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.

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.

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!

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 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

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

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).

You sound like Melvin from the movie Madagascar

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

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.

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.

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

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.

Thank you for not having any video intros and just going straight to the point.

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

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!

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.

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).

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 KZfaq vlog. AF

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.

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.

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.

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.

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

Either you read a few pages or u watch this guy. The physics behind it is important to know for your next step in truck or car mods! Thanks bro

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.

Thanks, glad you like the videos!

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

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

I love the quality you put in your videos. If i never saw your subscriber count, i would have thought you had a million subs

I came here after looking into the ford voodoo engine, a flatplane crank V8 that sounds like a muscle car V8 despite its left to right firing order, and found out that it has 4 to 3 to 1 exhaust headers. That's why it sounds that way, and naturally I was like "how??" This video helped me in understanding what exhaust headers even do.

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.

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!

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

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)

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

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

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

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.

You're going to have a mean machine by the time all these videos are done.

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!

Hey just wanted to say great video's, I have been building motors for awhile now and you explain it better then most of the guys I have learned from. Keep up the great work!!

When people mention running open headers it refers to disconnecting the exhaust from the Header Collector. So the only parts the Exhaust has to flow through are the Cylinder, Cylinder Head and Header, once it reaches the end of the Exhaust Header (Or Exhaust Manifold) Collector the exhaust vents to atmosphere, instead of having to go through Exhaust piping, Catalytic Converters or Mufflers, which are restrictive. In some applications this can lead to more power and it makes a lot more noise :)

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.

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

Technically they may be the same, but car guys see it this way: Headers refer to equal length pipes designed to smooth out exhaust flow and increase performance (exactly what you see in the thumbnail). Exhaust manifolds are stock pipes coming off the cylinder bank, they're not equal length and do not help with performance. Both are simply that group of pipes in the video, beginning at the cylinder bank and ending at the pipe bolted on after the cluster.

What about equal and unequal headers??? What are the differences except from the design?? I'm an Impreza STi owner so you understand why I'm asking and I would be glad to learn more... Keep up the great work!!!

Literally just got these headers today and this caught my eye due to not knowing which one is more suitable for daily driving

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

There's a third way a header increases horsepower: Sound Reverberation. Sound will bounce off the collector, come back, hit the head/manifold plate and go back, pulling the next exhaust pulse with it, and at certain rpm's the header will perform best as the sound bouncing off the head is in time with the exhaust valve opening.

Love your videos and i respect that you are an engineer with knowledge, however we all work in the "professional world".

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

These videos help me so much. I am working on designing an "ideal car" because I'm fifteen with nothing better to do, and I want to have experience in designing cars if that's what I end up doing for a career. I'm thinking v10 or v12, 3.0 liter 1990's f1 style. Awd, with torque vectoring, and turbo charged. I'm also working with an Ohio state university student with a Chrysler internship on redesigning the way valves work and move, because I really hate how restrictive they are. The goal of the car is pure acceleration. I think I'll be relatively relaxed with top speed. Let's say a goal of 200 mph (hah got you there). Because of acceleration being our goal, we'll use the 2014-2015 f1's hybrid engines as a reference point. I recall you going over a new turbo technology you saw at an event. We'll combine that new tech with the split turbo technology of f1, to keep the intake cool. Since I'm a group B rally enthusiast, let's put a twin screw super charger after that turbo.

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

i just want to say thanks for making these videos, its greatly appreciated and keep it up!

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

I understand that the peak torque curve changes depending on the header used. My question is that if a vehicle used both the same exhaust pieces except for the header to compare torque numbers as well as the curve, will the 4-1 header out-perform the 4-2-1? Here is my example to better get the answer I am looking for: Scenario: Only thing affecting curve between headers is max flow potential. Just keep it simple and in your mind that the motor is supposedly capable of the flow for the 2 types of headers and that the chance that the 4-2-1 header may cause flow restriction that may actually cause tq loss. 4-2-1 Header - 100tq @ 2000, 150tq @ 3000, 200tq @ 4000, 190tq @ 5000, 175tq @ 6000. 4-1 Header - 100tq @ 2000, 150tq @ 3000, 200tq @ 4000, 210tq @ 5000, 215tq @ 6000. Both numbers are the same until after 4000. This does show the 4-2-1 header as having peakier tq in the lower rpm's for the curve, as well as the 4-1 header having more of a higher tq curve. But, the 4-1 header curve for this example shows no loss of what the 4-2-1 header was capable of doing and also shows an extra bump in tq in the higher rpm's. Though the curve peaks higher for the 4-1, it also has more tq and covers all of what the 4-2-1 header was capable of without any low rpm tq loss. Please help me to clarify this as I don't want to buy a 4-2-1 header if the 4-1 header does not have any actual tq loss in the low rpm's in comparison to what the 4-2-1 header curve looks like. I don't see any point in buying a 4-2-1 header if it gives your car a max tq of say 200 at 4000, when I could get a 4-1 header that still has the 200tq at 4000, but also has the additional tq in the higher range that I would not have if I were to choose the 4-2-1 header. There would be no point in getting a 4-2-1 header if it has a better low rpm tq curve simply because it were too restrictive and disabled any high-end tq.

