Optimizing engine airboxes in cars

[@jooky87]

This explains how well my BMW e39 was engineered for aero and air intake

[@indopleaser]

wish this channel was pumping out the quantity of videos from 2 years ago. some of my favorite channels right here

[@JCnordic2983]

I developed a errand intake from the grill on my Honda element. And i've tried to explain to people that the cooler denser air with a larger diameter intake with utilizing bernoulli's principles. This allows for a better torque curve extending up into the hire RP m's on small displacement edges. I like your examples.

[@Fosgen]

This is all true. I have experimented with airbox intakes up to size 3/4th size of airbox. 140 mm wide airbox, supplied with 100 mm aluminium air duct, picking air below car. I had biggest temperatures drop of air intake using this intake, with temperature only up to 10 centigrades higher than nominal. Due to dirt it picked up from street visible on paper air filter I changed it to 60 mm intake, using rubber hose, from highest pressure zone, vertical surface of bumper. It is screwed with 6 stainless security torx screws and other end is connected to airbox using steel hose clamp. Intake temperature is usually 15 to 17 centrigrades higher than nominal. Cheap and fairly easy mod. Sport cone filters are pointless, as their filter possibilities ale poor. I used sport filter for test. It only made turbocharging noticeably louder to driver. After 1000 km, you could already see fine dirt inside all intake piping.

[@zanuarrosyidi4034]

Can you share the pict?

[@Fosgen]

@@zanuarrosyidi4034 Car is long gone.

[@herniagaming]

Drawing air from underneath the car is pretty dumb, as you said it picked up dirt that was likely from the tires kicking up whatever they drive over, not to mention the hydro locking risk since it's much closer to puddles on the road and close to water that can spray off the tires. An intake pipe should always be as high as possible on the car to avoid this risk, this is why 4wd guys buy snorkels cause the intake is much higher leading it to breathing in less shit and they avoid hydro locking because the intake pipe is nowhere near where most water will get to it. Another good location would be just under the headlight or on the vent on the bonnet, that way it's away enough from the road to not pick up too much water or road debris and dirt.

[@rustywater3219]

Thanks for the idea of using PVC. You can likely use the PVC as a mold for fiberglass if you're really worried about how it looks.

[@MrSaemichlaus]

I've seen a Toyota Supra (bignumtt on KZbin) where one headlight was completely replaced with an air intake box of identical outline. It's a huge intake area and basically in a perfect spot. Only usable on track in daytime, but it sure adds something to the power.

[@JulianEdgar]

Yes, a good approach that's been used for many years.

[@zanuarrosyidi4034]

After change size bigger intake tube i feel different, better throttle respon and the bonus intake sound good. Thank you for sharing this

[@JulianEdgar]

Glad it helped

[@zanuarrosyidi4034]

Hello, i have 1 more question for you. if bigger inlet is not possible, is it possible to make two inlets?

[@JCnordic2983]

I also built a carbon fiber nect dorectly in to air box above rad behind the grill plummed.

[@vincereynard4890]

The sixties Elan (and +2) had an air cleaner mounted in the nose with it's inlets pointing backwards towards the rad. Then a grt big tube leading back to a fibreglass airbox connected directly to the Webers. I thought it looked strange at first, but, it seems, Lotus knew what they were doing.

[@ienjoyworkingonmuddycars.9793]

the Australian accent always gives credibility to car related advice

[@THEANIMALGUY]

So basically have a large air box and other parts (to have minimal resistance to flow)that's not close to hot stuff(so the intake air is as cold as possible)and with a big entrance where the speed of the car would force air in like a parachute

[@alitheretrokid]

I have a 1995 ford probe that follow many of these fuel economy principles very well. The air intake pipe is located in a very ideal area and the car has one of the lowest drag coefficients of the 1990's, not to mention the 3 spoke wheels with very little churn. I was able to average 41 mpg in this 30 year old car going 70 mph, even though the gearing is very low and the engine was turning 2900 RPM. I plan on installing an undertray all underneath the car and do a tune up on the engine as well to see if I can hit 45.

