Commonrail: Need more fuel

[storx]

OK,

I know 2Micron is working amazingly on the installing of an CP3 pump on our cars, But today after a new change to my tune.. i have felt the wrath of the dreaded rail pressure low MIL.. basicly using more fuel then the CP4.1 pump can supply over a longer gear... its really gear dependent because 1st, 2nd no issues what-so-ever.. but 3rd.. it starts at the same RPM's like clockwork.. every pull.. exact pressure amount at the same RPM's... then 4th is even sooner on a WOT pull.. same rpms.. same amount of pressure...

I called up my buddy from colorado who has a crazy duramax to pick his brain and he told me that this happens all the time on duramax's... the ratio of the pully.. to supply falls short as you increase in power..typically only happens on turbo upgrades he said..

He told me that they have 2 options on the duramax.. if you are not a racer and just need a tad more fuel to max out the turbo that is not much larger than stock.. you buy an pulley upgrade that comes with a new belt and custom size pully that overdrives it sum to get more out of it. This is considered a mild performance fuel upgrade..

But he told me when you go big power and need way more fuel.. you have to stack pumps to supply the rail with enough pressure..(not thinking this is logical for us)

Since stacking wouldnt be nearly possable for us.. and the cp3 upgrade isnt ready for us.. maybe we could have a custom pulley made for the ones that are pushing mild power upgrades... tell cp3 option becomes an easy upgrade.. cross my fingers for the day its ready comes soon...
http://forums.tdiclub.com/showthread.php?t=367804&highlight=cp3

I am no expert injection pumps.. but would this effect our cars any? not sure if there is some kind of timing required on the pump or what not.. or if we could just push it a little harder with an upgraded pulley..

The other option i learned about is stroking the pump.. not sure how logical this would be since its just a fragile unit and the cp3 pump is worlds better.. basicly adds a larger cam lobe on the pump shaft to get more stroke from the internals to pump more volume..

 

[ducesrwld]

i'd be curious how much extra a little bigger pulley would even make on these pumps. on the dmaxs I wasn't even aware or heard of putting a different pulley on. everyone I see either goes with a stroker pump (stupid expensive) or a duel fueler setup which is what i'll probably be throwing in mine.

 

[bhtooefr]

There's also using the CP4.2 instead of the 4.1. Twice the fuel, after all. The intake manifold may need to be redesigned to clear the pump, though, unless you can get the pump rotated forward some.

 

[DPM]

Is the restriction actually @ the plunger or are you hitting a flow limit elsewhere in the pump? Might be worth upping the supply pressure to ensure there's no cavitation on the inlet side. Tee a pressure gauge in post- boostpump?

 

[ryanp]

I've got upgraded pumps in the works, it seems some of the 2.0 engines we have hit the rail pressure problem sooner than others!

I think its worth getting headwork first as you can make these CR's smoke before you get that problem.

 

[bhutchins]

Is the restriction actually @ the plunger or are you hitting a flow limit elsewhere in the pump? Might be worth upping the supply pressure to ensure there's no cavitation on the inlet side. Tee a pressure gauge in post- boostpump?

nope, I currently have the Bosch 044 installed with a 1 liter surge tank, in place of the aux pump, and I still go into limp mode at 4500 rpm

caution: the bosch 044 is only rated for 500 hours life with diesel

 

[storx]

Is the restriction actually @ the plunger or are you hitting a flow limit elsewhere in the pump? Might be worth upping the supply pressure to ensure there's no cavitation on the inlet side. Tee a pressure gauge in post- boostpump?

I am running an 260GPH regulated diesel fuel pump and right now...

 

[storx]

I've got upgraded pumps in the works, it seems some of the 2.0 engines we have hit the rail pressure problem sooner than others!

I think its worth getting headwork first as you can make these CR's smoke before you get that problem.

what head work are you recommending Ryan, i ask because everyone i speak to doesnt have anything for our engines... Colt Cams had a beta cam available for a while.. but they told me they wanted to wait tell the person that they sold one to gets results on it before they make anymore.

I have had very little luck finding upgraded parts for the cylinder head without having to go completely custom.. i am wanting to find out if the 2.0T FSI motor valve springs and such would be compatible..

So far i have dremel'd the intake ports to match my intake.. with no real difference felt afterwards..

 

[RDC98tdi]

Wouldn't you want a smaller pulley on the wheel to make it spin faster? Assuming you are talking about the pulley directly connected to the pump.

 

[TDIMeister]

One would expect low rail pressure where the engine is developing close to maximum power (maximum fuel flow rate) but at relatively low RPM (low pump drive speed). All positive displacement pumps display a flattening flow output curve at higher speeds. This is probably what's happening. In this case the solution is NOT overdriving the pump but rather the opposite.

 

[Rub87]

What about the 4.2 of a 3.0 TDI as mentioned and just redrilling holes in the bracket to turn the pump outside so it clears the intake manifold?

One would expect low rail pressure where the engine is developing close to maximum power (maximum fuel flow rate) but at relatively low RPM (low pump drive speed). All positive displacement pumps display a flattening flow output curve at higher speeds. This is probably what's happening. In this case the solution is NOT overdriving the pump but rather the opposite.

