FASS fuel pump

[computer monkey]

I was interested to see if anyone has tried this fuel pump on a 6.5? Also will the 98 6.5 fuel pump handle the 15psi, if not does the FASS fuel pump have a regulator to turn the pressure down?

Thanks

[Turbine Doc]

I've not run a FASS but as far as 15 psi to IP I just saw recently an IP running 20 psi on a bench did not pose any problems, one thing that I observed was the final delivery per injector was more evenly balanced at higher IP supply pressure. At 6 psi feed pressure, injection volumes averaged 80 mm, some 70mm, and some 82 mm, with 20 psi all volumes per injector were 80mm, what this all means to performance I'm still sifting through, but generally even delivery has got to better (maybe/maybe not)????

I will say that since opening my supply fitting on the IP and outlet of the fiter manager to the engine to full 1/4" ID has netted some seat of pant gain, and also keeps my supply pressure above 2 psi on hard accel where it used to drop to .5 psi. I'm studying different pump offerings looking for the one that will meet higher psi and gpm, I'm looking for one that will maintain 7 psi minimum for all conditions, that if it fails will still flow through, JK has one that looks promising, he uses on D-Maxes.

[JohnC]

I haven't doen any testing to support this, but it would seem to me that since the injection pump has an internal transfer pump feeding the fuel solenoid and a pressure regulator bypass, it would not make any difference what pressure the lift pump was capable of, within reason. Excess pressure should be bypassed and even if the (lift) pump overwhelmes the bypass, that pressure should be moderated by the internal transfer pump.

Of course, this applies only to the electronic pumps. Excess pressure in a mechanical pump will raise havoc with the housing pressure control circuit.

[jspringator]

John C, Kennedy made a similar observation either in this board or the Place. As long as there is not a vacuum, there shouldn't be a problem. I checked my pressure at the water drain T and it does drop to nearly 0 at full load, but I don't think that is a problem. My idle pressure was high. I have to back my throttle out for either coolant tamp or boost anyway under long heavy load; fuel is not my limiting factor. I think my intercooler will solve both my boost adjustment and my coolant temp problem.

[Hubert]

Interesting.... Just thinking about it.

1) The engine will run fine with no LP for light to medium light load. IF... everything else is OK ie fuel filter good and air tight fuel line etc right.
2) Excess pressure just returns to tank.
3) If a problem heavy load the IP can starve for fuel and truck stumble.

What about the many complaints aboout a sporadic oil pressure switch and intermittent LP and/or other fuel metering issues.

Could some variations be temp change in fuel? The fuel manager heats fuel to maintain a certain viscosity for the IP to precisely meter fuel right. At low flow I would think its easier to maintain steady state temp ie the OE LP measely 2-3 psi. Mix in cycling LP or flow change and maybe causes a temp/viscosity change and metering changes slightly. And/or a constant flow through might also steady viscosity with even temp than variations due to 0.5psi through small fuel line and flow path through manager and engine valley etc.

How much difference would fuel at say 140deg F make if you quickly cooled it to 70F and vice versa????

[Turbine Doc]

Leveling out of the injector flows at the higher lift pressure on the test bench fluid was 140F, in my particular case what led me to quest for more fuel delivery, was being hooked up to my GN trailer loaded to about 12K, climbing a hill 2200rpm, no more acceleration, boost, or high EGT 750F was max, I was out of fuel and could not force anything out of it hard as I tried, snap-on scanner said 100% engine load and max fuel 80mm (reflashed PCM)

Last year I was going to go to experiment with dual parallel OEM lift pumps, thread is here somewhere, the thought being more gpm is needed more than psi, well when plumbing for that I found the the General's design is supplying the fuel filter mgr with 1/4" ID , but feeding the IP with 3/16" OD. IP IMO is starving for fuel when loaded up.

I had some special fittings made up so I'm plumbed 1/4" ID all way from tank to IP now, really made a difference same load same place and I can maintain to 75mph, could go more but 75 is plenty fast for that load.

