Fuel usage: "new" vs "old" diesel engines

Newer diesel trucks and cars have the same issue, they are more friendly to the environment yet burn much more fuel than the older ones. Look at all of the newer diesel pickups compared to the 7.3 or 6.0 power strokes and for cars look at the old VW Rabbit diesel compared to a newer diesel. I had the Passat TDI prior to the emissions scandal they required the new computer flash which killed the MPG and power apparently burning extra fuel isn't as hard on the environment as running an older diesel? I would follow the money.

Lookathat said:

Can I claim the prize for most efficient?
1966 Volvo Penta MD70, 6 litre diesel, 147HP, 8000 hours. 37' wooden ex commercial salmon troller.
1gallon per hour at 6 knots, 1300rpm.

Click to expand...

welcome to the board. always happy to see another Woodie that still floats

Derik said:

Newer diesel trucks and cars have the same issue, they are more friendly to the environment yet burn much more fuel than the older ones. Look at all of the newer diesel pickups compared to the 7.3 or 6.0 power strokes and for cars look at the old VW Rabbit diesel compared to a newer diesel. I had the Passat TDI prior to the emissions scandal they required the new computer flash which killed the MPG and power apparently burning extra fuel isn't as hard on the environment as running an older diesel? I would follow the money.

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Maybe you didn't know that the VW 'Dieselgate' was discovered when
independent on-road exhaust testing revealed higher pollutant levels than the
official stationary tests. The re-flash you are referring to was to try to get the
exhaust system to last past the warranty period so VAG wouldn't have to pay for it.

Follow the money, indeed.

Derik said:

Newer diesel trucks and cars have the same issue, they are more friendly to the environment yet burn much more fuel than the older ones. Look at all of the newer diesel pickups compared to the 7.3 or 6.0 power strokes and for cars look at the old VW Rabbit diesel compared to a newer diesel. I had the Passat TDI prior to the emissions scandal they required the new computer flash which killed the MPG and power apparently burning extra fuel isn't as hard on the environment as running an older diesel? I would follow the money.

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The old diesel Rabbit comparison isn't a great one. You could absolutely build a modern car that would get better mileage than the old Rabbit. However, much like the old Rabbit, you'd end up with a car that most people would consider (by modern standards) to be unacceptably slow, noisy, uncomfortable, and too small. So they don't build something like that now, as the manufacturers all know they'd sell about 8 of them.

Diesel Gate

I had two VW Passats during the Diesel gate, which most know was about emission violations. One of my cars was retrofitted and re flashed, it ended up getting about 10 less miles per gallon and lost about 10-20 HP (guestimate)

So the EPA is worried about emissions rather than MPG.

Yes if they sold the 1970-1980's VW diesel they might sale very few but it certainly would have nothing to do with their efficiency. I had a Mercedes 300D that if reproduced today would be on back order, check the price of a 2015 TDI right now they are in heavy demand.

Remember it's a big modern world and what goes on in the USA isn't always the norm.

Can someone give me a modern diesel manufacture for my dated 1985 Lehman 135's? with similar fuel burn and longevity? Soon I am sure CA will require I get rid of them and get something that burns double the fuel.

Derik said:

Can someone give me a modern diesel manufacture for my dated 1985 Lehman 135's? with similar fuel burn and longevity? Soon I am sure CA will require I get rid of them and get something that burns double the fuel.

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Closest modern equivalent is likely a JD 4045. They're at least as efficient as the Lehman's, if not more so. And they meet the current emissions standards. There may be some smaller, lighter stuff available in that power range as well, but nothing I'm familiar with. The JD can be had in higher ratings as well if desired and in the lower ratings is probably more durable than a Lehman (some variants of the 4045 are available as continuous rated).

Derik said:

So the EPA is worried about emissions rather than MPG.

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VW was cheating. They designed an engine control system that would detect when an emissions test was being performed, and enter in a special mode of operation that resulted in very low emissions to meet requirements. Then, when the car was being driven normally, emissions would increase massively, but MPG, efficiency (and possibly engine longevity) would improve.

