How important is engine displacement on same class of tractor?

[Hozzie]

I am down to the nuts and bolts of buying a new 70-75HP tractor. Basically down to Kioti 7320, Kubota 7060, and maybe a NH Workmaster 75.

I didn't really notice it before, but they all have quite different engine displacements.

Kioti - 149ci/2700 rpm
Kubota - 203ci/2400rpm
NH - 179ci/2300rpm

Seems to me more displacement at less RPM would in theory work an engine less and over time be more desirable. I like the Kioti overall, but am concerned a bit about such a big difference in displacement between it and the Kubota. Am I overthinking this?

 

[alexpops]

ALL THINGS BEING EQUAL (they never are) more volume ==> more torque. more HP ==> more speed (carries the torque higher into the rpm curve) In theory, you're right, BUT ... the explosion of more volume @ combustion (presumably with more fuel/air) puts more pressure on rings, rods & pistons. The turbo allows you to increase fuel/air pre-compression, but you need higher rpm to spool the turbo, the Kubota should have the higher torque across the rpm curve. What is it being used for? High speed mowing? Probably indifferent. Lower speed ground engagement like skidding logs/plowing? Kubota. JMO

 

[Hozzie]

Mostly being used for 12' batwing and loader work with grapple. Basically an all purpose tractor where I will use a 2 row bottom plow a couple times a year for my garden and run a tiller some for foot plots. I don't "farm" so it will have R4's on it so I don't tear up my yard.

 

[dodge man]

One may have a turbo? I agree all things being equal a larger engine won’t work as hard but I’d still get the tractor you like best.

 

[Hozzie]

They all have turbo's

 

[alexpops]

I'm guessing that for the loader/grapple work the displacement will keep the hydraulics powered up at lower rpm (assuming the pump is big enough in relation to the cylinders to not need high rpm for decent flow). For the plows/tiller displacement is your friend (depends on soil difficulty). I've never run a batwing, but if the cutting can bog you down, more torque and Higher RPM are probably necessary to maintain 540/1000 @ the PTO. Weight/Traction will come into play for the loader/grapple & plow work unless your plowing sand. I'd say, with the possible exception of the batwing & tiller, you could run lower rpms for all the work on the bigger displacement tractor & while it may not save fuel, it's easier on your ears. BUT ... if the emissions require higher RPM to heat up the exhaust you may lose that advantage.

 

[ericm979]

I think all tractor engines are so understressed and overbuilt that the difference in displacement between models in the same size class is pretty much meaningless when it comes to durability. A 3/4 ton diesel truck makes about 3x the HP per liter and those can go for hundreds of thousands of miles (100,000 miles at 40mph avg is 2500 hrs).

OTOH you might like the sound or feel of one vs the others especially if some are triples and some fours. The lower rpm one might be a little quieter.

 

[FERLING]

I am down to the nuts and bolts of buying a new 70-75HP tractor. Basically down to Kioti 7320, Kubota 7060, and maybe a NH Workmaster 75.

I didn't really notice it before, but they all have quite different engine displacements.

Kioti - 149ci/2700 rpm
Kubota - 203ci/2400rpm
NH - 179ci/2300rpm

Seems to me more displacement at less RPM would in theory work an engine less and over time be more desirable. I like the Kioti overall, but am concerned a bit about such a big difference in displacement between it and the Kubota. Am I overthinking this?

Weight of tractor will make the biggest difference between these three. The heavier the tractor the more traction.

 

[Hay Dude]

If all things were equal and quality was equally acceptable, I’d go with more displacement. If the block is heavier, it will dissipate heat better and should run cooler, but there’s other factors in play.
Kubota will give you a much more extensive dealer network and parts should be easier/faster. Plus Kubota is growing rapidly into related equipment sectors.

 

[Sawyer Rob]

Look at the weight difference between those tractors... Along with that, I also like lower rpm diesel engines...

SR

 

[Hozzie]

Thanks everyone. I have pretty well decided on the Kubota for a few different reasons including (right or wrong) the larger displacement.

It primarily also boiled down to little things like how hydraulic hoses were routed, protected, and other general protection plates that the others don’t have.

The hydraulics are also more responsive and I like the shift lever on the right side.

In the end, worth the extra money to not second guess myself.

 

[Boss 302]

I'm with the majority, go with the heaviest machine. In my experience it will probably be the Kioti.

 

[Boss 302]

Good choice, if you care to share how much lighter is the Kubota compared to the other two machines?

 

[Hozzie]

Not sure about the New Holland, but the Kubota is right at 200lbs lighter than the Kioti based on specs. I will have the tires all filled with Rimguard so weight shouldn't be an issue after adding the loaders. I would say both will be in that 8,000lb range.

 

[oosik]

Hozzie - good choice. If only 200 pounds difference between the two tractor is going to make a BIG difference - you are already a dead man. You will be putting right at 800 # of Rim Guard in each rear tire. Makes the 200# difference pretty insignificant.

Depending upon how you configure the new 7060 you could be surprised on the total unit weight.

I have a Land Pride 1560 grapple on my FEL, Rim Guard in the rear tires, Rhino 950 - 8 foot rear blade on the 3-point. Configured this way - my M6040 weighs 10,100#. That's +/- 20#. The accuracy of the ADM grain scales in Cheney.

 

[mo1]

ALL THINGS BEING EQUAL (they never are) more volume ==> more torque. more HP ==> more speed (carries the torque higher into the rpm curve) In theory, you're right, BUT ... the explosion of more volume @ combustion (presumably with more fuel/air) puts more pressure on rings, rods & pistons. The turbo allows you to increase fuel/air pre-compression, but you need higher rpm to spool the turbo, the Kubota should have the higher torque across the rpm curve. What is it being used for? High speed mowing? Probably indifferent. Lower speed ground engagement like skidding logs/plowing? Kubota. JMO

A smaller engine making the same power as a larger engine will have either more turbocharger boost or a higher RPM, or a combination of the two. You do NOT need more RPM to get more turbocharger boost, you can also get more boost by altering the turbocharger geometry and size.

Torque curves in turbocharged engines depend on fueling maps, turbocharger geometry, size, and wastegate setting much more so than engine displacement, assuming more than minimal boost pressures. You can have a very flat or very peaky curve depending on the setup.

Hydraulic performance at low engine RPM depends on the hydraulic pump displacement as flow will be a product of volume/revolution times pump speed.

Three-cylinder engines do sound different from four-cylinder engines. Personally I find threes to sound better than fours. Fours have a very specific buzzy/droning note while threes sound smoother. Larger fours are less buzzy than smaller fours as well, a 250-300 cid four is much less buzzy than a 120-150 cid one.

 

[EddinKY]

In cars I like small displacement, high revs.
Little trucks, the same.
Hauling trucks pulling trailers ..I vote for cubes
Work Tractors..cubes.
I am not a fan of turbos in tractors
Love turbos in cars and especially in race cars.