Air Filter System Flow Bench Testing | Unbiased Surprising Results

We test different filter combinations to show how each perform on a flow bench. All tests performed on a chrome 1 inch dropbase except for the velocity stacks. All tests performed using a superflow 600 at 5.5" of water.
RPC 14x3 cotton
Edelbrock 14x3 cotton
Edelbrock filter lid
Summit powerlid (looks same as rpc lid).
Paper 14x5
Paper 14x3
Chrome lid

[@seanb250]

I did this testing about 10 years ago chasing every gain for restricted class racing. It's NOT the filter elements, its the distance of the lid from the top of the carb, even when its one of those filter tops, because its still a physical object it interferes with the carbs ability to pull air from directly above it. Try this, flow the 3" setup with the chrome lid, then remove the filter element and set the lid up in the same position as it would be if the filter element was still there, the flow results wont be much different if at all. I concluded that a minimum of 3" above the carb top is required to minimize losses.

[@iainball2023]

At last, a voice of reason in a sea of madness. 😊 this is the correct answer. 👌

[@seanb250]

@@iainball2023 I appreciate that compliment, cheers 👍

[@sixter4157]

Nice test. I seem to remember reading Vizard and him saying a poorly designed stack is worse than a bare carburetor.

[@joshuaolsen8844]

Wow Joe, cool flow bench!

[@stickman-1]

The Stub Stack has always been the winning in all these type of tests. Also in regards to the filters, David Vizard has said that straight flow bench testing like this is invalid because an engine has pulses and those pulses effect the efficiency of the filter media. You should check out his videos.

[@josephnowak]

Thank you for watching and commenting. I have seen a bunch of DV stuff. In big picture a b comparisons on flow benches are relevant - maybe unvalided but not invalid. It is only the first step as it doesnt take in account the dynamics of the engine which can be done on dyno. Ultimately track testing is the true metric we want but this also has its complications with vehicle setup. Standardized component testing still has its place. The bench is detecting differences at an arguable low flow rate but as you stated this is not an engine with cylinder pulses. My arguement is there is some correlation most of the time but in fine details your going to have differences. Ultimately i want to use what I am discovering and try to apply it to my own car and see if there is any correlation to the vehicle.

[@joevalicenti2722]

David Vizard also said using manifold vacuum advance is better then ported (timed) vacuum advance for a performance engine.... and that has been proven wrong over and over again. Once I saw that, I quit trying to learn anything from him as he got this most basic info on how to set up a performance distributor curve wrong.

[@stickman-1]

@@joevalicenti2722 David has had brain surgery and he does make verbal mistakes. Also it depends on the situation I used both and for the engines I built, I agree manifold worked better. But that was the old days with distributors and different heads, etc. David is well regarded in the performance industry. I would not dismiss him on one point of disagreement.

[@joevalicenti2722]

@@stickman-1 Oh, this was well before that. Have to hunt for it on his videos. Some guy interviewed him on that topic and made a HUGE deal about it.

[@flinch622]

@@joevalicenti2722 I would think that perspective comes from a component mismatch somebody somewhere had? A vacuum actuated valve on a distributor [or anything else] is purposed for reacting to an expected signal range and stroking accordingly. An advance designed for manifold vacuum cannot respond correcty to ported vacuum and vice versa. The trick, I think, is to know if the VAV is forward or reverse acting. Generally, forward acting increases stroke with increased signal, whereas reverse will decrease stroke with increased signal. Some dizzys use a levered design, which complicates perspective. Mechanically the rod before the lever may do just the opposite for desired effect because the lever inverts the diaphragm rod function affecting rotor position. For reliability purposes, I do like the ported concept better, as timing changes with a manifold signal will cause the advance curve to shift. Basic holley design has ported vacuum sensing a very small hole just above a primary butterfly [when closed] and tubing connects to the metering block [for anyone that never worked on one]. Instructions floating about these days is kind of sad. If I had my way, these devices would be labeled 'idle retard valve', as their real function is to take advance out when throttle closes for smooth engine idle at stoplights. In other words, the vacuum advance lets the engine return to better timing as we step on the loud pedal. Like most people, I find pictures to illustrate this sort of thing helpful - here's one video that shows a test in action: kzbin.info/www/bejne/jXXCk5t6psRrqrs Looks like a reverse acting VAV to me...

