Continuous Rated Engines

This comes adrift from the Showtime and Minimum RPM threads.
I`ve heard some engines are rated for continuous use, like JD and Gardiner. What exactly does that mean? Who assigns the rating? Of the maker, common experience,and a rating agency, the first is most likely. How reliable is that? Any maker could claim it as part of a sales spiel, but it could all come undone in practice.
Which engines have such a rating, and why? The Dauntless experience suggests at least one FL deserves the rating. One member was astounded I didn`t already rate the FL, I didn`t, I own 2 of them, I`m still not sure. So, would we include the common FL 120 and/ 135? I`ve not heard Ford or Lehman did. Who apart from Richard has run one for days on end?
And let`s not get too fixated on the FL, there are plenty of other possibilities in engines out there.

ISO 3046 has the answers.

Our Lugger L1066T is rated for continuous duty at 2200 RPM @ 135Hp, which is exactly what we run all the time.

Continuous rated engines generally means it can be run at full power 24/7/365. Usually something like 25hp/liter or so. Higher rated engines can be run at 24/7/365, but not at full power. The high rated engine might be capable of making 60hp/liter, but can't do that continuously. Run it at 25hp/liter, either engine, and they both can go forever.

More:

Ski in NC said:

... Run it at 25hp/liter, either engine, and they both can go forever.

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Interesting. The FL 120 is 6.2L.

The 25hp/l I guess better applies to turbo engines, a nat asp engine is going to be hard pressed to get there at all. Go with the mfr's specs for rating class, some turbo engines are 30+ hp/l at continuous, nats will be much lower.

My naturally-aspirated JD4045 (80 horsepower) at "high cruise" (hull speed) of 2200 RPM is at 75% load (3 versus 4 max. gph at 2400 RPM). "Normal cruise" (one knot below hull speed) at 1800 RPM is at 43% load (1.7 gph).

BruceK said:

This comes adrift from the Showtime and Minimum RPM threads.
I`ve heard some engines are rated for continuous use, like JD and Gardiner. What exactly does that mean? Who assigns the rating? Of the maker, common experience,and a rating agency, the first is most likely. How reliable is that? Any maker could claim it as part of a sales spiel, but it could all come undone in practice.
Which engines have such a rating, and why? The Dauntless experience suggests at least one FL deserves the rating. One member was astounded I didn`t already rate the FL, I didn`t, I own 2 of them, I`m still not sure. So, would we include the common FL 120 and/ 135? I`ve not heard Ford or Lehman did. Who apart from Richard has run one for days on end?
And let`s not get too fixated on the FL, there are plenty of other possibilities in engines out there.

Click to expand...

Most any diesel can run continuously, just not at peak output. The ratings relate to the percentage of time the engine can run at peak power. My CAT is a 'C' rated 2200 rpm motor at 270 hp that can run 24 x7 for the rest of my life at 1500 rpm and is expected to run 1,000 - 2,000 hours per year. The 'A' rated is continuous at 2000 rpm and 215 hp with an annual hour time of 5000 to 8000 hours, and the 'B' at 2000 and 235 hp and 3,000 to 5,000 hours.

So it really boils down to how you use the engine that determines what rating is most appropriate, with higher rating accomplished by tuning down the max rpm and hp. In trawlers, since they rarely run at full power and only run 1,000 hours per year or so, the rating probably doesn't matter much. Although I am happy to be corrected on this impression....

Rating should be by the manufacturer. For older engines I have often seen it expressed simply as 'for continuous operation do not exceed 85% of max rpm'.

I have a pair of John Deere 6068's, with their M3 rating. This rating specifies full power operation must be limited to 4 hours out of every 12. On the other hand, their M1 rating for the same engine allows 24 hour full power operation ie continuous. The different ratings are achieved by the dealer changing the ECU via a laptop. Just how many things change I have no idea, but here is a couple: WOT comes down from 2600 to 2400. Power output drops from 201HP to 158HP. The maximum power and torque curves change shape a bit, and with M3 rating I still have the full 201HP available at 2400rpm. The engine has an electronic governor but is Tier 2 and not fully electronic - the injectors are not fully electronically controlled like the later common rail Tier 3 engines are.

