All,

Yamaha Fan and others including myself have elaborated on the subject of fuel lubricity, its quality - appalling in eastern Europe and Africa - and that it can destroy fuel pumps injectors and camshafts. This can easily turn a 5 year old vehicle into an economic write off, not "GREEN" at all.

Whilst a contributors statements arguably make sense, most do not state the written source or author(s) that their data is derived from. For me the quality of the contributors argument is instantly devalued, because only with the availability of the original data can a rational judgement be made and quantified.

If contributors could add a link whenever possible the value of their contribution would improve immensely.

AND NOW FOR A CONSIDERED THOUGHT

If poor fuel lubricity in fuel pumps can shear cast iron camshafts (MY 2007 only) due to lubrication related frictional loads and an 1800 bar operating pressure, what does a hypothetical FL2 engine running at 100 bar fuel injection pressure (typical 1970's) offer in terms of fuel consumption, given that pump friction is much reduced.

I accept that an increase in emissions will occur, but politicians encourage that every time they say that "WE NEED TO GROW THE ECONOMY".

Regards, Toadshall

Higher injection pump pressure allows improved atomized fuel along with multiple staged injection creating a quieter smoother cleaner diesel engine.
the old DPA and CAV, bosch pumps were really very crude and didn't allow for performance or reduced emissions.

With high pressure pumps with electronically controlled injectors it allows for much more accurate injection timing balanced between ECU software & knock sensors for optimum performance.

fuel economy was good in the old days on some diesels but they didn't produce a fraction of the performance and the rev band and power curve was very limited.

The power required to run the HP pump doesn't have a noticeable effect on fuel economy as opposed to a low fuel pressure because you would loose all of the benefits that high fuel pressure achieves .

oldgeezer wrote:

With high pressure pumps with electronically controlled injectors it allows for much more accurate injection timing balanced between ECU software & knock sensors for optimum performance.

"The diesel engine doesn't have knock sensors"
do you mean the diesel engine or all diesel engines ?
diesel engines certainly do have knock sensors to monitor combustion and excessive diesel knock, some sensors are built into the diesel injector.
there are some diesel engines that optimize their performance using specific knock sensors in pairs in the engine block continually computing the timing in thousands of a second .
I should add the knock sensor also measures excessive fuelling that is also associated with diesel knock. On Fords this can often trigger fault code P2336 & 2337 or 2338 excessive knock on particular cylinder caused by an over fuelling injector read by the knock sensor.

Alex
"So these "injection compensations" are better said an indicator of the sum between compression ratio and injector health for each cylinder. "
Better known as quantity adjustment or injector fuelling percentages. designed to keep the tick over even and measured by the speed of the crank pully and divided into 4 to calculate the combustion acceleration of the pulley on each power stroke.

I've had in mind the FL2's diesel engine.
But also, from what I know, generally, the diesel engines doesn't have them.
Only a few recent common rail diesel engines have knock sensors to monitor, especially, the pilot injection, to achieve low NVH and in some cases to detect discontinuous combustions.

Hello All,

Your responses were interesting, and to me rewarding - I had taken for granted the huge steps forward in design to tame and reduce NVH in the diesel.

Yes, huge fuel injection pressures combined with high speed electronic control do wonders to make an inherently rough engine smooth, powerful and responsive. Emphatically though, it also makes them vulnerable to lower quality fuel. Reliability and vehicle longevity suddenly become an issue. The vehicle is economically written off much earlier in its lifetime if its sensitivities are ignored, unlike the CAV-DPA machines of the 70's - poor NVH maybe, but extremely tolerant.

I searched the net looking for reports of common rail engine fuel pump loads - I could not find any. Manufacturers are partly driven by an incestuous circle of rewarding lobbying between themselves and EU bureaucrats. Frequently during the summer months Joe Bloggs user informs the media that turning off his cars air-con compressor significantly improves his fuel consumption. My initial question was driven by this - could the diesel become more tolerant, and perhaps with lower fuel consumption if injection pressures were much reduced.

This would potentially give the vehicle a greater longevity, which in itself would be a green credential. NVH would be resolved with other technologies. Emissions would go up, but the UK government in line with others, wishes to grow industrial output - LandRovers in particular, which is much the same thing in terms of emissions.

Albert Einstein said: Make everything as simple as possible, but not simpler!

Regards Toadshall

Another good thing about electronically controlled injection systems is the fact that you can always rewrite the maps inside and experiment yourself with injection pressure, timing, corrections, etc.
So, in a way you have much more options than on the old diesels and you can "adjust" reliability as you want...
Just the proper tools and knowledge....

when I used to rebuild calibrate & phase diesel injector pumps and re-pintle injectors and shim them to the correct pressures we could do all sorts of adjustments to the pumps to achieve good performance.

In fact with some diesels i used to set the pump timing dynamically with a strobe and if its was set as close to 100% accurately as possible the diesel engines used to rev as smooth as a petrol and oh boy you could make em fly !

Now days with mapping its even more accurate but the power gains are huge compared to years ago

The effort required to run HP pumps does nit hinder performance or increase fuel economy.

Take an old P106 1.5 d 57bhp 95 nm torque average 44 mpg
Take newer ford 1.6tdci 94bhp 204nm Torque average 60mpg

just goes to show HP pump & good mapping is no contest for an old system