Fuel Filter Granularity

[edizio]

Hi,

So, I spent some time replacing the pre filters in my sytec bullet filters

This is the state of the paper filter that came out: -

Disgusting.. I replaced with: -

This could be the reason why the fuel pressure was dropping at high rpm/boost on the dyno after there was some residual heat in the system but I'll keep track of it because there could be a number of other reasons. I didn't bother changing the lift pump filter as I think that these don't tend to get that dirty and it's not been in long. Literally, 7000rpm @ 1.8bar after about 8 pulls on the dyno and fuel pressure was dropping from 8bar to 5bar and going lean which meant stopping for the day; I needed to get this fixed so it didn't get worse. It could still be a problem or the problem could just have been vapourising due to the pressure and heat from having an 8micron filter before the pump.

So that paper filter in the image is 8 microns which was sitting before the 044 bosch pump. This isn't really ideal, as I've subsequently found out that it can cause the pump to work quite a lot harder and could limit life (probably causing some level of vapour lock as well). What I've done is dropped in a stainless steel 55micron pre filter into the sytec bullets

I've checked with a few other sources and I'm getting some conflicting responses; some people are saying that 55micron filtering of fuel is sufficient and most modern cars don't even have fuel filters!

Others are saying that you need to filter further to reduce the risk of damaging the injectors.

I don't really think I should be filtering pre pumps at 8micron though, that's for sure.

The current setup is: -

450lph walbro lift pump into swirl pot which feeds 2x bosch 044 fuel pumps (both pre filtered by sytec bullet filters - now 55 micron/was 8), which then goes to the greddy injector rail and feeds both sides. The injectors are ID1000s and do not have the adapters which filter at 7micron per injector.

Any advice would be appreciated; I'd also be really interested to know how some of the other big power cars support fuelling and where the filtering is performed. I guess the point probably is that race cars break and get repaired and thus it's outweighing the costs with the safety measures.

Thanks!

Edited May 27, 2015 by edizio

[scotty nm35]

7 micron is too fine, I run 30 micron stainless mesh and have never had an issue. Anything under 10 will require changing regularly.

If you prefilter a pump with a fine mesh you will cause cavitation, I would say 100 micron would be better, seeing there should be a filter on the feed to the surge anyway, so the surge should only have clean fuel.

Do you have filters after the 044's? That should be the point of smallest filtration.

[edizio]

The 55 micron filters are now before the pump. I have some Earls filters after the pumps but the cartridges were removed because apparently they were restricting the flow. This could have been due to the paper filters that used to be in the previous filters. I expect the issue I saw on the dyno was indeed cavitation.

I was reading that bosch recommend 10 micron and anything over 30 can damage the injectors.

[scotty nm35]

Well I can tell you that 30 micron stainless won't cause the Bosch 1000's to block, (unless you run the little pre-filters in the adapter) and you won't be constantly changing filter cartridges.

[STATUS]

we use earls filters on the outlets of our 044s with one way valves and push close to 600rwkw, they should not the problem.

[edizio]

Very nice setup status. My system is in the boot although I can see the cooling benefits.

I've just ordered some Earls 35 micron filters for after the pumps. Going to keep the 55 micron filters before the pumps to see if that helps. Do you think 55 micron stainless steel filters before the pumps will cause cavitation?

[STATUS]

Very nice setup status. My system is in the boot although I can see the cooling benefits.

I've just ordered some Earls 35 micron filters for after the pumps. Going to keep the 55 micron filters before the pumps to see if that helps. Do you think 55 micron stainless steel filters before the pumps will cause cavitation?

i dont believe in pre pump (bosch) filters... they all have in built screens. i have had to remove plenty of pre pump filters due to flow issues.

ours is only under the car as i also hate feeding surge tanks with lift pumps if its not necessary, gravity does a great job and the simple setup above will not surge ever .... in fact we have run it dry at 2 events without warning lol

[edizio]

So I've had word back from an e-mail I sent to injector dynamics and they have stated that 35micron post pump filters are not enough to protect the injectors even though the article below says anything OVER 35micron will cause injector damage.

I do have the blue adapters but I can't be sure whether or not they contain the 7micron basket filters. I suppose my safest option is to take the fuel rail off and inspect the adapter personally.

http://i.imgur.com/XwgVgfm.jpg

It does seem, upon reading, http://help.injectordynamics.com/support/solutions/articles/131145-fuel-system-filtration, that they do recommend very fine filters before the injectors.

"Recommended filter quality: nominal rating 5µ, minimum 82% capture efficiency according to ISO/TR

19438; dirt particles >35µ are not permissible. The basket filter in the injector serves only to catch

residual particles. Nonconformance of the recommended filter quality can cause damage to and failure of

the components"

Thoughts?

[edizio]

Beginning to think that I should just bite the bullet and put 2 more bullet filters at 10micron in after the pumps and be done with worrying about whether or not the injectors are safe

[scotty nm35]

Why not run 1 micron filters then? Because they would constantly block, and that would be a pain in the arse, perhaps taking your engine.

ID don't make injectors, so perhaps Bosch would be a better place to ask if my 5+ years running the same Bosch ev14 1000's isn't enough for you.

