"No replacement for displacement"

[Jerry Farnham]

So I maybe opening a can of worms with this thread, but that is not my intent. I would like to open up an educated debate comparing what I believe to be archaic thinking, and doing more with less but not in a cheap Chinese way.

In a few conversations online and in person there has been some speculation about modern diesels putting out so much horsepower and torque then the engines of yesteryear. Thought being that it makes the engines less reliable, and the phrase “no replacement for displacement” is often used. I, as you can tell, do not prescribe to this type of thinking. I believe research and development replace displacement. I believe a team of engineers with degrees working with modern metallurgy replace displacement. What are your opinions? We have lots of experience here and a lot of product knowledge.

 

Topic

[Tony Athens]

David,

Glad you jumped in here as you have a lot to bring & share with the boating community………So welcome aboard and a great 1st comeback to make anyone with the “diesel disease” get his brain working.. ..

Your post makes me think a tad since as I am pretty familiar with the Gardner engines—Not so “hands-on” with them, but I have read & studied about them extensively for at least 20 yrs and interacted with my older Bro for years that had one in a TUG BOAT for about 10 years.. Yes, a very solid diesel engine build with the “best of the best” with good ol’ English Engineering from the 40’s & 50’s.. Yes, these engines could & did last for decades running most of their life at 5-10 HP liter of output with maximum ratings in the range or less 20 HP per liter, and with most less than that……. So lets’ take that engine and do a comparison to something that would make more sense –

Remember this is really about displacement, not max HP output… Let’s use a 25+ yr old late 80’s to 1990’s design from Cummins—The QSM 11………..10.9 liters of displacement, a wet linered engine, had about 2700 lbs on IRON in the engine, and is physically about the same size ( maybe at tad more compact) ………Let’s look that the LOWEST HP rating of the engine only—–350 BHP at 1800 RPM…A much more “apples for apples” comparison, although this is also about “can a smaller displacement engine replace and larger displacement engine”….

Want to put both on these engine on a dyno at 125Hp using about 5-6 GPH and see how long they last? I have solid data on this model QSM going over 40,000 hours running at 200+ hp average load and have never had a head off. Find me an 11L Gardner that has burned over 380,000 gallon of fuel without multiple rebuilds…In fact, find me one that can document 100,000 gallons of fuel burned without a rebuild…. I am not try to saying they are not the “best of the best” as to all, but that was 60 yrs ago.. JUST LIKE YOU SAID.…..Things have changed..

Now, let’s talk about a QSB 5.9 or 6.7 you want to compare a 11 liter engine to.………But, I do not want talk about the max HP they can produce, I want to compare it to a “like for like” application of the Gardner engine you referenced in a typical application that that engine would be installed in, and USED in, over a 10-30 year period..……

Can we pick this boat? A full displacement 60ft motorsailer boat “GL Watson 55 ft MFV” This is really the type of vessel where these “beautifully made” Gardner engines made their place in history.. https://www.google.com/search?q=55ft+motorsailer&biw=1334&bih=618&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjFhtfSsMDQAhVP9WMKHZj0BTsQsAQIGg#imgrc=XRdHeSttgHewdM%3A

Look at this from the specs:
– 1,300 nm range motoring @ 3.5 gallons per hour @8.5 knots
– 3,150 nm range motor sailing at 1.5 gallons per hour

Now, for sure you are smart enough we to see what it is saying..
Ask the engine to make 70HP ( or less) and you can cruise at 8.5 kts.
Ask the engine to produce 40 HP or less, you can go 3150 NM..

So yes, this engine lasted a LONG TIME in years, & engine hours wise.. But now, ask yourself what did that engine really do over those years & hours that it has running or still running today? How many HP HOURS did it really make? Let see—The hour meter says 10000 hours and during that 10,000 hours the 11 L engine used 20,000 gallons of fuel?? Probably less, but let’s just say it did.. So, at 20,000 of fuel used over 10 years, what condition is the engine in today?…………………….This I can document today——QSB 5.9’s at 25000+ hours and well over 70,000 gallon of fuel thru ea of them and the heads have never been off.. Find me a Gardner 11L engine that can compare.

Anyway, I say a QSB 5.9 set up right ( that is the key) in a typical boat that a Gardner would be installed in will do the job as to power over the years.. As to all the rest as to other things like cooling systems, etc. etc. etc., that’s a different story.. That’s where “heavy Iron” can really shine. Remember the Gardner engine does not have Sherwood seawater pumps and light weight mixed metal aftercoolers and heat exchangers..

