Hahaha, I'll do my best to entertain you for the next 9 minutes. :)

Engineering Explained update: it was good

Ryan Aponte Hey I just saw that you left this exact comment on ss717's vid :)

Supercharged Mustang GT yes I did :)

it was good. I learned that I missed my chance a few months ago to see a HP increase by driving around when the eye of Hurricane Irma passed by, due to lowered atmospheric pressure.

Praise be.

now I want to know how to calculate length/diameter for my project honda.... :/

How much you paid for it on craigslist (a) Amount of monster stickers on the car (c) Desired ricer factor (1-10) (b) a / c + b = diameter in mm

StanceArmy Jimmy same here

Yeah because s2ks are from the 90s 🙄

Isn't it necessary to help boost mpg?

The guy who did my muffler delete on I4 said these engines need a bit of back pressure. I definitely felt a loss of torque at lower rpm. Also I’m surprised that so many mechanics think no tuning is needed after a muffler delete. My area doesn’t have that so yeah car sounds nice and loud with lesser torque which means loss in performance. ☹️ I do have a k tuner. Do you know if I can tune muffler delete by myself? And if so how? @Engineering Explained

@@Febreeze_Odor_Eliminator you believe that coming from a guy who chops mufflers off for a living? The only reason you “need” back pressure, is because it was tuned for it, from factory. So of course it “needs” it, but engines are just air pumps, why have a higher differential in pressure, when could just NOT

@@rocketkinger2506 so if I straight pipe my 4 wheeler, I just need to rejet it and it's good? After I upgrade the intake

@@rocketkinger2506 That's a lie

Who needs headers? I use those save the turtles metal straws instead, cheaper that way

@@Snow-vo1yi gives you that perfect exhaust note too 👌

Unequal length straws

@@Snow-vo1yi Headers are just really big metal straws

I would love to have side pipes for each cylinder out of the fenders.

thanks for the love Jason!

5 4 3 2 1 happy white board!

That is what I am doing, I even wonder if I will be going to celebrate at my cousin's in an hour or 2:)

Or last 60 minutes of 2017..!

No Roadkill #72....It didn't come out on time. So end the new year learning valuable stuff instead of watching Junk Food.

Ya mate, that's not going to happen. Play this youtube video for the cop, you may go to jail.

@@netprowlerp you must be so much fun at parties, I bet you're idea of "rebellious" is missionary with the lights off.

@@ljgarrison6910 😂😂😂😂

@@ljgarrison6910 Hahaha. have to tell that to my wife. She would beg to differ.. Ya, not everyone here is 12 years old.

@@netprowlerp he was making a joke. And you took it too seriously finally calling his audience 12 year olds without knowing the real ages. The only thing you should be telling your wife is organizing counseling cause you're way to serious.

back pressure.🤭🤭🤭🤭🤭

Whatever you want to call it, if you have no back pressure at all, it sounds like ass. You need some kind of baffling and resonance to tune the sound and make it sound good.

@@80s_Boombox_Collector so engines don't get damaged with free flow exhausts? Dragracers rebuild after every race so yeah

Them rebuilding has nothing to do with “back pressure “ or lack there of. Correlation =\= causation.

@@tejaspadhye I thought the lacl of tread on the tires caused them to need to rebuild

Interesting comment. I think it was in the first minute or two of the video that the feller explains why some back pressure is good.

@@CalebDiT Did you watch the same video?

@@CalebDiT No, he mentioned it and shrugged it off as if it was to complicated for us poor folk to understand. He never explained it. Also the title of the video is "Back Pressure is Bad!".

@@CalebDiT What he said was having a balance of velocity and restriction is ideal, not that having some back pressure is good. More restriction increases exhaust velocity but inhibits overall flow of exhaust, less restriction allows more exhaust flow but lowers velocity.

@@Talos_Valcoran87 You and the video maker seem to understand what is necessary, but you don't like the terms. "Back pressure is bad, but some calculated restriction is ideal." It's a contradiction to anybody truly listening.

+TheGhost ....lol, you're absolutely right!

More like among wannabe tuners and builders.

+Mathieu Levasseur .....lol, also true

wish this video was available before i wasted so much time explaining this fairly simple concept to people. could have just dropped the link and walked away lol

engine masters on the motortrend channel did dyno tests with different full exhaust systems and pretty much theres no such thing as too big of exhaust but you do lose a some power and torque at the very start like below 2.5k rpm. what people don't really look at though is partial throttle tuning and just going bigger everywhere can hurt that response and drive-ability.

