Exhaust Header - Explained 

Actually, I am an engineer, working in the professional world..

Just gotta say, i love your videos, Im a first year Freshy engineer on a Formula SAE team and these are such a great way to get introductory information. Keep up the good work!

Yes, and yes. Check out my "automotive careers" link on the "about" page of my channel.

Been waiting for an explanation of this these bad boys! Thank you sir

I also want to now if denting the headers can affect their performance by anything significant.

do you have any video showing if there is any power gain by doing only a muffler delete?

I want to major in Mechanical Engineering aslo, would you recommend it and are the classes hard.

i got a question, so which headers contribute to a Louder exhaust sound? Larger diameter pipes or Smaller? 4-2-1 or 4-1 ? if u can answer that, that would be great! thank you

on a turbo charged vehicle is it OK to get aftermarket headers on a non tuned car. I have a full turbo back catless at the moment but that is it. car is a (gf8/gc8 ej205 wrx).

I've got an stainless steel OBX after market header, that should be ok right?

how do u relate torque peak with an exhaust heder?

if i was to put a twin turbo kit on an all stock car, what all would i have to do?

First, I like your channel, and i'm subscribing, so don't take this the wrong way :-) but... You missed the science behind the main reason for using an aftermarket header... it is *Not* the larger diameter header piping (although that *can* help... or hurt... "sometimes"). The main rationale for a header is to create an equal length of piping from start to finish for each of the individual pistons on the engine. Why? - The pistons fire in very rapid succession, and when each piston releases it's exhaust gases into the exhaust system, it represents a pressure spike in the exhaust system. Each of these pressure spikes seeks to equalize pressure by expanding down the exhaust pipe, eventually exiting the exhaust. - At the rate of piston firing in typical engine use, any given piston's exhaust pressure spike has not yet dissipated before the next pressure spike from another cylinder arrives (more noticeably so at higher rpms). So the pressure spikes from the cylinders start to overlay each other, kind of like people waiting in line to go through a ticket booth. This generates exhaust gas pressure, and the higher the pressure, the more it creates back-force on the engine's pistons which push out the exhaust, robbing power. - While larger diameter exhaust components are helpful for reducing gas pressures in the exhaust, thus reducing resistance to the engine's job of forcing exhaust out and in turn the amount of power it takes to pump the exhaust out... there is another factor at play which a header is specifically designed to address: *The spacing of each cylinder's exhaust pressure spikes in the exhaust system.* - In a typical original equipment exhaust manifold, the goal is often to use as little metal as possible (cheaper/lighter), and take up as little space as possible, while getting exhaust to the catalytic converter as quickly as possible so that it heats rapidly, reducing emissions for legal reasons. This results in exhaust manifold piping where the pistons nearer the catalytic converter having a shorter distance to travel to enter the main exhaust, and pistons further away from the catalytic converter having a longer distance to travel ("unequal exhaust path lengths"). - The pistons fire in a cycle where each piston's exhaust has equal timing between it and it's neighbors, so at any given RPM, the exhaust pressure spikes are occurring at equal intervals. But when they travel through piping of different lengths, these exhaust pressure spikes can end up closer or further apart when they reach the catalytic converter and remainder of the exhaust. If you want to go back to our people waiting in line analogy, imagine two people side by side in line, both trying to get through a ticket booth which is only one person wide, at the same time. - A header is designed *specifically* to reduce (short header) or eliminate (full header) that timing differential, by making the length of pipe for each cylinder going to the catalytic converter identical, or nearer to identical than stock. So that your people waiting in line to go through the ticket booth (spikes of gas pressure in the exhaust which must dissipate to reduce exhaust pressure) are in a nice single file line which moves through the ticket booth efficiently. (( For reference, when you see an engine's power band (in both HP and Torque) following a curve where you get diminishing power returns at higher RPM, that downward curve (which seems to prevent an engine from continuing to ramp upwards in power at higher RPM's) is very heavily influenced by the resistance of gas movement. Friction, and oscillating weight such as pistons, valves, & rods also affect it, not to mention losses in the drive chain taking it to the wheels. But back to gas movement... If you tuned the *entire* breathing system of a car, including: filter, intake, throttle body, intake manifold, valves, valve timing (cam), exhaust ports, header, cat, and cat-back... you could shift the peak of an engine's power output several