Side question: is the floor of frunk strong enough to stand in after removing the frunk liner to change the filter? I have a high wing and can’t see myself reaching over the high wing to remove everything in order to change the filter.

 

I've talked with the aFe engineers when I purchased my low restriction system for my two C7s as well as the C8. It the C7 case they used a larger filter, housing and intake area duct.

They show a 27% increase in flow rate for their C8 replacement. Yep like K&N, does not catch quite as small a particle but for as long as I keep my Vettes (will be getting my 7th soon and my 1st was an 1988) not an issue!



Been using K&N for years. My Street Rod has a large 14 inch OD X 5 inch High Oiled Cotton K&N. It has a K&N Nylon Prefilter ( I mostly use for looks.) Understand their is a lot of BS re filters, has been for years. K&N has an excellent tech article that also discusses how you can use SAE test specs to get an answer you'd like. IMO one reason, for example you see can Frame say they are better than AC etc. Just pick the right test dust- IT IS NOT SPECIFIED. Can read the last 6 page of the Appendix in this PDF that show the K&N Lab equipment and discuss filtering and flows:
netwelding.com/C8_Air_Intake.pdf


aFe are good engineers. They do not quote a few questionable dyno measurement hp gains with their simple replacement filter. I bought it for the possible increased sucking sound as I get in my Street Rod (and it could be cleaned.) Was disappointed in how much quieter the C8 Exhaust was versus my C7s. As Tadge said, they direct intake air closer to your ear to get some "good" engine sounds since exhaust location and cabin insulation make NPP not as loud as the C7!
aFe do have a C8 System using 2 of their larger area cone filters where they quote modest hp gains. BTW, unlike my Street Rod where at WOT the sucking intake sound is about as loud as the 8.2 Liter exhaust with long tube headers, 3 inch pipes thru Borla straight thru short muffles- the C8 gained little!

 

I'll provide a greatly oversimplified example of how nanotechnology could be used to make a filter with a lower pressure drop while maintaining the equivalent filtering capability.
Picture two meshes with 1/4" holes. One made with wire the diameter of a coat hanger, the other made with wire the diameter of lockwire. Both would have the same absolute filtering capability but for a given size the mesh with the smaller wire diameter will have more open area and less of a pressure drop. However the mesh made from the smaller diameter will develop more of a pressure drop as contamination builds up due to contamination blocking more of the open area and at some point the pressure drop of the two filters would be the same with an equivalent amount of contamination.

 

^^^
Yep, good explanation, may well be a very good filter media. But the key is those using it, or any media can also make a comparison to prove their point.

Doubt many will read my 8-page appendix that includes Tadge Post re air filters and how they have different engine wear, engine life requirements than aftermarket folks.

This is abstracted from my 6-page appendix that follows Tadge post etc:
Plant Tour WIX Filters
Our local ASME Section toured the ~380,000 square foot WIX filter plant in SC (no longer there.) We saw and discussed the high speed, automated operation of both oil and air filters. They made and labeled filters of NAPA and many others. The engineer conducting the tour when asked why they use paper said: “It’s Cheap!”

Design Research and Testing of Oiled Cotton Filters
Some folks may be interested in the technology involved with filter design and testing from K&N.

I found the ISO 5011 test used to measure filter effectiveness most interesting. It provides a method of testing BUT >10 different dust sizes can be selected! That explains how you can see test data that always has the filter being promoted on top! Pick the right dust size or filter holder and results change dramatically! The auto air filter industry uses the ISO 5011 testing protocol when testing filtration efficiency and dust capacity. The test protocol calls for the introduction of a measured amount of "test dust" into the air filter at a selected airflow rate. The test is then terminated after the filter reaches a selected level of restriction (terminal test pressure). The test protocol then measures the percentage of dust retained by the filter (efficiency) and the total amount of dust held by the filter (capacity).

Here are some pics from the PDF:
Paper was not always used! My '50 Ford used and Oil Bath Air Filter! It was effective but messy to clean!


The reason I like oiled cotton is I can clean it "properly" much more frequently (at essentially no cost) than I would replace dry filters. When new, air flow is high. As miles are accumulated flow reduces (at a fixed pressure dif.) Just have to clean and oil properly so no oil fouls the mass air flow sensor. Done properly, should feel NO OIL as when you receive it new, when it comes preoiled. My cleaning/oil process takes overnight and touching up areas that show no oil! Covered in PDF.