Happy New Year!!

And a happy new year to you too bro!

First of 2018 here😂

no one says clutch

Squidwards crib does buster

And I understand his frustration so well.

The argument of what back pressure is, is an argument as old as hot rodding.

*some guy at the auto part store says something about back pressure* EE: races home and starts writing furiously on a whiteboard while collecting valid explanations.

I get aggravated when most people open their mouth, I cannot believe he is as cool headed as he is!

I think he knows his team have let him down, some of the stuff at the beginning of the video is very messy, not false, but over simplified and a a result not accurate. Back pressure is not air trying push back into the exhaust (and I think he knows this), it's the positive pressure built up by exhaust gases inside the exhaust system, the higher the engine rpm, the higher this pressure, which is why some high performance vehicles switch between 1 or 2 exhaust backboxes at specific rpms to alter the "back pressure" in the system to maintain higher performance and fuel economy throughout the rev range.

Guys, I keep blowing engines. What happened. I listened to a guy on youtube. Do you have bananas for brains?

Lmfao

*losing

MCM put a potato in the exhaust of an old Corolla and it actually made more power.

"Yeah, we're not gonna fall for a banana in the tailpipe."

Mean Man You're incorrect

Kevin Norris ... said the old guy.😜

I thought the high and low end power came from the length of the header/manifold tubes?

i had a 150cc scooter, and the studs that hold the exhaust to the exhaust port broke one time, and made the scooter so slow, it was normally able to go 60ish mph, and with the open exhaust port, it could barely go 15mph

Devin Royce was it 2 stroke?

Nice work!!! And you are absolutely right, this is GOLD for all amateur tuners! My advise to budget track cars; Keep stock exhaust diameter, remove cat, get "straight through" resonator and muffler (with a tail/end dia' similar to exhaust dia' = no deep tone, pure race sound), this will roughly give you same performance boost as a expensive $1500, from headers and back, race exhaust @EE: if you don't take into account the Euro and newly establish similar US emission restrictions (completely disregarding the cat here) the backpressure is needed to recirculate some of the exhaust back into the intake, to burn unburned fuel, at given loads at specific rpms. So in modern cars it's needed to fulfill legal requirements ;) PS not all engines need this system, but if you increase 1st weight in your search terms and 2nd search increase engine volume/capacity and cross those you'll find it being implicated more and more

Yep. Beat me to it.

you cant have scavenging without backpressure. you don't need it... drag cars don't have scavenging. lmao

You DO need at least some back pressure to get good sound. Try taking off everything after the headers. It will sound like ass.

@@80s_Boombox_Collector Sound doesn't help it go, contrary to what every Honda driver around here seems to believe.

@@Jupiter__001_ No, but good sound makes it more enjoyable.

Engineering Explained exaust dynamics is a really complicated problem. 2 stroke engines needs back pressure tho.

Does any car have variable length exhaust piping? from your explanation the best performance would come from "decent" non restrictive diameter piping with variable length "wide-chamber" to control low pressure wave timing. Is there anything like this on the market? Thanks, and keep up with your great videos!

Am I correct that in some cases, a more restrictive header might be used to increase lower end power/torque, but hurt the over all maximum power?

Engineering Explained You're great man, keep it up.

i couldn't agree more with you comment on the education. (p.s. "you" are my favorite professor! )

Painting flames on it adds another 5 hp.

That is exactly what they did- old drag racers know this.

Happy to hear it, thanks for watching!

Yea he's spot on, think of your exhaust and intake for that matter like sucking a milkshake through a small diameter or larger diameter straw. Or sticking your thumb over the end of a garden hose.

I thought you owned a toy company? You changed to radar equipment after the war?

Ha, thanks for the fun comment, happy new year!

Should get an award for most efficient KZfaq creator.

If you ever want to do a charity fund-raiser, take the current whiteboard that's been used in so many EE episodes, sign it in permanent marker, and stick it on ebay.

Good comment but get rid of the freaking emojis lol

gooz0mbie Thanks, but that's what happens when you give old people "smart" phones... Dad jokes and emojis.😜

@James D 😶😶

It’s not that hard of a concept

"and welcome" It was just too much for the poor guy to handle. He must have been on one of those "three cups of coffee" days.

Did he say hello? I noticed some pictures. Then something about "scavengers"

You lost all credibility at this comment

So basically, early emissions systems were crappy and complicated, and were doomed to kill power unless there was an electronic babysitter to reign everything in efficiently? Big shocker.......