thousand RPM's higher, allowing it to climb to a significantly higher peak, at much higher RPM, before diminishing returns bring it back down, and also provide a broader power band which helps reduce time spent shifting gears. BUT most of these components *by themselves* offer very little benefit, because the stock components are like a whole set of bottlenecks, and power gains are minimal when you only remove some of the bottlenecks. A header is the glaring exception though, as it can help *any* exhaust system move air significantly more efficiently. Although from a labor standpoint, if you're installing a header, you probably should do the whole exhaust anyway. Similarly a turbo or supercharger has a very strong single-upgrade benefit because it can brute-force it's gains through a restrictive throttle body & intake manifold. )) *** Header Advantages *** Headers can reduce exhaust pressure *significantly*, or more accurately reduce variances in exhaust pressure, so that any given diameter of exhaust piping, catalytic converter, muffler, etc. can work most efficiently. At low RPM where exhaust pressure is minimal, there are little to no power gains, but at high RPM's a header will make any exhaust system have much more efficient gas movement, keeping exhaust back pressure to a minimum. A good header can help reduce the need for excessively oversized cat-back tubing, reducing weight and improving ground clearance. It also makes a smoother sound at the exhaust. While a un uneven rumble may sound cool, a smooth deep exhaust note is the sound of efficient air flow. A header can add more power (by itself) by increasing the efficiency of even a stock exhaust system, than a cat-back can. It's also much more of a pain to install though. *** Header Disadvantages *** Headers add weight. All that extra piping is more metal for your car to carry around. For normal driving in the 500-2500 RPM range, headers will weigh more than they're worth. Which is one of two reasons they aren't factory equipped. Headers put more travel distance between the engine and the catalytic converter (another minor help for reducing exhaust pressure), but that makes the Cat take longer to heat up after starting an engine cold... and that will make your pollution emissions significantly less favorable. Some schemes that auto makers have tried to overcome this issue is to put a mini-catalytic converter in each header pipe, or to electrically heat the Cat at startup. Some performance Cats are designed to somewhat alleviate this concern with more pure platinum coating, etc. Another possible disadvantage is that some exhaust headers have oversized piping, but if the exhaust ports on the engine block are smaller, that creates a sudden change in exhaust diameter... while the explanation is quite a bit more in depth, in simplest possible terms, you can think of sudden squared off changes in exhaust diameter as being "very NOT aerodynamic" in terms of moving gas through a tube with minimal resistance. Conical changes in diameter are not problematic, but squared off changes in diameter are not good. Large diameter header tubing on standard diameter exhaust ports could potentially rob a bit of power even at low RPM. I'd recommend getting standard diameter piping on the header (matching the factory engine block ports) *OR* milling out the engine block to match the header diameter if you want really big pipes (milling the exhaust ports is probably only worth it if you're going to increase the engine's gas pressures with a turbo or supercharger). For similar reasons (avoiding abrupt changes in pipe diameter), I'd recommend a low-resistance performance catalytic converter with nice gentle funnel shapes fore and aft, a low resistance muffler, and to avoid using a resonator. Likewise, the design of a header's "collector" (where the pipes come together) is crucially important as well. ALSO: A 4to2to1 header will perform well *on a 4 cylinder engine* for piston ignition sequences of: 1-3-4-2 and 1-3-2-4, but less well with ignition firings of 1-2-4-3, 1-4-3-2, and 1-2-3-4. Meanwhile a 4to1 full header will perform equally well with any ignition sequence. This is all due to getting the people going through the ticket booth as equally spaced and spread out as possible. If two neighboring cylinders in the right or left pair of a 4to2to1 header fire one after the other, then that creates additional pressure on one side in the 2-pipe stage of the header. Personally I think a 4to2to1 header is the better choice, being generally lighter, and having staged collection (merging of pipes), but only *IF* the ignition sequence on your car is one of the two sequences with which it can perform to it's best potential. In terms of parts & labor, it's almost always cheaper to get a car with a larger displacement engine than it is to tune a smaller engine to be more powerful. However, I get the hobbyist interest. And with gasoline at around $3/gallon, 100,000 miles at 20mpg is $15,000 in gas, while 100,000 miles at 30mpg is $10,000 in gas. I doubt you'd usually see that large of a gas mileage difference, but there can definitely be some back-loaded savings on tuning a smaller engine. Plus "the engine in the car you already have" is always priced very attractively.

