One Vs Two

Richard wrote;
"Turbos work well in an application which requires a broad rpm range."
Hmmm? I would'a thunk the opposite. Turbo's don't really do much till you get to the upper end as I understood it. Haven't had a turbo diesel and don't contemplate getting one so have no need to know but I'm like a curious cat and want to know. I had a great turbo gas Jetta VW that had a lot of turbo-lag. 3 to 5000rpm was really strong. Drove a Cummins truck w a turbo and the lag was there but mild compared to the VW. But I know you know a lot more than me on this so I'll twist my head around it. Thanks for the course change.

Re what Yanmar said on cruise rpm I feel it supports my "small engine turning up" theory but Yanmar says some strange things. My head is still in the small engine turning fast camp for efficiency but I know mid-range engine speeds can produce great economy.

Products are made to support the latest trends like fuel efficiency. Get a high number whatever the cost on the sticker in the window of cars. My Jetta had an EPA rating of 36mpg hwy and it delivered but top gear (5th stick shift) was too tall for me. I rarely used it.

Ski in NC said:

The problem with the attached curves is the BSFC curve at the top is for full power all through the rpm range. Throttle on the stops throughout. Not realistic for a boat. A better curve would show bsfc along the prop load curve. That would be something we could use.

Click to expand...

Ski,

Do you have any idea why the BSFC at prop load curve is so difficult, if not impossible to find? I understand the prop load curve is rather arbitrary as well.

Check out this diesel and associated information. And like most modern (last 50 years anyway) engines turbocharged. 50% thermal efficiency, 102 RPM, 2 stroke, 5 million ft pounds of torque, whew!

http://wartsilasulzer-rta96-c-engine.htm

sunchaser said:

Check out this diesel and associated information. And like most modern (last 50 years anyway) engines turbocharged. 50% thermal efficiency, 102 RPM, 2 stroke, 5 million ft pounds of torque, whew!

http://wartsilasulzer-rta96-c-engine.htm

Click to expand...

Link won't open... for me.

I have seen pieces on that engine, about 45 feet tall and 70 or so feet long IIRC. I think if you google it, you can find a you tube on it.

Many boats,

I was rushed, so didn't explain well.

First, I'm not sure there is a significant difference between gas and diesel turbo engines on how it relates to the turbo.

EPA has really skewed the market in that the consumption test, mpg, has a significant amount of idle time.

Idle kills gas engines when it comes to consumption, therefore car makers developed turbos, which allowed for a smaller engine, thus less consumption at idle, while giving the engine "V8" power under heavy load.

In that sense, a turbo charged engine was significantly more fuel efficient at max hp as well as at idle.

Seemingly a win-win.

But, it's only a win if the engine is well maintained and not abused, eg turned off without some cooling off time.

Also, costs significantly more to build and much more to fix.

The cost difference would never be returned in fuel savings.

So for over the road use, turbo charging makes a lot of sense.

Watch the rpms of your car during a normal commute. It's up and down all the time.

But boats are driven differently. Fast or slow, boats are usually run in a small range of rpms, or maybe two ranges, but seldom more.

Thus in a boat, it is easier to spec an engine to the boat and it's intended use.

Now, we do see a lot of turbo charged boats.
Why, since diesels consume very little at idle?

I don't know, but am guessing that turbo charged diesels exist in boats, mostly because it is such a small market compared to over the road applications, where having a smaller engine is an advantage in being able to fit it into an engine compartment, be it a truck or car.

And in the horsepower wars, that's probably a big advantage.

Also, size also matters in boats, so turbo engine helps that and 99% of boat owners don't care about fuel consumption, or are members of TF, but do like more hp, even if it's wasted.

"Do you have any idea why the BSFC at prop load curve is so difficult, if not impossible to find? I understand the prop load curve is rather arbitrary as well."

IF the mfg used real observed BMEP at various loads ( NOT theory prop curve numbers, or simply peak HP numbers) folks would be able to select an engine on the basis of how well it should work in a specific boat.

For a specific type boat , one engine would be the clear winner.

This is called a fuel map , and is harder to come by than plans for a T-88 small nuke.

Turbos will add to Hp when needed for hill climbing , or in marine applications give somewhat better fuel burn per HP IF the unit is operated with positive boost and a proper EGT from the load.

The danger/hassle with turbos is two fold.

The turbo and all its inter-coolers hurts efficiency till the engine is on the turbo.

No boost is bad , but 5-30 lbs will help , depending.

The other hassle is after a big high boost load the turbo is hot , usually glowing red.

The turbo must be allowed to cool down enough so its lube oil does not burn or coke .

In this case 5 min of idle to help the turbo life is worth the idle time slight hassles from no load running.

Many folks will spend more time ideling than is required for cooling attempting to enter their slip.

