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I called Oregon Fuel Injection today to talk with them about the new Racor kit. I asked them what they thought about switching the filter from 10 micron to 2 micron. They could have sold me either one, but they said their testing showed that having both the primary and secondary filters being 2 micron caused too much stress on the facotry pump.


I was interested in what everyone elses opinion is on this subject. I'm thinking I might want to go with the 10 micron filters now, and upgrade to the 2 micron filters after I figure out what I am going to do about a lift pump.
 

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I have been running the 2u Racor as a primary for about 10k. I have no idea if it is creating problems for the pump. I do plan to add a lift pump. The 2u will plug up quicker than if it was in the secondary position, so I carry at least one spare.
 

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if that were the case wouldn't a vac test @ the test port show too much vacuum?
 

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How much vac is too much? I assume cavitation is the danger for the pump?
 

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I went with the standard Racor arrangement due to the fact that Racor suggested a two stage filter system was more effective and that's why they chose to set it up that way.


Made sense to me when I talked to the engineer who called me in response to a voicemail message I'd left requesting information on the kit and specifically the 10 micron versus 2 micron filter question.
 

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Not what I wanted to hear...
 

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I have a Racor R660 (2micron) installed as a Pre-OEM along with the stock factor OEM. I went through a fair amount of expense to make sure when I added my second filter that it added a very minimal increase in suction (as measured at the test port). I have posted my results before, so I will be very brief here. Basically the before and after vacuum measurements at the fuel system test port (using a Kent-Moore Vacuum Gauge) were the same. The LSB on the vacuum gauge is 0.5 inHg. So I can effectively measure to 0.25 inHg. I could not measure a difference. This validated a filter insertion loss of 0.1 inHg (which you can get from the Racor specs). I recently measured my set-up with 4000 miles on both filters. The vacuum level has increased by about 0.5 inHg. We have approximately 5 inHg of head room before this measurement becomes restrictive (at least according to the numbers that I have read in the service manual - about 7 - 8 inHg max under test conditions listed in the manual).


Possibly what this individual meant was that as both 2 micron filters are used up, the summation of the restriction will be larger. This is true. This just requires one to be on top of the situation with a good maintenance schedule.


On edit - if you want to get maximum life out of both filters, then the 10/2 combo would be good. With the 2/2 combo, I anticipate changing the Pre-OEM filter more often. I will accept this downside (expense) to get the extra filtration offered by this combo.


Thats actually the good thing about this set-up, you can choose the combination that you want. For me, it is 2/2. For others it is 10/2. At least you have the choice and you can change your mind later



Edited by: OC_DMAX
 

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Based on info Zeeb passed to me earlier I ordered my Racor kit, from Greg, with a 10u filter. Thanks for the info Zeeb!!
 

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IIRC - vac spec measured at the test port is 3.5-8 InHg. <3 is a vacuum leak and >8 is a clogged filter. Eric please correct me if i've misquoted you.


i've checked 4 stock trucks, they were anywhere from 3.5-4.75 InHg. i only measured mine after the cat filter install and it is 4.25 InHg. my buddy's dmax with my kit reads 3.50 InHg. my other buddy's with my kit reads 4.0 InHg. and the last truck i tested was also 4.0 InHg. so how could it strain the factory pump too much and still be in spec? the truck i took the 17,800mi CAT filter off of measured 4.25 InHg. If I am missing something please let me know. I'm just trying to figure out how having 4.25InHg after running almost 18k on a filter is a bad thing. still well within spec right?
 

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Someone posted the pump max vacuum quite awhile ago and we aren't even close. If we exceed the max suction head it will be evident because the truck will run like it has 8 bad injectors. Later! Frank
 

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Based on what most have done.... I went with a BIG 2 micron secondary filter. Big filter gives you the flow. It's been measured before.

Have not heard of any problems....

Diesel Injection Services said the same thing. I said yea yea, just send me the 2 micron.Edited by: hoot
 

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Are you measuring the vacuum at idle? If so, the fuel requirement under load and especially towing would be vastly increased, and there could be pump issues under this demand. I believe this would be true even with mega sized filters. Does anyone has a cab mounted gauge that is running two 2 mic filters? Does the vacuum stay within established designed limits? I would appreciate the real world results. I've read of fuel starvation problems on some dyno runs. I know many aspects of this issue have been beaten to death, but I am still in the look and learn stage figuring out what would be best for me under my circumstances. Would frequent changes of two 2 mic filters keep within the designed vacuum under heavy loads? Do I need to run a guage, and finally what are your experiences in terms of filter change frequency, both primary and secondary? Thanks for any input.
 

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Are you measuring the vacuum at idle


Yes, I am measuring it per the GM Service manual. This test is used to determine whether a filter is causing a restriction. This test must be done statically (vehicle not moving). And yes the vacuum level changes as a function of load and MORE IMPORTANTLY acceleration. The 8 inHg limit is for static measurements. Some of the people who are running the "big power boxes" and accelerating quickly are probably pushing 15-20 inHg with just a single filter (a guess on my part). This is a much larger issue than two filters on a stock truck.


The factory filter is rated at 48 gph. The R660 is rated at 60 gph at a spec'd drop of 0.1 inHg at this flow rate. We are not running anywhere near 60 gph. The R690 filter is rated at 90 gph, don't remember the drop.
 

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I just saw a new Cat stationary engine with the same filter head and 0749/0750 filter as we are running. It was a big six either a 3406 or C15. Considering the difference in fuel consumption between that and our trucks I can't believe it will cause any problems unless run clogged for extended periods.
 

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RE: 2 micron and restriction, pump stress. The dirt that the OEM filter allows to pass would definately reduce pump life vs. clean fuel with slightly elevated restriction..
George Morrison
 

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Jeli... that is SOOOOOO true!! I grew up around diesel trucks...and all of my Dad's CAT 3406 engines now have a Bosch injection system on them...what do every one of them have...two filters stacked. Those engine flow a LOT of fuel. Granted, they have a different pump design than we do. However, the theory is still the same. These 2 micron CAT filters are designed to flow a LOT of fuel through them with very little restriction on the pump. I say put the 2 micron filter on and forget about it for several thousand miles.
 

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I have dual Racor filters pre-OEM. Right now I have a 30u and 2u. They have 7,000 miles on them and 10,300 on the OEM. The truck has never shown any signs of fuel starvation and runs great. Next filter change I will replace the 30u with a 10u.
 

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Several have tried to figure a safe way to get a guage in the cab. I too have looked into it and have found it to be very expensive. I have 3 filters on my truck. First is a 10um pre lift pump, then OEM and then a 1um Mega. I have the pressure set at about 1/2 psi at idle. Reving the engine does not show any significant drop in pressure. I also seen around 4.5"Hg when the pump is off. That is the 3 filters, pluse going through the lift pump. I did see the idle smooth out with the lift added.
 
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