For my M3's, load factors must also be below 50%. Load factor is defined as fuel burned over a period of time divided by full power fuel consumption over the same period. The other 8 hours out of 12 must be at cruising speeds. Cruising speeds are defined as 200 rpm below WOT, or 2400 rpm for my M3's.

In practice, due to hull shape and weight, gear ratio and prop size I find my sweet spot is in the 60 to 75% of WOT area. So, 1500 rpm for 7.9 kn at 15 lph total up to 1950 rpm for 9.5 kn at 30 lph total. There has to be a good reason to want the extra 1.6 kn at double the fuel consumption! And for me to run at 10 kn or more uses a lot more fuel for little real benefit, as I'm still in displacement mode for my SD hull shape. If I wanted to plane I would need at least 50% more installed HP and probably more like double. It gets hard to do that at reasonable fuel consumption once you are over 40 ft with all the space and comforts of home and associated weight on board.

It seems that many Lehman owners also tend to operate in the 60-75% of WOT area and expect and report long service life. I suspect that if you ran a high rpm car diesel engine like that, ie 60-70% would you also get long reliable life. If so then car diesels would seem to be a pretty good option for a planing boat. Just choose the right size so you can keep the loading down.

For most practical purposes with a modern common rail fully electronic motor you can pretty much dial in the ratting equivalent use with the throttle. Or you can have a tech from the company come down and hook your motor to a computer or exchange a chip and set up a new ratting. What happens is that the electronics tell the motor how much fuel it can burn and how much HP can be pulled out at what RPM. So a 6+ Li engine can be M1 (continuous rating) at say 180Hp at 2200rpm or bumped up to 300+ Hp at 2600rpm at M4 pleasure use say 4/12 hr max rpm cycle. If you run the M4 at 1800-2200 rpm you can use it like an M1 24/24 You are just pulling less power out of the unit and stressing it less so continuous use will not harm it. A good genrator motor should be set up like an M1 particularly if used for long periods. A ocean crossing vessel would also benefit from M1 ratting or reduced throttle due to long continuous running hours.

N4712 said:

Our Lugger L1066T is rated for continuous duty at 2200 RPM @ 135Hp, which is exactly what we run all the time.

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If so, this would equate to a fuel burn of about 7 gph if you're pulling 135 hp. Most N47s seem to have a normal rate closer to 5 gph for coastal and 4 gph for blue water cruising. What is your fuel burn and RPM at coastal and economy cruise?

sunchaser said:

If so, this would equate to a fuel burn of about 7 gph if you're pulling 135 hp. Most N47s seem to have a normal rate closer to 5 gph for coastal and 4 gph for blue water cruising. What is your fuel burn and RPM at coastal and economy cruise?

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From what we've seen we burn 6GPH with genny, we don't have any fuel flow monitors yet. But that's just what we've seen when we compare our log book to fuel levels.

BruceK said:

, Who apart from Richard has run one for days on end?

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Once an engine is up and running it's in it's happy place. It's starting and stopping, heating up and cooling down that's hard on an engine or motor.

Here's is some info on CAT engine ratings.

http://tinyurl.com/pdzm4uq

http://tinyurl.com/ohcbhg9

Where does torque fit into this, I may have been living under an illusion that as hp was dialed down then torque increased, kindda a whack a mole or ohms law with voltage and amps.??

Boatdiesel.com has a wealth of information and comment on this and similar issues.

A true continuous duty engine is a de-rated version on the same block as say, a higher horsepower but intermittent use version. Thus you will see the same engine with different version putting out different HP at the same RPM.

Mule; Here is a full explanation of the mathematical relationship between torque and HP
HP = Torque x RPM ÷ 5252

Power and Torque: Understanding the Relationship Between the Two, by EPI Inc.

I agree with most of the comments so far and 25 hp per liter is a good rule of thumb for 24/7/365 use of turbocharged engines.

