HP and Engine Displacement

[Ronster]

I noticed that the B7610 has 24hp @ 2600rpm and the B2630 has 26hp @2800 rpm. Both engines have 68.5 cu.in. displacement. Would that mean if you wind the B7610 up 200 extra rpm it would produce 26 hp? I'm assuming the rated engine rpm gives you 540 rpm at the rear PTO.

 

[orangebluegreen]

Another good one.....

The JD 4115 is rated at 24HP at 2650rpm with a 73.22CI engine.

So does a bigger CI 24HP engine do more work than a 68.5CI 26HP engine? My bet would be yes the 24HP engine will outperform the 26HP, but then that's probably why they don't publish torque which is more important IMO.

Another example of this in gas engines...the Honda vs. Kohler and Kawasaki. The same number HP will show less torque on the Honda from what I have seen.

HP is obviously being used by sales departments.

 

[AntrimMan]

I am interested in finding published tractor torque and HP curves.
It is useful when making comparisons to know where the torque and HP occurs in relation to rpms. Never mind the max numbers.
Diesels I'm not sure about but gas jobs typically don't make many ponies untill you rev them up and then only are most powerful in a relatively narrow rpm range.
It may be that torque and HP are incestually related.
There is probably some engineering guru that could suggest a simple way to correlate torque with HP.
There it is, discuss amongst yourselves. /forums/images/graemlins/grin.gif

Martin

 

[Ronster]

I e-mailed Kubota and asked for the torque ratings for the B7610 and B2630. We'll see. /forums/images/graemlins/grin.gif

 

[KirkMcD]

See if the engine is listed here.

Then click on the "Net Intermittent Rating" to see the curves for the engine.

 

[hbaird]

Horsepower = (Torque times RPM) divided by 5252
Harold

 

[wsx7]

Dynamometers actually do not measure HP. A dyno measures torque, and then uses a simple formula to calculate HP. hbaird gives the correct formula in his response.

Go to Google, type in "horsepower and torque" and you will get all the engineering/technical discussions you will ever want to read. One of the comments I like best is "Horsepower is what you read about. Torque is what you feel."

 

[bikemiser]

This is a basic question but I have not gotten a clear answer that I can understand. If dynos measure torque then calculate HP why isn't the max. HP and max. torque at the same RPM ? Is this a stupid question ?

 

[hbaird]

No, it is not a stupid question, most don't understand. All internal combustion engines make both horsepower and torque from idle to the redline or max rpm. Torque increases from idle, as more fuel is added, until the load from pumping air through the engine increases faster than the torque increases. The horsepower will continue to increase until the airflow can not get any greater. Generally speaking you can get more horsepower from a given engine by increasing the ability to reach higher rpm. Torque is best increased by more cubic inches.
Harold

 

[Ronster]

I thought torque was the turning power or leverage the engine had as it turned the crankshaft. Wouldn't then an engine with a longer stroke have more torque than a same displacement engine with a shorter stroke?

 

[AntrimMan]

No, not really. In order for the smaller stroke engine to have the same displacement there needs to be more pistons or larger bores. Either one means more power put to the crank.

Martin

 

[AntrimMan]

Yes, I get it. If the manufacturer was to show HP vs RPM curves one could easily calculate the available torque for any given RPM. Thats why I would like to see the curves and not just a maximum statement. I did check the engine website posted above and sadly mine was not listed.
I feel that my machine doesn't provide any noticeable difference in performance over 2300 RPM while the max HP is stated at 2700. So, they can tout HP all they want, after 2300 it is just more revs. Am I crazy? The curves will tell. Not that any of this is meaningful. The machine has all I need at the moment.

Martin

 

[JoeL4330]

I believe you will find that the engine RPM setting to achieve correct PTO speed (540 rpm) is (deliberately) a few hundred RPMs past the torque peak. Then, if the PTO attachment bogs down the engine slightly (for a moment or two), the engine actually increases its torque output, so it can ride through such little glitches without really bogging down. In a sense, it has a little "reserve" power.

 

[odleefs]

AntrimMan,
You are sane. (At least reganding your post in TBN! /forums/images/graemlins/grin.gif)As stated earlier and more evidently visualized by looking at any of the engine curves listed in www.KUBOTAENGINE.COM, you may notice that after a given point, as RPMs increase, torque decreases and brake HP flattens...this is why you don't appreciate a significant increase in umph! after 2300 RPM for your tractor. Note even more importantly in this era of inflated fuel that at higher RPMs, consumption of fuel goes way up for little, if any, HP gain. /forums/images/graemlins/shocked.gif