What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Fly EFII FF-2 Pre Filter - Not what it's cracked up to be?

bullojm1

Well Known Member
About a year ago I switched out my Airflow Performance fuel pump for the Fly EFII pump due to some low fuel pressure readings I would occasionally get on my IO-360. I elected to use their FF-2 90 micron pre-filter as it was much smaller than the AFP filter, and I sort of liked the idea of just buying a new one every year. It was a great upgrade - the Fly EFII pump was much quieter than the AFP pump.

During my annual this year, I came to the checklist item of "Clean and inspect the fuel filter". Well, this should be easy, I can just order a new filter on ACS or from Fly EFII. Well, $45 for a new filter + shipping seemed a little high, especially for a filter I know they sourced from somewhere else. So I pursued my favorite game of figuring out who makes a part someone else brands for their own and buy it off of Ebay or locally to save a buck or two.

It was a lot more difficult of a task than I thought it would be! It took a good hour, but I isolated the filter to being a Baldwin BF7519 / NAPA Gold 3269 / Donaldson P550446. NAPA had them in stock locally for $45, and Ebay had it for $22 shipped. Cool, I just saved enough to buy a nice (small) steak dinner.

Fly EFII Image of the filter (lower, FF-2 Pre-filter)
fuel_filters2.jpg


A picture of the Baldwin BF7519
DSCN7351.JPG



The one thing that bothered me was I couldn't figure out how the EFII fittings worked to adapt this filter to an AN6 fitting. The first thing I noticed was what appeared to be a compression fitting on the ends of the filter. Sure enough, that is what they used:
DSCN7353.JPG


I was sort of shocked. I know it does not experience any pressure as it is on the intake side of the fuel pump, but I would expect something a little higher quality in the fuel system other than a compression fitting.

When I took the compression fitting off of the filter housing, some of the rubber grommet had deteriorated and left some small pieces of rubber inside the filter connector. Now, I don't see this as a safety issue, as the only time the rubber could erode like this is when the connector is removed. But still, not what I would expect in an aircraft fuel system.
DSCN7354.JPG


Knowing the part number, I wanted to know what the filter micron level was. It was advertised as 90, but the only reference I could find was 149/150! (https://www.michelecaroli.com/info.php?oempartnumber=BF7519&donaldson=P550446, https://www.finditparts.com/products/2525254/wix-filters-33269). I could be wrong here, two references to the same filter both agree.

There's just too much here that I don't feel comfortable with to keep using this filter. I am planning to switch to the AndAir FX375-MK serviceable filter now.
 
Suggest you go back to the AFP filter, I use a Flow-ezy myself. The Andair is to small IMO.
 
Suggest you go back to the AFP filter, I use a Flow-ezy myself. The Andair is to small IMO.

Agree with Walt’s assessment of the Andair filter. I ordered the Andair pump, filter, and valve package when I built my RV-10. Took one look at the filter when it arrived and decided to use it on my lawn mower instead. Used the AFP filter instead, and as Mike pointed out, you only need to clean the filter screen at zero cost.
 
Agree AFP

Agree, AFP is the way to go.
Purpose built by or for AFP and easily serviceable.
It also has a relatively large screen area and if you were to accumulate debris
it would certainly take a lot to stuff it up.
I have 2 in my 10, one under each seat.
 
I assume one would be flamed if they mentioned that the filters provided by SDS for their systems are very high quality and are cleanable? That was just one of several reasons I chose SDS over EFII.

Not trying to poke the bear. Well, maybe just a bit 😉
 
Pre-filter issue

For those using the EFII pre-filters although one does not need to be concerned about fuel leaking the issue is if you don’t get a good seal you will get air entering your system. (Ask me how I know). The air bubbles will damage the seat on the fuel pressure regulator. (Air bubbles make the regulator chatter). A good test is to use a clear fuel line (temporarily) to visually look for air bubbles in the fuel rail.
 
Thanks for the advice all! In my head I had it out that the AFP fuel filter was so much longer than the Fly EFII FF-2 filter. Turns out the AFP is only slightly longer - only 1/4" difference. Should be an easy retrofit. I gain a lot more filter surface area otherwise used to mickey-mouse a compression fitting to an AN6 fitting.

