Fuel map

http://ecomodder.com/wiki/index.php/Brake_Specific_Fuel_Consumption_(BSFC)_Maps

This is a site that basically is looking at fuel maps for autos .

But the VW diesel is covered and is usefull as a comparison.

<h2> Volkswagen Jetta TDI 2.0L 2009</h2>

Notice the HUGE difference att reduced power. When run in the "seeet spot " the fuel use is 196 , run at very low load its 360.

Almost 50% more. at low speeds.

The folks who wonder about the "cruise prop"* can* see the fuel difference , the difference in noise aboard and engine wear would be even greater.

These are onlt representave , each engine will be different , but at last an actual set of fuel maps can be seen.

This VW map is probably closer to what would be seen on a 50-300hp marine conversion.
<h2> Volkswagen 2.0L 5 cyl diesel</h2>




-- Edited by FF on Tuesday 14th of December 2010 06:48:53 AM

Good stuff FF, Thanks.

Huh What?

Hiya,
** NOT relivant!** An auto "sweet spot" is NOT the same as a marine "sweet spot" IMHO,* And don't ask "Why not?" FF!!!

Hiya,
** NOT relivant!

Yousa. I agree

A diesel is a diesel, all will have a fuel map , and the "best" place to operate the engine will vary , and the fuel lost to being out of the best range can add 50% to 300% to the coat of a HP to move the boat.

The hassle for most is its cheaper to plug along than have a vessel with CPP or CPP and 2 speed ZF marine tranny.

Not a big problem for most of us with used boats ,

but at todays INSANE new prices , one would expect efficiency , FR resin and marine servicable fuel systems. At least in the "higher" end boats.

FF wrote:but at todays INSANE new prices , one would expect efficiency , FR resin and marine servicable fuel systems. At least in the "higher" end boats.

Click to expand...

The people who design, build, and operate higher end boats are well beyond tilting at your fuel map windmill, FF.

*

Comparing this Volkswagen to our boats, you might as well compare them to a 747. It offers absolutely no useful information. Chuck

To quote Bob Smith -
" if your boat needs 80 hp to go 8 knots, it makes no difference whether the engine is turning 1800 rpm to develop it or 1600 rpm. the fuel burn is the same."

R.

ralphyost wrote:

To quote Bob Smith -
" if your boat needs 80 hp to go 8 knots, it makes no difference whether the engine is turning 1800 rpm to develop it or 1600 rpm. the fuel burn is the same."

R.

Click to expand...

Absolutely correct

*

Not being a chief engineer, I'm over my head very quickly on this information.

But as the owner of a TDI 1.9 VW engine, I found the fuel map informative about efficient transmission shift points and optimal rpm range when downshifting for long uphill climbs.

For my boat engine, I'm happy with knowing the best rpm/torque range for the power level desired, and have installed a propeller that makes this happen.

"I'm happy with knowing the best rpm/torque range for the power level desired, and have installed a propeller that makes this happen."

Great idea , but usually conflicts with Mfg self serving demand to prop to get max RPM the engine is capable of.

IF it will operate at say 2300 on the pin, its not going to be efficient at 1300 - 1500.

FF's dreamboats ...

I am not sure about the graph and what it means, but most engines do have a sweet spot where they run, sound and feel right.* Under the discussion of Flow Scans many replies refer to a Sweet Spot.* So in one discussion they are saying a boat has a sweet spot, and on this discussion you are say there is not a Sweet Spot. The *671 in our trawler seem to have a sweet spot is between 1300 to 1500 at hull speed/fuel efficiency and sounds/feels right. **So I am confused once again?
*
So if you do not agree then please give an explanation.*

Phil, I don't think anyone is saying our engines do not have a sweat spot, It is just that FF's diagrams don't have any relation to our boats engines. Chuck

Capn Chuck wrote:

Comparing this Volkswagen to our boats, you might as well compare them to a 747. It offers absolutely no useful information. Chuck

Click to expand...

Well, now, that depends on which 747 you compare them to.* I agree, comparing my boat engines to a 747-100, -200, -300, or -400 is totally irrelevant.*

However, if I compare the performance parameters and fuel maps of one of our FL120s to the similar data from the*new GE engine on the 747-8, now THAT is a much more relevant comparison.*

The one thing I have yet to figure out, however, is that*in order to take advantage of and apply*the comparison data*we are required to operate the FL120s*in the same ambient temperatures and air pressures as the 747-8 engines.**We haven't figured out*how to duplicate the*environmental conditions encountered at 41,000 feet in the engine room of our GB36, but I'm working on it and feel*that I'm getting close*to a solution.

But when we do our initial calculations show that our FL120s will have the same "sweet spot" in terms of fuel efficiency as the GE.* As soon as we determine what this power setting is, I'll post it here so everyone with FL120s can take advantage of the data.

It is just that FF's diagrams don't have any relation to our boats engines.

The concept is ALL diesel engines will have different efficiencies at different rpm/load settings.

A fuel map simply makes the relationship easy for some to comprehend.

A marinized industrial or tractor engine is far from a auto engine in terms of power over a long period.

Engines can be operated more efficiently by selecting the load and rpm .

Since many boat motors were selected by the advertising dept , or by what was cheapest at build time the concept that improvements can be made is the reason for needing the knowledge a fuel map shows.

YRMV

Marin, I look forward to your findings. Chuck