine. The 355D used all the same attachments as the gas counterparts so I suspect they just set it up to work at 3000 RPM. Bumping it to 3600 will increase blade tip speed (noise) and increase engine noise as well. I'm going to give it a go, I just need to figure out how to at this point. Not sure if its an adjustment or an actual shim in the fuel pump....if its the latter I will likely leave well enough alone.

I saw a comment earlier abut the snow blower....this machine uses a single stage snow thrower....RPM is king with these.
 
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