DSCN7356.JPG
 
EFII Post filter

Anyone have the specs for the EFII post filter? Specifically, the filter sq in. area? The billet machined 10 micron from ACS looks good but would like to compare filter areas. SDS I believe uses a 40 micron post filter and basically the same or similar systems. I would not want to blind the post filter causing the spring to lift. (It's not like getting access to the tunnel is easy for everyday filter cleaning)
 
Filter inside

Anyone have a used EFII post-filter they are willing to cut open and look at the filter media? I plan on doing it next annual but that is a way off.
 
What does EFI use?

Can someone give me the specs for the EFI (Ross) filters? I understand they are cleanable and that is a plus. The web site a little troublesome to navigate. Thanks
 
I replaced mine with a Flow-Ezy 3000 series 3-AN6-74. It can be found in the Flow-Ezy Motorsports Catalog. They don't want to hear that it is for an aircraft, so just say it is for an "off-road" vehicle. :)

Very close to the overall length of the original EFII filter. I used the original tubing with it, but later remade the tubing so it fit perfectly. It is also slimmer than the EFII filter, so I had to put a different sized cushion clamp around it.

Before:
IMG_5013-M.jpg


After:
IMG_5022-M.jpg


It is serviceable by just unscrewing the canister to get to the filter element inside which is mesh stainless steel screen that is easily cleaned.
 
The post-filter only needs to have small enough filtration to protect the injectors - nothing else is needed. 40 micron is sufficient for that - smaller is not needed. Go do your homework on the EFII/SDS history, who built what, who marketed it, who designed it. That's all I'm gonna say :cool:
 
Digging this thread back up, now that I'm gathering goodies for the winter annual... I'm going to replace both the pre and post filters. I'm guessing based on Bruce and Walt that the 90-micron pre-filter I would get a Flow Ezy 3-AN6-74 74-micron, and the 10-micron post-filter I could get a Flow Ezy 3-AN6-40 40-micron? I can't seem to find any pricing info. How many AMUs are we talking here?

Anyone ever heard of / experience with EMUSA Racing? Just random Googling and research shows they have a reusable 40-micron filter. Price screams el cheapo though. https://www.speedyracer.com/40-Micr...N6-AN8-AN10-UNIVERSAL-HIGH-FLOW-TURBO-1007984

Who else other than AFP (and maybe Ross/SDS) to consider?
 
Digging this thread back up, now that I'm gathering goodies for the winter annual... I'm going to replace both the pre and post filters. I'm guessing based on Bruce and Walt that the 90-micron pre-filter I would get a Flow Ezy 3-AN6-74 74-micron, and the 10-micron post-filter I could get a Flow Ezy 3-AN6-40 40-micron? I can't seem to find any pricing info. How many AMUs are we talking here?

Anyone ever heard of / experience with EMUSA Racing? Just random Googling and research shows they have a reusable 40-micron filter. Price screams el cheapo though. https://www.speedyracer.com/40-Micr...N6-AN8-AN10-UNIVERSAL-HIGH-FLOW-TURBO-1007984

Who else other than AFP (and maybe Ross/SDS) to consider?


I’d go with the Holly 162-551 100 micron pre pump and the 162-550 10 micron post pump filters. They’re very high quality and have replaceable filter elements.

https://www.holley.com/products/fue...and_filters/filters/efi_filters/parts/162-551

https://www.holley.com/products/fue...and_filters/filters/efi_filters/parts/162-550
 