So in this case, your input is 100% right on as to more modern castings , fuel & air systems, better metallurgy, improvements in valve and seat metallurgy, crankshaft forging techniques, metallurgy improvements and bearing materials all say that there “is a replacement for displacement”………………….

But again, IMO, it all comes down to each application and the term “No replacement for Displacement” needs to still needs be part of the overall equation…To me, it’s not quite dead yet but is getting closer each year.

Tony

[David Marchand]

Let me try to advance the discussion by talking about some of the developments that have made it possible to get 50,60,70 and in some cases even 80 hp per liter of displacement out of a marine diesel and allow the engine to last.

Engine casting and metallurgy- Thin wall casting techniques coupled with better metallurgy for crankcases and other high stress parts have let the engine withstand higher stresses with no deformation or cracks.

Piston, piston ring and lube oil spray technology. Piston lube oil spray has allowed the piston to run cooler at high power levels. Without it, pistons would melt.

Valve and seat metallurgy.

Crankshaft forging techniques, metallurgy improvements and bearing materials.

Turbo charging and after cooling- Turbo charging by itself doesn’t allow the engine to last longer, but it is responsible for the engine’s ability to produce 4 times more horse power than a normally aspirated engine. After cooling and particularly sea water after cooling, cools the intake air down after compression in the turbo which generates tremendous heat. If you didn’t take that heat out first, the piston would melt and the valves would break off.

There are probably hundreds of other improvements in manufacturing, design and metallurgy that improve power and life.

But can an engine that makes 70 hp per liter, even if run at half of that, last as long as a slow speed, normally aspirated engine built with modern materials and manufacturing, well no.

A good example is the Gardner 6LXB, a 10.5 liter 6 cylinder normally aspirated engine that makes 127 hp at 1,500 rpm. That is half the rpm of a Cummins QSB 5.9 380 and 1/4 of the power per liter of the QSB. I will bet the Gardner will last four times longer at say 100 hp as the Cummins does at 250 hp.

But an interesting question is: how long will the Cummins last if run at 100 hp. I suspect that the Gardner will do well, because it has more bearing area, piston side area and a heavier, distortion free crank case and head and a longer stroke and connecting rod for reduced piston side load. But who knows. The Cummins has the pedigree of being designed to run at 4 times that hp and twice the rpm and with all of the metallurgy and manufacturing techniques that went into its build, it might win.

David

[Tony Athens]

No Replacement for Displacement

Jerry,

Good topic to discuss and as you alluded to, lots out there as to opinions, perceptions, old wives’ tales, and of course, real engineering and science ..

Don’t really know where to start as there is so much that would have to be discussed, but maybe let’s start with what I call “heavy iron”, but limit that to the types of engine we are really dealing with—A generally accepted definition would be diesel engines that operate above 1000-1200 RPM.
So what do I call “heavy Iron”? To me, these are engines that were designed & made for both commercial & recreational market in the 50’s thru the late 80’s when we first stated to see a major shift in the design of the modern high performance diesel engines.

Engines that I classify as “Heavy Iron are those that had HP outputs in the 8-10+ Lbs of iron per HP——Take a 8-71 Detroit at 3000 lbs and 320HP, a CAT 343 with rating of 250 to 500HP and 4500 + lbs.. a Cummins 903 weighting in at just under 3000 lbs at 300 HP, or Cummins 855 at close to 4000 lbs and in the 250-450 HP range. These heavy iron engines seem to last for decades with 1000’s of them still in use today.. The main reason for this is the very low HP output per LB of iron which offers them the “internal beef” to withstand what seems to take out way to many light weight modern engines—Overheats & over-loading, and failure from corrosion of the light weight saltwater cooled components. In so many words, heavy iron engines are way more forgiving to the “nut behind the wheel” who is really in control when it comes to overall operation and long term maintenance of the engine.

So, can a modern engine designed in the last 20 years that puts out 300 – 500 HP, could easily weight close to 50% less that waht it is repalcing, develop its useable HP or needed torque at 100’s of RPM higher that what it is replacing, replace a heavy iron engine and give comparable long term service over the decades that follow its in-service date? Is it really true that there is “No Replacement for displacement? ……..

