Perkins 4108 fuel map

[Roberto]

Hello,
despite having loads of documents about the engine, I could not find its "fuel map", a graph similar to the one below which is for a bigger engine.
Has anyone got one?
regards

 

[coopec]

Is this any help?

How to bleed a Perkins 4108 marine diesel engine ?

 

[Boater Sam]

I cannot imagine why you would need one, do tell.

 

[rotrax]

I cannot imagine why you would need one, do tell.

Me too.

Smacks of rivet counting.

A Perkins 4108 is a good, reliable, albeit old tech engine. If it starts and keeps going, what more do you want?

 

[penfold]

DIY common rail conversion?

 

[Roberto]

I cannot imagine why you would need one, do tell.

Mostly intellectual curiosity: I have made a few accurate consumption measurements with a given propeller pitch settings at different rpms, plus one or two with a different pitch. They are all paired with measured boat speed values, same external conditions, flat calm.
For a given boat speed, differences in consumption between the two propellers cannot be explained by changes in the basic specific consumption/rpm curve (rpm vs g/kwh) which are quite small, rather they indicate the engine is working in quite different areas of the graph, or maybe that propeller behaviour is different (slip, etc).
Working backwards from measured data I think one can make a better estimate of all those parameters and coefficients which are usually used the other way around: designing an engine/propeller system from given displ/speed requirements etc. implies a number of them.
Just curious

 

[Roberto]

Is this any help?

How to bleed a Perkins 4108 marine diesel engine ?

Hello Coopec,
my question was more on the theoretical side, I agree that bleeding the high pressure side is not the most user-friendly activity with that engine

 

[B27]

Hello,
despite having loads of documents about the engine, I could not find its "fuel map", a graph similar to the one below which is for a bigger engine.
Has anyone got one?
regards
View attachment 164889

What this is actually saying is that fuel consumption is pretty close to 245g/kWh over a wide range of operating conditions.
It's a bit less efficient at very low loads, high revs or close to being overloaded.
Mostly, it's within 5%.

There is an optimum torque load, but some of that is due to the base consumption that the engine would use with no load just to run at a given RPM.

So how do your figures work if you just assume 245g/kWh?
Most normally aspirated diesels run in the low 30s of % in terms of power out vs calorific value of the fuel.

I think the efficiency of different propellors can vary by much bigger %.
Blade area, slip angle, inter-action with the hull etc, blade shapes and sections, it's a lifetime's work to understand fully.

But also, small changes in conditions can have a big effect on consumption. A few knots headwind or tailwind, slightly different speed through the water, a bit of slime on the hull.
At cruising speed, which I keep on the low side for quietness, I think my engine is using a fair % of its power turning itself, the water pumps and the alternator if the sea is flat.


I read a lot about this last winter then gambled on something 'near enough' on ebay. I'm very pleased with the result.


Dave Gerr's Propellor Handbook was a help.

It's interesting to see the same data plotted as lines of RPM on a power y axis against an rpm x axis, or a few other ways you can plot the data. For one thing, it can show we often drive our cars in the wrong gear!

 

[Roberto]

Mostly, it's within 5%.

"Mostly" seems to be the problem, my data appears to bring things beyond this limit.
I am quite comfortable with propeller theory (at least regular sailboats propellers), I am looking for something more detailed about this specific engine, should anyone have it

 

[B27]

I'd be interested if you care to share your propellor data.

Some folding props have quite interesting blade cross-sections which I've not really seen properly explained.

I wonder how much a used engine installed in a yacht might vary from the maker's data?

 

[Roberto]

I'd be interested if you care to share your propellor data.

Some folding props have quite interesting blade cross-sections which I've not really seen properly explained.

I wonder how much a used engine installed in a yacht might vary from the maker's data?

I have everything in a spreadsheet with countless columns with calculations of all sorts, I'll try and condensate it to something more readable
Btw propeller is a Max Prop, perfectly flat blades.
regards