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Discussion Starter #1
Took some snapshots of my fuel system doing full throttle runs with a Tech 2. Note the green line is covered by text from the legend (sorry couldn't fix that). Also some measurements and shown in both PSI & MPa, and some are shown in both mph & km/h. I was running the TTS Extreme during the test. I did about a half-dozen runs. Sometimes my fuel pressure would keep up better than others.


Sounds like I need a lift pump for big HP! Has anyone run this on their truck with a big stack and got similar results?














Edited by: Diesel Power
 

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very interesting.........could be the difference between mac and me in ct.........mine is a stanadyne fm100 supplying up to 7psi to the stock fuel filter
 

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Well the HP pump does control rail pressure from the supply side. It also could be possible that the RPCV is flowing all it can while the injectors are using it faster that the RPCV can supply.... Pressurized supply might help but I would be wary of the consequences to overall pressure control.

Imagine a spike well over 23000 psi due to pressurized supply and a sudden drop in demand from the injectors. The relief valve.... your saving grace.

I would be real careful pressurizing the fuel supply. Might work but it needs to be looked at real close.

Edited by: hoot
 

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As a point of reference, any idea what the graphs might look like on a stock engine under the same test scenario? Edited by: OC_DMAX
 

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Hoot,


Why would suplying fuel, say at 10 to 15 psi to the suck side of the pump do anything more than ensuring a steady supply of fuel and keep the pump from loosing prime? (didn't want to use the C word and start something) Surely it couldn't increase the pump output pressure by more than 10 or 15 psi could it?
 

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Discussion Starter #6
From what i've been told a stock engine will resemble mine in the beginning and then fluctuate slightly above and below the desired amount. I didn't run it that way though :)


sdaver- i'm sure you're right. one of you is running out of gas and the other isn't...


not to mention 2 extra tires dragging on the bat-truck
 

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I believe the RPCV (railpressurecontrolvalve) acts as and amplifier of sorts. When designing the HP pump they had to come up with a way to control 23,000 psi. They came up with a valve that works on the low pressure input side. The reason they did this is it's much easier to design a durable valve controlling low pressure than one that controls incredibly high pressures.

Now I'm no absolutely sure if pressurized fuel would do as I described but I certainly would look into it.
 

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Nick's truck is the perfect example of what I've been telling you all for months. Feeding pressurized fuel to the inlet of a high pressure pump is nothing new and it will help the pump outlet pressure. My only reservation on the Dmax is the fuel is first feed to the EDU and I donot know how much pressure that will handle without leaking. Nick's truck dropped pressure as the graphs show and it never set a check engine light, like some would like to believe. So you don't know it's happening unless your checking it!


The stock system is fine for upto +200 RwHp give or take alittle, above that the system needs help. We have also seen several bad Hp pumps. Bosch shows a lift pump in all there common rail design books so I donot see how adding what they already show is going to cause a problem. Dodge uses one in there common rail system design but it's only good for about 500 RwHp so we need something a bit larger than there's. Once I find a good one it will be on Nick's and Big Dipper's trucks.
Edited by: Diesel Tech
 

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Interesting, so the recommendation for 0psi at the test valve may not be valid. And the fuel system weak link is the common rail fuel pressure and not so much a fuel injector limitation.


It would be nice to hear some input from Quad.
 

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"Once I find a good one it will be on Nick's and Big Dipper's trucks."
Edited by: sdaver
 

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I'm sure the lift pumps aren't putting out much pressure. Maybe a lift pump is all you need. Dodge uses the same HP pump with a lift pump.

Why not just install an old pressure box? How were they able to work with no lift pump?
 

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Um trying to feed the pump with a lift style pump on the vacum side... The rail pressure PSI is on the exit side ...Someone needs to bone up and find a EDU for research ...





Mac
 

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sounds like a good job for a diesel boy spy
 

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Another aspect to think about,,,, I suspect the extra acceleration of the vehicle that you are creating with these fueling changes is also affecting the ability of the stock fuel system (on the vacuum side of the fuel circuit). The dynamics of the vehicle need to be considered. The harder you accelerate, the more suction is required to move the fuel from the tank to the high pressure pump. While this effect will not be noticed on a dyno (vehicle not moving), it should be taking place on the street or track. So to make more HP requires a higher vacuum level to move more fuel (from the tank to the pump) and the greater acceleration created with this additional HP requires a higher vacuum level to move all the fuel (from the tank to the pump). Just my thougts and maybe something to think about when sizing your lift pump.Edited by: OC_DMAX
 

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Back to the ideal IMHO would be a high volume, low pressure impeller type pump. Anybody know of one?


I still think the "bursting" my TST comp box exhibits at higher setting may be fuel starvation, but of course I may be wrong.
 

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OC Dmax your right on track. A64 call TST they will tell you about the bursting. Extra fuel supply won't cure it.
 

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A lift pump??





Never heard of the idea...
 

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Ray403Dmax said:
Interesting, so the recommendation for 0psi at the test valve may not be valid. And the fuel system weak link is the common rail fuel pressure and not so much a fuel injector limitation.


It would be nice to hear some input from Quad.

Seems the Ford guys on Dieselstop.com would like some input from quad also.
 
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