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Feed The Beast, Part I & Part II Improve fuel to IP

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IIRC The Cummins LP uses Banjo fittings.In reality the theory behind the failure of the Cummins LP is the vibration from the engine and them mounting the LP on the engine. ON the frame it may be ok. Fass or Airdog is more than a LP, it is a whole filtration system and it works very very well. it also eliminates teh OPS problems these trucks are prone to so don't knock it if you don't know what it is. It also removes air from the fuel that would be there normally and prevents cavitation of the fuel/IP. I'm not saying everyone needs to run out and buy one but if you got the dough, It's the very best.
 
With the low pressures we run our fuel systems at I'm not sold on the "air bubble" reduction in fuel being that big of an issue,

Possibly with too much return except on WOT with a normally high gph pump like FASS/Airdog, and we might contribute to foaming the tank,

This is why I'm plumbed 2 pumps in parallel relay powered via OPS/PCM control of relays.

This way in the event (have not seen it yet) that the FRB-5 can't keep up I switch on the GM pump to augment it and go from 45 gph to 70 gph combined 2 pump flow potential, barring restrictions. I could see on a long grade and very heavy load the possibility I might need the extra oomp of 2 pumps.
 
TD,

If i plumb both in, say cummins L/P followed by my stock L/P wouldnt it reduce the flow and put a strain on my stock L/P? If i did the doubles shouldnt i put my stock L/P before the cummins L/P? But even if i did that would my stock L/P put out enough to feed the cummins L/P? (Sorry that was a lot of L/P's LOL). I have a fuel pressure gauge, its not in the cab tho, but i open the hood to check the oil and fluids frequently.
 
In series would be fine for redundancy too. If one isnt flow on fail then it wouldnt. So with the older questionable Cummins pump (could fail with no flow) then in series wouldnt make sense. But two stock type or Walbros in series would be fine for better pressure and redundancy. Easier plumbing too.
 
Cummins pumps are flow on fail. That is the problem. It would have been better if they were not. They commit suicide and the Truck keeps driving but the strain on the lousy diaphrams is too much.
 
Acesneights1 said:
Cummins pumps are flow on fail. .
Click to expand...

May or may not flow, I positioned the one in the pictures so that it did not flow, as a test after the fact from talking to Diesel Pro & GMCTD who told me that when that happens the VP44 dies instantly as fuel is is the lube for the pump which even though the truck stops from lack of fuel supply the pump is self destructing while coasting down to a stop.

I have never owned a VP44'd vehicle, but in world of fuel injection I'll have to take DP & JD at their word that is what is happening, they have yet to steer me wrong. They said Cummins only supply is bad ju-ju.
 
I can't beleive I am going to say this....But I disagree with GMCTD. I had a 2nd Gen Cummins with a VP44 which we all have come to know as "The Lemon" and the LP died and the truck kept running fine but it burned up the diiaphram in the VP. I'll see if we can get Rich to chime in on the cummins LPs'.
 
Never gutted a VP44 myself, so maybe I'm remembering what I heard incorrectly as to what actually fails. At any rate JD, Mike (DP), and Eric at Hoesli Diesel (guy who recommended the Walbro) said the early Cummins lifts were POS that when quit killed the VP44s due to no flow, and I was able to create a no flow of air pressure by rotor/vane positioning, so I decided to not go there with that lift pump choice.
 
schiker said:
In the beginning I wondered what the advantages of FTB mod were and thought some of it could be better fuel through put and thus cooling of the IP by more fuel. Which I think is a benefit but not where the power comes from. I read that the FTB mod helps more even output to each injector during upper fuel deliveries. Or the fuel balance.

A while back I took an IP apart and see its a simple yet complex mix of timed ports & some valves/springs etc. I have heard the term transfer pump internal to the pump but never saw such a mechanism. I have heard terms fill and spill chamber plungers, cam ring, rotor, and fuel solenoid. I recognized those parts but didn't quite understand the spill and fill chamber and exact flow path. I don't fully understand it nor can explain it but kind of understand it should work like this....???.....

Simplified not exactly but the lift pump helps lift fuel from the tank to the IP. And fills the IP body with fuel. The plungers sling outward due to centrifugal force drawing in the fuel from the "fill chamber". Or as GMC might say the pressure of the fuel actually pushes in due to the lower pressure created by the plungers moving out. Anyway it fills the plunger stroke chamber. With rotation relative to the camring the plungers are forced back inward to build pressure. If the fuel solenoid gets power to close this closes one of the exits possible to the spill chamber. When the fuel solenoid closes this path the fuel must due to increasing pressure travel out the injection lines and pop the injectors. Now the injectors squirt and with a stroking mechanism internal once it strokes it also pumps a little fuel out the return lines (at much lower pressure than injection pressure because there is no resistance to flow and this small pump out rate is low). As the rotor turns further it allows another passage and or the fuel solenoid lets off such that the plungers push to wards the spill chamber. At certain rotation the spill chamber can transfer back to the fill chamber with a check valve or can vent back to the tank. All of this happens really quick at a flowrate depandant on rpm.

