HP Rating for D1105 engine

[mikeyd]

I own a ZD28 mower with the D1105 engine which Kubota rates at 28 hp @ 3000 rpm. The problem I am having is that they rate the exact same engine at the same rpm at 24.8 hp on other equipment. For example, I have a deposit down on the new RTV1100 coming out in April. It comes with a D1105 engine, same as my ZD28 yet they rate it at 24.8 hp at 3000rpm. Same engine, same rpm .....where did 3 hp go and, more importantly, can I get it back. I know, I haven't even taken delivery of the RTV1100 and already trying to soup it up. Can't ever get enough hp's!!!!!!!!!!!!!! In researching I found other Kubota equipment with the D1105 and some are 24.8 hp and others 28, all at 3000rpm. What gives?

 

[DmansPadge]

I don't really know why they do that... but I think a lot of the time it will be something simply like different fuel injectors that change the HP.

 

[art]

Some engines build a lot of torque and not much horsepower. Some don't build to much of either and probably last a long time. It takes a well machined engine to turn a high RPM as well as using good metal. There are torque differences in most engines by application and I think that is what you will find here.

 

[mikeyd]

Yeah, that's what I am thinking too, maybe just different injectors. My dealer says he can cross reference the injector part numbers once thr RTV1100 comes in. If it is only the injectors that is a real inexpensive way to pick up a 12% gain in power for the RTV.

 

[psdx]

Both the ZD28 mower and RTV1100 actually use engines with the same displacement - 1123cc, however this does not mean they are the same exact engine. Kubota sometimes uses a different head and/or fuel delivery system that will vary the power output.

The B2620 uses the D1105-E2-D21 engine - 26hp @ 2800rpm
The RTV100 uses the D1105-E2-UV engine - 24.8hp @ 3000rpm
The ZD28 uses the D1105-xx-xxx engine - 28hp @ 3000rpm

I could not find the exact model number of the ZD28 engine, but I believe the B2630 & RTV1100 illustrate the point. Perhaps someone can comment on the specific differences to help understand the difficulty associated with modifications for hp increase.

 

[mikeyd]

Thank-you PSDX...no doubt there is a some kind of difference in the motors. My understanding is that the ZD28 uses the D1105-e2-uv so again why the difference? Plus on the other engine you mention, the D1105-ec-d21 when they say 26 hp is that gross intermittent HP because that would be identical to the D1105-e2-uv rating for gross intermittant. The continuous rating for both engines is 24.8, again identical.

I guess what I am trying to figure out is why would two motors with same model number, same displacement and run at same rpm be given different HP ratings by Kubota. I agee that it has to do with fuel delivery or perhaps the head design, the question is what is it and is it simple enough that I can pick up the extra 3hp easily and inexpensively when the rtv1100 gets here. I mean if it is just a matter of buying 3 injectors and installing them on the rtv thats quick easy hp for little money. I can see alot of rtv1100 owners who wouldn't mind a little more power if it is quick and easy and inexpesive.

 

[AB2]

Here are a few more hp ratings for you. The B2400 engine is the D1105-D10. The B2410 engine is D1105-E-D16. The B7610 engine is also D1105-E-D16. They are all 1123cc and rated at 24 engine gross hp at 2600 rpm. I suspect that all the D1105 engines that have been discussed produce the same power and the differences are only due to ratings at different RPM. For example 24 hp at 2600 rpm, 26 hp at 2800 rpm and 28 hp at 3000 rpm. There may be even more confusion if some ratings are gross continuous or gross intermittent or net continuous or net intermittent etc.
The different ratings may have more to do with marketing than anything else. For example I have a B2400 and the 3pt hitch is rated to lift 1280 lbs. The B2410 replaced the B2400 and the 3pt hitch is rated to lift 1356 lbs. They actually have exactly the same lift capacity. There are 2 sets of holes in the lift arms on both tractors and the B2400 uses one set and the B2410 the other set of holes. Switching which holes are lifted by the rockshaft changes the rating and trades lift capacity for distance. The higher rating may have helped to sell more B2410 tractors even though there is no real change.
You can see hp and torque curves at Kubota Engine America Scroll down to the super 5 series and click on the hp rating.
If you want more power there is a turbo version of the D1105 shown at that site… 6.5 more hp.

 

[mikeyd]

Thanks AB2. However, on both my ZD28 and on the RTV1100 the HP ratings are measured at the exact rpm...3000. This is according to Kubota's own specifications. I have already gone to the Kubota engine site, as well as others, and have yet to see any D1105 engine rated at 28 hp(Peak,gross, intermittant or otherwise), they are always rated at 25hp.

So, the question remains, you have identical engine model numbers, same manufacturer, same displacement, same design, same rpm(3000), one puts out 25hp and the other 28hp. It has got to be more fuel or air , better exhaust etc. which means different injectors, head design or something similar. What I am trying to figure out is what exactly is it so I can make the changes to the RTV1100 engine and pick up the 3 ponies.

Yeah, the turbo is a possibility, especially as Kubota already makes one for this engine. But, I imagine that the cost would be substantial. As I see it, if the only difference in the motors between the 28hp and 25hp D1105 engine is, let's say, the fuel injectors, then that would be a real cheap way to pick up 12% more HP's. Plus, installation would be a breeze.

 

[psdx]

As I see it, if the only difference in the motors between the 28hp and 25hp D1105 engine is, let's say, the fuel injectors, then that would be a real cheap way to pick up 12% more HP's. Plus, installation would be a breeze.

If you really want to know, find the part numbers for the injectors on a lower HP and a higher HP D1105 engine. Perhaps the B2630, B7610 and ZD28 would be good samples. The parts manuals can be found here: Kubota Parts Manuals

If someone does the looking - let us know what you find.

 

[mikeyd]

Thanks PSDX......I went to the parts manual and looks like the injectors. Crank, flywheel, cylinder head, injection pump all the same. The injectors show a different part number as between 25hp and 28hp, also some models show different governor part number. Anyways, thank you so much for directing me to this site. Once the rtv1100 comes in I can just compare part numbers to my zd28 and get down to specifics. Thanks again.