Commonrail: Need more fuel

[JSWTDI09]

I'm no expert on these things, but it looks like the CP4.2 only has a single fuel metering valve (just like the 4.1). Are you certain that the issue is in pumping volume and not metering volume? I assume that the fuel metering valves are not identical in these two pumps, but I'm just thinking about where the most significant "choke point" might be. Doubling pistons will only be helpful if they can actually pump twice the fuel (or at least significantly more fuel).

Also, does the CP4.2 have the same double cam driving the pistons up and down? Two pistons moving at half the frequency will not necessarily pump more fuel (unless they are significantly larger pistons).

Again, I'm no expert. I'm just sharing my musings.

Have Fun!

Don

 

[TDIMeister]

Didn't somebody post that there's an inline CP4.2 also?

 

[storx]

I'm no expert on these things, but it looks like the CP4.2 only has a single fuel metering valve (just like the 4.1). Are you certain that the issue is in pumping volume and not metering volume? I assume that the fuel metering valves are not identical in these two pumps, but I'm just thinking about where the most significant "choke point" might be. Doubling pistons will only be helpful if they can actually pump twice the fuel (or at least significantly more fuel).

Also, does the CP4.2 have the same double cam driving the pistons up and down? Two pistons moving at half the frequency will not necessarily pump more fuel (unless they are significantly larger pistons).

Again, I'm no expert. I'm just sharing my musings.

Have Fun!

Don

I am no expert either but i was up for a few hours lastnight reading up on the CP4.1 and CP4.2 and it seems that fuel volume is controlled by holding the Fuel Pressure Metering Valve open to increase volume and closing it to stop the volume.. or something along that. I was just trying to understand how it works to see if there was maybe something simple we could do to maybe increase the max pressure.

After looking at my logs,
1st gear WOT i spike to 1948bar @ 3928rpms - pulls all the way to 5500rpms
2nd gear WOT i spike to 1902bar @ 3956rpms - pulls all the way to 5500rpms
3rd gear WOT i spike to 1848bar @ 4024rpms - below requested 4577rpms
4th gear WOT i spike to 1802bar @ 4088rpms - below requested 4202rpms

 

[v8 coupe]

I see 4.2's are now on fords and dmax's as well so I would think maybe one of those would be a good option since they are much larger HP ratings then our goals.

 

[Rub87]

http://bit.ly/1eetEI
18 left on this one, keep eye on it

Stuped ebay gives crap link, item number is :161121664025

 

[storx]

On the CP4.2, does anyone know if there is any way to swap the head of the pressure side to make both come out the same side?> to make lines easier to install...

 

[Rub87]

Not possible

 

[storx]

Not possible

not trying to act stupid.. but trying to learn more about it.. but could you explain why.. it appears the mounting position is interchangeable in pics.. just like to know otherwise.

 

[bhutchins]

just tie them together with stainless tube

 

[Rub87]

Its because the suplly port is on one side of the head, so if you flip it around, the will end up no where and the head will get no fuel. If you have another head of the other side, or a pump with the exits on the same side it can work offcourse

 

[storx]

Its because the suplly port is on one side of the head, so if you flip it around, the will end up no where and the head will get no fuel. If you have another head of the other side, or a pump with the exits on the same side it can work offcourse

I just realized the pump 2004LB7 took apart is not like all the 3.0 TDI pumps i am seeing on ebay. His pump must be from something else.. Ill have to read into further to see if he stated it and i overlooked it.

Here is the pump he took apart for cp4.2 overview.

Based on this, IF you were to buy one of the 3.0 V6 tdi pumps that are all over ebay... you could swap one of the heads with the old head of the cp4.1 and have them both on the same side?

 

[Rub87]

Is there a problem if they do not face the same side? Just find a y piece and suitee line and off gou go

 

[storx]

Is there a problem if they do not face the same side? Just find a y piece and suitee line and off gou go

with them on both sides it would make for a easier, cleaner look...

Rub87, i know people mentioned that the injection pumps are set at a specific pressure.... since the spike in pressure is less the later the gear i am in, is there a way to up these gears pressure values to match what 1st and 2nd start at?

 

[v8 coupe]

do we know if a 4.2 and a 4.1 are interchangeable Sorry if this hass been discussed didn't see the info

 

[DieselDubs83]

We are working on a dual fed fuel rail. Our goal is bolt-on CP4.2 kit for fueling extreme HP builds.

-Les

 

[Revelc]

I wonder if high pressure oil injector systems will ever find their way into smaller engines... I would rather flush a block instead of replacing an entire fuel system if a pump takes a dump. But then again I don't know much about the performance side of diesel..

 

[Rub87]

We are working on a dual fed fuel rail. Our goal is bolt-on CP4.2 kit for fueling extreme HP builds.

-Les

nice

.... since the spike in pressure is less the later the gear i am in, is there a way to up these gears pressure values to match what 1st and 2nd start at?

you are sure that the pressure at the hp pump inlet isnt tapering off, right?