[@rad87gn]

Nice tests!! :)

[@jlsracing997]

Just saw a velocity stack air filter base from Speedway motors. Love to see that tested and see if that theory proves out.

[@tiitsaul9036]

Interesting. Well done.

[@broke_dongle]

I watched a DV K & N comparo and why it beats paper. I run a tunnel ram with the Mr.Gasket air filters and tried to find cloth type filters that small. Good vid. New Sub.

[@rickhaiman9904]

Would live to see one of those ancient tornado side vane gizmos tested once and for all with a modern flow bench like you used, Great Info, Thanks

[@lewisbrodnax7898]

I had one of those on a 86 Chevy van I bought,used of course. Seemed to work well so I kept it on for a long while. Don't know what happened with it but I think it will turn up now that I will be looking for it

[@rebekahfrench5747]

Try a raised radius base opposed to your tested square droped one.. australian ford Cleveland style. Filter base height is about the level of carby flange with a raised radius feeding into carby throats..

[@davidleskov5078]

I saw a similar set of tests with similar results. But the other test included a big stainless steel salad bowl ftom Walmart with the bottom cut out. It performed the best, kinda like your drop base with a filter but no top.

[@LHMetalworks]

You might be thinking of the Engine Masters test. IIRC they found a K&N powerlid on top of that salad bowl to be almost/as good or better than just the bowl, wish I could remember. They may have also tried the bowl +lid+round element and found less flow. Shame they seem to have pulled the episode from YT at least, might have conflicted with some advertiser's preferences.

[@barthanes1]

I think you should try the velocity stack spaced above the carburetor some distance. This allows it to pull air down through the mouth, and also entrain air in around the base as well. Just a thought.

[@DuneWest]

I had one of my BBC 540cid engines on the dyno about 20 years ag0---We dyno'd the engine with a K&N filter 5" -6" tall and when we removed it we lost about 3-4hp with an open carb with no air filter. I was pleasantly surprised...those K&N's work and flow well---at least in my reference

[@V8Lenny]

It was running lean without K&N restricting flow.

[@NBC_NCO]

We really dont know what's happening to the air after it passes through the filter. My thoughts are... The air becomes scattered from the filter elements and then has to rejoin the other air particals in a chaotic manner. If the air filter was placed upon the velocity stack... you might see some ganes. In short... I would guess moving the air filter as far away from the Throttle blades as possible would be best. Oh...and add your clay.

[@NBC_NCO]

One more thing. Turn your Chrome lid upside down.

[@user-eo5yy2lz3t]

We evaluate the profile post filter on a daily basis.

[@jasonbrown7258]

I would like to see flow testing on oil bath air filters. We had them on our tractors and our ford F800 dump truck. We just used 30weight motor oil. That oil would be filthy when changed sometimes you'd have to scrape the debris out of the bottom. I've always thought they did a good job of filtering out the dust. It would be interesting to see how they flow.

[@cyrusvirus6928]

Stub stack seem to be a win but they're $75. I had a mr. gasket air filter spacer kit ($15 now) and one of the pieces I used as a stub stack. Just had to sand a little and tape to the base.

[@peskypeet]

A lot of people who run circletrack that are carb limited use a flat base (sometimes called a mini ram, yet others call it a 3/4inch raised filter base) with a 4-5inch filter. I suggest you try that setup. Bryke Racing 700-126, Titan 1237010. I know nothing of their quality since I've always had to run a dropped base because of hood clearance issues.

[@josephnowak]

Thank you for posting these. I never heard of either brand. The jello mold style with smooth transitions might do really well. Another one i saw recently is the rc2 performance ac10615. Not as affordable but is probably the most similar to the clayed setup that i did.