Other manufacturers did not do this and instead engineered systems that provided both low emissions and high mileage. VW cheated and got caught.

As far as modern FL120 replacements, I'd love to re-power my trawler with a pair of small naturally aspirated Betas, maybe 60-75hp/ea. I have no need for 240hp to push a 41' trawler at displacement speeds. They'd be much cleaner (inside the boat and through the exhaust), wouldn't leak oil, and would greatly improve engine room space. They'd almost certainly be more efficient as well as they'd be more appropriately sized to my vessel. No way it would be "worth it" though, even at $7/gal, unless I was almost constantly on the move.

Derik said:

So the EPA is worried about emissions rather than MPG.

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Cart before the horse.

Pollution standards are set and the manufacturers are required to meet them.

VW could have engineered a better system but opted to cheat. Their choice.
This was done to save money, hence increase profits. It worked for a while.

Having vehicles that do conform has changed the world for the better.
I know. I lived in Los Angeles throughout the '70's and the air is far, far better now.

Yes VW Cheated as did other manufactures, I didn't realize this until I started shopping for other diesel cars/trucks. Dodge , Nissan, Renault Mercedes, there is a long list of Diesel Manufactures that did the same. VW was the poster child of course but that was mostly political because of what was going on in the US with auto manufacturing.

Cut emissions but burn more fuel seems like that's the cart before the horse but I guess some buy into the myth that we are getting clean energy from overseas. No logic or Science in almost anything coming out of the EPA, or CARB forgetting it's global and not regional. China India and the rest of the industrial world could be getting worse but as long as Los Angeles, DC and New York is better people think they are solving the problem.

I am not sure about Marine Diesel Engines that are easy on the environment but almost every diesel engine in a car or truck has issues now at around 100,000 miles, unless you delete the DPF.

Natural gas was the clean fuel but now that's not allowable since we have the electric push driven by politicians who fully know that 80 percent of our electrical production is from Fossil Fuels.

Makes me want to Sail!

slowgoesit said:

[


1st pic, Gardner 8LXB main engine (pardon the mess in the ER) red hydraulic pump on front of engine.
2nd pic, HYD servo's
3rd pic, generator on left coupled to hyd motor on right
4th pic, close-up of generator data plate.

Click to expand...

Hi, any chance of model/part numbers for the hyd servo and hyd motor?
If I can mcguyver a hydraulic gen together for small money I"d be keen.

Thanks

Derik, slightly reduced MPG is the tradeoff for greatly reduced emissions.
MPG is not the holy grail, just a griping point, apparently.
Ironically, driving style has a greater effect on overall MPG's.
If you want your diesel engine to last longer preventative maintenance is the key.

ranger58sb said:

I guess... but I'd also guess that some of the engine output is spent on dragging all that extra weight around...

-Chris

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Yes if you have a weight sensitive light weight boat. But, some of us have 8,000 lbs of lead ballast in the keel for stability and trim.

Can someone provide an objective citation that improved economy comes at the expense of efficiency? Because to my mind it's counter intuitive - efficient combustion of a hydrocarbon produces CO2 and H2O. Overall stats I could find show this is the exception, not the rule. But I couldn't find specific diesel (i could find trucks that show similar trend, though less pronounced). There could be a counter-current within the data, but without a citation, the macro data clearly suggests that efficiency follows reduced emissions which makes sense - extraction of more Btus makes more power and leaves less harmful byproduct (which is why I cited the California program to replace fish boat engines)

See below of what i could find. EPA comparison of actual emissions compared to efficiency. The counterintuitive trend - increased emissions and decreased efficiency- appears to be a 20-year anomaly from 1985-2005. Is it possible the anecdotal comments on this thread are dated?