 

[kai.od.ua]

When the estimated date of presentation?

 

[bhutchins]

Looking forward to a solution from going into limp mode every time I hit 4500rpm in 3rd or higher

nice

you are sure that the pressure at the hp pump inlet isnt tapering off, right?

I'm currently running a Bosch 044 pump (I know, not ideal for diesel) in place of the aux pump, and Storx is running a cummins aux pump in addition to the factory aux pump, and we both have fuel rail pressure drops

Oh... and a adjustable back pressure valve.... between the o44 and the backpressure valve pumped up, I can pop off fuel lines between the aux pump and HPFP. forget about the factory spring clips, they wouldnt even stay on through a VCDS fuel line purge. Really have those hose clamps cranked on.

 

[Bobby Singh]

Bosch 044 pump is gas pump right?
Could you not double this pump up?

Interesting thread.

 

[storx]

Its not a fuel inlet issue as i have SOLID pressure going in.. its HP out that cant keep up.. I thought these pumps were set to a MAX, but mine pretty much follows my boost curve up to max ACTUAL pressure.. then is slowly tapers off from there.. I wish i knew how to keep the 1800-1900bar of fuel i see at 2600-2800 all the way to redline..

From what i have read on Duramax forums on there CP pumps with tuning.. rail pressure is all controlled by the duty cycle of the fuel control metering valve and the pop off pressure regulator. It may be called differently on ours.. but these where the words they used often over on duramax forums. I know they talk alot on how they will increase the threshold on the pop off sensor to not allow it to bleed usable fuel off, with some of them removing this sensor completely on racing trucks allowing there rail pressure to be purely controlled by the metering valve pumping in the fuel.

Something i been thinking about doing is replacing this sensor with a new one. I have spoke to VW about it and they said there system shows its peak limits being 1800bar... so does this mean it cant control anything above 1800bar?

 

[2004LB7]

From what i have read on Duramax forums on there CP pumps with tuning.. rail pressure is all controlled by the duty cycle of the fuel control metering valve and the pop off pressure regulator. It may be called differently on ours.

this is correct.

in the duramax world we call the "metering valve" a "fuel pressure regulator valve".

it is controlled by a pulse width modulated currant. the currant is used to overcome the spring pressure and close the valve. incresing the duty cycle closes the valve, lower duty cycle alows the spring to push back and open the metering valve. if you unplug the connector on the metering valve it will go into "max pressure" mode, ie all the way open.

the ECM used in duramax is limited to 2000 MA of currant. the tunes usaly use somewear around 400 MA to 1500 MA. the metering valve one our CR VWs is likely very simular

 

[2004LB7]

I have spoke to VW about it and they said there system shows its peak limits being 1800bar... so does this mean it cant control anything above 1800bar?

this document seams to hint otherwise:
https://www.google.com/url?sa=t&rct...UqXKsCkWxxx5RTFqDks68NQ&bvm=bv.53899372,d.d2k

it is probably all in the tuning

 

[Rub87]

stock railpressure goes to 2000 bar..

 

[v8 coupe]

I'm still waiting for an answer. Has anyone tried the 4.2 pump? Will it talk with our ecu? if it will I'll gladly throw one on already found several good used LML units which are good to a rated 180lph according to some data I have.

 

[Rub87]

sure.. in the ecu there are some labels which you could change, like delivery and torque it takes to drive the pump, but there is a big chance it will also work like this without changing them

 

[storx]

this document seams to hint otherwise:
https://www.google.com/url?sa=t&rct...UqXKsCkWxxx5RTFqDks68NQ&bvm=bv.53899372,d.d2k

it is probably all in the tuning

That is a different injection pump all together..

 

[storx]

stock railpressure goes to 2000 bar..

Rub, have you heard of anyone that has found the maps to adjust the metering valve duty cycle? i ask because i don't believe anyone has yet after talking to a few people over it. I know RyanP is searching for it aswell, and he is working on the 3.0TDI's because the way he replied to me.. it seems they are having worst of an problem with rail pressure with uprades.

 

[bhutchins]

some good info here on both Audi and Mazda TDi race engines
Racecar Engineering – Engine Supplement
http://chelseamagazines.com/files/download/169

 

[jvjump]

Ok new to vw so bear with me. Why don't me approach this issue like the trucks already have. When building the truck we first start with fuel pumps lots of fuel at around 20 psi and good filter with clean fuel will make a hpfp live a lot longer. Want to push fuel for a few things, helps cooling, help lubricate, and always have a good supple when pump needs it. Also good filtration these pumps are working at high pressure. Dirty fuel just eats them up. We need around 2 mic to help. ON my trucks we will run 28,000 psi put a little dirty fuel in that mix will eat pumps and injector tips. After we get hpfp pump to live why can we not mod it to run more fuel volume like on the trucks.