Why so little power?

hemichallenger

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Motors built in the 70s that made 400 plus hp were 855 cubic inch and larger. Ntc 475 cummins,kta models. Cat 1693, 3408 were 400 and up to 600 hp. These all were about twice the cubic inch. The multi fuel motors were like the 1160 cat that was the old verision of the 3208 another low horse power models made for light duty trucks.
 

stumps

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Torque baby, torque! Diesels make torque, and gas engines make HP!

I can't tell you how many times I have heard that false claim, and it makes me cringe every time!

HP and torque are mathematically related numbers:

Torque = 5252 HP / RPM

And,

HP = RPM x Torque / 5252

Give me HP, or Torque, and tell me how fast the engine is turning, and I can give you the other.

Because of the long strokes necessary to gain the high compression ratio needed to heat the air in a compression-ignition (CI) engine, and the strength the parts need to handle the high compression ratio, diesel engines are heavy and slow lumbering beasts. For a given amount of HP, a slow turning engine will put out more torque than a fast turning engine.

For example:

Let's take an engine that puts out 140HP at 1500RPM (perhaps a deuce?):

Torque = 5252 x 140 / 1500RPM = 490 Ft-Lbs

Let's take another engine that puts out 140HP at 10 times the RPM, or 15,000RPM (perhaps a motorcycle?):

Torque = 5252 x 140 / 15000 = 49 Ft-Lbs

How can we compare them, to the uneducated eye, the deuce is dripping in torque, but the motorcycle is weak?

Well, lets use a gear box, and bring the speed of the motorcycle engine down to the speed of the deuce engine.... that would take a reduction of 10 to 1. A 10 to 1 gear reduction will multiply the torque by 10 times, bringing the motorcycle's torque up to the same 490 Ft-Lbs as the deuce engine's !

The sole and only reason to prefer a CI diesel engine over a spark ignition (SI) gasoline engine is fuel economy. Compression ratio is directly related to fuel economy: The higher the compression ratio, the more effectively you can use the energy contained in the fuel.

There was one other thing that influenced the use of CI diesel engines. Gasoline was pretty exotic back in the day, and highly flammable. Exotic means expensive. Diesel oil was closer to what came out of the oil well head, and required less refining than gasoline. Diesel oil was cheap dirty fuel with a higher heating value than gasoline. It only makes sense that commercial trucking companies, which are profit driven, would select the cheapest way of getting their loads delivered.

The commercial truckers got an added benefit that was a pleasant surprise: The massively heavy, slow lumbering diesel engines were so overbuilt that they lasted longer than the lighter weight gasoline engines. The truth is, that very early gasoline engines were also massively heavy, slow lumbering engines, and they too lasted longer than lighter weight gasoline engines.... but were less fuel efficient.

-Chuck
 

TexAndy

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How do they determine the torque rating of an engine?

One foot long lever with a weight on then end of it connected to the output shaft and then keep adding weight in one pound increments till the engine can no longer turn?
 

saddamsnightmare

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July 2nd, 2010.

Permit me to weigh in on this too. Back when the deuce was designed (as a gasoline engined truck -1948, it was not uncommon for one drive axle road tractors (civillian) to make do with a 115 HP gasoline or diesel engine pulling a 28 foot trailer and doing maybe 45-50 on the road. They often used two speed rear ends and 4 to 10 separate gears to get you up to road speed in a half mile to a mile, or so. The deuce, being an off road designed truck, do not need either complexity or power, as either misapplied in the hands of an 18 or 20 year old G.I., can lead to problems. Plus, the deuce is a long stroke diesel with fairly heavy (by modern standards) and relatively imperfectly balanced rotating loads... Many a G.I. (and I suspect a few members on here), have found out what happens when you push a Multifuel over the red line, and from all accounts, the results are memorable.....
The (1963) S.404.114 Unimog I have, has heavier axle gearing (7.65 to 1) and the usual 6 speed transmission, and it makes do with a 80HP Mercedes gas engine of about 134 CID pulling a 6100# tare and 9100# loaded truck, and no one has ever accused the Unimog of being lightening fast, but it has gone places few civillian trucks can crawl into or out of loaded, and it will pull the bumper off of most civillian trucks.... There are quite a few S404.114's surviving, much like the deuce, they were designed as working trucks (or tractors, in the case of the Unimog), to be simple, robust and long lived. Apparently even Mercedes miscalculated the longevities for the S404.114's.. as the last one was built in 1981!
With care, a deuce might well outlast its owner, with unmitigated abuse, pretty unlikely (and the owner may not outlast the deuce, depending on what stupid move he made last with it....)! Few civillian trucks from 1971 are seen on the road today working like my deuce does, 98+% of the time, when called on it works. The suspension, though crude, is robust and flexible, going places that would stick or break a comparable sized civillian truck... So, my hats are off to the REO engineers 62 years later....[thumbzup]
It's just an opinion, but one can get banjo music outta of a jug (according to Briscoe Darling), and the deuce is pretty good at making music....;)
 