Last edited:
Filters for EFI systems

I was not going to upload these pictures but in light of recent discussion thought the VAF subscribers can review and make up their own minds. (Seems normal for VAF readers) Since the fuel system and its reliability and integrity especially for an electron dependent fuel system was important have been reviewing several options. A friend of mine who races airboats with Lycoming engines put me on to a filter he recommends. After researching FUELAB seems their product and documentation is pretty well done. (Please VAF review and let me know what you find) After my last conditional I opened up FF1 and 2 and found the prefilter almost spotless. I am not concerned about clogging one of these and with the new set-up wing root seems clogging both in a year almost impossible. I worry more about pressure drop going into the suction side of my pump not filtration efficiency. The post-filter is another issue. It was filthy and had more "stuff" in it that I thought possible. The new set-up will still contain only one post filter. It is paper and replaceable and can't wait to see the first filter removal. Fuelab does make a glass filter for this application, but it is 6 micron and will wait to see what the 10-micron filter looks like. Notice the O-ring used is internal and fits nicely on the output filter housing. There is absolutely NOTHING wrong with the Holley filters and I have shown pictures of their 100 gph and 175 gph units. I wanted a filter with AN6 fittings on each end already in place. I'm sure the Holley's will perform fine. Fuelab makes a nice 100-micron pre-filter that would work well in non-wing root applications.
 

Attachments

  • filters2.jpg
    filters2.jpg
    234.3 KB · Views: 91
  • filters1.jpg
    filters1.jpg
    165.7 KB · Views: 66
  • filters.jpg
    filters.jpg
    138.8 KB · Views: 73
Picture of internal O-ring

Left off this picture. The 100-micron filter is stainless.
 

Attachments

  • Screenshot 2022-12-10 202846.jpg
    Screenshot 2022-12-10 202846.jpg
    115 KB · Views: 74
Last edited:
The Holley 162-562 and 162-563 filters that SDS uses are 40 micron. We use them on our wing root filter system on the RV14----different length 40 micron filter for the RV10. In 3+ years of doing root filters, we havent seen any issues at all.
Once the system goes through the initial flushing of the lines/hoses, and the post filters are cleaned, as long as the tanks have clean fuel you shouldnt have any issues at all. We have several discussions with Ross about this, mainly because of the automtive injectors. Conversely, AFP uses a 74 micron filter as its pre-filter upstrean from the boost pump. Yes----they do have a 40 micron version.

Tom
 
The Holley 162-562 and 162-563 filters that SDS uses are 40 micron……
Tom

So Tom, it’s good to hear that no problem have been observed with the 40 micron pre pump filter. Do you think the 100 micron is too small? Do you think they could cause problems on the suction side of the pumps? That’s the only potential problem I can think of if running that fine of a filter.
 
Suggest you go back to the AFP filter, I use a Flow-ezy myself. The Andair is to small IMO.

+10

I just helped a hanger neighbor deal with an ugly fuel system problem. when the troubleshooting was done, it turned out that he got a good dose of some white, fibrous material in his fuel tank. servo strainer was full of it and was constantly plugging the restrictors, as it was also bypassing. Unsure if someone dropped part of a paper towel or one of the gas providers had a filter coming apart in their delivery system. No mass spectrometer in my hanger :)

He had an andair filter and it couldn't handle the debris load and was bypassing, allowing this stuff to also plug the strainer in the servo and it also bypassed, making a mess and requiring a tear down of the servo.

By visual examination, the AFP filter looks to be almost 3 times the area of the andair. Unsure if the outcome would have been different with an AFP filter, but it seems he would have had a 3X greater chance of dealing with this issue without filter bypass with the AFP. We often only think about the few random pieces of debris that might get in there and not a problem like this. My experience now tells me that those type of issues are out there and therefore, filter size matters. I talked ot Don at AFP about this and he has seen a lot of issues with FBOs not changing out filters and causing similar problems. Apparently they have a documented time in service limit and once past this, the paper starts to breakdown and go out with the fuel. I speculate that he knows better and why he made such a large filter.

Larry
 
Last edited:
Since we are including post pump filters in this thread, I thought I'd offer up that I use the tried and true GM fuel injection filter on my Rocket. I figure that since my fuel system is essentially "automotive" at its core, why not use the filter that has proved its worth on MILLIONS of GM cars and BILLIONS of collective miles? I dont know the micron rating and I dont care. If it keeps GM out of warranty work for trash in the injectors, thats good enough for me.

Its about $12 bucks and I replace it at annual.
 