My question is to the many intones that for turbo powered engines it is always a good idea to let the engine (turbo) cool at idle for 5 minutes after heavy turbo load:


How often (when ever - in boats) does any boat owner simply shut down their engine immediately after applying heavy load to the turbo?


As FF mentions in last sentence of post #97... just idle time for slip entry is usually more than needed. I add that even the minutes of idle for anchoring or canal travel to fuel dock is ample cooling time.


So again I ask, cause I'd like ta know - How often (when ever) does any boat owner simply shut down their engine immediately after applying heavy load to the turbo? Sport fishers, ocean racers, rescue boats??? Who could/would possibly go from heavy turbo load to complete engine shut-down without at least some to several or more minutes of low RPM cooling time?

Makes me think that the premise of too hot turbo shut down often mentioned is 99% an non plus. Am I correct... ?

Art said:

My question is to the many intones that for turbo powered engines it is always a good idea to let the engine (turbo) cool at idle for 5 minutes after heavy turbo load:


How often (when ever - in boats) does any boat owner simply shut down their engine immediately after applying heavy load to the turbo?


As FF mentions in last sentence of post #97... just idle time for slip entry is usually more than needed. I add that even the minutes of idle for anchoring or canal travel to fuel dock is ample cooling time.


So again I ask, cause I'd like ta know - How often (when ever) does any boat owner simply shut down their engine immediately after applying heavy load to the turbo? Sport fishers, ocean racers, rescue boats??? Who could/would possibly go from heavy turbo load to complete engine shut-down without at least some to several or more minutes of low RPM cooling time?

Makes me think that the premise of too hot turbo shut down often mentioned is 99% an non plus. Am I correct... ?

Click to expand...

I've seen high performance boats, pull into a marina quickly, docking quickly, shutting down and the occupants gone. Typically performance boats that would have turbos. Sport fishers do it too. Now those in the know, don't. But you did answer your question, I think.

However, one other group. Some newcomers. They've been taught over the years that you shouldn't leave your car running. They also feel like they're wasting "gas" if just idling at the dock. So, for them it's education to diesels and to letting a boat engine properly warm up and cool down.

The whine I hear is due to a world filled with turbo diesels.

Turbo-diesel - Wikipedia, the free encyclopedia

Today's emissions specs and the mandated ultra low sulphur diesel fuel formulae have driven current engine manufacturers to turbocharging. Hotter engines burn cleaner and that's going to be the new normal going forward. Sadly tier4 is such a high bar that most of the tf member's engines won't ever be able to pass, even with the addition of turbos after coolers exhaust scrubbers etc...

As far as shutting down a hot turbo, I had a damper plate disintegrate after an hour of running at 2000 rpm and I deliberately ran the engine in neutral reducing rpm periodically to cool it down. I learned the importance of keeping turbo bearings from coking up from the air cooled Porsche turbo days.


Via iPhone.

So it's emissions standards that make the turbo std equipment on larger engines and different emissions standards allow the smaller engines to be sold w/o turbos. The 4cyl JD must be the upper end of the lower standard NA engines at the moment .. but due to change soon re something Sunchaser said.

Suits me w my little engine.

I know Yanmars aren't quite typical engines but is the the low specific fuel burn the rpm point of greatest efficiency? I see on Larry's JH Yanmar that point is close to 3500rpm. Even high for that 3800rpm engine. Seems from recall that most 2500rpm engines have the lowest specific consumption down at around 1800. A much greater percentage of rpm down from rated power. The JD is 700rpm down. That's where I run my small Mitsu .. 700 down. Is that typical of the lowest fuel burn? I ask of those that browse such information regularly. Also as I recall those typical specific fuel burn curves are representive of WOT. If that's correct how do they vary at low loads that trawlers run at?

My understanding from reading the EPA regulations is that Tier 4 engines will not be mandated on smaller diesels used on boats. At least not for the next few years.

The problem is that Tier 4 engines are almost certainly going to require DEF. An engine might use between .1 and .3 gallons of DEF for each gallon of diesel burned. That does not sound like much but if you have 2,000 gallons of fuel on board you know need a 60 gallon tank to hold the DEF. A 60 gallon tank is going to take up some important space. Do you take out fuel tankage, water storage, food lockers, the wifes shoe storage? This is getting serious. :lol:

The bigger problem with DEF is that if you run out, the engine will run at reduced power levels. I can just see that happening in a storm, going over a bar, in a pass against the tide, etc...

Hopefully, my understanding of the Tier 4 requirements is correct AND EPA does not mandate these requirements. Tier 3 is bad enough.

Later,
Dan

DEF is an additive?

Would be nice to know.

Never heard of it.

manyboats said:

DEF is an additive?

Would be nice to know.

Never heard of it.

Click to expand...

Yes, my bad. I had meant to spell out DEF but forgot.