M35Brown

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Thanks Cranetruck;
You said it all.
Lets hear from some of the members that have installed the Dodge Cummins 5.9 high HP/Torque engines into a Deuce. How do they perform?
Deuce engines, farm tractor engines, and heavy equipment engines are designed to run at max HP rating all day long, at OAT Temps of 100deg. And above. As Cranetruck stated, the new Dodge Cummins will not operate at 350+ all day.
I am not knocking the Dodge Cummins, I have a new 6.7, and after a lot of mods, I like it.
 

stumps

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How do they determine the torque rating of an engine?

One foot long lever with a weight on then end of it connected to the output shaft and then keep adding weight in one pound increments till the engine can no longer turn?
They measure the HP with a dynomometer, and measure the RPM's with a tachometer, and calculate it with the formula: Torque = 5252 * HP/RPM

The traditional dynomometer is a generator with an adjustable resistor load bank. Measure the voltage across the load bank, and measure the current going into the load bank, and multiply, and you have the power (in watts) the engine is producing: HP = watts/746

All of those charts and tables showing torque and HP vs RPM were calculated from the HP vs RPM data that came from the dynomometer.

-Chuck
 

fuzzytoaster

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If you still think that torque does work, go and try to buy a 100ft*lb light bulb.
I think I got one of those from China, no joke. rofl

July 2nd, 2010.

Permit me to weigh in on this too. Back when the deuce was designed (as a gasoline engined truck -1948, it was not uncommon for one drive axle road tractors (civillian) to make do with a 115 HP gasoline or diesel engine pulling a 28 foot trailer and doing maybe 45-50 on the road. They often used two speed rear ends and 4 to 10 separate gears to get you up to road speed in a half mile to a mile, or so. The deuce, being an off road designed truck, do not need either complexity or power, as either misapplied in the hands of an 18 or 20 year old G.I., can lead to problems. Plus, the deuce is a long stroke diesel with fairly heavy (by modern standards) and relatively imperfectly balanced rotating loads... Many a G.I. (and I suspect a few members on here), have found out what happens when you push a Multifuel over the red line, and from all accounts, the results are memorable.....
The (1963) S.404.114 Unimog I have, has heavier axle gearing (7.65 to 1) and the usual 6 speed transmission, and it makes do with a 80HP Mercedes gas engine of about 134 CID pulling a 6100# tare and 9100# loaded truck, and no one has ever accused the Unimog of being lightening fast, but it has gone places few civillian trucks can crawl into or out of loaded, and it will pull the bumper off of most civillian trucks.... There are quite a few S404.114's surviving, much like the deuce, they were designed as working trucks (or tractors, in the case of the Unimog), to be simple, robust and long lived. Apparently even Mercedes miscalculated the longevities for the S404.114's.. as the last one was built in 1981!
With care, a deuce might well outlast its owner, with unmitigated abuse, pretty unlikely (and the owner may not outlast the deuce, depending on what stupid move he made last with it....)! Few civillian trucks from 1971 are seen on the road today working like my deuce does, 98+% of the time, when called on it works. The suspension, though crude, is robust and flexible, going places that would stick or break a comparable sized civillian truck... So, my hats are off to the REO engineers 62 years later....[thumbzup]
It's just an opinion, but one can get banjo music outta of a jug (according to Briscoe Darling), and the deuce is pretty good at making music....;)
Well said. The deuce was a well designed machine that can still contend with most modern day vehicles IMOP. I have yet to find a vehicle that can sit through years of abuse and neglect then with a little jump can crank on only one row of pistons. Thats a whole new level of respect for these machines.
 

