R4041/XR4040 Engine/PTO HP differential

[nova3930]

I'm investigating the LS tractors as an option to maintain 16 acres I'm currently building a house on. In the course of comparing tractors I've noticed something odd in the specs.

I get that the primary difference in the R series and XR series is the emissions standards and different engines required to meet those standards.

When comparing shuttle to shuttle, the R4041 has an engine to PTO HP drop of 6HP whereas the XR4040 has a HP drop of 7.6HP. That's the difference between a 14.6% drop and a 19% drop respectively. As an engineer I can speculate as to transmission, PTO or quite simply test methodology differences but I'd like to know for sure.

I've noticed a similar differential with the R3039 and the XR3037 as well although reversed with the R series having higher losses.

Does anybody know what's going on with the specs?

 

[Guesseral]

Noticed the same thing myself but I don't know the true answer I always assumed it was just the different engine being all clogged up with stuff. I think they still use the same transmission as before with a different engine pushing it, but I could also be wrong on that. Guess I'm not to much help!

 

[RKJeepXJ]

I think the difference is in the power curves and where each number is measured. Engine HP is taken as max HP produced by the motor up to its max operating RPM. PTO HP is taken at whatever RPM setting provides 540rpm to the PTO, that may or may not be the same as the max enginer HP RPM. That make sense?

 

[nova3930]

Noticed the same thing myself but I don't know the true answer I always assumed it was just the different engine being all clogged up with stuff. I think they still use the same transmission as before with a different engine pushing it, but I could also be wrong on that. Guess I'm not to much help!

The engine HP drop is easily explained by the different engine. That would even be explained by more emissions controls or different tuning if they used the same engine.

If they used the same transmission/PTO setup then either the absolute HP drop or the percentage drop (my $ would be on percentage) should be the same assuming consistent measurement methodology.

 

[Guesseral]

Hay your the engineer I'm just a dumb electrician, yea what you said.

 

[nova3930]

I think the difference is in the power curves and where each number is measured. Engine HP is taken as max HP produced by the motor up to its max operating RPM. PTO HP is taken at whatever RPM setting provides 540rpm to the PTO, that may or may not be the same as the max enginer HP RPM. That make sense?

Yeah, hadn't considered different engine power curves. The R engine could easily have a "fatter" power curve putting out more power at the appropriate RPM for PTO operation. That's a very probable explanation I think...

 

[nova3930]

Hay your the engineer I'm just a dumb electrician, yea what you said.

One thing I've learned in my short career as an engineer, occupation/education and intelligence are two totally different things. The number of idiots out there with engineering degrees is astounding.

 

[Guesseral]

One thing I've learned in my short career as an engineer, occupation/education and intelligence are two totally different things. The number of idiots out there with engineering degrees is astounding.

I very good friend of mine also an engineer (structural) is classified as a genius, but there is no way I would allow him to screw in a light bulb! :thumbdown:

 

[nova3930]

I very good friend of mine also an engineer (structural) is classified as a genius, but there is no way I would allow him to screw in a light bulb! :thumbdown:

Believe me, I know what you mean. I'm thankful everyday I had a father and two grandfathers that taught me

1. common sense and

2. practical hands on skills

Having actually done things with my hands helps me realize when other engineers want to do stupid crapola lol

 

[GManBart]

I think the difference is in the power curves and where each number is measured. Engine HP is taken as max HP produced by the motor up to its max operating RPM. PTO HP is taken at whatever RPM setting provides 540rpm to the PTO, that may or may not be the same as the max enginer HP RPM. That make sense?

Not exactly. The engine HP rating is at "rated speed" which may be below the maximum RPM the engine can turn. The two are usually pretty close, but not always identical.

I'm wondering if the difference between the 4041 and 4040 is due to the larger displacement engine in the 4041, which could mean it has a flatter power curve...something along those lines.

 

[nova3930]

Not exactly. The engine HP rating is at "rated speed" which may be below the maximum RPM the engine can turn. The two are usually pretty close, but not always identical.

I'm wondering if the difference between the 4041 and 4040 is due to the larger displacement engine in the 4041, which could mean it has a flatter power curve...something along those lines.

Take this with a grain of salt because it's based on some guess work and extrapolation but I think that's exactly what's going on. I can't located the exact engine model numbers on either the Mitsubishi or Shibaura websites so I'm guessing on the engines used on both based on series and HP rating. The numbers on the R4041 are an extrapolated de-rate of the R4047 and the Shibaura engine data only went down to 2200 RPM so I had to do an exponential curve fit on the limited data and extrapolate down to 1500 RPM. All that being said, it appears the Mistubishi engines have a power curve that's a lot fatter on the low end, which you'd expect with a larger displacement engine.

BTW can anyone tell work is exceedingly boring today?

 

[kingrace78]

Nice Graph. Why are tractors sold by HP not by torque. I would think torque would be more important than the hp.

 

[jaydee325]

Nice Graph. Why are tractors sold by HP not by torque. I would think torque would be more important than the hp.

Torque is the twisting force on a shaft. Torque gets a load moving.

HP determines how fast work can be done. Most farmers are concerned with how long it will take to get a field plowed for example.

So while an 18 HP steam engine may be able to pull a 500 hp modern tractor across the lot (I know there are other factors involved but bear with me). Torque (and weight) is a big factor here. The 500 hp tractor is wasting all its HP throwing dirt into the air.

Now hook a properly sized plow to each tractor and plow a 500 acre field. The 500 hp will get that work done in a fraction of the time.

Both specs are important. I also like to see the Hp/torque to RPM graphs as that can tell a lot about the characteristics of an engine.

 

[Bladehauler]

I thought the difference in HP was the a/c compressor draw .

 

[jaydee325]

Sorry, dual post.