I say that “No Replacement for Displacement” is far from as true as it used to be, but there are many caveats that need to be understood & that require a thorough understanding.. Terms here would be first & foremost— DUTY CYCLE which goes “hand-in–hand” with a complete understanding of the actual application.

For these new generation of engines to “cut the mustard” so to say, one needs entire new understanding of what makes these engines do what they could or can do, and that requires a completely new thinking as the long term care and maintenance…
Flash Back about 25 years.
Back in 2001-ish, Calif started getting serious about offering grants in high annual hours commercial boats to replace old “heavy iron” & gross polluting diesels with modern ones from the current era (IMO certified to EPA Tier 1 in those days).

Detroit 6 & 8-53’s 6-71’s, 8-71’s and 8-92’s were the most popular back then. Cummins had the 6CTA 8.3 rated at 350HP/2500 RPM.. Could this engine replace a typical Detroit 8-71 rated at 318HP at 2100 RPM, or even a 8-92 rated at 360HP at 1800 RPM? ? Yes it could BUT only if it was geared to turn the same prop the 8-71 did running at 1200 RPM using a 2:1 gear (600 RPM prop speed) .. The Cummins has to do that work in 1600-1900 RPM meaning that we had to use a 2.5 gear or possible even a deeper ratio. What the 8-71 could do at 1200 RPM needed at least 400 RPM more from the 6CTA.

Going from Heavy Iron the “light iron” worked, but required a though understanding on each vessel, how it actually operated & a complete retraining of the vessel operator, meaning “Detroit Mentality” need to go. It some cases, although the Cummins had the HP, it just did not have the “duty cycle” grunt needed for the application needs..
Now let’s fast forward to today

 

With the latest generation of Common rail engines like the Cummins 6.7 and QSL9, a whole new set of questions POP up as to what can replace what these days.. To me it still all comes back to the duty cycle of the intended application after the dust settles.. And that is far from the WOT “show & tell” speed on seatrial day..

Here might be a typical scenario —Can Cummins QSB 6.7 do what a Cummins 6CTA8.3 430 can do, year in a year out for 10-15 years ?? I say maybe yes and maybe no..

The latest QSB 6.7 425 has an intermittent commercial rating, but so does the 430C. If you need about 280 BHP at cruise power (14 GPH or so) making 17-20 knots in your 34 ft lobster boat and need to travel from Point A to Point B 60-80 miles each way about 100 times per year in your job, the 6.7 would have to be propped to make that power at about 2550 RPM vs. the 6CTA at about 2150 RPM.. Both would be operating well within the designed power output range.

So, which one will last longer, which one would be the easiest to deal with over the 10,000 hr expected life, which one would yield the least cost of ownership over 10 years, and which one would be easier to have a “2nd life” with a rebuilb at 10,000 Hrs?…………………..I am not going to answer that and leave it here as food for thought..
But I will say this, ‘No Replacement for Displacement” may still have a place in the decision making these days.. On 100-300 year recreational vessel that is being build “new” these days, I’d say, it means way less than just 10 years ago, if anything at all……..

Lot’s to ponder, but your own research and the real understanding of your needs coupled to your own “hands-on” capabilities taking care of the engine is really the true answer…

 

Tony

[William Walter]

• Just a note here as a precaution I bought two brand new water pump s for my trip north from Florida to New York.the only failure I had on trip was a shaft that broke on port engine water pump that was brand new.luckily I was looking at the temperature gauge when it failed and I didn’t overheat.im definitely interested in a system that shuts down the engine if there’s a loss of water flow.l believe my generator will do that.not to often your looking at the gauge when you have a failure.could have been much worse.Bill

[Rob Schepis]

Agreed Jerry, that was my point – due diligence in maintenance and protection.  I certainly wouldn’t trade my B’s for Big Iron – I like my “walk around” engine room with only 13ft a beam  🙂

[Jerry Farnham]

I get your point that with out the extra “meat” damage is more likely, but if maintenance is kept up with there should be no issue. So I guess my opinion does have an asterisk saying as long as regular maintenance is taken care of.

[Rob Schepis]

No Excess Iron

We are very aggressive here with equipping the engines/gears with redundant and additional alarms so one thing that immediately comes to mind is the importance of avoiding a serious overheat as the high output low displacement (high HP/Liter) has zero excess iron to absorb an overheat so damage is usually imminent..the seawater side maintenance is crucial..as is all the “spinning things” up front so the belt stays in place and the coolants flows..

[Author]

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