You have to understand the basics to understand it all. Some videos are simpler than others, ultimately (hopefully) it provides a good understanding of the overall system.

You sound like Melvin from the movie Madagascar

Finally someone who doesn't swear by turbos. Engineering at it's finest indeed! I love the mathematical breakdowns, really helps me understand the concepts of these videos. Very good work, mate! Cheers!

Your honestly a huge help man. I'm really into cars but I have literally no one to teach me anything about them. I thank you for these videos even tho learning from them is looked down upon by others. They still help me and inspire me.

Header comes directly from the engine head, it's the first tubing the exhaust goes into after leaving the cylinder head. The downpipe is directly after the turbo (exhaust side).

Let's ask Google. Tube: "A long, hollow cylinder of metal, plastic, glass, etc., for holding or transporting something, chiefly liquids or gases." Synonyms: "Pipe" I don't know why people get so caught up in semantics.

Absolutely, it's not as simple as saying this component gives this much power. Everything works together.

This type of header would not be compatible with a turbo (it places it in a bad spot).

Perhaps, if it's really heating up the engine bay a lot/the intake manifold. Also most exhaust manifolds have a heat shield, and this requires removing it so it could potentially help.

Once I get into tuning my car and actually swapping out components, I'll be doing some dyno tests for sure, and will certainly explain them. It may be a while until this time though, saving up for a new car so my Integra can become a project car.

Actually there are some headers that do this, but I think the reasoning lies in creating the scavenging effect, and having the pulses create a low pressure zone which acts like a vacuum. Things wouldn't exactly line up well if it were to all join at once.

No, it's simply routed that way to expel the exhaust gas at the back of the vehicle.

Yes, sometimes curves are put in to keep the length of the pipes equal, could also be done for space constraints.

Check out my video "how exhaust systems can increase horsepower" which explains why you don't simply want one huge pipe.

Haha I have an exact video that explains exactly what you ask for. Do a simple search on my channel for DOHC.

Most of what I saw only differed by a few hundred RPM, and most of the time it seemed the 4-1 did a little bit better. Definitely didn't pool a very large sample of dynos though, so it'd take a bit more to reach more conclusive decisions. I hope to get more into it over time.

As long as everything hooks up right you shouldn't have a problem with emissions.

I don't know who you are, so I certainly don't hate you. Define tubing/piping please.

You should also touch on aspects like - Sequential vs non sequential pairing of 4-2-1. There was an Exup Valve on a header that would switch between the two pairings. - Long tubed primaries vs short tubed primaries. Some headers will split the primary secondary length 50/50 but I've seen some primaries that are closer to 60% of the length perform like a 4-1, while still reaping the benefits of the 4-2-1. - Then there are collectors that have venturies/choke points in them to alter their performance. - Stepped headers and stepped port vs port matched head -> header

Yes, if you're only using this for city driving rather than at a track where you stay near the higher RPM.

Back pressure is not needed, velocity is what you want. Check out my video "how exhaust systems increase horsepower." Here I discuss the balance, you may not have enough power to warrant a larger exhaust, thus it may actually reduce performance slightly.