[@peskypeet]

@@josephnowak I don't know why but going back 30+ years air filter assembly's have always intrigued me. I believe both K&N & R2C make/ made (I think R2C is out of business) that molded carb throat style in both dropped base & above the carb inlet style. I even had a K&N StubStack in the mid 90's. I agree the molded to the carb inlet style should provide the best flow but no matter the company that type is definitely not cheap. Unless you're class racing with limited carb cfm you'll be better off spending money elsewhere because the returns aren't going to be anything surprising especially since you have the better newer style high flowing HP main body. In a static situation like on a dyno the style with the base higher than the carb inlet should provide more air. Afterall it doesn't have to make nearly as drastic of a turn. As always never forget a flowbench is not a dyno and neither one goes down the track and has to deal with wind turbulence across the inlet and the madness of the underhood conditions. But both can be used to * show trends. * I've seen two dyno tests from magazine guys (one being in the early 2000's) who tested many air filter setups on a dyno and they both showed the air cleaner base above the carb inlet gave more HP. I suggest you do a search for Engine Master's Episode 27 video where they test air filter assembly's on a BB Chev making over 750HP. Why it isn't on YT and why they don't mention the carb used I couldn't tell you but it's an interesting video with an interesting conclusion.

[@peskypeet]

@@josephnowak Oh, and those two I listed are pretty much at the lowest price I could find. Seems everyone else wants about 89+ for pretty much the same part. KZbin is deleting my posts for some reason. I gave a few names and part numbers but no prices or links and they deleted the post.

[@josephnowak]

I think i may have seen that engine masters if its the one where they modified a salad bowl. My dad always tells me that way back in the day the moroso with the bubble lid did really well. I am definitely going to revisit this subject at some point with some different test subjects on the flow bench. My car has limited hood space so real life testing would be limited to drop base stuff unfortunately.

[@peskypeet]

​@@josephnowak I always liked the looks of the MOROSO top. I think most of the success of the dropped MOROSO design is in the bottom pan. It's dropped just enough (1.25-1.5inch actual drop I think) to not cause much of a restriction when combined with a minimum of a 3inch high filter. Using the tallest filter you can get away with is almost always better as it gets the lid further away from the vent tubes and the carb inlet allowing a more gradual turn into the carb and better metering, not to mention if not blocked more area will be easier to pull air through. (Opinion- If I had the choice of using an air filter top with a bubble and a 3inch filter or a flat top with a 4inch filter I'd go with the flat top and taller filter for the increased effective filter area and again getting the top away from the vent tubes and carb inlet. The style like the Titan 1237000 is flat and gets the stud and nut away from the hood. That style can often let you employ that extra inch.) The deep drop bases of 1.75-2inch on a 14inch wide assembly seems to position the pan to close to the bowels and causes a bit of a dead spot. Over the years one 1.75-2inch deep dropped base that has proven itsself time and time again is the GM factory L88 base. Because it is a steel moulded piece and not the spun aluminum variety it fits a little closer around the carb opening and bowels allowing a little more area for the carb to pull from.

[@mattthomas3207]

I run the solid top and 5x14 paper filter with seals on top and bottom base where filter meets base and my carb and inside plates are spotless

[@josephnowak]

The tall paper filter is definitely a really good economic route. Taller the better in general from what I have seen and tested if you got hood clearance.

[@arturozarate1752]

R2C makes GREAT air cleaner assemblies. Drop base and venturi insert for a 4150 Holley HP along with a 5" filter is almost unbelievable in flow. Check them out.

[@josephnowak]

Last time i tried searching their products on summit they were out of stock. I think something happened w R2c... Either poorly managed or out of business. Il try searching again on this.

[@coryament]

the bottom plate that goes on bottom of filter has too much drop and depending on the filter it puts the lid closer to the carb or farther away.

[@ruppyhouse]

I'd be interested to run the same tests against a flat base instead of the drop base and any other bases that you can find.

[@nashvilleoutlaw]

How can you test a classic chrome lid and not flip the lid😂😂 because it's raised in the center. Legend says when flipped it decreases the void of dead air above the carb. Or cut a funnel down to fit between the carb and lid. Both tricks are to fix the problem of air coming in from all directions and creating drag directly above the carb.

[@josephnowak]

Thank you for commenting. Went through my data again and your right. I never flipped the lid which would of been a good test. There will be a follow up test for items missed or not tested yet.

