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Old 09-26-2007, 04:36 PM   #1 (permalink)
Turbine Doc
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Fuel filtration

Okay folks,

Straight from the horses mouth, per Stanadyne tech line/fuel filter Engineering the OEM on engine filter is a Stanadyne part regardless who's box it comes in, also it is a 5 micron filter not a 10 which is what GM manual says it is as well as some sellers of their boxed brand of the filter.

I shared some thoughts about fuel fitration; had the Engineer I talked to @ Stanadyne done the design vs GM, he would have included a 10 or a 30 micron filter pre lift pump, rather than have the on engine filter as the only protection.

5 micron in his mind was well sufficient for our needs, 2 micron is for common rail, and that also would have a pre lift pump 30 or 10 micron filter were it up to him to spec out the system.

He liked my feeding the beast mod concept, by design the GM fuel filter mgr is capable of supporting 45 gph with proper maintined pressure 4-6 psi, he was concerned with me prefiltering with a GM pump and possibly losing flow, but when I told him I was going FRB-5 Walbro he looked it up in his files, turns out it is a 60gph not 45 as I was told by another source. As it turns out he also worked at Walbro for a while prior to going to Stanadyne.

As for psi vs gpm discussion, maintaining psi for delivery consistency from the IP is what was more important than gph until you get to point where you have neither, sort of what I saw on a IP test bench with lower IP inlet pressure the accumulated fuel in each delivery measurement chamber at max output would be from 72mm to 84mm for a avg of 80. When upping IP fuel inlet to 15 psi, across board all measured deliveries per chamber were 79-80mm.

Excessive return unused 60 gph vs factory 15 would only lead to accelerated fuel filter replacement, so maybe a good thing to "polish fuel" as each time crossing filter more stuff would be caught, I told him about vac switches to alarm when a filter got to that point and he liked it as well.

So with that information, I think I'm just going to stay with the 2 filter arrangement 5 micron on engine as the final, and the 10 pre lift pump Racor 460 element, instead of adding a 3rd 2 micron element just prior to the IP.

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Old 09-26-2007, 05:25 PM   #2 (permalink)
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Wow. Excellent info, Tim! Thanks for the research!



1995 2-door 1/2 ton Tahoe 6.5 TD. Red/Silver Two-Tone with Grey Leather. Positraction Rear End, 3.73, 4L80-E, 4WD, HyperTech chip, Flowmaster crossover and downpipe, modified intake plenum, '97 air cleaner assembly with factory filter, 3" lift, Model 280 flex-a-lite electric fans (which solved cooling problems caused by body lift), Centerline wheels, PowerSlot brake rotors, 175K miles. Hellwig front and rear swaybars. Rancho adjustable shocks on all 4 corners, Heath Remote mount FSD. 0-60 in 9.5 seconds.

1999 3/4 Ton Suburban 6.5 TD SLT Kid Hauler. 124K miles. Black with Tan leather. Hellwig sway bars front and rear. Flowmaster downpipe. Remote FSD under-the-bumper with Kennedy 72" harness and SSDiesel FSD Cooler. PowerSlot brake rotors. THIS RIG IS FOR SALE HERE: https://www.dieselplace.com/forum/45-...condition.html
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Old 09-26-2007, 06:06 PM   #3 (permalink)
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Very good reading and research

McRay 1999 Chev 1 ton 3500 6.5 automatic Trans
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Old 09-26-2007, 09:04 PM   #4 (permalink)
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Thanks for that info TD....it is appreciated...
07.5 LMM DMAX, 2500 HD, LT, PCV re-route, resonator delete, Edge EVO/RACE - level 2, colibert gooseneck hitch, Tekonsha PrimusIQ Controller, Bushwhacker Pocket flares, Scorpion color match bedliner and rockers, levelled, 285 General AT2's, AFE 4" exhaust, PPE tierod sleeves --> coming soon: lift pump, Trans Go Jr.

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Old 09-26-2007, 09:14 PM   #5 (permalink)
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Great info. It's good to get from someone that knows the system well.

"Feed the beast" might be a mod to add to the list.
Look here-> GM 6.5 FAQ's <-Look here

1998 K2500 4x4 - Cheyenne Long Bed, 6.2 / 6.5L Repower ceramic coated pistons, std compression
Stock 6.5 - 168,000 mi - Loose Balancer, Broken gear case, Broken Crank, Broken block - #2 main journal
FSDCooler relocated to the bumper, dual 105A alternators, high idle switch, otherwise stock (for now ), 4.10 gear, purchased /w 134000 miles.
Oil: Rotella T6 5/40 (Synthetic) Fuel: B20

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Old 09-26-2007, 09:15 PM   #6 (permalink)
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Iíve been rethinking my fuel system these past couple of weeks since I started freeing up the restrictions in it with the IP Inlet Modifications. I installed a 2 Micron Racor R30 over 2 years ago while keeping the Factory Filter in place. Removal of the Factory Filter, in my opinion was another way to unrestrict flow. The Water In Fuel light is not that important to me and I donít really believe I need the heater. Time will tell.