The 70's???? You've got to be kidding me. Or is that as far back as you remember? Because exhaust tech as you explained goes way back beyond the 70's vehicles.

D.E.B. B what he's saying is it really originated in the emissions days, which started very late 60s and came full swing in the 70s, that's when it really became an issue and the backpressure idea came to light

D.E.B. B - Catalytic converters became mandatory in the early 1970's. The tech was not the same in the 1960's. My first car was a 1967 Camaro one owner, low miles PERFECT...$1200; it was very simple (points, carb, drum brakes (all of them), and it had about 3 vacuum lines under the hood). My second car was a 1975 Monte Carlo. The Monte Carlo had dozens of vacuum lines, a cat, front discs, HEI ignition, AND IT WAS SLOW AS MUD. *Car tech changed drastically between 67 and 75.*

Catalytic converters did not become mandatory, it only seemed that way. Exhaust emission limit levels kept being reduced, and because of that, MOST auto manufacturers began using a catalytic converter in 1975 because they couldn't figure out any other way to meet the emission standards. That was the beginning of no lead gas,because the lead would supposedly coat the tiny platinum catalyst pellets inside the converter (I don't remember ANY cars using a cat con before 1975, and then all of a sudden, it seemed like all of them did). However Honda's CVCC engine (in Civics and Accords) was able to meet the emission standards WITHOUT a catalytic converter all the way until 1980 (except in California, I think that Honda needed cat cons there in '78). Exhaust tech did not change; as he mentioned in the article above, was just part of the science involved to get the engines to make certain amounts of power at selected points in the torque curve, while keeping the noise to a minimum. Short open pipes were usually used on vehicles that needed to make maximum power at high rpm's. Longer, smaller, more restrictive exhausts were used on street vehicles that had to be quiet. Somewhere in the middle were exhausts which were a compromise between the two. And for some bizarre reason, the aftermarket often did better than the OEM's; my Honda 750 bike with a Supertrapp exhaust made much better power than the stock pipe, yet was also relatively quiet (that was the exhaust where you could add or delete some discs to tune the exhaust). And yes, the vacuum line rats nest of some of those smog engines was enough to drive us nuts! One little crack in those rubber lines would make the car run terribly! I vividly remember taking polaroid pictures of the top of my engine, pulling off the Autolite carb and replacing it with a pre-smog Holley, plugging up all those little holes, and running it like that until the next emissions inspection when I'd reverse the whole shebang! Ahhh, the good old days!

I think it more comes from people putting oversized diameter exhaust on their vehicle and losing power/torque because the exhaust velocity has slowed down too much. They don't realize there is a difference between free-flowing and oversized.

Their carburetor was set up fora high back pressure exhaust and they put on a low back pressure exhaust and now it don’t run the same. That’s when they say they “ need back pressure”

that's what I thought when I had a rusty hole in the exhaust but my emissions were bad untill I fixed it. And it's not an old car.

Loss of power due to oversized piping is a bit more complex If the working routine of the engine is not modified, it will keep on kicking the same quantity of gas out for a given load, no matter what pipe size is used The loss of power is not due to the fact it looses velocity on getting out of the engine but on the pressure in the cylinders A bigger pipe allows more gas out so the cylinders will be emptied easier but If the cylinders feeding/emptying scheme is not modified, some of the mix supposed to ignite wil slip through the exhaust system before it is consumed, which turns out to leave less mix in the cylinders, giving that loss of power It's pretty simple Bigger exhaust implies better ignition timing

@@sethmanukula176 Yeah exhaust valves usually open before BDC

Nice to know your god created the internal combustion engine... Carry on

Zoomies😍

mcf3778 I think/hope it was a joke (ish)

No!!

Yeah it was a terrible joke and some people failed to see it.

Happy New Year!

Scott Stonefield I’ve been watching this dude for 4 years and just today learned his name is Jason...

Many years ago, engines ran a fairly large amount of overlap (intake valve opened well before the exhaust valve closed) in order to scavenge all the old burned fuel out, with a large amount of muffler backpressure. If you ran straight pipes with no backpressure, the incoming (cold) air/fuel mixture would flow out the (hot) exhaust valve, and could cause the exhaust valve to warp. As muffler design has improved, we can get lower backpressure with similar noise dampening, so I believe the overlap is now shorter. So maybe valve warp would not be a problem anymore, but I don't know.