[@user-eo5yy2lz3t]

Don't bother. We designed countless, sophisticated lids and this high pressure area has little impact on the profile and of total performance @@josephnowak

[@Hjfvvdst]

I think the chrome top helps turn the air. I have seen a chrome top with a long horn probably 3 inches pointed down. The claim was significant. Don't know if the claim was accurate.

[@alphaghost1633]

Saw these same results on air filter "filter" lids -- They are a performance loss every time The thinking was it causes to much turbulence - I think it was David Vizard that did the test t

[@kh40yr]

My $75 K&N Powerlid is on the wall of shame for right now. Was causing too much underhood heat to pass thru my ProSystems 830 due to a tight fit up to the hood. There was almost 2 inches clearance, but it was still to tight. The Powerlids + High flow will shine with a well sealed cowl induction setup, and that's where they should be marketed to, but they would loose money then, so they claim it works for every setup, which is NOT the case. If your hood is close to the Powerlid, it will add underhood heat thru the carb, and thus possibly give you headaches, until you swap back to a tin top.

[@josephnowak]

Thank you for commenting. Hot air can definitely give issues in an underhood application. I just wanted to say that the powerlid is a brand that is not a k&n. The k&n xstream is probably what you have which is differnt that what i tested. I hope to test an xstream in the future to show the difference.

[@jacobcurran5543]

I'd like to see a 14 inch velocity stack base

[@davecavender8227]

Try a flat 14 in base and a 14 in volosty stack

[@canadianoddy8504]

I belong to a website for ATV's and one of our members is an engineer that worked for many of the filter companies in the USA. His comment on our site was that if you want more flow get a bigger area filter. He said the "high flow" K&N type filters don't really "filter" at all. The objective of a filter is to keep crap out of your engine. So the real question you have to ask yourself is ----- Do I want flow or do I want to filter the air ? Your test in this video was only about flow and we all knew before you even started that the velocity stack or an open hole would be best. It was a no brainer. Now if you did a test about filtration we all know the pleated paper will win and a paper filter will flow more the bigger it is. The worst one for filtration would be the K&N. That's the take away I got from the comments on our atv site. I did like your idea on experimenting with the clay. Good work on that.

[@josephnowak]

Thank you for commenting. Your exactly right on that this video was flow focused. There is an entire procedure for doing filtering performance iso 5011. In my limited scope of drag racing filtration for that short period of time is not important. In a dirty environment it becomes much more important. Normalizing to what people know and then testing a bunch of random selections is what i did. Filtering efficiency as it relates to iso 5011 is another level of science which maybe i will get to one day or not.

[@alphaghost1633]

Wrong - k&n filters clean better than others Watch the real tests dont listen to so called experts especially an engineer !!

[@arturozarate1752]

Btw, that was wild with the velocity stack. Stay away from the filtered tops. They're too turbulent. I'm gonna check out the mods you did to that main body. I had to use a Proform 950 on that 496 and I feel like it held me back...I wish I had the time to test different carbs and filters. Good luck.

[@josephnowak]

My car has some electrical issues right now that im sorting out but all real life on vehicle testing seems to be decent so far. It didnt mess up my fuel curve like i thought it would

[@danielkoch6815]

Would like you to also conduct this test with an Edelbrock Pro Flow . Everyone says they're garbage, but how much worse can they be than some of these?

[@josephnowak]

The edelbrock 14x3 is in the pro flow series. Which one were you thinking of?

[@einstein3509]

What happened to me on the chassis Dyno surprised me. I have a 1971 Chevelle with the functioning cowl induction hood with the factory air cleaner that properly mates up to that hood. I was tuning it on the chassis Dyno and we got it tuned correctly. Then someone suggested to take the air cleaner off because I'd get more power. Nope!!! I lost 7hp with the factory air cleaner off. We ran it twice with the same results. Then reinstalled the factory air cleaner and I got my 7hp back. Every run was with the hood open. So the cowl induction part had nothing to do with it. I didn't see that coming!!

[@josephnowak]

What works on one car doesnt always work across the board. Its interesting to test some of the stuff out. I want to do some quarter mile testing with and without just to see the difference. Thanks for sharing your experience!

