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Old 07-16-2016, 09:43 PM   #1
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Considering Reorganizing Fuel Filtration

I have a Cummins QSC 8.3 540 HO engine.

Filtration system is currently 2 Racors with 30 micron filters (only one Racor is used at a time--I can switch from one to the other but have never done so) which feeds into the 2 micron on engine filter.

I think that replumbing the system so one Racor has a 30 micron which feeds into a 10 micron filter (currently the never used spare 30 micron) and then goes to the 2 micron on engine filter would be better.

Any comments appreciated.

Thanks
Ken
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Old 07-16-2016, 09:54 PM   #2
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There will come a day when you will wish you could simply switch from one filter to another!! Better to have 2 x 10 microns in parallel with one a reserve. If you really feel the need to change, add a depth prefilter such as a Gulf Coast that feeds both parallel Racors.
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Old 07-16-2016, 10:00 PM   #3
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So, you're saying change the current 30 micron filters to 10 micron (leave them in parallel) and put a 30 micron filter in front of them.

I like that idea.

Thanks
Ken
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Old 07-16-2016, 10:11 PM   #4
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You should read Tony Athens' (Seaboard Marine) article for his article on filtration setup.
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Old 07-16-2016, 10:13 PM   #5
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I use two microns throughout, although I've some 10-micron filters on hand I might use in the Racors which are "upstream" of the two-micron filters on the engine. Unless one loads up incredibly dirty fuel, I don't see the need for larger-than two-micron filters.

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Old 07-17-2016, 12:09 AM   #6
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Originally Posted by ktdtx View Post
I have a Cummins QSC 8.3 540 HO engine.

Filtration system is currently 2 Racors with 30 micron filters (only one Racor is used at a time--I can switch from one to the other but have never done so) which feeds into the 2 micron on engine filter.

I think that replumbing the system so one Racor has a 30 micron which feeds into a 10 micron filter (currently the never used spare 30 micron) and then goes to the 2 micron on engine filter would be better.

Any comments appreciated.

Thanks
Ken
What problem are you solving? Have you been having fuel issues? Are you about to change cruising grounds? If it ain't broke, I wouldn't fix it.
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Old 07-17-2016, 04:02 AM   #7
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The dual Racor set up is designed so you can switch the primary filter underway without having to bleed or stop the engine. Putting them both in line would defeat this purpose. Many of us use two micron filters in these dual Racor housings. Divided opinion on whether two or ten is better.
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Old 07-17-2016, 04:12 AM   #8
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So, you're saying change the current 30 micron filters to 10 micron (leave them in parallel) and put a 30 micron filter in front of them.

I like that idea.

Thanks
Ken
Yes. You will need the parallel connection at some point. Don't ask why I know

You may as well put 2 micron in both, I do, but it does depend on your engine. If it creates too high a vacuum you will need to go back to 10.
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Old 07-17-2016, 05:08 AM   #9
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Use the filtration sizes recommended by the engine manufacturer! There are very good reasons to use a larger primary in front of a smaller on-engine. The above-mentioned Mr. Athens discusses the reason why quite well, though note he is also sells filtering products (his big "mud catcher" might be a consideration in front of your current Racor set up if you are super paranoid).

Two micron primaries make less than zero sense to me, why unnecessarily clog your primary early and starve the engine of fuel? There's a reason most engine makers spec a 30 as the primary, though some modern styles use 10's.
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Old 07-17-2016, 06:47 AM   #10
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Either the fuel is mostly clean or it is trash.

Folks attempt to get clean fuel as the price between house fuel and off road diesel is low , they go to a marina and pray..

I think the fuel system should be the chooser of filter size.

For an engine with virtually no returned fuel , the staggered 30-10-2 works fine .

AS the filters will be cleaning unknown out of the fuel.The filters must be EZ to replace , out of the ER is best.

For a DD or other engine that returns most of the filtered fuel a 2 in the primary works just fine.

The ability to continue should a filter in the pair plug ,just by switching a lever is great.

After a few hours all the fuel in the tank will have been filtered multiple times .

The std on engine 10 has little trouble cleaning the few chunks that get past the 2., so lives a long life.
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Old 07-17-2016, 07:21 AM   #11
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I think that replumbing the system so one Racor has a 30 micron which feeds into a 10 micron filter (currently the never used spare 30 micron) and then goes to the 2 micron on engine filter would be better.
If you have the twin-filter unit supplied by Racor, then having the filters in series is not an option. The valve positions are left, right, both (parallel) and off.

