[SPIKE ARRESTOR]

Originally Posted by Sudarshan

most welcome . (a fuel circuit chart will also do )

Attaching a generic layout for clearer understanding.

Now with this reference what is the position in CRDe & electronically controlled units ?

Priming location in fuel filter:-

Is the Bleeding part important or its simply not there ? (Can do without that ? )

It is still important. Despite everything, there are possibilities which may result in air getting trapped in the fuel lines hence priming / bleeding becomes imperative (hence the hand primer is provided). All depends on how much air is trapped. Attaching a pic showing the inlet and outlet locations.



Hope it is clear now.

Spike

[Sudarshan]

Originally Posted by SPIKE ARRESTOR

Hope it is clear now.

Spike

Thanks for the information .

its very much clear now .

I still have one doubt , is there any bleed screw on the high pressure pump ? ( just like the old FE pump ? )

Thanks

Sudarshan

[Sutripta]

Logically,the rail should have a bleed, at a point farthest from the pressure pump connection. However, given the pressures involved, chances of serious injury are extremely high. Thats why I think there are no user accessible bleeds.

I guess at CR pressures, air just dissolves in the fuel. And a piezo injector is electrically opened, so air should not be that serious a problem. Of course, without fuel (lubricant) you are likely to ruin your pump.

Prateesh, comments.

Regards
Sutripta

Edit: Are engines or injectors susceptible to bends?

[Mpower]

Originally Posted by SPIKE ARRESTOR

Attaching a generic layout for clearer understanding.

Hope it is clear now.

Spike

I don't see the electric in-tank lift pump.

[star_aqua]

Originally Posted by Sudarshan

I still have one doubt , is there any bleed screw on the high pressure pump ? ( just like the old FE pump ? )

As Spike said all you need is to fill the diesel and crank continuously till it starts. For second try priming is preferred with key ON. Bleeding can be done only in low pressure circuit but not possible in the high pressure circuit. The CR system will take care of bleeding in high pressure circuit automatically. While cranking if there is no pressure buildup in the rail, the system goes into venting mode for a while which will vent out the air through injectors and switches to pressure build up mode. this repeats until the minimum pressure to make injection is achieved.

[SPIKE ARRESTOR]

Originally Posted by Sutripta

However, given the pressures involved, chances of serious injury are extremely high. Thats why I think there are no user accessible bleeds.

Yes, pretty true.

I guess at CR pressures, air just dissolves in the fuel. And a piezo injector is electrically opened, so air should not be that serious a problem. Of course, without fuel (lubricant) you are likely to ruin your pump.

Yes, it is recommended that engine must not be started without fuel, every HP pump has a minimum quantity of fuel specified for operation.

Edit: Are engines or injectors susceptible to bends?

Bends from?

Originally Posted by star_aqua

The CR system will take care of bleeding in high pressure circuit automatically. While cranking if there is no pressure buildup in the rail, the system goes into venting mode for a while which will vent out the air through injectors and switches to pressure build up mode. this repeats until the minimum pressure to make injection is achieved.

Well said

Spike

[Sutripta]

Originally Posted by star_aqua

...While cranking if there is no pressure buildup in the rail, the system goes into venting mode for a while which will vent out the air through injectors and switches to pressure build up mode. this repeats until the minimum pressure to make injection is achieved.

Hi,
A couple of questions.
A) How does the ECU know there is no rail pressure?
B) Venting done only through injectors?
C) When through injectors, when? Power stroke, or exhaust stroke.

@Spike
Re: bends, was joking. (Bends = Caisson disease)

Regards
Sutripta

[star_aqua]

Originally Posted by Sutripta

Hi,
A couple of questions.
A) How does the ECU know there is no rail pressure?
B) Venting done only through injectors?
C) When through injectors, when? Power stroke, or exhaust stroke.

Regards
Sutripta

A) through rail pressure sensor
B) it is only for the systems which doesn't have pressure control valve(PCV) or else PCV is used.
C) exhaust stroke

[Sutripta]

^^^
Hi,
Do you know what type of sensor? And what accuracy? > 1000 bar, hot or cold, is not a joke.