[@archygrey9093]

Alot of old Holdens here in Australia had reverse cowls, basically hood scoops that faced backwards and were apparently quite effective as they'd pick up the higher pressure air near the bottom of the windscreen whilst not sucking up bugs and rain or creating drag like a forward facing scoop does. Might be worth looking into, probably won't be as high pressure as the front but there'd be far less distance of piping needed that may negate that effect

[@JulianEdgar]

As you said, the pressure is much lower so not preferred.

[@zchettaz]

Turbulence can also occur after the airbox exit depending on how the piping is shaped and routed (i.e how many bends/angles the airflow needs to negotiate). This led me to go with an OTR (over the rail, sometimes called, over the radiator) intake, which ticked all the boxes - flat (40mm) and wide (300mm) filtered mouth that funnels air from the high pressure area in front of the radiator directly behind the grille and straight lines it into the throttle body (90mm). It certainly improved the throttle response and car seemed alot happier, by that i mean, it was less sluggish

[@georgekurgansky5986]

Firstly, loved your aerodynamics video, seriously considering getting your books! What are your thoughts on intakes that have a large intake which runs same size for a foot then goes to a bell mouth to a hole half the diameter, which expands over 3 inches back the airbox to end up roughly the same size as the mouth? It kind of looks like a funnel used backwards, my citroen saxo has one of those. I expect it's to cool the air down by forcing it to expand as the engine pulls it in. I took it out and put a pipe there, it's a 1.1 engine, but I've not measured any difference in MPG or sound or coolant temperatur for the following months. I expect intake vacum is increased with citroen funnel and the air temperature is a bit cooler and perhaps that helps it on a very hot day. Otherwise it may be of benefit at higher rpm to have a no restriction. Do you think there is much value in including airflow restrictions for oversized intake funnels? I'm wondering if I build a 1 foot by 2 foot intake funnel to the side of the radiator and go back to a rallycross track I was on a year ago, hack the MAP and thermostat sensor and get the engine squirting out maximum fuel. I wonder shoudl I try to make any effort in cooling the air down by using the same thing citroen did but just much, much larger. Sorry it's a bit long but I notoiced you didn't excplain the role of intake restrictions. Is it worth testing?

[@JulianEdgar]

I can't see the design you're talking about having any measurable impact on intake air temperatures. Can you link to a pic?

[@georgekurgansky5986]

@@JulianEdgar i.ytimg.com/vi/bfqr6K7T8w4/maxresdefault.jpg It's a significant restriction.

[@JulianEdgar]

Interesting, but I think I'd be getting rid of it.

[@Surestick88]

Likely to cancel out intake sound. The design you're describing sounds a lot like what you see in some mufflers.

[@catmunkyafzainizam5137]

Agree with you sir.coz I have did it.it feel more power at night n morning or raining time.cold air make more oxygen.

[@Mikelectric]

Im buying your book now

[@JCnordic2983]

A vertical grill would be as high as the outer edge the bumper?

[@user-gd9cx4gz2t]

@JulianEdgar Thank you for your brilliant insights into airflow performance optimization. It was enlightening to watch. Can you please shed some light on the impact of Snorkels in relation to airflow and the impact on performance? Appreciate if you could differentiate Forward Facing Ram Head vs Reverse SS snorkels.

[@JulianEdgar]

Forward facing snorkels are good for performance.

[@user-gd9cx4gz2t]

@@JulianEdgar Thank you for your response.

[@CdnBullyboy]

I built a new intake/filter system several years ago for my 65 VW squareback when I built a bigger motor, it would have been nice to have this video back then.