You currently have the ability to change primary filters very quickly by just moving a valve handle. This is a really good option to have when you engine start to loose power in the path of an oncoming ferry, in a narrow channel etc.

Edit: And yes, definitely use the filters recommended by your engine manufacturer. There will be sound engineering behind their numbers.
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Old 07-17-2016, 09:21 AM   #12
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For a DD or other engine that returns most of the filtered fuel a 2 in the primary works just fine.
Not so. Detroit exlicitlly specified 30 micron primary for the 53 71 and 92 series 2 strokes. Secondary OEM was a 7 micron. Approximately 2 micron screens at each injector. I knew one old time DD mechanic who has never needed to clean an injector screen.

Ski, how about you?
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Old 07-17-2016, 09:31 AM   #13
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IMO we need to be careful when advising filtration on modern common rail engines. Experience with older engines that would swallow most anything doesn't really apply.
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Old 07-17-2016, 11:30 AM   #14
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Use the filtration sizes recommended by the engine manufacturer!
Repeat after Caltex. Repeat after me. Repeat after shoalwaters. Repeat. We keep trying to reinvent things that engine manufacturers, and on other things boat builders and equipment suppliers, have thoroughly engineered and tested in depth and in ways that we can't possibly do as an owner of a single unit. Why don't we trust them to know what they are doing? Why would we trust someone on an internet forum instead? I don't profess to have engine or fuel system or paint or teak or any other technical knowledge but I believe my engine manufacturer has knowledge. I trust them on how to best filter, I trust them on the lubricants to use, I trust them on what loads are best for running.
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Old 07-17-2016, 11:44 AM   #15
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What problem are you solving? Have you been having fuel issues?
After running for some number of hours the engine surges occasionally, sometimes as much as +/- 150 rpm and it is resolved for some period of time after changing the on engine 2 micron filter.

The thought was going from the 30 micron Racors to the 2 micron on engine was letting some 29 micron "junk" thru.
We've been running the boat since early May (Anacortes to Juneau area) and burned some of what I believe was "old fuel" but at 2-4 gallons an hour it takes a while to go thru 900 gallons.

Next time I change I'll try to cut open the 2 micron filter.

Thanks
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Old 07-17-2016, 12:07 PM   #16
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[ The above-mentioned Mr. Athens discusses the reason why quite well, though note he is also sells filtering products (his big "mud catcher" might be a consideration in front of your current Racor set up if you are super paranoid).

Two micron primaries make less than zero sense to me, why unnecessarily clog your primary early and starve the engine of fuel? There's a reason most engine makers spec a 30 as the primary, though some modern styles use 10's.
I've pretty much followed that recommendation. I have a large Fleetguard 27 micron filter as the primary, dropping to a 10 Micron Racor, then on to a 2 micron on engine filter. Catch the big crap in a large capacity primary and let the downstream filters handle the rest. My engine ran fine (hard to believe) with this big Fleetgaurd at the head of the filtering stream....

All the Asphaltine problems have been resolved now, but at 300 hours this one was still catching crud and running just fine. I'm a fan of the "Mud Catcher" approach...

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Old 07-17-2016, 08:26 PM   #17
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Most diesels pump many more time fuel than burned with the rest returned to the tank. In most cases, fuel is filtered many times. If you ever get a plugged primary while under weigh you'll wish you could simply switch to a fresh filter.
If you have a vacuum gauge between the primary filter and lift pump, you'll get ample warning of filter plugging.
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Old 07-18-2016, 06:24 AM   #18
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Changing to a multi stage system is a good thing.
I currently have a 30 to 10 to 7 micron setup and haven't had any "filter issues" since I set up my system that way.
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Old 07-18-2016, 08:16 AM   #19
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Not so. Detroit exlicitlly specified 30 micron primary for the 53 71 and 92 series 2 strokes. Secondary OEM was a 7 micron. Approximately 2 micron screens at each injector. I knew one old time DD mechanic who has never needed to clean an injector screen.

Ski, how about you?
I use what the mfr's recommend on other peoples boats. DD's and other mechanical injection get 30mic primaries. Some common rail engines spec 10mic primaries.

On my personal boat, I use either 30 or 10mic, depending on what is on the shelf in the shop. I don't stock the 2mic.

I don't think it makes any difference and I don't give it any thought.
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Old 07-18-2016, 09:24 AM   #20
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The engine Mfg do not know how the engine will be installed , or how hard (height and distance) the engine will need to pull the fuel up to and through the filter .

Happily both of my vessels have gravity feed from the fuel tank, so the 2 micron has never been a problem.

Although in most cases" Da Book " should be observed.
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