BX2816 snow blower rpm question

[nbryan]

These engines are often used to power generators. To produce 60 cycle power the engine needs to run at 3,600 rpm.
Dave

Then why would my 26HP 3 cylinder have a power/torque to rpm curve that says it works best at 2500 rpm?
When you say "these engines", are you referring to all CUT and SCUT small diesels?
Just saying, if Kubota builds 3-cyl diesel powered generators in my 26 hp range then the engine would be designed, built and tuned to run at 3600 rpm, not 2500 like my tractor.

 

[PoTreeBoy]

These engines are often used to power generators. To produce 60 cycle power the engine needs to run at 3,600 rpm.
Dave

Or 1800 rpm. For 50 hz, 3,000 or 1,500 rpm, depending on the generator. I think I've seen these running generators at 3,000 but not 3,600.
(Assuming direct drive, of course.)

 

[Dave_eng]

Or 1800 rpm. For 50 hz, 3,000 or 1,500 rpm, depending on the generator. I think I've seen these running generators at 3,000 but not 3,600.
(Assuming direct drive, of course.)

I am trying not to argue with anyone but rather just mention some facts that have come up in my working life.
Generators in North America, not utilizing electronics like the inverter type, are 2 pole or 4 pole.
There are very expensive alternatives to this rule like huge V12+ Cat powered ones with multi poles.

To get 60 cycle AC power with a 2 pole unit the generator has to turn 3,600 rpm.
If there are 4 poles the rpm is cut in half.

Here is a Kubota V3300 engine powered generator utilizing 4 poles running at 1,800 rpm.

This engine also powers :
Kubota V3300 Engine for Kubota M6800, M8200, M9000 Tractors
These tractors utilize engine rpms much higher than the 1,800 rpm version powering the generator.

The following is a 2 pole Kubota V1305 powered generator running at 3,600 rpm.

The same V1305, but a different version, is used to power these tractors which run the engine at a slower speed than 3,600:

Today's diesels can operate at a wide range of rpm thanks to much improved metallurgy and manufacturing processes.

I suspect camshaft design including ramping up profiles of the lobes are changed to taylor the engine to its application.

Dave

 

[GreensvilleJay]

Since 'electronics' came out, it's become easy to 'adjust operating parameters' to get more power or economy out of a diesel ( or gas ) engine. Anyone can 'tweak' the 'numbers' though I suspect putting in the wrong ones can have expensive $$$ comsequences !

Old skool design for generators included good fuel economy, QUIET operation and smooth performance except for friend's welder/generator....

 

[RBsingl]

As Dave noted, the smaller displacement tractor engines are designed/rated at fairly high RPM and some are used with a 3,600 RPM governed speed in generator service. Increased noise and decreased operating efficiency are tradeoffs running at this speed but it allows a smaller displacement and thus less expensive engine to provide the rated generator power which makes it attractive to consumers.

I have a 40KW standby generator powered by a Mitsubishi S4S DT (3.3L 4 cylinder turbo diesel) and it is very fuel efficient running at 1800 RPM and is fairly quiet. But in other service (also commonly used in forklifts), rated RPM for this engine is 2500.

These smaller diesel engines were designed to withstand their fairly high RPM operation so although it may seem "fast" for a diesel, that is the design parameter. Above a certain RPM, the torque will start a steep drop but within the governed range of these small displacement 3 and 4 cylinder diesels it isn't going to experience an unusual increase in wear because it was designed for that operation.

I have owned several GMC pickups with the 6.6L turbo-diesel and these engines have a lower governed RPM under power but allow for a higher RPM for engine breaking. In early years, the tachometer had a mark for governed RPM under power @ 3450 with a shaded area up to around 4,500 indicating the area where it would run up to during engine braking operation but that was discontinued due to customer confusion so those markings are now absent from the vehicle display.

A F2690 (front mount commercial mower) I took delivery of last month is the first Kubota product I have owned. So far I have operated it for a couple of hours mostly chopping up some late falling leaves to give it a light break-in and I am happy with it. But compared to the owner's manual for my Deere compact utility tractor (a 955), the Kubota owner's manual is poorly written and lacking in detail. The manual is silent on operating RPM and with the digital display there is no rated RPM mark. The separate manual for its 72" mower deck simply states to operate the engine at full throttle.

So I am following the same basic method I have used for years with my Deere 955 compact with its 72" midmount finish mower and engaging the PTO at slightly off base idle speed and then increasing speed to near governed RPM for mowing and then dropping back to idle before disengaging. I will adjust as needed once I get some mowing time in with it this spring.

And on edit, this is the fuel consumption chart for the Mitsubishi diesel in my standby generator that shows how operating efficiency falls off when it is outside of the optimal operating range.

Rodger

 

[Downeaster]

Your tach will have a mark for 540 rpm pto speed.
This engine speed will produce the needed mid pto rpm.
The image from operators manual below.
View attachment 93414
Dave