High horse power four cylinders can’t sustainably do the same job as a larger six pot of similar HP. Tell me I’m wrong

Come the zombie apocalypse I know what engine I'd choose and it wouldn't be small capacity highly tuned turbo super charged with variable cams and valves and whatnot. When they're after your brains I wouldn't be confident mowing down zombies with anything but a 5.9 cummins or a cast iron 2v pushrod v8

High tech is no use stood on the headland waiting for a techie - it doesn't break down standing in the shed between jobs.
 

ColinV6

Member
Most of the 4 pots seem to have much smaller fuel tanks than their 6 pot equivalents. Making a hard days field work impossible without a fill up.
 

Cowabunga

Member
Location
Ceredigion,Wales
Most of the 4 pots seem to have much smaller fuel tanks than their 6 pot equivalents. Making a hard days field work impossible without a fill up.
That is indeed a major issue for many farmers. An MF 6470, even with the optional right hand mounted auxiliary tank, has nothing like the tank capacity of a 6480 six pot, which both makes it appear to some people that it drinks more [it doesn't] but that damned mid afternoon refill is just unacceptable on a hard working tractor that is working away from a refill tank. One of the criteria I've always used when choosing a prime mover is that it should be able to work for, ideally, ten hours flat out full power, but an absolute minimum of eight hours.

I work that out on the back of a fag packet [not literally]. So a 180hp tractor is 135kW. At approx 200gms/kW/h * 135 = 27 litres per hour on an average counting no-load work. Ten times that is a minimum of a 270 litre tank. 60 gallons. That's the absolute minimum I would even consider for an intensively used tractor of that size. Ideally it would have a 300 litre tank.

140hp = 105kW so 105*200=21000gms/hour. That's near enough 21 litres*10 hours= a 210 litre which is a 46 gallon tank. A 50 gallon tank would do nicely, that's irrespective of whether the tractor has four or six cylinders. It's more likely to have that size tank if six cylinder. As it happens the new MF 5S145 has a 200 litre tank, which makes a refreshing change for the better for a four cylinder tractor. It works out even better for lesser horsepower 5S models because they retain the same tank capacity.
Just checked and the 180hp MF7718S has a 305 litre tank, which is again acceptable by my calculation. Just about acceptable even if it was the 7719S model.

MF must use the same sort of calculation as I do when speccing their tank sizes these days. They didn't used to, because the old 6400 four cylinder tanks were inadequate once you got to higher than 100hp in my opinion. Even with the optional tank it was inadequate for the 5470 and 6470.
Similar issues occur with most other brands.

Not everyone needs to work flat out all day or work away from home of course, but it is increasingly likely to be a more regular occurrence these days with bigger farmers and contractors.
 

Wellytrack

Member
Most of the 4 pots seem to have much smaller fuel tanks than their 6 pot equivalents. Making a hard days field work impossible without a fill up.

Fuel use per KW between 6 and 4 is largely similar. By checking some DLG data a 4cylinder Perkins 6470 in comparison burned just under 10% less fuel per KW as the 6 cylinder 6475.

In saying that it’s also just 2/3’s of a 6 cylinder engine that’s overcoming the friction of having to push pistons and at idle speeds/low revs will burn less fuel.

Personally I’m amazed at the guts in modern 4 Turbos, particularly the Sisu ones. They just don’t know when to give up.
 

Cowabunga

Member
Location
Ceredigion,Wales
Fuel use per KW between 6 and 4 is largely similar. By checking some DLG data a 4cylinder Perkins 6470 in comparison burned just under 10% less fuel per KW as the 6 cylinder 6475.

In saying that it’s also just 2/3’s of a 6 cylinder engine that’s overcoming the friction of having to push pistons and at idle speeds/low revs will burn less fuel.

Personally I’m amazed at the guts in modern 4 Turbos, particularly the Sisu ones. They just don’t know when to give up.

