Hp vs fuel use

[Rooster cogburn]

Bit of a silly question but basically would a 6 cylinder 150 hp tractor use 50% more diesel than a 100 hp 4 cylinder both doing the same work say a 3m power harrow in same conditions. Roughly same age of tractor’s.

 

[Michael S]

Assuming that working depth and speed is the same the fuel usage should be similar; I have found that a more powerful tractor throttled back can use less fuel than a smaller one working at full stick but if you are working at PTO revs then they will most likely be similar.

 

[Wisconsonian]

Almost never. A 150hp engine doing 150hp will usually use less than 50% more than a 100hp engine doing 100. In most conditions I'd bet the 150hp engine doing 75hp for example, will use within 10% of the 100hp engine at 75hp. More if they're both operating the same speed, less if the bigger engine is running slower with a e PTO.

If you were talking about a 20hp load, then the smaller engine would do a lot better.

 

[Rooster cogburn]

So a tm150 wouldn’t use any more diesel than a 7740 in similar work

 

[Lakesdigger]

So a tm150 wouldn’t use any more diesel than a 7740 in similar work

Depends on the work, if it's easy work even for the 7740 then I'd expect the tm to use more but if the 7740 is working near it's limit you might find the tm similar.

 

[CPF]

I found out going from 150 hp to 190 hp
then 190 to 230 hp
Bigger ones going from 270 to 350 hp
All the tractors doing’s the same jobs , pulling near enough, the same kit .
The fuel consumption would come down because they was not on there, knees, because they we on top of the job. And was more reliable and tyres was lasting longer as well.

 

[Farmer Roy]

I’d always rather have a larger engine doing it easy, than a small one with its ring hanging out . . .

 

[David.]

Work done is effort over time, if the job is the same, the work is the same.
But the tendency is to push to the power available, so the bigger tractor will allow you to combi-drill, for eg, either deeper or faster.
If it is the faster option, the work to drill the field will be broadly similar, just completed quicker, resulting in increased fuel consumption over a shorter time.
A 150hp tractor may be heavier, with more power sapping bells and whistles, than a lightweight 100hp one, so it will always drink comparatively more.
It sounds counter intuitive, but you are not feeding the full 150hp all the time, only when it is working in full tongue hanging out mode.

 

[Farmer Roy]

Or, more power allows you to do the same job at the same speed, but with wider implements, which further increases your field efficiency & reduces amount of traffic over the field . . .

 

[snarling bee]

High engine revs are energy sapping.
Our RB25 sprayer had a 6 cyl JD engine with a fuel use meter. I can't remember the figures exactly but it was something like this (and yes it did rev to 2600):
NO LOAD
800rpm 1.5 l/hr
1200 2.0
1800 4.0
2200 10.0
2600 30.0

So yes, a 400 HP tractor workng easily at 1400 rpm will use a lot less diesel than a 200HP flat out.
Working at PTO revs however doesn't always help.

 

[David.]

They all drink when you get them barking.
Don't quite know where that gets you with tractors disingenuously badged as 210hp that are actually 170hp until the boost kicks in?

 

[sjt01]

You need to look at the specific fuel consumption curves for the engines. Here is one from a Fendt 412, unfortunately the x axis for rpm is unlabelled. You will see minimum SFC is around the point of maximum torque, so for minimum fuel use you should be operating at this point. Unfortunately this is a point at which additional load on the engine will cause it to stall, so without something like an intelligent vario, is not a good point at which to operate. With a clever vario, that will change the gear ratio as load increases, you can use this point effectively.

 

[yellow belly]

look at the nebraska or dag engine performance stats to see fuel consumption at power output /Torque on different machines
these give specific fuel use per kw /hp produced at measure fuel temperatures

at the same hp test the difference between tractors of different size is very small

pulling the same machine at same speed and depth generally use the same amount of fuel per acre
although a heavier tractor uses a little more moving forward

it is often easy to allow deeper cultivation depth with a higher hp tractor which increases fuel consumption per acre

 

[Rooster cogburn]

It’s getting complicated. My original question was to settle a work argument. We have a 7740 from new it ploughing with a kv reversible 3 meter power harrow. Mows with 8’ conditioner and was lifting grass with a class 51 harvester. None of the above ever made the tractor work over hard. My work colleague only grows spring barley same as us roughly 12 acres more. He has tm150. I know his is a very good tractor. My statement was our tractor was big enough for us and more fuel efficient. It also seems that tractors are now 50% larger doing the same original work load I would imagine to replace the 7740 with an equivalent tractor would be hard.

 

[Drillman]

While drilling yesterday a few messages were passed back and forth with a neighbour doing the same job,

Both on st nav steering which makes such things much easier.

My NH 7.210 with 4m combi his fergie 7719 on 3m combi. Broadly speaking fuel used per acre was the same. Despite him having a bigger tractor and smaller drill

 

[Rooster cogburn]

That would mean then if I was looking to change up the year’s I shouldn’t worry about fuel usage. Realistically there are far more 150hp tractors about than 100 hp. And not always much different in size or weight. So if I had a set amount to spend just buy what I happy with rather than looking for the smaller equivalent because the running costs will be similar anyway

 

[Lakesdigger]

Simply put you can't produce hp without burning fuel it is simply how the science works. You are burning fuel to release the energy stored within it and there's only a certain amount available and modern engines are all very close with regard to how efficiently they can do this.
The biggest change for yourself if you were to change to a newer tractor is the step forward to one with common rail injection and and advanced engine management. Using the tm as the example when working hard a modern 150hp tractor may use similar fuel to the tm but when on light duties the modern tractor will be sipping it in comparison (or at least should be if driven correctly).

 

[Drillman]

So a tm150 wouldn’t use any more diesel than a 7740 in similar work

The TM probably isn’t the best example to use as although there a very good engine when working hard that 7.5 litre powerstar engine likes a drink

we could empty the fuel thimble in 7.5 hours drilling quite easily with our TM135 and 155 and although the T7.210 tank is only 18% bigger it will do 10 hours plus on the same job Easily

 

[Wellytrack]

The TM probably isn’t the best example to use as although there a very good engine when working hard that 7.5 litre powerstar engine likes a drink

we could empty the fuel thimble in 7.5 hours drilling quite easily with our TM135 and 155 and although the T7.210 tank is only 18% bigger it will do 10 hours plus on the same job Easily

I would say the Powerstar as good an engine as was typical of its era, certainly I’d count it as frugal or economical as anything else of a different colour that was a competitor then.

 

[DrDunc]

Two tractors with 155hp at the shaft, both vario gearbox

Hauling stone from the quarry, round trip an hour, 12 tonne load, the same trailer and identical (hill ridden) route

One tractor uses 31 litre per trip, the other 26

Why?



One is a remapped Valtra N134D, the other is a deutz 6180 ttv