DEF is Diesel Exhaust Fluid and is used to clean up the particulates. DEF is water and urea. I have wondered if I can just use rain water or water from a water make and pee into a tank to make my own DEF? :lol:

A Ford pickup truck diesel engine a generation or so back, used diesel to burn the particulate build up from the filter. Owners were reporting really bad MPG because they were burning far more diesel to clean out the filter than was expected. The advantage of using diesel to clean the filter was that it was already on the truck and did not require another tank a fluid to buy but the fuel burn could be high/expensive so they moved to using DEF.

Later,
Dan

dannc said:

My understanding from reading the EPA regulations is that Tier 4 engines will not be mandated on smaller diesels used on boats. At least not for the next few years.

The problem is that Tier 4 engines are almost certainly going to require DEF. An engine might use between .1 and .3 gallons of DEF for each gallon of diesel burned. That does not sound like much but if you have 2,000 gallons of fuel on board you know need a 60 gallon tank to hold the DEF. A 60 gallon tank is going to take up some important space. Do you take out fuel tankage, water storage, food lockers, the wifes shoe storage? This is getting serious. :lol:

The bigger problem with DEF is that if you run out, the engine will run at reduced power levels. I can just see that happening in a storm, going over a bar, in a pass against the tide, etc...

Hopefully, my understanding of the Tier 4 requirements is correct AND EPA does not mandate these requirements. Tier 3 is bad enough.

Later,
Dan

Click to expand...

Catalytic Converter. No, I'm not saying that, but I'm suggesting the ultimate answer may be similar in terms of function. There is a product for generators developed by one who I believe may even be a member here. It is SeaClean.

SeaClean | DeAngelo Marine

There will likely be multiple changes required to clean up diesel exhaust. If it follows as it did with gas, it will include the product itself, so the fuel from the start, changes in the engines themselves, and some form of treatment from exhaust.

You look at gasoline powered automobiles today vs a few decades ago and the difference is huge. They're requiring less fuel, they're burning it more efficiently, and they're producing less polluted exhaust.

FF said:

"

For a specific type boat , one engine would be the clear winner.

This is called a fuel map , and is harder to come by than plans for a T-88 small nuke.


Yes, for all the marketing reasons we have talked about for years.

Turbos will add to Hp when needed for hill climbing , or in marine applications give somewhat better fuel burn per HP IF the unit is operated with positive boost and a proper EGT from the load.

I don't understand what you are trying to say.

Turbos give you more power per engine volume, displacement.

The danger/hassle with turbos is two fold.

The turbo and all its inter-coolers hurts efficiency till the engine is on the turbo.

No boost is bad , but 5-30 lbs will help , depending.

The other hassle is after a big high boost load the turbo is hot , usually glowing red.

The turbo must be allowed to cool down enough so its lube oil does not burn or coke .

In this case 5 min of idle to help the turbo life is worth the idle time slight hassles from no load running.

Many folks will spend more time ideling than is required for cooling attempting to enter their slip.

Click to expand...

Yep.

manyboats said:

So it's emissions standards that make the turbo std equipment on larger engines ?

Click to expand...

And higher power output and improved efficiency.

sunchaser said:

And higher power output and improved efficiency.

Click to expand...

Higher output. Yes.

Reduced consumption st lower rpms, YES.

Improved efficiency, ? show me the numbers.

Art said:

Makes me think that the premise of too hot turbo shut down often mentioned is 99% an non plus. Am I correct... ?

Click to expand...

Yes, for those of us who abide by no wake zones. After a "hard" run of 5 to 10 psi boost and not headed to a slip, a turbo trawler diesel boater likely is headed to an anchorage, where it takes about 10 minutes to find the right spot to get the anchor set. Never seen mine red hot, but heck they have the magic no roast paint still looking as good as new.

But wait, in FL the diesel go fasts race to the dock like Sonny Crockett and most certainly must cook their turbos (you heard it here) on a routine basis as they sip their Pisco sours ogling babes. Sounds kinda fun.

BandB said:

...
There will likely be multiple changes required to clean up diesel exhaust. If it follows as it did with gas, it will include the product itself, so the fuel from the start, changes in the engines themselves, and some form of treatment from exhaust.

You look at gasoline powered automobiles today vs a few decades ago and the difference is huge. They're requiring less fuel, they're burning it more efficiently, and they're producing less polluted exhaust.

Click to expand...

Diesel was cleaned up years ago which is one of the reasons for the higher price of fuel vs gas compared to the prices prior to ULSD.

One could by an inexpensive car in the 80's that would get an honest 50 mpg. On Gas. Not sure that is true today. Certainly a car today is producing less pollution but at some point we cross a point where we are spending a fortune for very little benefit.

One question I have about pollution and marine diesels with wet exhausts, has the EPA measured the soot pollution from said configurations? Does the wet exhaust remove/reduce the soot?