m16ty

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The traditional dynomometer is a generator with an adjustable resistor load bank. Measure the voltage across the load bank, and measure the current going into the load bank, and multiply, and you have the power (in watts) the engine is producing: HP = watts/746
I had a tractor dyno (attached to the PTO shaft) that worked off of hyd oil. It computed HP just like you say but used a hyd pump and a valve closed to create resistance. The hyd oil got very hot and you had to have a garden hose attached to it to keep it cool.
 

jimk

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The LD/LDT/LDS basically share the same internal parts. The difference in power is due to volumetric efficiency increases due to turbocharging. Additional boost (LDS) is problematic due to the lack of intercooling and the high compression ratio.

Big rigs engines designed for big power have high boost, intercooling/aftercooling, low compression, strong internals, steel crown pistons....

Multi-fuel RPM is limited by design. The design called for 134-185HP so the internals were selected accordingly. While 400HP might be available at , say 35psi w/intercooling, it isn't going to be very reliable with stock parts.

SS tractor pullers are a good example of tractor blocks making extreme power. Diesels often use 2 or 3 stage turbochargers w/ water injection. Manifold pressures of 200-250psi are not uncommon. Here are a couple interesting engine block failures.

Both these looks like single stage twin turbo on alcohol.
YouTube - Tractor pulling - Blown engine

YouTube - Tractorpulling insane engine blow up, Engine flys out of the tractor!
 

nhdiesel

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To add to what others have said, inline engines typically have more torque potential than vee engines. Compare the 4.9 liter (300) Ford I-6 to their own 5.0 liter (302) of the same era, and the 300 is the one you want for pulling a trailer or heavy truck. If you had a Jeep, the 304 worked well for spinning tires in mud, but the 258 worked better for crawling through nasty terrain at or near idle. Compare the inline Cummins engines to the Ford and GM offerings. The Cummins puts out more torque at lower RPMs.

I do want to clarify something in M35Brown's statement about Cummins engines. I agree with what he said as it applies to the newer Cummins design. Like the other mfg's, the engines have been designed for a more car-like driving experience. Between emissions regulations and buyers who wanted the power of a diesel with the driving style (mostly sound) of a gas engine namely the camper-towing crowd), diesels have lost lifespan in the name of meeting emissions and sound standards.

But go back a few years, to the 12-valve Cummins engines, and they were quite common in industrial water pumps, generators, and other commercial uses that required them to run at max. output 24 hours a day, and they happily did it. I wouldn't want to put the 6.7 Cummins, powerstroke, or D-max in that position!

Jim
 

four-thirteen

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Reading the LDS-465-1 multifuel manual, figure 1 shows a minimum of BSFC (brake specific fuel consumption) of 0.400 lb/BHP-hr. The BSFC is a measure of the mass of fuel consumed to make 1 hp for 1 hour. The 0.4 lb/BHP-hr number isn't great, a modern TDI motor will run in at about 0.33 lb/BHP-hr, or 20% better. The same modern TDI motor will make about the same power from half the displacement. So as far as performance per displacement, it scores poorly, and fuel economy is about the same.

Why? Without putting it on a dyno and running it though a battery of tests we are left to speculate. I don't believe the mechanical loses are very high for the motor, no more than any other motor of similar displacement. The 22 to 1 compression ratio hurts the cycle efficiency significantly. While the optimal compression ratio for IC engines for efficiency is around 17 to 1 depending on the cylinder geometry, the 22 to 1 increases the temperature at TDC significantly, allowing it to burn fuels with a low cetane number (like gasoline) that are unlikely to burn when injected into a lower temperature cylinder. The same temperature increase also increases heat loss to the block and head, which reduces the energy that can be used to push on the pistons. So more energy goes out the radiator and less out the crankshaft.

I am willing to bet restrictive heads and valves also hurt the performance. This would contribute to a low BSFC by way of increased pumping work to pull in the fresh charge and to push put the spent gases. It would also hurt the performance by reducing the amount of air the engine can pull in and thus reduce the amount of fuel it can burn.

