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Old 12th February 2011, 17:33   #16
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Originally Posted by star_aqua View Post
Here is a schematic overview picture of VE pump aka rotary pump with mechanical governor.
...
Running rich will increase the unburnt carbon but will decrease the NOx. F.E will go down. will it increase the power? yes but its not the CLEAN DIESEL POWER.
You rock man...Vijay Reddy
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Old 12th February 2011, 21:13   #17
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Hi,
Preface all my statements with AFAIK.

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Sorry Da, i didnt know the correct term. I meant to say the pump can be tuned to give more or less power/timing/idling, whatever. I mean to the highlight the lower spec setting. What is it called?
In a non CRDI system, the pump will deliver x cc per degree of crank rotation. Immutable. What can be controlled is when it starts and stops, thereby controlling the volume injected. One is controlled by the pumps 'timing', the other by the throttle, though indirectly. There are quite a few other settings, but this basic operation is not affected.

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The stoichiometric AFR is 14.7 : 1. i,e 14.7 parts air to 1 part fuel. Any higher quantity of air is leaner and a higher quantity of fuel is richer!!

Does it make sense?
Diesel. Excess air.

Quote:
Originally Posted by star_aqua View Post
Here is a schematic overview picture of VE pump aka rotary pump with mechanical governor.

Adjusting the delivery rate, if its lean it will cause NOx emissions due to excess oxygen. The excess oxygen causes flame tip temperature in the combustion to reach the peak values where the excess Nitrogen in the combustion chamber reacts with the excess oxygen to produce unstable Nitrogen Oxides. This is also the reason for the increase in engine temperature.
Running rich will increase the unburnt carbon but will decrease the NOx. F.E will go down. will it increase the power? yes but its not the CLEAN DIESEL POWER.

the mechanical governor part is explained here with more details. Bosch VW Type INjection Pump Governor Operation
Once again, what exactly is lean and rich in the context of a diesel?

Any difference in the governors of the VE and VW?

How does one set droop?

Is there any difference in the governor settings of the 550, and the civilian XD3s?

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Old 13th February 2011, 22:43   #18
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ahhh it is so much uncomplicated life with an Original Petrol Engine, till it smell water ie OT and completely kidding!
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Old 14th February 2011, 00:20   #19
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Once again, what exactly is lean and rich in the context of a diesel?
rich and lean can be expressed only on various load conditions. in simple way to explain, in context of diesel it is rich during hard acceleration and when their is turbo lag and goes lean once the turbo kicks in. All CRDE engines operate with lean mixture in most of the conditions as the governing is done very precisely based on the load conditions.

To be precise at full load if the injected diesel is completely burnt and if there is still some more oxygen left, then it is lean. Say if the oxygen is completely utilized and could not aid for the further combustion leading to unburnt carbon, then it is rich. I hope i answered something which you can accept to some extent

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Any difference in the governors of the VE and VW?
VE is bosch naming for all distributor type pumps and PE for inline pumps. VW is VolksWagen.

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How does one set droop?
Couldn't understand the speed droop setting in context of a automobile FIP. is it related to generators?

Quote:
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Is there any difference in the governor settings of the 550, and the civilian XD3s?
550s have FIPs from Delhpi, Bosch and Lucas. I may be wrong here but i think civilian and army XD3s have different makes of FIP.
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Old 14th February 2011, 08:03   #20
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To be precise at full load if the injected diesel is completely burnt and if there is still some more oxygen left, then it is lean. Say if the oxygen is completely utilized and could not aid for the further combustion leading to unburnt carbon, then it is rich.
Star, in real world when does this happen? Is this OK?

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Old 14th February 2011, 09:29   #21
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Star, in real world when does this happen? Is this OK?

Spike
most of the times the NA engines run rich compared to engines with forced induction.
during hard acceleration? during uphill driving?
its unavoidable with mechanical governors as the system is linear. one can observe during uphill climbing with our xdp engines, say you are climbin in 3rd gear with 50% acc ped dipped in at a constant speed. and if the gradient starts increasing at certain point with same acc ped position it starts emitting black smoke. at this point it is of no use even if you increase the throttle you don't feel any difference except increasing the black smoke. the right way is to decrease the throttle till you see less smoke. most of drivers do the mistake here by dipping in the acc ped further. you are simply wasting the diesel and not gaining any power. the earlier diesel engine's life is purely dependent on the driver. that's the reason most of our jeep engines doesn't last for a prescribed kms and it varies from one to one. the engine life purely depends on the driver. where as the crde engines have predefined life irrespective of driving style.
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Old 14th February 2011, 09:45   #22
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Originally Posted by star_aqua View Post
its unavoidable with mechanical governors as the system is linear. one can observe during uphill climbing with our xdp engines, say you are climbin in 3rd gear with 50% acc ped dipped in at a constant speed. and if the gradient starts increasing at certain point with same acc ped position it starts emitting black smoke. at this point it is of no use even if you increase the throttle you don't feel any difference except increasing the black smoke. the right way is to decrease the throttle till you see less smoke. most of drivers do the mistake here by dipping in the acc ped further. you are simply wasting the diesel and not gaining any power. the earlier diesel engine's life is purely dependent on the driver.====
That is one of the reasons I created 'that' accelerator( pedal travel ) meter ,

I wanted to investigate more on this factor .