[@tonicrvnts]

Something I read limg time ago: 1. The air intake should not be behind the engine because you are going to get hor air and you want cold air🌬️ 2. If you put the intake in the are of high pressure (like in the bumper) there is a chance you get rain/water that potentially can get into the engine 😬 3. I have seen exotic cars with the air intake in the roof which until now I know it is a low pressure zone 🤷

[@JulianEdgar]

1. Yes, nor behind the radiator. 2. Not really, if you don't go through flood waters. 3. Depends on how the intake is organised.

[@awaisiqbal8934]

Why not to provide weep holes to release in case of incoming storm water flowing through air intake

[@ElPants21]

How much did the cooler, denser design change fuel economy? Did your insight have the factory air intake intended as a hot air intake or was that coincodental? (Reduced power for a given throttle position -> more throttle for same power-> reduced pumping losses and hotter temps for teeny bit better thermal efficiency?)

[@filipczerwinski597]

This question just shows how bad throttles are. And yet I was wondering why diesel engines have 1/4 of the fuel consumption on idle.

[@fastinradfordable]

@@filipczerwinski597 Gasoline engines need to maintain 14:1 air fuel ratio. Diesels can be happy as high as 200:1 air to fuel ratio

[@filipczerwinski597]

@@fastinradfordable I know but my point is that it would've been a holy grail to throw the throttle out and have valve timing+duration only. The logic is that it's more efficient to have totally closed flow and then totally unrestrained flow discretely rather than having a partially open throttle and pulling air through it continuously at great losses. Am I wrong or there is a huge hope in these digital valvetrains after all? I also recall that these very tight air to fuel ratios are true for homogeneous burn but stratified injection enlarged this window slightly, right?

[@MoronicAcid1]

If gasoline engines were efficient, they wouldn't need catalytic converters to pass emissions. A warmer intake is going to ensure more fuel is burnt, which could be more efficient if it doesn't cause knock and make the ECU retard timing.

[@ElPants21]

@@MoronicAcid1 not exactly true about the catalyst. It's an apples and oranges thing. We can make a car more FUEL efficient with leaner AFRs or warmer temps but it will produce an excess of NOx emissions, one of the pollutants the Cat removes. (Carbon monoxide being one other) engine computers deliberately cycle between slightly rich and slightly lean of stoich to feed the cat with the reactants it needs to do it's chemistry, for the sake of pollution control only.

[@erichwise7734]

This is excellent. However I am trying to figure out how to use this information for a different use case, I have a large 4x4 and can't use a low intake as dust and water ingress are issues. Thought about making or getting an air induction hood but still worry about water ingress. Do you cover any of this? As it is right now the truck unfortunately just sucks the engine bay air as thats how it was done when I bought the truck. GM had it pulling from between the headlight and radiator as you describe. This is great until I do a river crossing though. Thought also about making a snorkel up by the windshield but there very little room.

[@JulianEdgar]

Snorkel is only approach, I think

[@EndritAl]

How HP this thing increase?

[@288gto7]

What about old chevy cowl induction hoods? I think right behind the cowl itself , the area between cowl and the windshield the air pressure was high and when you get on full throttle , engine vacuum drops and the cowl induction panels open to get that high pressure air that was stagnated between the cown and the lower part of front windshield but im not actually sure so i would like to know your thoughts on this since it was also a 1960s idea when they didnt understand aero very well in cars

[@JulianEdgar]

It's OK, but the pressure there is not as great as at the front of the car.

[@288gto7]

@@JulianEdgar thanks

[@GisterThomasGames]

Great video! I do wonder, does piping length greatly inpact performance? (decrease when piping is longer)

[@JulianEdgar]

Easy to measure the real-world, max power pressure drop of whatever pipe length you want.

[@chiquicat1]

Wouldn’t a wider diameter slow air flow speed leading to loss of power? Also, wouldn’t a tune be required to avoid flat spots in the power curve?

[@JulianEdgar]

Airflow speed isn't important ahead of the throttle body. In both MAP-sensed and airflow meter cars, the system self-compensates for the reduced pressure drop (increased flow).