Depends of course on the engine, number of cylinders, and size of the engine. If you check out my video on catbacks I give a fairly vague rule of thumb about how it may work. Likely need additional videos on this kind of topic in the future.

A looked at a variety of companies when I was still in school. Yes, definitely difficult to get into the automotive industry. I like where I'm at.

Interchangeable terms yes, "header" seems to be more common here when referring to aftermarket parts.

Same thing, many aftermarket companies simply refer to replacements as headers.

Dear Engineering explained. My question has to do with an exact situation with the C8 when one of the vloggers showed his receipt of a Kooks exhaust header. He did a "pull" with his stock header on the 2020 Stingray, 6.2 liter pushrod, V8 engine. After taking the initial reading for HP and Torque with the stock exhaust manifold, the latter was removed from the Corvette. In its place with the same other stock cats and pipes, resonators, pipes and mufflers and tips, the only difference that was tested, was the addition of the Kooks exhaust headers, where the stock exhaust manifolds formerly had been. (Although a short tube header system, the pipes appeared to be longer and with mandrel-bent turns to the, "collector." The diameter was slightly larger than stock. Then the C8 vlogger ran a dyno once again with temperatures the same; same gasoline, etc. Result: throughout the range, including at the cross-over, the Kooks headers provided readings that were 2 to 4 horsepower lower in both horsepower and torque, even at the crossover point, than were achieved by the stock manifold. What is the explanation for this? I wrote into Kook asking for an explanation and received no information at all. The only thing that might have affected this result, is that it appeared to me that the connecting flange of the Kooks header, had smaller opening than its pipes and also smaller openings than stock. However, writing into the vlogger, produced no response or answer to me, just a lowly fan, observing the RU-vid vlog. AF

I'm an application engineer for a forklift company.

I haven't really been upgrading it, primarily due to a lack of time. If I put any of these parts on there will certainly be a video.

Yes, this fits B series motors, and my Integra has a b18b1.

Eventually, I know this has been asked many times and I've been worthless about getting it done. I have good intentions I promise!

Appreciate the suggestions! I do have videos on cam lift, multiple valvetrain videos, but many of your other suggestions I am limited on. Cheers

Haha very welcome. I get a comment or two every now and then saying "you need a video intro." I disagree - I'm here to teach and an intro is simply a waste of time. Hence "hello everyone and welcome" is my intro. Glad to see the method is appreciated.

No, I'm just leaving it as is. If I do end up installing it, it's a ways off.

Haha I agree, I was simply replying to 1987 who was saying I was not even an engineer.

As I've graduated, I love not studying anymore ;)

just fyi for those in the dark. Primary tube size is always given for the outside diameter not inside diameter.

Thanks, glad you like the videos!

As it's a pretty generic statement, I'd say both could be true.

thank for your video and i have some questions to ask 1) For 4-1 and 4-2-1 exhaust system, which will have better air flow but lower air velocity? (from what you draw i think should be 4-2-1, but still need your clarification on it) 2) how does the air flow and air velocity of exhaust system affect the torque band shifting? (of cause in your graph did show the result of torque shifting, but i really need you further explanation on that)

Yes, and updates along the way. Haven't even started to be honest.

With the power band shift - that's not because of the way the headers are built, but because of their length - in a N/A car there are wave effects occurring in the exhaust that help scavenging around some RPM range, and that depends on header length. As 4-2-1 are in most cases longer they help in lower RPM range (also there are compounded effects from each joint point so 4-2-1 have a wider torque range).

Nice to watch his videos before he started reading provided marketing’s brochures

Hp, and Torq . . . Increase Performance. Staying Frosty 🥶

Not sure yet. If I don't turbo it I may.

alright alright, i thought i might see maybe one or 2 of your videos in my life of yours but evidently thats not the case now.... damn it you earned yourself a subscribe....keep up the great work

Mechanical engineering.