From what I saw on the IP bench test a couple of weeks ago, leads me to believe IP can benefit from both GPM & PSI upping so long as we don't go too far with it. How far is too far and temps and such as limiting factor info TDB for next time I get over to test shop 100 miles away.

When I get some of this post Katrina home repair out of the way I'll do some more R&D (wife looks at me real ugly like when I mention I want to work on the truck, "why is it broke???", no I say sheepishly, "then get to fixing what is broke" Yes DEAR" tail between my legs), I have pics over at the Place, I haven't set up an account to link here yet of what I'm describing.

[Hubert]

Tim,

Looking forward to seeing what R&D and data reveals when you can. I do think different steady state psi or flow can affect IP performance and was thinking why. I don't know what actual fuel temps may reach 140F seemed like a reasonable temp for fuel to reach with low to no circulating flow.

More argument for higher psi and thus more GPM flow is: isn't the basis for design of the pump mounted driver to be cooled by excess diesel circulating through the pump cooling FSD&IP and returning warm fuel to the tank. Wouldn't a pump using all the fuel and not circulating excess get appreciably hotter than an IP with circulating excess fuel. High milage pumps have a problem starting on "warm thin diesel" so temperature would have to certainly affect power/performance at least to some extent. [Or is it the IP gets warm and clearances open up due to thermal differences??] When I add certain additives that change lubricity (and I am guessing viscosity too) of diesel I can feel a shudder launching easy (manual tranny)and its because IP has a little difficulty trying to precisely meter fuel at low load/low rpm.

Improved metering variation and some psi output variation of IP may pale in comparison to the fuel starvation but it could have a nice little subtle performance improvement too. I can feel a sublte difference with ambient temps and fuel quality.

I am not sure what the disadvantages of higher excess returned fuel is. Might only affect colder climates where the fuel heater is really needed.

Again I appreciate your time in posting R&D data.

Hubert

[JohnC]

Random thoughts:

Unless you overwhelm the bypass valve with volume, you will never achieve a housing pressure greater than the bypass setting, which, IIRC, is about 6 psi. A 100 PSI pump will still net a 6 psi housing pressure under these circumstances.

After thinking about it, I'm still not sure, but there may be an advantage to having 6 psi at the inlet to the internal transfer pump over having minimal positive presssure. I think it depends on the nature of the pump. A positive displacement pump will pump the same volume of fuel at any positive inlet pressure. Negative pressure here is definitely not good, however.

Hot Diesel fuel has less energy content by volume than cold fuel due to decreased density.

When I had to replace the lines going to the fuel manager they were 3/8"ID, iirc...]

I think there definitely is a benefit to having excess fuel circulating under all conditions, especially if your FSD is a PMD.

YMMV, batteries not included.

[Turbine Doc]

3/8 Od on lines TO the manager, look at what comes FROM the manager, easy to check undo the clamp for IP supply, like trying to supply through a straw vs garden hose, actually if it could handle the environment/pressure, I'd surmise that a straw carries more fuel than the current supply hose FROM the manager does.

I will post some real numbers from the flow bench once I get an opportunity to do so. I run gage equipped full time on lift pump outlet, and there is night and day difference between what was pressure and what is pressure delivered, seat o pant I see a change, probably at 1st of year if Suncoast puts on another dyno event I hope to see an improvement on the rollers as well.

[Turbine Doc]

http://www.imagestation.com/album/?id=4288826053

See if this link works, I posted some of the images of plumbing mods to the filter manager

I think you have to set up an account to view them (free to register)

[rjwest]

Running 2 LP's in series, approxmate double s the fuel pressure,
normal 6 goes to about 11 - 12,
Can shut 1 off, other will draw through inop
Lift Pump, like a check valve,

Use 2nd LP when pressure drops on a hard pull,,,

[Kennedy]

I guess my word of caution would be that teh FASS is a big noisy can opener sounding beast. I have had mixed results with my KD lift pump on the 6.5 so far, but AWESOME results on the Duramax.