[@chiquicat1]

@@JulianEdgar Thank you, makes sense. Also, would smoothing out the inside of the airbox (cutting the fins) help? I heard air passes quicker but instead of being spread across the whole panel, it only goes in a concentrated area of the filter, so a bit hesitant to do this mod. Thanks.

[@davidparker9676]

These modifications work wonders on older cars with poorly designed intakes. However on newer cars, you may lose power all through the power band by messing with the factory engineered intake system. I have seen it first hand as well as seen it verified on the dyno with a popular aftermarket "Cold Air Intake" The new car intakes are tuned to the engine in very sophisticated way taking volume and pressure waves into account. This is a place where you may want to trust that the engineers knew what they were doing. Unless a performance intake had equal or greater engineering put into it, you may experience a loss in power and efficiency.

[@chobba]

How important is the smoothness of the inlet before the airbox? I'm currently using an accordion-like HVAC hose routed off the airbox into my wheel well area. I want to move it to a high pressure area, should I replace it with a smooth rubber/pvc hose?

[@JulianEdgar]

Yes

[@hartmannsson]

Thanks for the fantastic videos. Doing the modification pn the air intakes, did you notice much difference in noise characteristics?

[@JulianEdgar]

Sometimes a bit, but my approach (eg retaining the airbox) tends to make any noise increase fairly small.

[@brainwashingdetergent4322]

Do any of these mods effect how the ecm interprets the various sensor data?

[@JulianEdgar]

No.

[@beyondpistache8413]

I have observed many times inside an airbox ridges going in both axis (like the ones you see at the top of the lid at 10:00) I have always tought they were designed to increase structural solidity and I always dremel them out and made a smooth surface. Do these arches serve another purpose or is it better to remove them entierely?

[@JulianEdgar]

It's best to measure the pressure drop and then you don't need to guess...

[@Remenschneider]

Try a cemetery vase for a cheap bellmouth

[@GerryHavican]

It's not a funeral, make some noise.

[@ChainsawChuck13]

So what would you do with one of those common/off-the-shelf "cold air intake" kits that use conical filters and violate everything you just said, in order to make it better? I was thinking of getting a CAI for my '13 Veloster Turbo, but was told by other Veloster drivers K&N wouldn't make any difference because the intake tube isn't much bigger than stock and the and the biggest power bottleneck on that car is emissions BS anyway. I was told I'd need to go up to something called the Tork Motorsports Big Gulp to see much of a difference, and was wondering at one point if mix & matching the Tork intake pipe with a separately purchased K&N conical filter would be worth a little bit of extra power, however it would still be a typical COTS intake upgrade with no airbox and a big showy filter sitting exposed in the engine bay. Does allegedly increase power over the stock setup, and lets more intake honk into the cabin so it sounds faster, but apparently no optimal. So would it be better to take that route and somehow fabricate a custom airbox + duct for it, buy one of the airboxed CAI setups that I just realized existed, or just fabricate an entirely custom system out of PVC and cake pans?

[@JulianEdgar]

I would measure the pressure drop of the standard system so no guessing is necessary.

[@ChainsawChuck13]

@@JulianEdgar I did just buy your book, so in about a month or whenever Abuzon decides to stop being worthless, I'll hopefully be better equipped to figure those things out. The most surprising thing to me is to hear someone who seems to live in Europe placing such an emphasis on custom-fabricated parts for daily driving. I thought that stuff was basically forbidden over there

[@JulianEdgar]

I live in Australia.

[@ChainsawChuck13]

@@JulianEdgar Now I understand why you mentioned the PVC pipe intake not being noticeable

[@nolandavis6821]

It’d be interesting to see someone try a resonant intake. Like a slide whistle so the pressure would increase just as the engine needs to draw it in.

[@JulianEdgar]

Like every car already has post throttle body?

[@nolandavis6821]

@@JulianEdgar I guess I would’ve been a successful inventor in the past if that already exists haha.