But let me digress a little bit and talk about ratings in general. The manufacturer assigns the rating. For some, Yanmar in particular this is a marketing/financial ploy and has little basis in engineering, testing or experience.

For Yanmar recreational engines the ratings go something like this: full power for 2 out of 8 hours and 200 rpm off of top forever. And the warranty that backs that statement up is two years at 200 hours per year. See the disingenuity in those statements -.

Running a 70 hp per liter engine at 200 rpm off of top is something like 55 hp per liter. So Yanmar warrants an engine to run continuously at double what the JDs of the world say for at least 400 hours over two years.

Why? Easy, they don't expect to have a warranty claim in that period.

Yanmar is by far the worst in the use of this gimmick. JD one of the best.

David

The most honest engine raters are those that use their engines for commercial gensets, notably Cat and Cummins which are the most popular in the 100 to 200 HP range - operating at 1800 RPM.

The Cummins 6BT genset gives 24/7/365 numbers at 112 KW or 150 HP and Cat's C6 is rated at 138 KW or 185 HP. These two are 5.9 liter engines. One of the most popular gensets is the 7.2 liter Cat C7 rated at 150KW or 200 HP. All three can be purchased with a cradle to grave warranty if you adhere to the maintenance programs.

The Cummins 6B block in its marine propusion variant can be goosed up to 400 + HP and the C7s 450 HP so the genset versions are pretty well loafing. Alas the underachiving C6 has the same marine HP as genset HP for continuous duty at 1800 RPM. The Cat C6 (or Perkins Sabre 225 TA when rebadged and painted blue) sits in my vessel as the propulsion engines.

bayview said:

Mule; Here is a full explanation of the mathematical relationship between torque and HP
HP = Torque x RPM ÷ 5252

Power and Torque: Understanding the Relationship Between the Two, by EPI Inc.

Click to expand...

THis formula is a total over simplification and in fact only works on their little 12" crank example.

the relationship between torque and HP are dependent upon the engine design itself.

The formula is universal and based on definitions of torque and hp.

Torque is a measure of force and HP is a measure of the work done by that force over time.

djmarchand said:

I agree with most of the comments so far and 25 hp per liter is a good rule of thumb for 24/7/365 use of turbocharged engines.

But let me digress a little bit and talk about ratings in general. The manufacturer assigns the rating. For some, Yanmar in particular this is a marketing/financial ploy and has little basis in engineering, testing or experience.

For Yanmar recreational engines the ratings go something like this: full power for 2 out of 8 hours and 200 rpm off of top forever. And the warranty that backs that statement up is two years at 200 hours per year. See the disingenuity in those statements -.

Running a 70 hp per liter engine at 200 rpm off of top is something like 55 hp per liter. So Yanmar warrants an engine to run continuously at double what the JDs of the world say for at least 400 hours over two years.

Why? Easy, they don't expect to have a warranty claim in that period.

Yanmar is by far the worst in the use of this gimmick. JD one of the best.

David

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Thanks David for articulating what I was thinking.
I would also like to add a caveat.

Modern marketing nowadays plays fast and loose with the numbers.
Even the warranty may not mean the engine can run continuously. Now, I'm NOT talking commercial market, that's different.

But in the pleasure boat market they promise all sorts of stuff, because they know 98% of everyone will never run their engine like that and if they do and it blows up, the warranty claim costs less than giving up the "claim".

Let me put it another way. Does anyone who has worked with engines think that a turbocharged engine is more reliable than a non turbo engine under any circumstances???

Then there is the kind of failure. One of the reasons I felt so confident going across the ocean is that for a low revving engine, for it to experience a catastrophic failure is really rare. Rings can loose compression, gaskets and seals can leak, bearings can even be spun, but even with that the engine will still run and a probably quite a while if not pushed.

Turbos are another story. Just have the fire extinguisher handy.


IT's all about marketing.

Wxx3 said:

THis formula is a total over simplification and in fact only works on their little 12" crank example.

the relationship between torque and HP are dependent upon the engine design itself.