[@josephnowak]

What works on one car doesnt always work across the board. Its interesting to test some of the stuff out. I want to do some quarter mile testing with and without just to see the difference. Thanks for sharing your experience!

[@einstein3509]

@@josephnowak All I can think of is it has something to do with the curvature of the air cleaner housing. plus I have a 1/2" spacer under the cleaner housing for linkage room to move. we also found this out too. when I had a dual plane intake it seemed like every other plug was running rich. then I switched to a single plane intake and then all the plugs on the passenger side ran richer the the driver side. I lost a lot of hair on my head trying to figure that out. well, here was the problem. that factory air cleaner seals up to the cowl induction hood and the air cleaner snorkel points off to the passenger side which is bring in hot air from under the hood and being sucked into "mostly" the passenger side of the engine and the driver side is taking in "mostly" cooler air from outside from the cowl hood. how did I fix that you ask?? hahahaha I stuffed a sock in it.............hahaha into the air cleaner snorkel that is. now my engine only takes in air from the outside. problem solved all plugs burning the same now. now the only problem with doing that is. my AFR with change with the outside temp. it will run a little richer when it's hot outside and a little leaner when it's cool outside.

[@josephnowak]

Very nice! What type of setup do you have in your chevelle. Big block, small block? And carb, intake combo? Im a fan of single planes

[@user-eo5yy2lz3t]

This is a common occurrence and easily explained.

[@cycle47hall20]

Some sort of non restrictive air filter is a must, you want gas pulled thru the jet holes and the engine is only gonna process so much air anyway, be more concerned with getting things right for around 3500-4000 rpm, a/f ratio, and the rest should be damned close.

[@user-eo5yy2lz3t]

We design and test intake systems, air cleaner housings and filters and have done so for over 25 years. It was interesting to review your results and read the comments, many of which are well intentioned although misguided. Your results will change dramatically when you replicate true high performance engine demand. The lids with media incorporated into them perform significantly worse when used on actual applications. The reason is not related to turbulence. You can replicate this on your bench and watch the impact on the booster/venturi. This group would generally not be considered high flow air filters. Regardless of manufacturer, the oiled gauze media hasn't varied much in our testing. 75-80 CFM per square foot at .5" w.g. The cellulose media flow is slightly lower. In either case, filter efficiency is mid-level or below. The filters you tested would not provide adequate efficiency in performance applications operating in demanding conditions with high concentrations of fine dust.

[@josephnowak]

Thanks for your comments. Filtering efficiency is something i probably wont get into. It would be interesting to see how much bypassing each do. Desert dust seem to be the worst and also the go to for validating media (im not sure how much aftermarket filter mfgers do for this??). I have seen in data different media clog up at different rates and being able to carry more mass with different pressure drops while holding surface area (pleat design) constant. Equipment and time is my limiting factor right now. I didnt expect this to be a topic that got this much attention. Rarely anyone mentions the phrase filtering efficiency and knows what it means unless your in an industry or profession that studies it.

[@doxnoogle5782]

Love the test, but i have to say the most obvious test i was hoping to see was a drop base vs a flat / raised base. I question running the test at 5.5" vs something like 1 or 1.5" like it would see in reality. If nothing else, good example of how something may work or not work on a flow bench but does or doesnt make more power, ie, the "power lid".

[@josephnowak]

Thank you for commenting and noticing the flow target. Were just limited on our bench size. We will try to do some more testing with bases and at least establish an a b comparison to give viewers something to try with data.

[@ttyler2014]

I also would like to see raised vs flat vs drop bases. Tried to figure it out on a drag car years ago but there were to many variables.

[@Peter-V_00]

Unfortunately there is no hard fast universal rules when it comes to air filter no filter vs open carburetor vs a stack, in my experience for oval racing a 4-5 inch x 14 course pleat paper filter did a good job overall.

[@joevalicenti2722]

Velocity Stack - The problem with it is that BIG FLAT SURFACE BAR that holds it on!!! That is also causing the lift! Get rid of that and see what it does.

[@cagr4249]

As far as I know the main task of a filter is to keep away particles from entering the cylinders. If no restriction is accepted, just assemble a well shaped intake funnel without any filter. Therefore I would prefer to find a test that tries to find out which kind of filter serves best its pupose: filtration.