So does anyone have any empirical citation (vs anecdotal) that diesel engines buck the overall trend that reduced emissions results in improved efficiency? Maybe diesels have a different trend, but hard to support that observation without data. I can tell you from experience that a Willard 40 with an old Perkins 6.354 (135hp) burns around 2.5gph at 7-1/4 kts whereas one with a JD4045T (120hp) burns closer to 1-3/4gph.

I'll say it again. There are several reasons to own an old mechanical engine. Fuel efficiency is not one of them.

Below is the referenced fleet average report, with a screen shot plucked showing correlation of three phases

https://www.epa.gov/automotive-trends/highlights-automotive-trends-report

Peter

Have a 2015 Jeep summit eco diesel grand Cherokee. Thing was designed when Chrysler was sorting out its viability. So an amalgamation of input from Fiat, MB and Chrysler. It spends most of its time on the super slab so get 27-29mpg depending upon how hilly the state is. A small amount on double track or beach sand. Prior have had VW diesels in the distant past.
Think you actually get better performance and mph in a ECU engine as there’s a closer match in fuel/air delivery to needed torque/hp. Typically you’re doing 70-80mph on cruise control so with no acceleration little hp is required. My experience to date (>100k miles) has been with the system that adds piss to the exhaust . DEF systems suck. But there isn’t one in marinized engines.
Marine engines are run different ways. Some operators pick a rpm or speed through the water and run like that for hours on end. Others vary needed torque/HP with great frequency. Few of us have nor want the complexities of a CP prop to keep loading constant. Would think if properly spec’s at time of construction there would be little difference in efficiency between old school and new for those engines running at constant load but a slight improvement with common rail for those under constantly varying load requirements. Of course the old school NA engine is much more reliable and owner serviceable hence preferred in a marine application.

For the most part, lower emissions and better efficiency go together. However, there are certain cases where they don't. If you're targeting reduction of specific pollutants, there are cases where you end up sacrificing elsewhere to get it. And there are cases where certain methods of improving efficiency are constrained as they either make certain emissions worse due to high combustion temperatures, or they make it hard to get other components of the emissions control system to work properly.

A big example comes in the form of lean burn for gas engines. Running leaner under light load saves fuel, reduces CO2, CO, and unburned hydrocarbon emissions. But it also increases NOx production and makes it harder to get a catalyst to work well (meaning overall system emissions of various things will be worse, even if the direct from engine emissions are better). So depending on what you're targeting, it doesn't necessarily work out as the best balance even though it uses less fuel.

In the VW case, they desperately wanted to avoid adding DEF (urea) injection to the emissions system because of the extra complexity. The alternative method of cleaning up emissions is to run very high EGR flows, but this hurts fuel economy and has issues with soot buildup in the intake manifold and EGR path. Newer systems that have adopted DEF have dramatically lower EGR flows than the early years of DPFs and typically get better fuel economy, more in line with what the pre-DPF engines got.

For the dieselgate cars, VW cheated by having the car basically detect when it's being tested and crank up the EGR flow (and tweak a few other things) to clean it up for the test. But then they ran lower EGR flow the rest of the time. That's why the "fix it" tune hurts mpg on those (and other contemporary diesels that use DEF get better mileage than the post-fix VWs). That cheat is also why before dieselgate was discovered, the VW diesels got better mileage than the other non-DEF engines out there at the time (and nobody was quite sure how they pulled it off).

Diesel marine engines don't have catalysts, DPFs, etc. so some of the issues that constrain automotive diesel fuel economy don't apply to marine engines.

As we've seen in cars (think back to the early days of catalytic converters) sometimes the manufacturers don't do a good job of figuring out how to meet the emissions rules early on. But eventually they come up with better solutions and they often end up finding other improvements in the process (such as better engine control systems that were needed for emissions, but turned out to also be good for power). Think about what engines were available years ago vs now. The modern stuff is much cleaner, but it's also more efficient and makes power that was unheard of from the factory years ago, let alone with a warranty.

Peter

You raise valid points. Data abounds for the truly curious.