Attachments

  • IMG_20221211_081843799.jpg
    IMG_20221211_081843799.jpg
    306.9 KB · Views: 134
Last edited:
Mark--40 microns is about .0015 inches---100 microns is about .0039. I would think tht on the suction side, it would take quite a bit of debris to plug the screen---especially the size of the screens on the Holley filters.

Tom
 
Michael----I think thats pretty much what Robert did----YES GM has millions of these out there, and they work. You would think that GM and its engineers thought through the micron rating, knowing that there was a possility of some contaminated fuel the customer could acquire----since they cant control that.

All I know for sure is that 40 microns is pretty small, and those wanting to use a 10 micron unit thats .00039, thats really small.

Tom
 
A little research on these filters seems to indicate they are 10 microns - pretty fine. Not much of an issue at 50 PSI though (and clean).

My "pre filter" is the screen in the Andair gascolator (I'm using it as a convenient pre filter, not a water trap). Not sure what the mesh size is on that one either, but I've never found anything in it.
 
Mark--40 microns is about .0015 inches---100 microns is about .0039. I would think tht on the suction side, it would take quite a bit of debris to plug the screen---especially the size of the screens on the Holley filters.

Tom

Thanks for the reply Tom! I actually had it backwards. I was thinking that a 100 micron was smaller than a 40 micron. So the 40 micron pre pump filter actually gives better filtration than the 100 micron. Also, if you’re also using a 40 micron post pump filter, that’ll also protect the injectors better than the standard 10 micron. I like that better!
 
Thanks for the reply Tom! I actually had it backwards. I was thinking that a 100 micron was smaller than a 40 micron. So the 40 micron pre pump filter actually gives better filtration than the 100 micron. Also, if you’re also using a 40 micron post pump filter, that’ll also protect the injectors better than the standard 10 micron. I like that better!

No. 10 microns is finer than 40 and will pull more trash out of the fuel. Many sources indicate 10 micron is appropriate for EFI, 40 is appropriate for carbs.
 
No. 10 microns is finer than 40 and will pull more trash out of the fuel. Many sources indicate 10 micron is appropriate for EFI, 40 is appropriate for carbs.

Agreed. I had it backwards and was thinking that the larger the number the finer the filter….but it’s just the opposite. So a 40 micron pre-pump and 10 micron post pump filter should really give you some good filtration.

A lot of automotive pre pump filters are 100 microns, so Tom’s 40 micron will give even better pre pump filtration. The only concern I’d have with that fine of a pre pump filter would be the possibility of of not flowing enough fuel on the suction side of the pump. I’m sure Tom has the numbers worked out and this has never caused a problem.

I think the 40 micron post pump Holly filter that Tom uses is probably all that’s needed for the electronic fuel injectors and possibly prevents fuel starvation in the event the filter were to get clogged up. If the injectors can handle anything smaller than 40 microns, than I can see the potential safety advantage of the slightly larger micron post pump filter.
 
Input

https://www.holley.com/blog/post/how_to_choose_a_fuel_filter/

This article describes in general requirements and possible data for filter choices. We need to understand and choose what we are comfortable with. All of us are using different types of pumps, injectors etc., and some are more susceptible to cavitation and other issues. The dual electric fuel pumps used on the 2 major EFI systems use a pump that is not very tolerant of air in the system and cavitation. Since the maximum pressure that the suction side of a pump can generate is -14.7 psi and anything close to this reduces the vapor pressure and creates cavitation in the system. Heat, altitude, pressure drop (elbows, low micron filters), mix in mo-gas and we create lower vapor pressure and then the dreaded cavitation. I worry more about insuring we get a sufficient amount of fuel to the suction side of the pump than most other issues. After the pump we don't need to worry as much about pressure drop as the pump can deliver 2- and 3-times more positive pressure to overcome a tighter filter. Ross is a very good engineer and he understand the limits his injectors can withstand. I would have him in my pit crew anytime. The rest of us need to understand what our injectors can tolerate and go from there. For me as long as the filter has the capacity (filter sq footage) and capability to filter fines (The finer the better in my book) I will use it. Personally, I like filters with AN6 fittings already built in on each end without the use of extra fittings but once more the Holley filter is fine. (It does not have AN6 fittings built into the billet housing) Also being able to easily inspect the filter would be good. (Replaceable or cleanable filter)
 