[@josephnowak]

A simplified bench test could be done with paper style filters relatively easily with a dust chamber, fixture, monometer, and vac source. Measure starting mass and then ending mass = carrying capacity @ x inches of water. I havent seen any videos of this but i do know that it is a valid method. Any bypassing would have to be a visual check. Is this something that you were thinking? The cotton style filters are a little different. Vizard has a good episode on explaining k&n.

[@cagr4249]

@@josephnowak Thanks - I am going to look for Vizard's video!

[@user-eo5yy2lz3t]

We perform ISO 5011 and fractional testing on a daily basis. It's startling to witness what even a small amount of loading can do to pressure drop on poorly designed filters.@@josephnowak

[@bob8776]

“Suction pressure” 😂😂😂

[@user-david6265]

Yeah my 283 don’t run right with air filters on

[@4speed3pedals]

I don't know if it still reigns true but the carb base of a Chevy big block and the Z/28 and other engines with the chrome top that use the 14" open filter worked better than many carb bases. I do not understand why you didn't test the K&N X-Stream Air Filter assembly with the filtering lid and with a stock 14" lid. One other thing you could test is a salad bowl. Go to a store and pick up a large stainless steel salad bowl, a cheap one that is thin to keep the cost down. Cut the necessary hole in the base and flow it vs those funnel tops. I have been using K&N since the early 70's and will use nothing else. David Vizard talks highly of K&N. Throw those look alikes in the trash and get one for your vehicle. You flow bench will tell you also.

[@josephnowak]

Thanks for watching. I tested what me and my buddies had laying around. The chrome dropbase and chrome lid with the prc filter is sold as a summit kit for entry level price - i bought it originally for my big block car years ago. When I do another test i will have some k &n stuff. It was simply just what i had at the time.

[@4speed3pedals]

@@josephnowak A velocity stack with a filter and lid is supposed to flow the best.

[@Brian-gx7yx]

K&N needs to be evaluated

[@lawrencecarlson2425]

I think it's time for a redesign of performance filters. K&N has a great media. Maybe they could design something that flows better.

[@josephnowak]

As a consumer without seeing a test like this you only see the look of the product. Theres a lot of open faced lids on the market that look really good and at a price point that get people to buy them. The chrome top went back on my car for now. I would like to do some track testing but the car is down at the moment.

[@lewisbrodnax7898]

K+N flow great, if you use their oil on it. Remember(OK, I'm 69 yes, maybe you dont)the old Chevy air cleaners, those were GREAT!

[@user-eo5yy2lz3t]

Cheesecloth with a tackifier applied is not media and it certainly isn't great.

[@lawrencecarlson2425]

It’s just like exhaust. Anything more than zombies, is restrictive. I’m sure that the right vortex generator would help the intake.

[@rodchappell1677]

What would be the best for dirt late model

[@josephnowak]

Thank you for commenting. Dirt racing isnt an area that I have any experience in.

[@user-lx1nh7gg8o]

i'd think the filter lid is probably slowing the air velocity

[@user-eo5yy2lz3t]

You want high velocity? Use a straw. Velocity is the bane of profile performance. Slow, high pressure profiles are the goal.

[@_Otaku-kt8be]

Engine Masters did an episode on filters and horsepower salad bowl all always wins

[@josephnowak]

Thank you for commenting! We will probably do a salad bowl test in the future to try to normalize some of the results and get perspective of how well or bad things are. That being said if you dont have hood clearance or dont want to cut a hole in your hood, then it doesnt really matter how well a salad bowl does

[@rickmoody6984]

@@josephnowak I used a WOK frying pan for an air cleaner base. It's like a shallow salad bowl. It seemed to work good and it is a conversation piece with the handle left on it and the Goodwill $3.00 sticker on it too.

[@garyhosier4765]

That’s what I was going to say. Look for David Vizard. He presents it with experience from desert and dirt racing. I trust him but you are more experienced than I.

[@josephnowak]

I suspect you have seen it but his video on k&n is interesting. He doesnt bs on what works and what doesnt. I tried to focus on some of the knockoffs because when you dont want to spend the money for a k&n you end up buying cheaper that might not work. From my perspective im just trying to find out how well they work for my vehicle and some close friends projects. Il try to share when i can.