[@tortron]

Some sports bikes have telescoping trumpets that change lengths with rpm

[@archygrey9093]

Most new cars have variable length intake runners now

[@johnconnor513]

Love your videos sir. What about using air vortices in the intake?

[@JulianEdgar]

To do what?

[@davidparker9676]

I used one in my BMW intake boot. I don't have any data to back up my claims but it felt like it made more power. It could be a placebo effect, but it did make more power on my "Seat-of-the-pants" dyno.

[@lamontcranston8181]

Creating a vortex in the intake before the fuel is introduced would do nothing at all.

[@robertlondonse14]

My air filter is located at the side of the radiator, it has a 100mm tube to the throttle body, but the intake is about 50mm tapered to 40mm where the air enters, which always seems counter-intuitive? it is pointing downwards towards the front grill though.

[@JulianEdgar]

Best to measure pressure drop as described in the video - then no guessing is needed.

[@MoronicAcid1]

You need both pressure and temperature to determine a restriction, because pressure changes could correspond to changes in velocity in incompressible flow which wouldn't affect the flow rate. Temperature is also how leaks and restrictions are diagnosed in AC units where pressure is constant across each side of the unit.

[@makantahi3731]

what air speed in air duct between filter and throttle body is ok, my intake duct is 80mm same as throttle body and engine is 5.7 litre, 6000rpm max

[@JulianEdgar]

Air speed matters little.

[@that_guy6116]

You never mentioned snorkels used on racecars

[@mc1996]

Interesting, i know lots of cars that have wheel archs airbox mouth, mine is one example. Do you see any advantage on that? Maybe on the noise level? I cant see any point if the air pressure is very low and the moving air on that area can even be "sucking" air from the intake.

[@JulianEdgar]

Cheap and easy for the manufacturer. And, as you say, it will reduce intake noise.

[@yuk-erkmckirk9277]

my diesel hilux turbo had the original airbox intake in behind the headlight area. when i put a snorkel on it i had to remove an intake box from under the inner guard in order to mount the snorkel plumbing. what is this box for? it is actually in parallel with the intake prior to the filter airbox. also does the snorkel feed air better and cooler into the airbox than the original as it is higher and out of the engine bay heat.

[@JulianEdgar]

The box is probably a resonant box designed to reduce intake noise. Regarding the snorkel - better to make a few simple measurements rather than guess.

[@crazyhedgehog66]

Does this work on forced induction engines?

[@JulianEdgar]

Yes, measured ahead of the throttle butterfly

[@TairnKA]

Where would the best location on a mid-engine car be?

[@JulianEdgar]

If the intake duct is big enough, it doesn't matter where the engine is.

[@mikescudder4621]

I've looked at this several times over the years and not gone ahead with it because supposedly, air boxes are tuned to reduce/eliminate resonant frequencies for that specific engine... any changes in noise levels etc after your mods?? Also we have the traditional performance/reliability trade off... your going to pick up so many more dirt particles with a CAI, as someone who is only interested in economy, if i had to exchange my air filter twice as often (for example), the mod would probably cost more than any fuel economy benefits wouldn't you think??? Cheers for the info, i'm enjoying your channel. Cheers!

[@iEatSnow]

I am here for the audi, urs4 luv :)

[@miralemnermina142]

Wouldn't rain ruin a paper filter?

[@JulianEdgar]

Doesn't seem to on the many standard cars that have a mist of spray/fog passing into the intake. Have a look at the intakes on many high performance cars.

[@fastmonaro05]

Good videomate.

[@JulianEdgar]

Thanks!

[@001-j7l]

3:43 YES!

[@archygrey9093]

My old 1981 Hilux actually has a pretty smart system, the airbox hose goes into the fender and then the front of the fender has another pipe that comes out around the back of the headlight. So it takes fresh air from the front and uses the empty void between the body panels to transport the air and probably acting as an intake silencer and water trap at the same time. People modify them because it looks like its taking air from the wheel well when thats not the case at all.