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Old 14th February 2011, 10:55   #23
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What Star mentioned is correct for older engines, i have also observed the same. Best practice is to go light on acc pedal when this happens, now i know there is some science behind this

Also smoking increases proportional to engine heating/overheating???
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Old 14th February 2011, 18:21   #24
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Originally Posted by star_aqua View Post
most of the times the NA engines run rich compared to engines with forced induction.
Hmm, fair enough. Star, any possibility of this in CRDe?

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Old 14th February 2011, 18:29   #25
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Hmm, fair enough. Star, any possibility of this in CRDe?

Spike
No possibility of playing with it , that's the bad part of it

& so no more knowledge gaining

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Old 14th February 2011, 19:11   #26
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Hmm, fair enough. Star, any possibility of this in CRDe?

Spike
Its possible in crde in same situations as mentioned before, but way less compared to older engines. the main reason is the sluggish air system even in crde. it goes rich when the engine is loaded and if the air system is not ready to deliver the desired charged air. it all depends on the dataset. for the same engine you guys have variant datasets with different kw rating. for same driving conditions, the frequency of DPF regeneration will vary with different dataset. the higher kw rated dataset will undergo regeneration more frequently.
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Old 14th February 2011, 19:44   #27
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but way less compared to older engines. the main reason is the sluggish air system even in crde.
Yeah, I have done trials on this factor (with clogged and dirty air cleaners).

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Old 14th February 2011, 21:08   #28
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Originally Posted by star_aqua View Post

To be precise at full load if the injected diesel is completely burnt and if there is still some more oxygen left, then it is lean. Say if the oxygen is completely utilized and could not aid for the further combustion leading to unburnt carbon, then it is rich. I hope i answered something which you can accept to some extent
Fair enough. (Actually definition is upto the definer.) But with this definition, I would look askance at
Quote:
Originally Posted by star_aqua View Post
most of the times the NA engines run rich compared to engines with forced induction.

Quote:
Couldn't understand the speed droop setting in context of a automobile FIP. is it related to generators?
Though one comes across this term most commonly wrt generators, it is a characteristic of any (stable) governor. In automotive applications, the (intelligent?!) human is part of the loop, and masks most other effects. One can do without a governor, as in a petrol engine with a directly connected throttle. But FIPs have a governor.


Quote:
550s have FIPs from Delhpi, Bosch and Lucas. I may be wrong here but i think civilian and army XD3s have different makes of FIP.
Experts, please comment.

Quote:
Originally Posted by star_aqua View Post
its unavoidable with mechanical governors as the system is linear. one can observe during uphill climbing with our xdp engines, say you are climbin in 3rd gear with 50% acc ped dipped in at a constant speed. and if the gradient starts increasing at certain point with same acc ped position it starts emitting black smoke. at this point it is of no use even if you increase the throttle you don't feel any difference except increasing the black smoke. the right way is to decrease the throttle till you see less smoke. most of drivers do the mistake here by dipping in the acc ped further. you are simply wasting the diesel and not gaining any power.
There are so many things to discuss. Starting with governors, and the why of 'brick wall governing'. Why don't you do the honours?

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Originally Posted by Jaggu View Post
What Star mentioned is correct for older engines, i have also observed the same. Best practice is to go light on acc pedal when this happens, now i know there is some science behind this

Also smoking increases proportional to engine heating/overheating???
The throttle in a diesel is best thought of as 'set point indicator' for the governor. The fuel delivery is actually determined by the governor.

Re: overheating: Any marine engineers here? (Marine engines have exhaust pyrometers as standard fitment. And marine engineers are formally taught quite a bit about diesel engines.)

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Sutripta
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Old 15th February 2011, 01:05   #29
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Originally Posted by Sutripta View Post
Though one comes across this term most commonly wrt generators, it is a characteristic of any (stable) governor. In automotive applications, the (intelligent?!) human is part of the loop, and masks most other effects. One can do without a governor, as in a petrol engine with a directly connected throttle. But FIPs have a governor.


There are so many things to discuss. Starting with governors, and the why of 'brick wall governing'. Why don't you do the honours?
Well i tried to understand the speed droop and its the percentage of rpm drop from no load rpm to full load rpm for the same throttle. for generators its
said to be 3 to 4%. which means for 1800 rpm with no load, the max reduction should not be greater than 72 rpm when full load is applied.

the less percent of speed droop affects the drivability and for automobiles the speed droop is way more than the generators.

but such control is possible with a variable speed governor which are used in special purpose vehicles like tractors, any vehicle with PTO operations.

I dont have the pictures right now to explain the functioning of governor with various load factors. till then lets discuss with the below pic what do you think if the tension in the main spring aka governor spring is altered. what will happen to the speed droop?

FIP Flop-ve_pmp.jpg
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Old 15th February 2011, 20:26   #30
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^^^^
Hi,
My thoughts:
If the spring is made stronger (stiffer) droop will increase. If spring remains the same, and only preload is changed, operating point will shift, but characteristics (droop) will remain the same.

Re: lean/ rich, I think it would be useful (for my understanding at least!) if we could start off with the simplest, ie. a NA direct injection industrial (essentially single speed) engine fed with a jerk injection pump, with an externally visible/ controllable fuel rack. (Lots of questions that must be asked, things that must be said!)

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