 

The main point I was trying to make is it doesn't defy physics to have a filter that flows better without letting more contamination through. I have no idea if any aftermarket filters do this. They might but I'd need to see the data that proves it.

 

^^^
Understand, similar to AC Condenser mesh, plastic versus thin, widthwise and deep aluminum like Custom Grill Mesh. Same opening size, say 1/4 inch so each opening flows the same but the wider plastic covers more of the Condenser so overall flow is less.

 

I have practical experiences with those K&N factory oiled filters in my Chevy hot rod...it let in so much fine particulate matter that the carburetor idle jets got plugged and stalled the car when idling. Cellulose filters fixed that.

I get everyone's input but have yet to see any professional 3rd party study of a freeflowing filter (of any kind) providing superior filtration to the stock cellulose item. Not a graph...but a study with metrics/ demonstrated physics with the equations of the different tests, particulate matter size/density and teh test standards....something that is actually scientific and could be peer reviewed as the study I linked earlier.

This from that study and I've found nothing to dispute this as it is physics..

""Research shows that filter material characteristics are closely related. Each increase in efficiency and accuracy of intake air filtration reduces engine components wear, but it is related to flow resistance increase in the engine intake system, which reduces its power, and increases need for more frequent filter servicing.""

""A single layer polyacrylonitrile nanofiber filter is found to have minimum pressure drop resulting in higher quality factor for filtration applications. As the number of layers of nanofiber increases the pressure drop observed is higher compared to conventional filter.""


Anyone...or, simply buy into the marketing.

 

time to change out for an air filter is stupid. That is GM abuse of customers. Oil, ok, acid builds up and degrades the additives…but an air filter? Come on. This is GM admitting they think their customers are stupid.

 

This is from the Appendix in my PDF from the Executive Corvette Chief Engineer's Ask Tadge Post:
"We engineer all Corvette intake systems for minimum restriction and to meet many other requirements that aftermarket companies do not. We do not routinely test aftermarket induction systems or any other aftermarket parts for that matter. We have our hands full designing, building and testing our production hardware. Although simple in concept, induction systems play an important role in many vehicle performance areas. Aside from the exhaust, there is no greater noise source on a performance vehicle. Induction systems generally have many tuning elements that ensure the quality of the sound emanating from it are pleasing and harmonious with the exhaust note. These tuning elements also dampen the sound energy to help with pass-by requirements. Aftermarket companies don't have to worry about it, but as the OEM, we must guarantee that our products are quiet enough to be driven at full throttle by a microphone by the side of the road and meet certain decibel levels. There are pass-by laws in many states and pretty universal around the world. Although most people think of air flow into an engine as fairly continuous, it really is not. The opening and closing of valves and reciprocating nature of internal combustion engines means the air flow is really a series of pulses which make measuring the exact flow challenging. Intake engineers spend a lot of time optimizing the system to get excellent signal quality out of the MAF. In addition to efficiency, or fuel economy, the precise metering of air and fuel is directly correlated with tail pipe emissions, an area of extreme scrutiny by government agencies for we manufacturers. The air filter itself is the focus of many discussions on low restriction. Its job is to keep foreign material out of the engine. Here again, there are many trade-off decisions balancing restriction with filter life (service interval) and filtration quality. Sacrificing either of the latter two improve the former. We tend to be conservative to make sure that our engines are very durable, so that does open up an opportunity for aftermarket system. As with many of the questions on this forum, all vehicle design is a balance of trade-offs. We do what is legal and right for the vast majority of customers. Aftermarket companies offer products that strike a different balance that might appeal to some folks."

Doubt you'll find a peer reviewed study! Been using K&N filters in all 6 Vettes, my S-10 Truck and currently also in my 3000lbs, 53% rear weight 8.2 Liter BB with long tube headers etc in my '34 street rod. Have had that Holley 850 Double Pumper carb apart a number of times, changing jets for size, adding two large 50 CC accelerator pumps (with the proper cam as they offer 5, some with quick squirt but do not dump the full 50 cc's, which I use) to eliminate hesitation on high "g" launch. Took installing an oxygen sensor in a header to fine the reason for going lean. Had to add jet extensions to the rear bowl, plug for rear bowl power valve as fuel moves away from power valve opening and even jets on high "g" launch with 16.5 inch section sticky Mickey Thompsons in tubbed chassis.
Never saw any particles. Franky particles are (or should be) microscopic with any filter. Yep, with higher flow filters usually will not capture as small a particle as OEM paper filters. BUT IMO if you're finding particles could be a leak in the filter housing seal. But this debate has been going on for many years. All will believe what they want!