[@JulianEdgar]

Interesting.

[@lavrentievv]

Most front wheel arches are very very much above atmospheric pressure.

[@JulianEdgar]

Not based on my measurements.

[@lavrentievv]

@@JulianEdgar Wheel-well pressures are generally biggest drag contributor to front end CD, wheels make up up yo 40% of it. BMW 5 series G30 lowered their drag from 0.25 in the F10 to 0.22 thanks in part to front wheel-well slats to relieve the pressure and smooth the airflow. My VW Beetle and all the NA Mark 3 VW golfs had air intakes sucking air from the wheel well due to the known high pressure area. Modern cars might have front wheel coverings and slats like the BMW to relieve that pressure, but otherwise it's the biggest front end drag savings that can be made. Same with new Porsche GT4 RS

[@JulianEdgar]

Measure it for yourself. No need to guess or go on what others say.

[@PROofHAPPYWHEELS]

Please be mindful of PVC as I've heard it can release toxic gasses when hot, including chlorine. Maybe opt for something else instead.

[@JulianEdgar]

Good point. Plenty of ventilation is good - I typically heat and shape it outside.

[@jackthatmonkey8994]

Strange that you modified your Honda Insight intake like that. I would imagine Honda put it there to further decrease the effective volumetric efficiency of the engine to increase fuel economy. That was what the car was about after all

[@JulianEdgar]

How on earth does decreasing volumetric efficiency improve fuel economy?

[@hectorae86]

Next up ITB's

[@Arielxx01]

So, is it making more horsepower? And how much more?

[@JulianEdgar]

Yes of course. But since the change in power is also related to speed (aerodynamic pressure) you either need to do the power measurement in a wind tunnel or by acceleration tests on the road. The improvement depends on how bad the original system was.

[@Arielxx01]

@@JulianEdgar But should I be aware with changing the total intake volume (and resonance frequency or smth)? Is it worth throwing off the fabric resonator box (that from my knowlegde gives some horsepower too) to install bigger pipes and putting the intake where the much aerodynamic pressure is, like you said on video? And what about the intake piping total lenght - is it somehow related to horsepowers? (Longer/shorter intake = more/less horsepower? Im not telling about temperature, only the lenght of the piping)

[@JulianEdgar]

@@Arielxx01 If you want the very best power possible, it's worth testing each of the variables you mention. If you want rules of thumb that work in perhaps 80 per cent of cases, do what is in the video.

[@Arielxx01]

​@@JulianEdgar Thank you for explaining everything, but what about the rain for example, or the water splashing on front of the car, where you have this intake (as you have shown in 4:25)? I can imagine how much does it sucks air when driving 180 km/h and how much it sucks in the water that the car in front of you is splashing when it's raining. And if the water gets into intake it can damage engine so badly

[@JulianEdgar]

The approach covered at 4:25 is widely used in standard cars, where the bonnet shields the intake when it is closed. If you're worried about water, put a drain hole at the lowest part of the intake system (again, as is widely done in standard cars).

[@CdnBullyboy]

The vintage VW community has been branching into swapping Subaru engines into the early busses, the most common radiator location being under the belly of the bus laying flat between frame rails. The big question is how to get the best air flow through the radiator and the fans pushing or pulling that air. Just wondering if you might have some thoughts on directing airflow?

[@JulianEdgar]

Measuring aero pressures easily see what you are doing. Cheap and effective, especially for radiator flows.

[@CdnBullyboy]

@@JulianEdgar do you have a video detailing measuring air flows?

[@JulianEdgar]

All covered in my books.

[@enterBJ40]

Some Lamborghinis from the 60"s , Miura i think, have a spoon under the body protruding towards pavement in order to collect high pressure air for the radiator located somewhere in the middle section of car. Look IAN TYRRELL KZbin channel about this car. He is an expert and explains everything really nice and tidy.