I was thinking about one thing. I one runs the pump long enough, air or no air, pressure will build up. So it must be a timed thing. Is it?

Air in system/ venting: - Is it stored in the fault log?

Regards
Sutripta

[star_aqua]

Originally Posted by Sutripta

Do you know what type of sensor? And what accuracy? > 1000 bar, hot or cold, is not a joke.

Its made of steel membrane with metal thin film and more details which you are looking for is here http://apps.bosch.com.au/motorsport/...ghpressure.pdf

The hot and cold diesel makes lot of difference in the rail pressure when metering unit(fuel metering done at low pressure side) is used for controlling the pressure instead of PCV.

I was thinking about one thing. I one runs the pump long enough, air or no air, pressure will build up. So it must be a timed thing. Is it?

yes, exactly. there is a specified time for specific pressure to build up at specified rpm when pumping diesel. the time is very high for air as it is compressible and takes more revolutions and which means more time taken to build up the pressure. There is a timeout as the expected pressure is not reached within expected time.

Air in system/ venting: - Is it stored in the fault log?

'Air in system' fault will be stored in the fault log only if empty tank is not detected.

[SPIKE ARRESTOR]

Originally Posted by Sutripta

@Spike
Re: bends, was joking. (Bends = Caisson disease)

I didn't know that. Dada, BTW congrats on becoming a D-BHPIAN, you truly deserve it

Originally Posted by star_aqua

Its made of steel membrane with metal thin film and more details which you are looking for is here http://apps.bosch.com.au/motorsport/...ghpressure.pdf

Star, which sensor are we talking of here? The link doesn't seem to be working in my system, some problem may be.

Spike

[star_aqua]

Originally Posted by SPIKE ARRESTOR

Star, which sensor are we talking of here? The link doesn't seem to be working in my system, some problem may be.

Its the high pressure sensors spike. can be used for applications which need measurements upto 2200bar.
its a link to a pdf file. must be something wrong with your pc.

[Sutripta]

Originally Posted by SPIKE ARRESTOR

Dada, BTW congrats on becoming a D-BHPIAN, you truly deserve it
Spike

Thanks Prateesh. Appreciated.

Originally Posted by star_aqua

Its made of steel membrane with metal thin film and more details which you are looking for is here
......
'Air in system' fault will be stored in the fault log only if empty tank is not detected.

Hi Vijay,
Would suggest that you start a thread titled 'CRDIs for dummies'. But till such time here are a few more questions and comments.

Surprised to see that the pressure sensor is essentially a standard design, configured as a transmitting head. What surprised me was that
A) It was not a double diaphragm design.
B) It has a shelf life. (Why)

You had also mentioned that metering is done on the low pressure side. Could you expand on that please. Actually, lots of questions about metering. And total injection time.

Regards
Sutripta

[star_aqua]

Originally Posted by Sutripta

Would suggest that you start a thread titled 'CRDIs for dummies'. But till such time here are a few more questions and comments.

Will do when time permits

You had also mentioned that metering is done on the low pressure side. Could you expand on that please. Actually, lots of questions about metering. And total injection time.

The pressure can be regulated by metering the fuel on low pressure side as well as on the high pressure side.
The first generation CR system had the metering control on the high pressure side. The second generation had on low pressure side and later generations come with coupled control where the metering is done on both side.

The disadvantage of fuel metering on low pressure side is bringing down the rail pressure rapidly when desired is not possible and the pressure buildup is fuel temperature dependent in which metering cannot be done precisely. The advantage is pump load on engine can be varied based on the pressure requirement, hence more efficient.

when only PCV is used(high pressure side control), the disadvantage is the pump always works with its full load on the engine which is unnecessary, hence less efficient.
when both are used, the system is more efficient and robust as there is always a backup if one of the low or high pressure side control fails.

[Sutripta]

Hi,
You mean throttling the input? Will that not lead to flash boiling of the fuel, and maybe even cavitation?

BTW, what is the nature of the pump?

Regards
Sutripta