Engine efficiency Vs emissions is not complicated if one has a Cat handbook from two different eras. Diesel consumption from a genset built 60 years ago as compared to a similar sized unit built today shows lesser "emissions" and greater kWh output from an equal fuel burn. Dock talk and POV justification clouds the issue but the facts are in a bit of sleuthing.

First hand gasoline engine experience is stunning when I compare my emissions compliant Porsche Panamera good economy to that of a polluting low mpg muscle car of 5 decades ago. Ditto my new F150 getting about 40% greater highway economy Vs an F150 from the 1960s with as measured tailpipe emissions night and day.

The difficulty with links and nostalgic statements is one's POV can all too easily be "proven." As TT mentioned, BSFC says a lot if one takes the time to analyze it. Knot is spot on when he says look at the half century apart visuals in our major cities. Bottom line, power output is up and emissions down whether compression or spark related.

DD two strokes, lovely Gardners and classic Chevy small blocks have been usurped in new builds for perfectly valid reasons. But that doesn't mean we still don't love them.

mvweebles said:

So does anyone have any empirical citation (vs anecdotal) that diesel engines buck the overall trend that reduced emissions results in improved efficiency? Maybe diesels have a different trend, but hard to support that observation without data. I can tell you from experience that a Willard 40 with an old Perkins 6.354 (135hp) burns around 2.5gph at 7-1/4 kts whereas one with a JD4045T (120hp) burns closer to 1-3/4gph.

Click to expand...

Some of that difference is because the JD is a smaller displacement engine (4.5 liters vs 5.8) and is turbocharged, so it's naturally a more efficient way to get a given amount of power. Turbodiesels are almost always more efficient than NA diesels due to a typically higher effective compression ratio and smaller displacement (lower pumping losses and potentially lower friction losses) for a given power output.

The JD being newer tech helps as well, as the better injection system likely leads to less unburned fuel out the exhaust (particularly under light loads where combustion may not be great).

My GB 42 Classic running on twin DD 4-52's NA and drawing and returning to a 40-inch tall, 40-gallon day tank with sight gauges used 1.35/gallons per hour per engine, as calculated over 6500 nm. I was extremely pleased with this at a cruising speed average of 7.25 knots. and seemed to be more efficient than the typical Lehmans and way more efficient than the Cats in other GB 42s. I have twin FL 120's now on a much smaller boat and oh, how I wish they matched those Detroits in so many ways. But IF I had all the money to waste the Beta Hybrid would be my modern choice https://betamarine.co.uk/he-hybrid-propulsion/

Still if I was doing a new build I want a light long boat with twin Betas hybrids or small JDs. Excellent gph + nm/g with simplicity.
Currently have 540hp which will be rarely used to its full HP except to prevent consequences of low load use and on occasion for the joy of going fast.

Hippocampus said:

Of course the old school NA engine is much more reliable and owner serviceable hence preferred in a marine application.

Click to expand...

Definitely more DIY serviceable, but not sure about the reliability. Clean fuel is the Achilles Heel of common rail engines, but that's generally workable. They can be a bit temperamental with electrical items. But the fragile part of a marine engine tends to be the marinization, not the core power plant. Old school matinization often wasn't great - the Perkins 6.354 "manicooler" and the issues with #6 cylinder on FL20 bear testement. I'm very happy with my old Perkins but
I really considered repowering with a 20-year old JD4045 NA only because it has a fraction of the hose connections my Perkins has. Marinated very nicely.

To be honest, I'm a decent mechanic but not great. The Perkins probably requires more frequent checking and maintenance than a modern common rail. But it's work I am comfortable doing whereas when friends have asked my assistance with their newer common rail engines, I'm usually stumped. Same reason I rode old motorcycles (BMW). Frequent maintenance, but easy. I've probably adjusted valves in every state west of the Mississippi except Hawaii and Alaska.

