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Old 09-01-2014, 02:22 PM   #21
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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.
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Old 09-01-2014, 02:32 PM   #22
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Originally Posted by djmarchand View Post
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
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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Old 09-01-2014, 02:32 PM   #23
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Originally Posted by Wxx3 View Post

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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Old 09-01-2014, 02:37 PM   #24
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Originally Posted by Wxx3 View Post
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.
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....
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Old 09-01-2014, 02:52 PM   #25
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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.
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Old 09-01-2014, 02:54 PM   #26
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Originally Posted by Wxx3 View Post
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.
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.
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Old 09-01-2014, 05:02 PM   #27
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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.

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Old 09-01-2014, 05:08 PM   #28
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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.

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Old 09-01-2014, 05:48 PM   #29
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Quote:
turbocharged engines are always stressed more than non turbocharged engines.
That just is not true anymore, and for a good long while now. The true heavy duty continuous duty engines today are turbo charged.
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Old 09-01-2014, 07:58 PM   #30
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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.
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Old 09-01-2014, 08:02 PM   #31
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George:

Sure, there are big, slow commercial diesels with turbocharging that are stressed less than the ubiquitous Lehman, but that isn't any kind of a fair comparison.

We are talking about reliability here. Sure you can put a 5 ton engine in your 35 foot trawler and it will run into the next millennium.

But a fairer comparison is of the non turbocharged Perkins 135 with the turbocharged 160 hp engine. The turbocharged engine is producing more torque over the upper rpm range, so it is putting more force on bearings and piston side walls, ie more stress.

Or compare the non turbocharged Cummins B against the turbocharged models, or the JD, or the .....

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Old 09-01-2014, 08:11 PM   #32
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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.
I think if you are talking about the engines used in commercial equipment you can trust the manufacturer's ratings. Fleet managers aren't going to buy product from a mfg that lies about something so mission critical.

But as noted, ratings only describe performance and only come into play at very high throttle settings for long periods of time. At trawler speeds they are irrelevant, IMO.
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Old 09-01-2014, 08:20 PM   #33
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Could it be that use of a turbocharger is required to achieve the EPA requirements? The common Toyota forklift Diesel engines in the 6 and 8000 LB capacity machines we service are still coming new with a 4 and 6 cylinder non turbo Toyota engine.


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Old 09-01-2014, 08:44 PM   #34
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Originally Posted by djmarchand View Post

Or compare the non turbocharged Cummins B against the turbocharged models, or the JD, or the .....

David
For decades, over half a century now, there are turbocharged diesels getting tens of thousands of hours on the clock. This great success is accompanied by greater efficiency and cleaner burning engines, these are facts and not opinions.

The clock cannot be turned back. Ask a blue water Nordhavn owner of a turbocharged engine how much trouble the engine suffers at an M1 rating, I know the answer and you do too.

And prey tell, whose NA engine un the 150 HP range can you buy today? Zero is the answer for Tier 3 compliance.
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Old 09-01-2014, 08:46 PM   #35
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Look at the old Detroit 53, 71, 92 series life span when Johnson Towers got through with em. Pumped them up to where a non turboed engine would have a 20-30 thousand hour life span theirs 1200 hours then ready for MOH. Cat 3208, pass 350hp or so and they blew themselves up in no time. The 3208 natural cranked out around 220hp, last almost forever. As with all things in life, a compromise.
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Old 09-01-2014, 11:18 PM   #36
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Per JD,

Quote:
The M1 rating is for marine propulsion applications that may operate up to 24 hours per day at uninterrupted full power and have load factors* greater than 65 percent.
Which would be better for a FD boat that requires 85 HP to run hull speed in calm water/winds?
  1. An M1 enigne running 105 HP?
  2. An M2 engine running 121 HP?
  3. An M3 engine running 135 HP.

Quote:
The M2 rating is for marine propulsion applications that
typically operate between 3,000-5,000 hours per year
and have load factors* up to 65 percent. This rating is for
applications that are in continuous use and use full power for
no more than 16 hours of each 24 hours of operation.
Quote:
The M3 rating is for marine propulsion applications that
typically operate between 2,000-4,000 hours per year
and have load factors* up to 50 percent. This rating is for
applications that use full power for no more than 4 hours
out of each 12 hours of operation.
Loading is a very important limitation...

Later,
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Old 09-01-2014, 11:25 PM   #37
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M1 as you don't need more horsepower. And there won't be any need to "baby" the engine.
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Old 09-02-2014, 12:11 AM   #38
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Originally Posted by dannc View Post
Per JD,



Which would be better for a FD boat that requires 85 HP to run hull speed in calm water/winds?
  1. An M1 enigne running 105 HP?
  2. An M2 engine running 121 HP?
  3. An M3 engine running 135 HP.





Loading is a very important limitation...

Later,
Dan
M3, since you can then prop the boat a bit taller for the 135HP but run at lower rpm than if using M1. I doubt that it will make any noticeable difference for fuel consumption but it will be noticeably quieter. And you can run M3 continuous at 200 rpm below WOT, if you ever needed to. I don't think you would get anywhere near the 50% loading or the annual hours spec in normal cruising.

M3 WOT fuel use is 7.8gph. So 50% is 3.9gph, a bit under 2100rpm for the 4045TFM75 on the prop curve. Now, that's about 70HP. Sure, that's less that the 85HP needed for 'hull speed'. But in practice, you will spend most of your hours about a knot below hull speed, be using a lot less than 85HP and save an enormous amount of fuel.

To get your warranty you will have a sea trial with the dealer on board demonstrating that you can get to WOT. With that, plus the 100 hour break-in by the book, no 'babying' of an M3 spec is needed.

But the key point is, you want to change rating later? Just get the dealer to plug his laptop into the ECU and do it for you. Its that simple.

What is your waterline length and displacement? Do you already have a gearbox, if what ratio?
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Old 09-02-2014, 12:49 AM   #39
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some still don't get it. Low power per liter engines are" babied" by their rating. The same block hopped up to high HP can do that or run at the same low power of the lower rated engine if you want to "baby" it for identical results as the low power version.

All the maker has done with low power ratings is to take the high HP option away from the operator.
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Old 09-02-2014, 03:24 AM   #40
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I think I like this thread!

Totally agree that a turbo charged engine has gets to better fuel efficiency that can't be achieved with a NA engine. That said, I specifically chose my boat BECAUSE it had 210hp NA cats, because its one less component to go wrong, actually a couple cause the NA cat does not have an after cooler either. Always choices.

So while were defining the ever so elusive "max" continuous load, who wants to talk about the minimum?

I always see people worried about having too little load on a diesel, or that the diesel must have a significant load on it. Lets take idling off the table for a moment and just consider a boat under way at something more than idle. I'm just not sure I completely buy the whole too little load story, at least as it gets told most days. It seems there are very precious few stories of a lightly loaded diesel having issues.

Its worth adding to the conversation I think.
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