5 Micron isnít bad, but why not go down to 2 anyway? Common Rail or not.

There is no such thing as Overkill Filtration as far as Iím concerned.

Once I get the Walbro in place, Iím removing the R30 and going with an R90 10 Micron followed by a 2 Micron spin-on, both pre-lift pump. Iím gonna take your advice and go with the vacuum switch to see when it needs to be changed. I picked up an adjustable Hobbs that is preset to 9Ē, but I will readjust down to 2-3Ē seeing that the filtering capacity is huge. Readjust if necessary. The filter heads will probably support upwards of 1000hp and have a life expectancy 10 times beyond stock.

Do I need it, no. Just looking for something to do. Kinda like when I made my Bypass set-up and increased the oil capacity to 12qts. Next to Filtration, I like extra capacity in the fluid departments.

Between my fuel filtering capacity and my Oil Bypass set-up, I will probably be able to go 25,000 miles before a filter change.

Note on the Walbro: Numerous places on the internet, have it rated for 45gph. First Iím hearing of 60.

Good info TD. You got me started on this...
'06 ECLB LBZ...
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Old 09-26-2007, 10:40 PM   #7 (permalink)
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45 is what I though as well from my sources, maybe Stanadyne guy misread the chart he was looking at, either way 45 or 60 is significantly better than GM pump, pressures we operate at and "blowtorch size" hole in our squirters by comparison to common rail at 20kpsi vs 2200 ours runs 2 micro probably not even noticed, 2 micron is size darn near microbial in size I think size of our squirters could pass gallons of2 micron stuff forever.

Here is some info on fluid filters http://www.filtercouncil.org/techdata/tsbs/89-5R3.pdf Gets kinda deep in description toward the end, there is nothing wong with running 3 filters just not necessary for the 6.5 IMO.
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Old 09-27-2007, 07:04 AM   #8 (permalink)
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I'd save that 2 micron post lift pump. Lift pump is somewhat "sacrifical" in my mind. Pre-filtration would be good to get the lumps out, but you have more to work with pressure-wise than vacuum wise. It will be easier to "push" the fuel through 2 micron than suck it through a 2 micron.

Flow/GPH is variable on delta P across the filter. You could blow 1000 GPH across those filters if you want, but the pressure drop would be extremely high. The rating points would be needed to compare. Either of the two 45 or 60 would be prudy accurate. Just one would have a greater delta P.
Look here-> GM 6.5 Reference Material & FAQ's <-Look here

Diagnostic Links & Common Failures: Turbo System * Lift Pump/OPS * PMD * Stalling

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Old 09-27-2007, 08:19 AM   #9 (permalink)
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Originally Posted by Billman;2028614;
I’m removing the R30 and going with an R90 10 Micron followed by a 2 Micron spin-on, both pre-lift pump....
Better to mount the 2 micron spin on post lift pump up close to the IP.

1. LP could fail and send pieces to the IP.
2. System build up from age. Hose deterioration etc.

As the system ages "gum" varnish etc builds up system wide. From the hoses breaking down to fuel line deterioration to a bit of fuel residue sediment etc. Thats why its good to run clean fuel all the time and at least use a cleaner fuel additive ocasionally (I don't know but at least every maybe 3-5 tankfuls or at oil changes?) to help keep system clean. The filter near the IP will catch more line "gum" and hopefully allow the clean "polished fuel" to keep the IP and injectors clean.

I believe thats why the ULSD causes all the problems in older trucks. Its not really bad fuel. For one its just cleaner and flushes all the crud out and unfortunately clogs IP's and Injectors depending on system lines, buildup, and filtration setup.

I did not mean anything by questioning psi vs gph thought. Just trying to point out that if you get a pressure drop at IP inlet then the significant flow restriction is before it. I can't remember all the techie stuff but it takes pressure, velocity, area etc to fully characterise flow. But monitoring a pressure gauge at IP inlet tells the biggest part of the story.

I think the feeding the beast mod is really good especially for modified trucks and required for increased fuel delivery programs. I gringe when I see my guage drop to ~.5-1 psi under load measured at IP inlet and believe the OEM system is marginal for stock setup and undesized for more HP.
1997 K2500 6.5TD 5spd ~ 140,000 miles, remote FSD, remote oil filters, T.M., 3"DP & 4" exhaust. Gauges: EGT, boost, fuel pressure, Prodigy, B&W Turnover ball.
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Old 09-27-2007, 08:55 AM   #10 (permalink)
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I'll take my chances and mount both pre-lift pump. Pressure readings are within inches of IP. I started at the front and am working my way towards the tank to remove any restrictions.

The new pump should take care of all the flow/pressure problems.

The last restriction I need to overcome is the sock/sending unit. I have a new one waiting to go in. I would like to modify that before it makes its way into the tank. GM/Delphi didn't do the nicest job on bending the lines below the lock ring/mounting plate. They started life at 3/8, but the bends in that line brings it down below 5/16 from the looks of it.

I'm pretty sure I'll have all the fuel I need. Very clean fuel.

'06 ECLB LBZ...
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