But the key is there is no real transfer pump internal to the IP its really the centrifugal force slinging the plungers out that build the differential pressure from the fill chamber, to plunger chamber, and then to the spill chambers. And when ALL the fuel is injected to combust (at high fuel delivery rate) it reduces the positive transfer pressure inside the IP from spill to fill and recirculation to tank. Such that with better supplied lift pump volume to keep the spill and fill chambers completely full it helps the plungers "draw" or pump fuel and keep the fuel circulating optimumly internally to the pump.And why the IP can draw fuel its a pump that must pump fuel with each revolution but its the timing and other mechanism that control the injection pulse, recirculation internal, or return to tank.

What do y'all think of that
Click to expand...
This is actually the first time i read this whole thread,good information overall.

Sorry Schiker,but i feel i have to rectify this statement,as there actually is positive displacement transfer pump internally in the IP wich is pushing stock upwards of 153 PSI in the rotorhead.The pressure is adjusted on the test bench with a hollow torx screw with below it a springloaded solid rod valve and is located in the IP inlet under the hosebarb.
On high performance IP's the pressure is upped to 160 psi.

I aint sure,but i think a guy could adjust this a bit at the time with the IP on the engine and a 200 PSI gauge hooked up to the the testport on the bolt next to the PMD mounting pad.The pressure needs to be tested at WOT to get the max reading.

Maybe something to look into to up performance?

I thought you guys might want to know this.
 
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Thanks. I don't mean to make any inaccurate posts and appreciate the correction.

Yep. I found the transfer pump later and this is one of my earlier posts on the subject. Wish I could go back and correct all my "thinking" posts/threads. I try sometimes but uhhh I guess I think or ramble and sometimes extrapolate out loud too much.

On your idea of testing this port during operation I am thinking when pushing the limit of DS fuel delivery you would need some type of hydraulic pressure recorder for this test port and test all combinations of rpm and high fuelrate command. IF.... there is not enough accumulation volume for when the transfer pump flowrate is low ie low - mid rpms. I am curious if you really looked at this plunger charging pressure might/probably pulses (very fast and varies instanously due to cam profile and other factors too). And you want to maintain optimal pressure at all times illiminating any low charge pressure "dips" . Trucks can run with no LP and before FTB performance was good just with FTB performance goes up.

Thinking for constant displacement pump output the output is measured in volume per time and pressure rise comes from resistance to flow. The transfer pump will "automatically" increase volume output when the RPM's increase but at higher RPM's fuelrate output is limited (due to I think peak injection pressure). So it might be worse at some mid RPM ie 2000-2600. But be ok at higher rpms ????

Matt posted a thread where FTB really made him feel stronger at normal driving range ie 2000 ish rpm. Could he have a weak transfer pump that the New LP is helping more ????
 
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a weak Tr pump is certainly possible as i have found in a couple of my IP's that the plastic ring that keeps/forces the vanes out against the pump body was worn to the point that the springload was all but gone and the vanes had lost all contact with the body.
I dont know what effect that actally has as centrifugal force tends to keep the vanes to the outside anyway.
But pump press can certainly be tested IMO,the hard part is getting to that test port with the intake being in the way.
 
So i completed the FTB mod, and notice no difference. But i plumbed my first fuel pressure gauge about 1 foot after the L/P and am only reading 4.75PSI on a liq. filled gauge at idle. So i bet you im still sucking it dry. The stock pump is a POS. I get a good puff of black when i hit the throttle but then it clears up.
 
How about the thought of eliminating the factory IP fitting all together and replacing it with a free flowing piece?

I know there is the little safety screen in there.... but still, that could be added before the IP if one was worried, even a clear inline filter that far up the filtered path shouldn't ever clog, as it has to be larger than the little screen on the fitting.

Just a thought.
 
I did some measuring last night on the orifices down stream of the stock inlet barb.
IMO there's no need to drill the four 1/8"- 3.2 mmcross holes in the IP fitting/reliefvalve as the combined stock hole area (31.5 sq mm)is bigger than the 1/4"- 6 mm hole in the FTB mod nipple( 28 + sq mm).
furthermore,the bores in the IP housing leading to and from the TRF pump to the rotor head narrow back down to 3/16"-5 mm dia.
wich is the same size as the stock inlet barb.
IMO not much gain to be had beyond replacing the inlet barb for the bigger one

Matt,you cannot eleminate the IP inlet fitting as it contains the TRF pump relief pressure valve.
 
The FTB mod is a 3/8" nipple so its larger than 1/4" the holes in the IP fitting match up to 1/4" size, and when you drill them they match up to what 3/8" line would be. So I believe there is benefit. When you are talking supply and demand, it doesnt matter if the demand area has a small inlet, you want the supply to be as high flow capabiliy as possible.

Otherwise why would people do FTB mod at all, why put 3/8" line where there was 1/4", why put a 4" intake system on when the intake itself will go down to the equivalent of a 2" system. Etc....

Why, because the smaller the line the more pressure you need to be able to keep up with demand.
 
Had this in my FTB thread, so I'm bringing it over

3/8" fuel line = .11 sq in
4 x 3/16 holes = .11 sq in

1/4" fuel line = .05 sq in
4 x 1/8 holes = .05 sq in

So you see there is a reason for boring the holes. You only want to restrict the flow at the final inlet point if possible, and have strong enough supply pressure to keep the whole thing happy.
 
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