Note Tadge does not say aftermarket filters are bad, just a different set of criteria than they use.. In fact GM offered a low restriction system as an option for the C7. Looked like it was built by aFe as had the same appearing clear plastic as the aFe I added!

My aFe install on C7. System used a larger oiled cotton filter in larger housing and intake air tube. GM offered similar with GM name (and price.) aFe offers a pair of their cone filters in larger housing for the C8 as others offer large lower restriction filters as well. Do they capture as small a particle as OEM paper or paper like filters. Nope. If you keep your Vette for 100,000 miles something to consider.

 

Walt is spot on.....I have had several modified diesel trucks over the years and always used the factory air filters. A lot of the guys in the diesel forums would swear about
using a "high performance" air filter. Many of the guys would have an oil analysis done by Blackstone Labs or a similar company on a regular basis. It turns out that the guys running the aftermarket filters would see high levels of silicon in their oil samples. It's not worth the risk.

 

^^^
Yep, in my former business life we had several hundred cabs pulling liquid gas trailers. Always did an oil analysis as we expected the diesel engines to last several hundred thousand miles. Need to catch a possible bearing or rocker arm failure early. They probably used OEM filters as well. If you put 100,000 on your Vette good idea. For many of us, it's a non issue.

 

True, most trade off to someone else but what is the real advantage of 5 (supposedly) HP over good filtration....

 

It can be larger that 5 hp with larger filters, housings, in some cases cold air (C8 already has cold air coming from the rear fender scoops.)

But one is as Tadge mentioned:
"Aside from the exhaust, there is no greater noise source on a performance vehicle. Induction systems generally have many tuning elements that ensure the quality of the sound emanating from it are pleasing and harmonious with the exhaust note. These tuning elements also dampen the sound energy to help with pass-by requirements. Aftermarket companies don't have to worry about it, but as the OEM, we must guarantee that our products are quiet enough to be driven at full throttle by a microphone by the side of the road and meet certain decibel levels. There are pass-by laws in many states and pretty universal around the world."

Can attest that at WOT the 14-inch diameter 5-inch-high K&N oiled cotton filter on my street rod makes as loud a "sucking sound" as the exhaust in that 8.2 Liter BB with long tube Sanderson Headers, 3-inch stainless pipes, short Borla "Hot Rod" mufflers existing just before the rear wheels. (with tubbed 4 bar link suspension no room over the Currie 9" Ford Rear!)

The aFe system I installed on my two C7s added significant Sucking Sound. Not much in the C8. All filters start flowing less as miles accumulate (make actually improve slightly initially as the large opening fill with debris.) Then all will reduce flow. I always cleaned my oiled cotton filters well before I would consider buying new filters. Once you learn to; clean, wait until they are fully dry, oil the tops of the pleats, wait a few hours as the colored oil wicks down to the pleat bottom, touch up white unoiled areas with a few drops and wait until there is a uniform color with NO oil feel (just as when you get them) there is no issue of oil contaminating the Mass Air Flow Sensor.

We'll all do what we want!

Yep at WOT, my street rod intake "sucking sound" is as loud as the exhaust that exits before the rear wheels!

 

Here are the conclusions from the filter study posted by @prb :