Peter

mvweebles said:

Can someone provide an objective citation that improved economy comes at the expense of efficiency? Because to my mind it's counter intuitive - efficient combustion of a hydrocarbon produces CO2 and H2O. Overall stats I could find show this is the exception, not the rule. But I couldn't find specific diesel (i could find trucks that show similar trend, though less pronounced). There could be a counter-current within the data, but without a citation, the macro data clearly suggests that efficiency follows reduced emissions which makes sense - extraction of more Btus makes more power and leaves less harmful byproduct (which is why I cited the California program to replace fish boat engines)

See below of what i could find. EPA comparison of actual emissions compared to efficiency. The counterintuitive trend - increased emissions and decreased efficiency- appears to be a 20-year anomaly from 1985-2005. Is it possible the anecdotal comments on this thread are dated?

So does anyone have any empirical citation (vs anecdotal) that diesel engines buck the overall trend that reduced emissions results in improved efficiency? Maybe diesels have a different trend, but hard to support that observation without data. I can tell you from experience that a Willard 40 with an old Perkins 6.354 (135hp) burns around 2.5gph at 7-1/4 kts whereas one with a JD4045T (120hp) burns closer to 1-3/4gph.

I'll say it again. There are several reasons to own an old mechanical engine. Fuel efficiency is not one of them.

Click to expand...

Sorry, mine's anecdotal.

I have a 2002 Dodge with the Cummins 6BT 220 HP engine. It's factory original. With 518,000 miles, it still gets 19 MPG in the city and 24 on the highway.

After checking Dodge's latest offerings, the 2022 gets 12 MPG city and 18 highway. Motortrend's test on the 2020 with the same manufacturer's ratings, yielded 20 MPG highway.

So did the economy suffer for cleaner emissions?

Ted

Simi 60 said:

Hi, any chance of model/part numbers for the hyd servo and hyd motor?
If I can mcguyver a hydraulic gen together for small money I"d be keen.

Thanks

Click to expand...

I'll see what I can come up with . . .

O C Diver said:

Sorry, mine's anecdotal.

I have a 2002 Dodge with the Cummins 6BT 220 HP engine. It's factory original. With 518,000 miles, it still gets 19 MPG in the city and 24 on the highway.

After checking Dodge's latest offerings, the 2022 gets 12 MPG city and 18 highway. Motortrend's test on the 2020 with the same manufacturer's ratings, yielded 20 MPG highway.

So did the economy suffer for cleaner emissions?

Ted

Click to expand...

The answer is in your post above. The 2022 Cummins engine produces 370 HP
and 850 lbs-ft of torque. That's the smaller of the two diesel options offered.
It's not surprising that 60% more power comes at a 20% cost in economy.

I'm with you in preferring the 6BT if that's what you're saying. That's a keeper.

KnotYet said:

I had a very useful hydraulic cruise generator on my last boat.
It was driven by the main engine, a Perkins 4-236 of about 85 HP.
The pump was a variable displacement swashplate type like those used on big
rigs for refrigerated trailers. The generator was 5kW driven by hydraulic motors.

It was pretty simple and completely trouble free.
A good DIY'er could easily put one together. The Dynaset generator looks easier still.
The voltage stayed very steady once the main engine was above idle speed.
The pump output has to be matched to the generator size and motors used.

Click to expand...

Thank you for the information!

Later,
Dan

slowgoesit said:

Dividing into Four major areas:

1. Hydraulic pump, attached to front of main engine via splined shaft, Eaton Model 70553.
2. Electric/hydraulic servo's to first switch source of hydraulic pressure, either main engine, or backup Isuzu diesel engine. Then select destination appliance to use pressure: In our case, chose between bow thruster, generator, or get home hyd. motor which couples to main shaft via chain and sprockets in the event the main engine is disabled.
3. Hydraulic motor, attached to generator: No data plate found
4. Generator itself: Stamford 12 KVA, 120v, 100amp

I can adjust the Hertz to 60 cycles by looking at a gauge, and turning a valve by the servo's to fine tune. For instance if I chose cruise rpm of 1300, then set it, then chose to bump my main engine rpm to 1400, I will have to manually set the hz down to obtain 60hz again.