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Negative, Ghostrider.

Wxx3 said:

THis formula is a total over simplification and in fact only works on their little 12" crank example.

the relationship between torque and HP are dependent upon the engine design itself.

Click to expand...

Not really. The relationship between torque and horsepower is a physical constant that can be programmed into a calculator that is completely independent of engine design. Horsepower & Torque Calculator - Metaris

Congrats on your crossing, by the way....

Torque is supposed to be the force on the crankshaft ... won't even idle your engine. Hp is work done. That's what moves my boat

If I'm running at 1400rpm and advance the throttle the boat will increase in speed as does the engine. During the time I advance the throttle and the time the speed and engine rpm is increasing torque is either making it increase or helping it increase. Once it stops increasing hp takes over and does the work of pushing the boat.

That could be true or it could be a scrambled mess of facts and opinions I've heard in the past.

Wxx3 said:

Thanks David for articulating what I was thinking.
I would also like to add a caveat.

Modern marketing nowadays plays fast and loose with the numbers.
Even the warranty may not mean the engine can run continuously. Now, I'm NOT talking commercial market, that's different.

But in the pleasure boat market they promise all sorts of stuff, because they know 98% of everyone will never run their engine like that and if they do and it blows up, the warranty claim costs less than giving up the "claim".

Let me put it another way. Does anyone who has worked with engines think that a turbocharged engine is more reliable than a non turbo engine under any circumstances???

Then there is the kind of failure. One of the reasons I felt so confident going across the ocean is that for a low revving engine, for it to experience a catastrophic failure is really rare. Rings can loose compression, gaskets and seals can leak, bearings can even be spun, but even with that the engine will still run and a probably quite a while if not pushed.

Turbos are another story. Just have the fire extinguisher handy.


IT's all about marketing.

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Really! With 99%+ of diesel engines sold today having turbos the jury voted decades ago. My experience includes up to 4000 HP commercial diesels working at full WOT throttle load over 50% of the time and with quad turbos and JWAC.

A look at the automotive diesel market shows the same, few if any diesel NAs are sold today in the automotive or light truck market.

And we are speaking of tens of millions of these turbo diesels in use today with the turbo diesel market growing dramatically to permit mandated fuel economy standard to be achieved.

As someone said horsepower is the rate of which work is done. Lifting a 550 lb weight at one foot per second vertically requires exactly 1 horsepower. And horsepower is both an energy term and a units definition. 1 hp = 550 ft lbs per second.

Torque is force applied in a rotational manner at some defined lever arm radius. It is a force term, but has no standard units definition. For US units it is lbs x feet of lever arm.

As someone else said (or was it the same person?), there is a defined mathematical relationship between horsepower and torque. Measuring torque in lb feet, horsepower = torque x rpm / 5252. The constant 5252 is derived from the geometry.

With a two foot cheater bar and my overweight 225 lb frame I can apply 450 ft lbs to a stuck lug nut. But since it is not moving, ie zero rpm) I am using zero horsepower.

For any further enlightenment, read a high school physics text.

David

sunchaser:

You and Wx33 are both right but you are talking past each other. I agree with Wx33 that non turbocharged engines are more reliable. Why? There is no turbocharger (or associated air cooler) to fail and turbocharged engines are always stressed more than non turbocharged engines.

But does the market embrace turbocharged, aftercooled engines for their light weight and compact size for the horsepower produced. Yes, absolutely.

David

turbocharged engines are always stressed more than non turbocharged engines.

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That just is not true anymore, and for a good long while now. The true heavy duty continuous duty engines today are turbo charged.

My 2.2L diesel turbo car engine produces 150KW/204bhp, and 450Nm torque. does that help, probably not.
Ratings are at risk of manufacturer abuse but is there an independent rating agency? If there was would you trust it? Remember the GFC, and the BS from ratings agencies, like "Poor Standards", (as I like to call them). Could be experience and the ratio of output: cubic capacity, is the best guide. Though I think I`d take the word of Lugger, JD, and their ilk.