On the one car I did with 2260 it only happened around peak torque at slightly over 90mg of fuel and at cold engine conditions. at higher rpm the exhaust was too restrictive so fueling had to be lowered.

 

[storx]

i dont know if the custom pully they use on duramax is smaller or larger.. i cant confirm this so i am honestly not sure if its over driven or under driven..

 

[JFettig]

Storx, I thought you said you were making 300hp? no need for more fuel

I have a CP3 that I might try to adapt when I get around to it, not sure how it'll like 1:1 drive with the crank though.

CP4.2 has been discussed in another thread. The Powerstroke pump would probably work nicely with an adapter plate since the snout of the pump is a little longer. It also had more lift.
http://forums.tdiclub.com/showthread.php?t=387252

 

[Rub87]

Is it just me or ist the cp3 alot bigger at any angle so it will never fit the stock position no matter how you clock it?

 

[JFettig]

There are a few different sized CP3's, a truck CP3 might not fit but I got mine from a Liberty CRD -2.8L.

 

[andy2]

Most of the duramax/cummins guys just add a second HPFP.They commonly use 2 unmodified pumps.

The second pump is driven with the serpentine belt.they just run a longer belt and find a spot for the pump.

 

[TDI-JAY]

When you REALLY need some more fuel, TRIPPLE CP3's!!

2 more pumps on the top of the motor (fancy pullies) and the factory in the valley. Holy cow thats some serious fuel.

 

[ryanp]

3 turbo's and 3 pumps, nice!!!

 

[steve05ram360]

would a fuel rail with greater volume & larger feed lines help? I would think the FP roll-off would improve. There is a "race version" rail for the Cummins where the rail internals have been extrude honed for more volume. Also some have put the 6.7 rail on their motors which supposedly has more volume than the honed 5.9 rail.

Just tossin that out there...

edit: you also mentioned the larger lift pump install, what about the fuel lines out of the tank, going to the filter, aux pump (044?) and to the HPFP? Are they still OEM or did you go larger?

 

[Rub87]

I would think that the rail volume on itself will not help, as diesel is fluid and only very minimal compressorable. on the other hand it changes the pulsations in the rail, especially big influence when running multiple injection per stroke. therefore the ecu have pressure wave compensation to account for the pulsation in fel pressure at the nozzle. this correction is based on railpressure, inj quantity and time between injections.

if you change the rail you can be on the sure side that this correction will not be correct anymore, but offcourse if emissions do not count it doesnt really matter if the pilot is 1.2 or 1.7 mg =)

 

[steve05ram360]

The thinking is that (as an example) if you have a liter of fuel in the stock rail and under high demand the use pulls half a liter in say "x" amount of time the HPFP has to keep up under harder conditions vs if you had a 2 liter sized rail and pulling the same amount from it. The pump would have an easier time keeping up.

 

[Rub87]

if it was a compressible fluid, like a gas sure, but a fluid is only very little compressible, so it will not make a big difference as it would make with for example an air compressor tank.

 

[v8 coupe]

are there other applications of the 4.1 pump or is this basically it's only application?

 

[bhutchins]

if it was a compressible fluid, like a gas sure, but a fluid is only very little compressible, so it will not make a big difference as it would make with for example an air compressor tank.

what about a hydraulic accumulator?

http://www.grainger.com/Grainger/PARKER-Piston-Accumulator-4WB45?Pid=search

 

[DPM]

too much storage and you'll have issues too. You need to be able to dump pressure on throttle-off too...

 

[storx]

With the 4.2 pump...there is talk that it MIGHT fit...was this ever fully determined?...since it will bolt up easily otherwise

Sent from my SGH-M919 using Tapatalk now Free

 

[Rub87]

imo just clock it 45deg ouwards, dunno out of my head if there is room on transversal apllication, but its worth the try, they are cery cheap an available on ebay.de

just need to find a Y piece for the HP lines

 

[storx]

From what i am seeing, It appears there is just barely enough room.. if you look at the way the holes are drilled it appears they offset it enough to make it fit on purpose.

 

[storx]

imo just clock it 45deg ouwards, dunno out of my head if there is room on transversal apllication, but its worth the try, they are cery cheap an available on ebay.de

just need to find a Y piece for the HP lines

What are they going under? I ask because i searched for cp4.2 on both ebay.com and ebay.de and i get nothing but 4.2 v8 waterpumps and other parts coming up..

Also if i could understand how these pumps are timed, as in setting them up during install. I be game to try out the CP4.2 pump if we come to an agreement that it would actually help with the lack of fuel pressure issue.

 

[Rub87]

I think its not the end of the world if you time it wrong.. you can choose to line 1 piston up with the original cp4.1 and then the other 90 deg pump angle afterwards, or time the pump that the center of the 2 pulses match with the single pulse from cp4.1..

http://www.ebay.de/sch/i.html?_from=R40&_sacat=0&_nkw=3.0+tdi+hochdruckpumpe&_pgn=2&_skc=50&rt=nc

I have seen them go for as low as 200 euro, 250-300 should be doable if you keep an eye on them

that it helps with lack of fuel pressure is quite easy to understand as the pump has twice the plunjers, so logically twice the fuel if the plunjer diameter and lift is the same. 3.0 tdi have dynoed over 370hp with stock pump