One of the drawbacks of HYDRAULIC bow thrusters is that when you are most in need of the thruster, many times you are in slow speed maneuvers, say coming into dock, and therefore the main engine rpm is low, and your hyd pressure/flow will be low, resulting in a weak bow thruster response.
HOWEVER, since we have a CPP, docking is generally conducted with main engine rpm of around 1100, varying pitch for speed, and fwd, or rev. So we have plenty of hyd pressure for the bow thruster.

Enjoy!
...

Click to expand...

Thank you. Added the generator to my list.

We are looking at using a CPP, engine RPMs would be up when docking so the thruster(s) would have the needed power.

Thanks,
Dan

dannc said:

Thank you for the information!

Later,
Dan

Click to expand...

I should have detailed information stored away so PM me if you need me to find it.

KnotYet said:

The answer is in your post above. The 2022 Cummins engine produces 370 HP
and 850 lbs-ft of torque. That's the smaller of the two diesel options offered.
It's not surprising that 60% more power comes at a 20% cost in economy.

I'm with you in preferring the 6BT if that's what you're saying. That's a keeper.

Click to expand...

The newer truck is also a bit bigger, heavier duty and more capable than the older ones of the same class. That costs a bit of efficiency as well.

Slowgoesit I owned probably 15 trucks with Gardner engines in the 60's 70's and providing you serviced them correctly they were virtually indestructible. The Gardner was designed to be low revving high torque, coupled to a 6 speed box they would lug heavy loads up hill and down dale day & night whilst being easy on the fuel.
Yes they smoke when first started up until they reach working temp. You can reduce this slightly (& pollution) if you run then on 20% paraffin, brilliant engines all you have to watch on the 8LXB is to fit a larger capacity water pump or the No 8 cylinder can run a bit hot.
Superb engine and wish they were still making engines.

Irish Rambler said:

Slowgoesit I owned probably 15 trucks with Gardner engines in the 60's 70's and providing you serviced them correctly they were virtually indestructible. The Gardner was designed to be low revving high torque, coupled to a 6 speed box they would lug heavy loads up hill and down dale day & night whilst being easy on the fuel.
Yes they smoke when first started up until they reach working temp. You can reduce this slightly (& pollution) if you run then on 20% paraffin, brilliant engines all you have to watch on the 8LXB is to fit a larger capacity water pump or the No 8 cylinder can run a bit hot.
Superb engine and wish they were still making.

Click to expand...

We're pretty tickled with it! People are often taken aback by just the SIZE of the beast though!

Guys and Gals

You're beating dead horses here / /

You're missing the point. It's the "Refined Fossil Fuels" that are the pollution culprits... not the engines!

Each and every one posting has good points about the efficiency [or inefficiency] of different brands and types of liquid hydrocarbon fuel burning engines. Cause plenty of good input has been made in this thread.

HOWEVER!!

All the billions of [cars, trucks, boats, planes, generators, lawn mowers, chainsaws, leaf blowers... etc, etc] refined fossil fuel powered combustion engines emit non-recycled, carbon positive new pollutants to one degree or another into the atmosphere.

The trick is to produce Full-Cycle, Carbon Neutral liquid hydrocarbon fuels [gasoline, diesel, jet] to run the billions of ICE powered equipment required to keep civilization running.

This is in process of getting ready to be accomplished... by capturing and reconstituting the 100 year built-up massive overload of atmospheric CO2.

I can't go into all the details... there are hundreds to thousands of doctoral papers regarding this. Suffice it to say [in simplest terms]: Atmosphere contains more excess carbon dioxide than any combined group of currently developed and operating fossil fuel deposits in the world. In layman's terms... Due to humanity's extraction of and burning of fossil fuels, their emissions have made the atmosphere to become the largest "hydrocarbon reserve/resource" ever discovered. And, that resource will create/become the new-source liquid hydrocarbon, Full-Cycle Carbon Neutral fuels to help power the world while simultaneously greatly helping to abate climate warming. Mark my words! - Art