Last edited:
Paper elements - take care

From Airflow Performance:

https://airflowperformance.com/wp-content/uploads/2020/09/FUEL-FILTERS.pdf

A fuel filter should be installed in the system before the fuel boost pump, and after the selector valve. The filter may also incorporate a gascolator. If this type of device is used, then the gascolator should be installed at the lowest point in the fuel system. Airflow Performance does not approve the use of any paper element type fuel filter. Paper element filters will restrict the inlet of the fuel pumps due to their fine filtration and their susceptibility to clogging from picking up water. If the inlet of the fuel pumps are restricted, the pressure on the inlet becomes depressed, this will cause the fuel to boil and the vapor will flow into the fuel controller causing it to malfunction. This problem is not as evident when float carburetors are used, since the float chamber will allow the fuel vapor and bubbles to escape. A screen type filter should be used. The filter size must be based on the total fuel flow through it, not just the engine fuel consumption.

This again depends upon the type of fuel system in the aircraft, returning or non-returning. The filter Airflow Performance recommends for this application is P/N1090079 or 1090079-74. This maintainable filter incorporates a 125 or 74 micron pleated stainless steel filter element with a anodized aluminum housing. It is recommended to use a 40-micron maintainable filter in composite aircraft applications.
 
Mark---our testing included a newly built RV10 with a Barrett IO540, AFP equipped. We installed our 40 micron wing root filters, and there has been no performance issues at all. Granted, its not a SDS/EFii with electronic injectors, but even those planes that we've equipped have not reported any issues.

Tom
 
Where I think you may find some issues is with folks that are running automotive fuels with ethanol. The higher vapor pressures associated with those fuels (especially winter blend) will make them susceptible to forming vapor bubbles in the pre-filter with a pressure drop across the filter. On my IO360, I ended up installing larger, higher flow rated prefilters to get the pressure drop down for the fuel flowing across that filter. The electric pumps associated with AFP, EFII and SDS fuel systems do not like vapor bubbles, and you can hear them complain mightily when bubbles come into the suction line.
 
Last edited:
Where I think you may find some issues is with folks that are running automotive fuels with ethanol. The higher vapor pressures associated with those fuels (especially winter blend) will make them susceptible to forming vapor bubbles in the pre-filter with a pressure drop across the filter. On my IO360, I ended up installing larger, higher flow rated prefilters to get the pressure drop down for the fuel flowing across that filter. The electric pumps associated with AFP, EFII and SDS fuel systems do not like vapor bubbles, and you can hear them complain mightily when bubbles come into the suction line.

That’d be my only concern with running a 100 micron pre-pump filter. The suction side is really the only place that may give you trouble. I know you and I both run ethanol fuel in our airplanes, so vapor pressures and pump cavitation are things we think about and topics we’ve discussed before. Fortunately in my -8, I’ve never had problem and I run a 100/10 micron combo. For systems like our, it’s really important to mount the pumps at the lowest part of the airframe so the pumps aren’t having to pull uphill.
 
GAAAAAH! Heads up all. Just got off the phone with Flow Ezy. They have discontinued their whole performance motorsports filter line. I was all set to order the 3-AN6-74 and 10 filters. They had very limited 3000 series housings, and don't even have the 10 micron filter any longer.

Back to research... :/
 
Agree, AFP is the way to go.
Purpose built by or for AFP and easily serviceable.
It also has a relatively large screen area and if you were to accumulate debris
it would certainly take a lot to stuff it up.
I have 2 in my 10, one under each seat.

Sent you a PM Ernst.
 
EFII Post filter

Just FYI, the EFII post filter is cellulose, (Paper, 10 microns, using it now) along with the Holley 10 micron. (Both seem to work very well to date). After my initial Fuelab 10-micron filter (cellulose) at 25 hours plan to switch out to their 6-micron ceramic filter. I do prefer to not use paper long term.
 
Filter

I will be switching out my stock post filter at the next condition inspection but for another data point, I have 270 hours on the stock filters with no issues.
 
Back
Top