Dude thank you for these videos, you do a great job of explaining and making good sense of how things work. Especially a car enthusiasts such as my self thats at an amatuear level with understanding how things work it makes sense!!! aYou my friend have gaing a new subscriber

Thank you so much for all of your explanations. I've learned about cars and machinery in general with your videos more than with any other resources. Again, thank you so much, I look forward to more of your videos!

Correct.

can you do a video on long tube vs shorty headers?

Does wrapping headers make the headers more quiet?

I will of course! Just need more time haha

Yep

Haha that's the plan!

I have a civic 1999 LXi with a stock engine of D15z4(87hp). You mentioned that an upgrade to a 4-2-1 header won't help in this kind of small engine. So, how can I add more kick or more HP into this? I don't want a turbo package upgrade as this is expensive. I just want to see other options if there are. Please advise.

I'm sorry if I didn't catch it in the video but what bearing does the length of the headers have on back pressure? From what I have gathered from info online and my experiments with my 36-year-old 350cc single cylinder bike, reducing back pressure to a very low amount results in large gains at high revs (just like you said about shifting the peak output up the rpm band) but a drop in low end output. How does the header length fit into this?

I like that you talked a bit about the types of collector designs. If you look at some of the nascar cup car headers, they have various designs including 4-1 and 4-2-1 for each cylinder bank, as well as various pipe diameters of each step. It's really just tuning based on the track they're running, but it's surprising to see so many different configurations.

Why did I go with Headers? Simple. They don't crack like cast iron.

Nice job on this video. You really should discuss the primary pipe length as it is the single biggest factor for the tuned header. A shorter pipe length move the peak torque higher up the RPM band while a longer pipe length moves this down the RPM scale.

Any chance we can get some info on High Airflow catalytic converters and if its even worth it? CA legal of course...

For me I have rsx k20a2 type s in the car I have 4-1 header with Muggen down pipe and 2”5 fully piping on eBay parts I feel my car have more torque and top end raced , I have raced b series wrx Sti rsx and 9gen full both on still beat them ❤ I just say 4-1 vs 4-2-1 header depending how is the driver racing and shifting

My old Porsche 944S had a 4-2-1, also known as a Tri-Y exhaust system. It sounded pretty good and seemed to flow pretty well.

I've been going through a lot of your videos. You're an excellent teacher. You teach like how I teach others. I'm going to school to teach and while I don't know what topic specifically, but I do know that I will remember the style of your teaching for sure!

What about Longtubes vs short tube headers?

awesome vid.. i have a 2014 veloster turbo.. will buying a aftermarket header increase my performance

So ceramic coated or painted with something like VHT? Which is better in terms of performance and longevity?

bullshit. cars exhaust were designed by manufacturers for a reason. why would you want to modify them?

How's unequal length headers on parallel twin sounds like?

What would you recommend for a 2016 Honda CR-V? 1. 4-2-1 headers 2. Long tube headers 3. Short tube headers? Also, what's the difference between 4-2-1, 4-1 and tri-y headers? Can I mix and match them, let's say 4-2-1 long tube headers or 4-2-1 short tube headers?

Hi I own a car with 67 horsepower at 6000rpm, 91nm at 4400rpm. Should I change the header for more hp or should I just sell it... It's Perodua BEZZA 2020 1.0 3 cylinder engine, It is an 1KR-VE Engine from daihatsu. Is it ok to put in turbocharger into and change the header?? The car is very low on hp and my regret of buying it... So help me out please

Hi, I just found out that my 1991 VW Golf stock exhaust header has a mechanism that allows it to swerve a little, which after-market exhaust headers don't have. I am wondering if this is the reason that after-market exhaust headers crack so easily?

SOMEONE PLEASE ANSWER THIS: Using a Corvettes LS motor as an example, even the new C7 Stingray, why don't manufactures use efficient headers such as 4-2-1 long tubes on stock engines instead of the apparently "less efficient" exhaust manifolds?