[edizio]

That quote I posted from the injector dynamics website was a quote from Bosch.

I do believe that your injectors are running great after 5+ years but I've just been reading in so many places now that 10micron is recommended before the injectors. I was well and truly sold by what you said but then I got the e-mail back from before I asked this question. I'm aware ID1000s are just rebranded bosch injectors but I'm curious at how they can be misguided when it comes to their product.

Apologies if I've caused offence; that wasn't my intention.

I'm looking at getting 2x http://www.glencoeltd.co.uk/sytec-fuel-filters-swirl-pots-water-separators/sytec-motorsport-fuel-filters-bullet/bullet-motorsport-fuel-filter-jic6-jic6-filter-blue/with the 8 micron filters to replace the 35micron earls because I think the earls are pretty poor flowing too. I've already got 2 of these before the pumps with the 55micron filters so I'm sold on their quality and ease of fitting.

Edited June 1, 2015 by edizio

[scotty nm35]

No offence taken, just trying to sort you out. Your choice if you listen.

If you use 10 micron you may need to change the filter every few months from my experience, otherwise your fuel system may lean out. (and I don't particularly like paper elements anymore for e85.)

Do you know the micron rating on the stock Ryco filter? Most guys just run that, so whatever micron those run will be perfect I guess.

[edizio]

So apparently 20 micron absolute is ryco. Seems like a really unclear area when it comes to filtering fuel. Just can't really be affording to replace injectors on the slight chance a bit of crap gets through.

For sure the car is fueling very consistently now but that's with only 55 micron pre pump. Car is garaged until I sort this. I'd hate to fit the 10s and end up having fuelling problems again like when I had paper filters behind the pumps.

[scotty nm35]

The injectors have a filter inside, so they won't be damaged or block instantly, or ever from my experience of running 30 micron. You can get them back-flushed and cleaned if they get dirty, but you may not read one injector leaning out on a wideband to know it it's flowing less. The only way to tell is to put them in a flow test bench, hence why I bought one.

Not sure what filtration Bosch recommend for before the 044 either, but most of the socks I have seen don't have much in the way of filtration. I would probably be ditching the prefilters as Trent mentioned, or swapping to a coarse mesh.

[GTSBoy]

Paper filters will be very fine (pore size). It's absolutely trivial to make good filter paper medium in the 10-20 micron pore size range. More to the point, any paper filter does not rely on the paper itself to create the filter medium. It is in fact the initial buildup of solids on the filter element that does a lot of the filtering - changing the pore size down from the native pore size of the filter to a smaller value based on what is held up on the paper.

Bosch will be absolutely right in their recommendation for a fine pre-filter (pre to the injectors that is). This they would have based on a great deal of R&D and wide experience of the use of their injectors all across the world. Remember, we live in a very 1st world country. Many things that we take for granted here do not happen in other places. Such as supply of pretty clean fuel from well managed refineries, storage depots and transport systems. If you were Bosch, designing injectors for Australia, Western Europe, Kazakstan, Botswana and Ethiopia, you'd put out a blanket statement saying that good pre-filtering was essential. Otherwise you'd have >50% of your injectors failing.

Scotty's experience is solely based on using them in Australia. Seeing as most of us are in Australia, that's probably pretty good experience to base some recommendations on. But there is also a possibility that he or anyone else will get caught out occasionally by some crap in the fuel. Remember the details of Scotty's advice, because the details are important. He says to use a relatively coarse stainless mesh main filter AND NOT TO USE THE in-injector filters. That's because the crap that gets through the 40 micron main filter will clog the tiny little strainers in the injectors very quickly. If he ran a 10 micron main filter then the little injector filters would last a lot longer. But then he'd be changing the main filter more often.

You choose your option and you stick with it. Don't go half this way and half that way. You either do minimal filtering like Scotty does, and keep your fingers crossed - which should be OK. Or you go the whole hog and you use staged filtration and lots of it. If I were going the whole hog I would do a stainless strainer like Scotty does, followed by a decent paper filter. The rocks get caught on the strainer, the fines on the paper. If a 3 month inspection shows a cleanish paper filter, then you can probably leave your filter service intervals to be longer. If it's really dirty after 3 months, then you just do the replacement and live with it. The big benefit of in-line filtration like this is that you won't get just one injector leaning out. And unless you get a really savage load of crap in one tank, the pressure drop across the main filters should increase gradually, which you might at least have a chance to notice if you check every once in a while.

[edizio]

Thanks! Really useful advice. I'm going to go such the fine paper solution after the pumps.

It seems I'm probably being a bit over cautious by not driving the car until I get the new solution though

[edizio]

Ok, so today I've ordered 2 new sytec bullet filters and -6AN braided piping to replace the -6AN stainless piping I had going to my earls. The sytecs are high flowing and have very little pressure loss and should be good with the 8micron filter option. I'm happy to clean these regularly for peace of mind that my injectors are safe.

Just out of curiosity, the pre pump filter to pump is -8AN, but the pump to post pump filter is -6AN. I'm not really sure why this is but the car runs nicely so I wasn't going to change anything other than the filters. I appreciate the top end might need a few fuel tweeks so I'm happy to sort that.