[@garyhosier4765]

Ah. Yes. Knock offs say their the same then flop although I expected better from a big name like Edelbrock. Thanks

[@zynzy4u]

A few clues- turbulent flow versus laminar flow. Venturi in the carb are intended for straight down flow with open, non-turbulent air above. With the filter top there are two air inputs, one down and one sideways which causes turbulence and therefore, less air flow through the carb. The filter element itself can be made with different materials which have different porosity leading to more or less air flow. In short the tallest, largest diameter air filter will be the best. As I recall back in the day many racers did not use filters. Those who did successfully had 5"-7" tall filter that was about the size of the vertical projection of the engine. That means two feet on a side more or less square.

[@user-eo5yy2lz3t]

Turbulence isn't the issue with these lids. Negative pressure impacts the booster signal. You can replicate this at home.

[@zynzy4u]

@@user-eo5yy2lz3t The reason the horn thing lifts up is it is an airfoil. Worst idea ever. You saw decreased flow with the top filter. How does that relate to negative pressure at the boost venturi?

[@mustangracer5124]

No K&N ?.

[@josephnowak]

This test was done with what we had laying around. There will be a k&n tested in the future to help normalize results

[@jeremyfoster9739]

I will stick with K&N filters

[@davidwalker7383]

None of that testing will apply to an engines performance. Being that an engine can only pull in a fixed amount of air, it's best to stick to the stock configuration. The only way to get more air into an engine, is to make the engine bigger.

[@josephnowak]

Thank you for commenting. A fixed amount of air is all relative to the parts that are on the engine. The induction system including the heads valve train and cam make the system. It becomes an issue after changing these other parts that greatly increase the fixed amount of air to the point of outflowing your inlet, whether it be an open tube, open carb or air filter.

[@user-eo5yy2lz3t]

Changes as mentioned impact volumetric efficiency and engine demand at a given displacement.

[@user-uj5kn6co5q]

Here is a dyno test that had a tapered back plate making less power than a right angle back plate. why? kzbin.info/www/bejne/kGPcY2CDhtd6hZosi=029nsgVzYt0zsgqI

[@josephnowak]

I dont have a direct answer but mainly thoughts on how much further this shouldbhave gone. This shows how finicky air flow can be but it also leaves dyno related questions unanswered. They had wideband oxygen sensor data - if you look at the setup its there. It would of been nice to see that data or at least touch base on if it was the same or different, if there was one in each bank even better. A test without the element installed would of been nice too - it would eliminate the question about the step in the base. With carbs its not just the air but also the fuel and what the air flow does for pull on the fuel circuit. There is also fuel and air distribution that is a unique ingrediant with a vtwin - one cylinder will pull hard than the other due to the uneven crank angle between firing cycles which makes the jetting a compromise. Overall i enjoyed the video.

[@petercunningham3469]

No real reason not to run an air filter . If your car runs a tenth slower with one who cares besides shit ring seal will rob both performance and money. K & N 4 inch x14 and Cold Air done right is reliable and makes power.

[@recoilrob324]

4bbl carbs are flow rated at 1.5" water restriction...why use 5"? NO motor is going to pull that hard on them and while all testing is interesting and some comparisons can be drawn from the results.....keeping things more realistic would offer the possibility of more realistic expectations from the results. Just like pulling 28" when flow testing heads....I'm not seeing how this is relevant and could lead you to places that more sensible testing might not lead you.

[@josephnowak]

4bbl is flowed at 1.5"mercury. 1.5" mercury is 20.41" water. This flow bench is certified to 600 cfm. We are pulling less not more as we are restricted to 600 cfm. I get it that it isnt perfect but its an a-b across a range of products and normalized to no filter. Head flow testing is an entire different animal. If you try to go through listed flow charts for heads its almost never an a-b comparison. Many times the bore size is changed per cubic inch recommendations and you have to read into the fine print to see it.

[@recoilrob324]

@@josephnowak Oh man...my bad....got my restrictions messed up. Your are right that it's mercury and not water. Again...my apologies for the mistake.