Ik this is DECADES old but i have a question... ima instal headers regardless but since i have a yonoka catback exhaust system and i wanna know once i install the headers and then getting the tune.. would it make my car start to pop? Cuz my car makes suttle pops like sooo low pops but you can hear just not loud like most cars are.. so my question is will it start to pop? Also i did an exhaust delete hence why it pops very suttley

I drive an 08 Scion XD with a 1.8 liter in line 4. Been considering doing a full exhaust replacement (headers, midpipe, and muffler). Should cost me around $1,100 give or take. Wondering if the hp and gas mileage would justify the cost? Any comments are welcome.

i have a question, whats the difference between SHORT and LONG tube? (exhayst manifolds) i wanna put top mounts for my nissan 300zx z32 (vg30dett) and i was wondering if i have any problem with the long tube.. :/

I've a small amounts of fund& I dont know which upgrade is better for torque of my car. My car is 1.2cc with mileage close to 200k. So, should I buy an aftermarket alloy rims to replace stock alloy rim which Very heavy or replacing stock header to 4-2-1 header? Hope somebody could help me out, thanks🕵

I am building a custom header for a Mazda MA 2.0 carbureted engine. It will be 4-2-1. My question is, do the tubes have to be all the same length for each cylinder? I have it mocked up and the tubes are all within 2 inches in length of each other. It wont be making much more power then the stock 96ish HP so I am hoping that wont matter to much. Also does it matter where I join the 2 pipes in to 1? I would like to run 2 pipes all the way back to the rear axle and join them together there with a X pipe and then duel tips out the back of the truck.

You look a bit like James Blake.

Great, but, is there a difference between 4-2-1 long tube header vs 4-2-1 short tube header, and 4-1 short vs 4-1 long? or is just design? I have a 1.6 GA16de, and I just want low end torque, here in my country there are too many mountains. Thx in advance.

Are the obx headers worth it? I just ordered it for $265 which I thought for the price why not .... I also ordered a weaponR shirt ram intake and I bought a Spec D exhaust... Idk I just didn't want anything to crazy or too expensive. Just wondering if it's all worth it. U guys think I'm gonna get a nice sound w that combo? And is it worth it or should I have gone w the expensive stuff?

I think 4.1 header would provide more torque at lower rpm which is contradict of what were explained by you. This is persisted per honda b18cr 98 spec explanation video, they decided to plug a 4.1 header to a revised b18cr bcoz to bring down the peak torque to midrange rpm which is very usable for tight turn circuit. Please comment back should me have a wrong understanding. Thanks.

what kind of headers should I get, I have a 2.3l i4 with roughly 100hp, it's already straight piped just wondering if 4-2-1 or 4-1 is better. Also I'm getting them custom made.

Question 'I am getting a ceramic header installed" what difference Is that to the regular stainless steel upgrade and Is it a far better option?? I have a 2003 wrx Subaru Impreza with 200kwts running 21p,boost and a 3inch exhaust. thanks.

I suggest you to talk about the droning effect . I've installed a 4-1 OBX header with a magnaflow catback on my golf 2.0 and the droning inside the car is just sick, destroyng my ears. I caped one of the output pipe of the muffler to retain some back pressure. returning like standard "performance" it fix the noise quite good, but it no longer work very much now. at least ,I can just remove the cap if i want ...

about the difference between the two go see the specs of the integra type r 95-97 (4-2-1) and the 98+ (4-1) in term of performance there's no difference! go see best motoring type r legends! both cars did the same time on 1/4 mile (14.207)

Hey, I really need help. I am looking to get new exhaust for my 1997 Lincoln Towncar, but know nothing about which ones I need. The brand would be either Magnaflow or Flowmaster. Can someone please help?

What's a good website for headers for a 1997 ls integra? B18b1 I've been looking but can't find a site eBay has cheap 60$ headers but I don't want cheap becus it'll ruin over time.