For the same horsepower that could be a 4000 litre saving over a 2000 hour year assuming the same horses for both tractors. That's approx £2000 saving annually or £1/hour worked.
 

dave mountain

Member
Livestock Farmer
Fuel use per KW between 6 and 4 is largely similar. By checking some DLG data a 4cylinder Perkins 6470 in comparison burned just under 10% less fuel per KW as the 6 cylinder 6475.

In saying that it’s also just 2/3’s of a 6 cylinder engine that’s overcoming the friction of having to push pistons and at idle speeds/low revs will burn less fuel.

Personally I’m amazed at the guts in modern 4 Turbos, particularly the Sisu ones. They just don’t know when to give up.
Whether that 10% would prove correct in real world use I'm not sure, although I do doubt it. If so I would say that particular comparison would be the exception rather than the rule, having compared t6.175, t6.180, t7.170 n154 and t154. the difference in fuel consumption will vary between 4 and 6 pot being more economical depending on the exact tractors you are comparing, the difference in internal losses between a 4 and 6 is negligible, the only time a 6 might use more is at idle, and that is due to the displacement not the number of cylinders. With modern 4 pots getting bigger displacements this difference disappears anyway. All this aside, a 4 will never be as smooth as a 6 due to fires per revolution.
 

daveydiesel1

Member
Livestock Farmer
Location
Co antrim
What i dont understand is they say there making bigger 4 pots because of emmissions but if a 180hp 6pot passes the emmissions tests why will a 140hp 6pot not pass the same test?
 

Two Tone

Member
Mixed Farmer
We have a JLR Engineering Director that lives in our village who I was chatting to about this very thread.
His comments were that:
A 4 cylinder engine will require a bigger flywheel than a 6 cylinder engine.
Assuming that both the 4 & 6 cylinder engines have the same total displacement, any additional friction from the total surface area of 6 cylinder's pistons and rings within the bore are more than compensated for by the fact that there are more cylinders firing in every revolution of the crank shaft.
Associated vibration in the drive train will be less from a 6 cylinder than a 4.
Fuel usage differences between the 2 are negligible.
Manufacturing costs are obviously cheaper with the 4 cylinder.
That aside, his own personal preference would be the 6.
 

2wheels

Member
Location
aberdeenshire
Displacement is about making room for more air (For oxygen to burn the hydrocarbons) - Or you can force a similar amount of oxygen into a smaller cylinder using a Turbocharger with or without an intercooler.... Been going on in mainstream UK farming since 0971 when Ford brought out the 7000.

valmet were using turbo charged engines before the rest of agricultural tractor manufacturers.
 

Cowabunga

Member
Location
Ceredigion,Wales
The idea that four cylinder engines are not as smooth as six is a load of twaddle. There are out of balance forces in both. Both use different kinds of balancers to ensure smoothness as all revs and loads. Four cylinder engines are commonly fitted with two balancer shaft running at twice engine revs to counteract the secondary forces that occur at every 180 degrees of crank throw.
Six cylinder engines almost universally need dynamic balancers on the nose of the crank to counteract destructive torsional vibration of the crankshaft even though both primary and secondary forces should be balanced.
If either type of engine was not balanced they would not last long and would sound like a bag of rocks inside a washing machine.
 
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mf7480

Member
Mixed Farmer
The idea that four cylinder engines are not as smooth as six is a load of twaddle. There are out of balance forces in both. Both use different kinds of balancers to ensure smoothness as all revs and loads. Four cylinder engines are commonly fitted with up to two balancer shaft and six cylinder engines almost universally need dynamic balancers on the nose of the crank to counteract destructive torsional vibration of the crankshaft.
If either type of engine was not balanced they would not last long and would sound like a bag of rocks inside a washing machine.

But wouldn’t it be fair to say the majority of 4 cylinders literally do sound like a bag of rocks in a washing machine
 

SFI - What % were you taking out of production?

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Red Tractor drops launch of green farming scheme amid anger from farmers

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As reported in Independent


quote: “Red Tractor has confirmed it is dropping plans to launch its green farming assurance standard in April“

read the TFF thread here: https://thefarmingforum.co.uk/index.php?threads/gfc-was-to-go-ahead-now-not-going-ahead.405234/
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