It would be nice if someone had some dyno data they could share so I could put some numbers to these ideas. A measure of CFM at a given RPM would be able to tell us the volumetric efficiency, which would be fairly telling. Another measure would be the power output and fuel consumption at a fixed RPM and various loads, which could be used to tell the mechanical efficiency.
 

jesusgatos

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Reading the LDS-465-1 multifuel manual, figure 1 shows a minimum of BSFC (brake specific fuel consumption) of 0.400 lb/BHP-hr. The BSFC is a measure of the mass of fuel consumed to make 1 hp for 1 hour. The 0.4 lb/BHP-hr number isn't great, a modern TDI motor will run in at about 0.33 lb/BHP-hr, or 20% better. The same modern TDI motor will make about the same power from half the displacement. So as far as performance per displacement, it scores poorly, and fuel economy is about the same.

Why? Without putting it on a dyno and running it though a battery of tests we are left to speculate. I don't believe the mechanical loses are very high for the motor, no more than any other motor of similar displacement. The 22 to 1 compression ratio hurts the cycle efficiency significantly. While the optimal compression ratio for IC engines for efficiency is around 17 to 1 depending on the cylinder geometry, the 22 to 1 increases the temperature at TDC significantly, allowing it to burn fuels with a low cetane number (like gasoline) that are unlikely to burn when injected into a lower temperature cylinder. The same temperature increase also increases heat loss to the block and head, which reduces the energy that can be used to push on the pistons. So more energy goes out the radiator and less out the crankshaft.

I am willing to bet restrictive heads and valves also hurt the performance. This would contribute to a low BSFC by way of increased pumping work to pull in the fresh charge and to push put the spent gases. It would also hurt the performance by reducing the amount of air the engine can pull in and thus reduce the amount of fuel it can burn.

It would be nice if someone had some dyno data they could share so I could put some numbers to these ideas. A measure of CFM at a given RPM would be able to tell us the volumetric efficiency, which would be fairly telling. Another measure would be the power output and fuel consumption at a fixed RPM and various loads, which could be used to tell the mechanical efficiency.
Somebody's got to have put one of these on a dyno, somewhere, sometime...
 

JasonS

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Reading the LDS-465-1 multifuel manual, figure 1 shows a minimum of BSFC (brake specific fuel consumption) of 0.400 lb/BHP-hr. The BSFC is a measure of the mass of fuel consumed to make 1 hp for 1 hour. The 0.4 lb/BHP-hr number isn't great, a modern TDI motor will run in at about 0.33 lb/BHP-hr, or 20% better. The same modern TDI motor will make about the same power from half the displacement. So as far as performance per displacement, it scores poorly, and fuel economy is about the same.

Why? Without putting it on a dyno and running it though a battery of tests we are left to speculate. I don't believe the mechanical loses are very high for the motor, no more than any other motor of similar displacement. The 22 to 1 compression ratio hurts the cycle efficiency significantly. While the optimal compression ratio for IC engines for efficiency is around 17 to 1 depending on the cylinder geometry, the 22 to 1 increases the temperature at TDC significantly, allowing it to burn fuels with a low cetane number (like gasoline) that are unlikely to burn when injected into a lower temperature cylinder. The same temperature increase also increases heat loss to the block and head, which reduces the energy that can be used to push on the pistons. So more energy goes out the radiator and less out the crankshaft.

I am willing to bet restrictive heads and valves also hurt the performance. This would contribute to a low BSFC by way of increased pumping work to pull in the fresh charge and to push put the spent gases. It would also hurt the performance by reducing the amount of air the engine can pull in and thus reduce the amount of fuel it can burn.

It would be nice if someone had some dyno data they could share so I could put some numbers to these ideas. A measure of CFM at a given RPM would be able to tell us the volumetric efficiency, which would be fairly telling. Another measure would be the power output and fuel consumption at a fixed RPM and various loads, which could be used to tell the mechanical efficiency.
This agrees with what I have read in that the high compression ratio hurts efficiency due to higher frictional losses. The engine design books that I have read state that the minimum compression ratio that permits easy starting should be used.

I read some of the farm tractor forums to see what is said about the multifuel as used in other applications. They are occasionally swapped out with the users getting higher horsepower AND lower fuel use. But, the multi is what it is and cheap to aquire.
 
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