1. A characteristic feature of the aerosol separation process in the filter media is an initial period characterized by low separation efficiency φw, filtration performance dzmax and pressure drop Δpw. The air downstream of the filter element may contain large dust particles (28 µm), causing premature wear of engine components, in particular pistons, piston rings and cylinder sleeves, affecting its performance and durability.
2. The initial filtration period (time until the required filtration efficiency is reached-φ = 99.9%) varies and depends on the filter medium used. A nanofiber layer or a PTFE membrane applied on the substrate made of conventional filter media (cellulose, polyester) significantly increase the separation efficiency φw and filtration performance dzmax. The initial filtration stage is several times shorter than for the filter element made of standard filter media only, which significantly reduces the wear of engine components.
3. With an increase in dust mass retained by the filter element (with an increase in dust mass loading km) the filtration performance and separation efficiency of the tested filters and pressure drop increase. Filter elements with a nanofiber layer and a PTFE layer show twice the rate of increase in pressure drop Δpw compared to the filter elements without those layers. The service life (vehicle mileage) until the permissible pressure drop is reached will be shorter, requiring more frequent filter element replacements, on one hand increasing the operating costs, on the other, due to higher filtration performance and reduced wear of engine components, extending the mean time to repair. The presented phenomenon of interrelationship increase in efficiency and accuracy of inlet air filtration with a significant increase in flow resistance applies to all filter materials with nanofiber layers. Data of bed with a PTFE layer are based only on the results obtained by the authors during their own research.
4. After reaching the permissible pressure drop Δpwdop = 3 kPa, the filter elements with a composite filter media retain km = 108–135 g/m2 of dust. For the same pressure drop Δpwdop, filter element A (cellulose) achieves dust mass loading km = 209 g/m2, almost 100% higher. The filter elements with a nanofiber layer or a PTFE membrane retain the dust at the surface, blocking the air flow through the layer, increasing the rate of an increase in pressure drop. It shows that in the filter beds with a nanofiber layer, a surface filtration process takes place, instead of a depth filtration process. Those type of filter media can be used in the filtration systems with pulse jet cleaning feature, significantly increasing the service life of the filter element.
5. The results of the experimental study partially fill the gap in the field of basic properties of materials used in the design and selection of panel filters for the inlet air of the internal combustion engine.

Note the parts I put in bold. Basically filters initially let more contamination through when new and filter better with age at the expense of pressure drop. The filters with nano fibers initially filter better than cellulose but load up twice as fast and require more frequent service intervals all else being the same.

My point is that you aren't necessarily letting more contamination through with a nanofiber filter.

 

All this BS about aftermarket ones being worse than the stock filter, it will hurt your engine, blah, blah, blah!! It's a freakin air filter!! Don't trust the Attack Blue, then don't buy one.

 

^^^^^^
C7Me,
This is a typical but false conclusion that air filters are not really that important. They wouldn't say that about an oil filter, but engine manufacturers realized early on how important clean air is to the long life of a motor. The 1955 Chevy had a standard equipment air filter as did all cars of that era and before but an oil filter was an option. And the optional oil filter was only a bypass filter and not even a full flow filter. It's a fact that dirty air contaminates the oil system and will prematurely wear out an engine. Some comments about the stock filter from Paragon Performance:

 

It sounds like those comments are marketing speak from the manufacturer, not Paragon. I have used high flow aftermarket filters on all my cars and motorcycles my whole life and never once had any engine problems. I think some people are just too paranoid about something so minor, and something that will never happen.

 

^^^
It's obviously a AcDelco description of their Corvette stock filter. Paragon chose to display it on their website and I don't think they would have done that if they disagreed with what was said. And something that does happen in the real world that are unavoidable are dust storms and following another car or truck that kicks up large amounts of road dust. It's those unavoidable conditions when you want an air filter that takes out those small particles.

 

1. Engine is not protected with any high flow filter. The factory filter is intended to produce a pressure drop which drives PCV at wide open throttle keeping the engine clean and healthy.
Disabling/removing the filter (making it flow "more" by removing or replacing it) Will change the PCV system - the crankcase pressure - leading to circulating carbon blow-by contaminant products in the engine oil and increased deposits, wear and tear of the engine. Even if the filter is superior in terms of filtering, it will increase engine wear and tear because of this influence on piston ring behavior and blow-by gas scavenging.

2. Debris/Particulate filtering needs to be OEM or superior. You can produce superior to OEM filtration by keeping the OEM filter in place and adding a secondary filter box (pre-filtering) thereby also producing secondary pressure drop which will enhance PCV action and increase engine longevity and cleanliness.

If your goal is increasing power you need to look into supercharging. Not air filters.
The correct crankcase pressure for wet sump performance is 1" to 3" Hg
For Dry sump it can be more.

 

Again, making a mountain out of a molehill! If high flow filters were as bad as some of you say they are, then there would millions of blown engines all over the world and the makers of those high flow filters would be out of business.