Having an electrical system to remove the soot would be better than having to use DEF, but I question Tier III for small boats. In the JD case I mentioned earlier, Tier III is going to burn more fuel. The engine is not more efficient than the Tier II engine.

Later,
Dan

Wxx3 said:

Improved efficiency, ? show me the numbers.

Click to expand...

Many SAE papers and studies in this regard, but to keep it simple I'll cite our old friend at boatdiesel


Fuel and Horsepower

dannc said:

Diesel was cleaned up years ago which is one of the reasons for the higher price of fuel vs gas compared to the prices prior to ULSD. Dan

Click to expand...

I was surprised to see diesel at $2.48/gallon and regular gas at $2.75 a few days ago at same shore station. Fluke or is something local happening in gas glut/diesel shortage quandary?

sunchaser said:

I was surprised to see diesel at $2.48/gallon and regular gas at $2.75 a few days ago at same shore station. Fluke or is something local happening in gas glut/diesel shortage quandary?

Click to expand...

WHERE WHERE WHERE! :lol:

Diesel here is 2.79 at most stations with 87 gas about 30-40 cents cheaper. I wonder if the clerk dialed in the wrong numbers.

In my truck's log book I have paid under $1 per gallon for diesel but that was before USLD, higher diesel fuel taxes, and higher demand drove the price over 87 gas.

The drop in fuel prices has sent the local fuel prices all over the place. Stations that used to be the most expensive are not now and the cheaper places can be the most expensive. The stations have to guess the future cost of fuel for the next purchase and some times they are going high or sometimes low. I think the volatility of prices is driving them nuts.

Later,
Dan

dannc said:

You can't put a non Tier III compliant engine in a new boat, so for us, using an mechanical engine in a US documented boat, is not possible. I would LOVE for someone to prove me wrong!

Click to expand...

No one here has a "new" boat. Manufacturers and dealers have all of them.

Diesel weighs more than gas , so there is more there , there.

You pay for what you get , hydrocarbons to burn.

"I think the volatility of prices is driving them nuts. "

No what drives the cost of gas is the requirement for 44 different gasoline mixtures , by Zip code.

I prefer twins.

ranger42c said:

Hmmm.... Full load peak torque for our 6CTAs is indeed right at 1700 RPMs. Looks like fuel consumption (prop curve) at 1700 RPMs would be about 7 GPH, per engine. Don't have our speed tests file here, but I'll compare that as soon as I can. Seems to me, the hull is a pig at 1700 RPMs, though...

-Chris

Click to expand...

Ski in NC said:

1700 might be a happy spot for the engine, but might be horrible for the boat!!

My boat is ok but not great at 1700, but likes 1900-1950. Close enough for me.

Both engine AND boat must be happy with cruise rpm.

Just a rule of thumb. Real sea trial data are much better.

Click to expand...

Checking our speed tests... 1500/1600/1700 RPMs is in our no man's land, can't plane, mostly plowing. 1800 RPMs is the slowest on-plane speed I tried, and to get there I have to go faster (get properly up on plane) and then pull it back down.

For us, then, 1800 RPMs is approx.13.3 kts and it's still a little "plowy."

I don't have fuel flow scan meters, so can only guess at consumption and economy. The fuel consumption curve suggests 8 GPH per engine, so 16 GPH total, and at 13.3 kts that'd be .88 NMPG.

But the boat is more comfortable at:
- 2000 RPMs, 20.8 GPH, 17.50 kts, .84 NMPG, or
- 2200 RPMs, 26.8 GPH, 20.65 kts, .77 NMPG.

And the hull really performs best -- on plane -- at 2400 RPMs, 34.8 GPH, 23.20 kts, .67 NMPG.

No good news there. We usually run at about 7-8 kts, just below hull speed.

Unless weather and sea states dictate faster speeds, in which case we try 2000, if that doesn't work, 2200, if that doesn't work 2400... or whatever else it takes to make the ride comfortable.

-Chris

sunchaser said:

I was surprised to see diesel at $2.48/gallon and regular gas at $2.75 a few days ago at same shore station. Fluke or is something local happening in gas glut/diesel shortage quandary?

Click to expand...

Me too. My local Chevron dealer is selling diesel at $3.05 and gas (California summer blend) for $3.75! (The refinery is only 20 miles away.)

sunchaser said:

Many SAE papers and studies in this regard, but to keep it simple I'll cite our old friend at boatdiesel

Fuel and Horsepower

Click to expand...

Thank you.

I can live with that number, 7 to 10% increased efficiency in BFSC.

In the bigger picture though, it doesn't change my point, that to get a 10% increase in fuel efficiency, one pays 50% more for the engine, and that extra cost will never be recouped.

Though for an over the road trucker it well be.

Good point.