When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I just purchased the air filter for my EFR setup yesterday. I got a little confused trying to use the air filter size calculators and trying to apply the values to actual filters, so just bought the biggest K&N offered in 2.5" inlet. Bigger's always better right? I think your filter is probably restrictive though.
All air filters are restrictive. A clean cotton filter is typically just a tad less restrictive, per square inch, than a paper filter. It's not a massive difference. They mostly just look cooler.
The standard rule for air filters is that, for a given material, larger is always better. There's no absolute rule which says "You need xx square inches of surface area for every 100 HP." If you're chasing that particular dragon, install the biggest thing you can physically fit under the hood.
If not, install whatever is convenient. The Bugatti Veyron uses paper air filters.
Paper or "fabric" air filters can filter finer particles than oil bathed cotton gauze (K&N style), this is why pretty much all of the "super car" builders use them.
The Buggati's are HUGE and very expensive.
What they cannot do is continue to filter large volumes of air after they get dirty, this is where the K&N style filter shines. It will continue to function until it is extremely nasty.
The oil used in the K&N style can sometimes jack with hot wire mass airflow sensors, this is another negative aspect regarding the super car application.
The one that is pictured is too small for the flow capabilities of that EFR. Bigger is better. At least twice the area is needed IMO.
I believe controlling the airflow into the airfilter is as important as having a big enough filter.
The filter should be separated from engine compartment heat by building a box for it behind the head light and feeding air from below the head light.
Another option is to build a dedicated housing below the head light and feed this housing from the front air dam just above the splitter (high pressure area).
The improvements in a higher pressure more dense (cooler) airflow can outweigh the restriction of the airfilter itself significantly.
I just purchased the air filter for my EFR setup yesterday. I got a little confused trying to use the air filter size calculators and trying to apply the values to actual filters, so just bought the biggest K&N offered in 2.5" inlet. Bigger's always better right? I think your filter is probably restrictive though.
Had a MUCH smaller one on a 2554 FM setup once. You can imagine, the 2554 inlet size is smaller than the EFR, 1.75" I think? Service writer ordered the biggest filter with a 1.75" or whatever it was inlet, and it was maybe half the size of the filter you pictured, tapered. I think 4 of them are used on 750-1000cc motorcycle carbs. Car made 230-240 on the dyno with a different filter/intake, but brought the small filter for testing purposes. Made no difference, zero filter was negligibly higher.
Location: Detroit (the part with no rules or laws)
Posts: 5,680
Total Cats: 804
Just a really weird and completely off topic piece of information I would like to add.
When I put my race engine (old school sbc) on the dyno it made the most power with a big round filter on the carb, the biggest one I could find. Followed closely by the high ram velocity stack then flame arrestor. (Having a bare carb was actually not that good, see engine masters episode) I did not have the opportunity to try a salad bowl unfortunately. Dyno guy said something about calming the air flow down before it enters the carb. Obviously completely different than a turbo application but something to think about.
But moral of the story. Always test. Gains will probably be tiny, and sacrificing a little power to ensure that the engine doesn't ingest some foreign object is totally worth it. Go bigger, but if you can route a smaller one to cooler air it will be better.
It's always amused me somewhat that the manufacturers of the very largest turbochargers (the ones typically found hanging from airplane wings) do not specify any air filter at all.
It's always amused me somewhat that the manufacturers of the very largest turbochargers (the ones typically found hanging from airplane wings) do not specify any air filter at all.
I get that. But they also have components made of very expensive, erosion-resistant materials.
EDIT: Question for those running the AEM, as I am. There is a specific liquid that they recommend for cleaning these filters, but I have yet to find somewhere to purchase it. Now that K&N bought AEM filters, all I can find is the solution that is meant for the oiled kid of filters.
Thus.... What have you found to clean the AEM filters? Or do you simply replace periodically? @technicalninja
yes that filter is too small.
but way worse is that you have it hanging off the turbo, which will 100% fail and either melt off or fall off at some point
It's always amused me somewhat that the manufacturers of the very largest turbochargers (the ones typically found hanging from airplane wings) do not specify any air filter at all.
Very few contaminants at any altitude over 1k from the ground for the reciprocating folks, and they all HAVE air-filters for the engine's intake charge. Big ones. They don't have air filters for the propellers...
Businesses exist to repair erosion damage on props however. There is such a critter as a "Prop Shop".
For the turbine powered, not turbo charged, it's a bit different but the low trash at altitude still applies.
Run one through a volcanic plume and BAD **** happens.
But I'm guessing you know this Joe and were being funny...
Mr. Makinson. Clean it with whatever your heart desires, be careful, it is simply cotton gauze between 2 mosquito nets. You don't want to damage the fibers.
When PERFECTLY clean it will be white. Only white ones I've ever seen are brand new ones that haven't been oiled. Once apon a time the K&N were un-oiled at delivery. They came with a can of oil and you had to oil it yourself the first time.
This was DAMN handy as they had enough oil in that can to oil them multiple times.
I usually finish the cleaning with Alcohol. The filter will be GREY, the close to white the grey is the better.
I've NEVER replaced one, just cleaned and re-oiled. I try to use the K&N oil as it is dyed red and it makes it easy to see if you're completely oiled.
Mr. Makinson. Clean it with whatever your heart desires, be careful, it is simply cotton gauze between 2 mosquito nets. You don't want to damage the fibers.
When PERFECTLY clean it will be white. Only white ones I've ever seen are brand new ones that haven't been oiled. Once apon a time the K&N were un-oiled at delivery. They came with a can of oil and you had to oil it yourself the first time.
This was DAMN handy as they had enough oil in that can to oil them multiple times.
I usually finish the cleaning with Alcohol. The filter will be GREY, the close to white the grey is the better.
I've NEVER replaced one, just cleaned and re-oiled. I try to use the K&N oil as it is dyed red and it makes it easy to see if you're completely oiled.
Tech: I am asking about cleaning the dry type AEM, not the oiled kind.
Nevermind, I found it.
Last edited by DNMakinson; 12-15-2020 at 08:41 PM.
I have the sx-e compressor cover and the sucker has a 3.5" inlet. I threw on a 3.5" reducer to 2.5" flanged air filter, not sure if that had any effect but my 6758 spools so slow. You think the filter size would have any effect on spool time if it's restrictive?
Not at boost threshold (100kpa), unless it's really restrictive.
What a restriction BEFORE the compressor does is makes the compressor work harder from the point you can actually see a pressure drop at the compressor inlet.
A manometer is the required test equipment for this check.
Conversely if you can see ANY pressure increase at the inlet the turbo has an easier job of compressing the air, adds a tiny bit less heat to the charge and you have a slightly cooler (more dense) charge.
A drop of 1" is common, a drop of 3-4" is bad news.
The reverse holds true for pressure.
Corky Bell found 4-5" of loss here on the stock MSM set up.
Big time gains from a simple sizing upgrade were applied here FIRST on this set up.
We want the highest pressure possible at the compressor inlet.
Needs to be as cool as we can make it as well.
We're eating oxygen molecules and we want the molecules as small as we can make them...
12-10-2020, 10:40 PM
Turbo air filter restrictive?
0