headers are made of steel using individual tubes so that each exhaust port has a tube then all tubes from the same bank exit into a collector, ideally each tube should be about the same length, that way the exhaust is tuned either for power of for sound or both exhaust manifolds are usually made from cast iron, some have individual runners

Great video, I was able to translate all of this to my motorcycle because it too has an in-line 4 cylinder engine, as well as exhaust headers. It's a 2008 Yamaha R6.

I like your videos man because you're giving me an idea on witch mods I should get on my car to gain more horsepower so I can have more fun on the roads. Nick

Read about the Tomei exhaust manifold for the sr20det, its a unequal length manifold, in theory it should make a turboed car more responsive and faster spool up.

Thank you for making all these videos! When I become president of the world I will make them mandatory for all tuners to watch.

On those curves you showed, it seems that the main benefit of the 4-1 is at high RPM. If I am reading it correctly, the 4-2-1 is actually better at low RPM. Since most of us do our city driving on the low side of that curve, the 4-2-1 sounds like the best fit.

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

We need more engineers like you thank you for all your work

I like how you kept it simple and to the point. Thanks

Both would be correct. The sensor measures the ratio of oxygen in the exhaust gases compared to unburnt hydrocarbons to work out the air to fuel ratio. This ratio is measured in λ (Greek letter lambda) with λ 1.0 being the stoichiometric ratio of 14.7:1. Smaller lambda values are richer and larger values are leaner.

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

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

You explain very well about the topic! I'm enjoying your series!!!! Really good!!

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

ZOMG Thank you. I agree with both you and Jose on this matter, straight to the point, no time wasted. Love your videos man.

You don't necessarily want bigger pipe for a header, you want faster exhaust velocity which is why 4 to 1 header is better. Larger piping means more top end power with a trade up with less low end power. The biggest difference between stock manifold setup and a header is removing the catalytic convertors which are a restriction meant to reduce emissions.

Man litterally all the info I need to know you have, thanks man haha just learning and learning.

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

You should do a vid explaining the difference between DOHC- SOHC and OHV (Highlighting disadvantages and advantages between them if there are any) ---- by the way keep up the great work

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

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

Great explanation of the torque shift of 4-2-1 vs 4-1.Thanks

You can find the routing of exhaust system for that purpose in the large vessels such as 50,000 DWT Bulk Carrier Vessel.

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

Thanks for putting this up bro, I remember asking about this couple weeks ago.

Headers with a stock exhaust will look great, but power increase will be far more enhanced if you remove all (not some) of the small diameter bottlenecks downstream. Go too large though, and you slow exhaust gas velocity and reduce scavenging. Also, large diameter pipes can have fitment issues and may increase cabin temperatures. Large diameter exhausts are usually noisier too, if that's a problem. Oh, and headers are usually a bear to install.

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

you should also do videos of you adding parts to your car like turbos, brake pads, rotor, cams, stuff like that.

Thank you for taking the time to explain this!

You are an amazing teacher, just wish your explaintions were more simple...

Yep

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

Correct.

I apologize if you covered this, If you want to replace your stock exhaust header with something with larging piping, how would you connect the larger piping to where it connects to the engine? I'm guessing it has a specific diameter. I didn't know if there was another piece you would connect to make it fit or not. I love you videos I'm learning so much.I also have a vw rabbit a/t 2007 2.5 that I would like to start fixing up.

Plan on doing any videos showing us the completed vehicle when the time comes? I'd be interested to see what all these nice parts do to it performance wise when all is said and done.

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

Great vid as always. Thanks for the education. Have u considered having a quick quiz at the end of ur vids...might be a good idea

this guy is the man.

So, a larger exhaust must beg for a larger/less restrictive intake. Which means, more oxygen and a stronger combustion…creating more power. Just trying to connect the dots here. Lmk if this makes any sense. Thank you!

I'm an application engineer for a forklift company.

Thank you very much for explaining the item. can you please tell us what are the risks that may happen after installing it.

Really enjoy your videos! If you do install the parts you've been getting, make a video!