Have you heard of "pressure wave termination boxes"? It's a trick used to simulate having open headers (no exhaust) while actually having a full system The inverse trick exists too. Headers designed for use with cat converters immediately after them (but in use on a non-emission car) can have a temporary (and hopefully smooth) decrease in pipe size to simulate the wave reversal characteristics of a cat converter. Wave tuning is cool. I play with it on Engine Analyzer. I've seen (simulated) volumetric efficiency of 112% at times

Just use parts engineered by well known manufacturers like Borla

or just use what he just said and if you use bigger diameter piping, tune it correctly. most cars come stock with 2-2.5" exhaust piping. you are gonna have some back pressure at the header collector, downpipe/cat. use the available bp to balance it out and a tune to dial it in.

It's just pressure vrs flow

you can't really damage anything with the parts that you can mount on a road car. But something similar to the stock exhaust or well-engineered aftermarket is better for sure.

@@MrHaggyy like a Flowmaster hush power 2 muffler and two or two and a half inch pipe to the rear bumper?? Or is this too free flowing?? It's a V.6 tiburon.

Haha yup, I don't think I could find a better example of an engine designed with this goal in mind, than the Porsche 918's. Reverse-flow heads, and the entire exhaust system is like 6 or 7 inches long

Talk to the racers if u think back pressure is bad.

Its about the pressure wave, a completely open exhaust won’t scavenge and mid range torque is lost

Jennifer WhiteWolf Multiple EP national champ Joe Cogbill had engines for his 96Rock Speedster specific for fast and slow tracks. IIRC the fast track engine had a 1.75” dia. exhaust and put out 172 HP. The slow track motor utilized an exhaust of 1.625” dia. exhaust and put out a max of 158 horses but more in the lower rpm.

jockellis; do you race too? You comment about 96rock makes me think you're from the Atlanta area.

Ornery Hermit Well, I went to the Skip Barber 3-Day school at Roebling Road and raced Karts on ovals but no other wheel to wheel racing. But if I can ever get my 914 project car finished I want to go hill climbing. I interviewed Joe for a story for VW & Porsche Magazine but could never figure how to save it to my Radio Shack Model 4 and it kept disappearing.

Wow. Talk about a small world. My first racing school was also with Skip Barber at Roebling. We ran Formula Dodge open wheelers (no wings). Then I did the SCCA school in a rented Miata at VIR. Been racing spec miata and Spec Racer Ford's since then. Will actually be at Roebling Road again later this month for a SCCA event.

Ornery Hermit How fast could the FDodges go around that last turn onto she straight? Did Bruce McInnis run the school?

Stock 289 High Performance Mustang from Ford, 271 HP. Shelby Modified High Performance Mustang 306 HP?

Why not? The pressure waves make sense as well.

Also some eary fuel injection motors computers are too simple and dont know how to do anything but stock

It's the same concept be it ecm or carb. If you change something to the car, motor intake exhaust etc, you have to tell the computer you made those changes otherwise it will keep doing what it was programmed too. Same with carb if you dont adjust or change the jets it will keep doing the same thing. Causing the idle issues, spitting unburned fuel air out the back, and other things

kinda... how an expansion chamber (tuned pipe) works in stages. when the pressure is moving back to the piston from the exhaust it's in the compression/intake stage it's good (helpful). any pressure that moves back during the power/exhaust stage (back-pressure) is bad. the reason the pipe is so fat in the middle is to reduce back-pressure in the power/exhaust stage.

thats why 2 stroke enduros have those resonators.

@@gatorage850 A clearer explanation is that a tuned pipe is designed to allow sound waves to reverberate back to the exhaust port when the air/fuel mix is compressing. This allows a sort of pressurized charging by pushing the air/fuel mix that would otherwise be wasted back into the combustion chamber. Tuned pipes are only effective at a range of RPMs that time the reverberation of the sound waves with the compression of the air/fuel mix. The fat part of a tuned pipe is at a distance from the exhaust port mathematically calculated by the exhaust gasses moving through the given diameter of the exhaust pipe at the speed of sound, usually 1/3 wave. This is why a power band fades away as the exhaust becomes overheated as well.

@@kaisersose5549 I was trying to keep it short/simple and just showing the pressure on. mostly the end result of the wave affecting gasses near the piston. not trying to explain the whole wave process for how technical and confusing it could be for someone new to understand/picture clearly or want to read.

Miguel Ruiz the only type of engines that needs back pressure are 2-strokes I think that’s where they got that from

@@zippyoya typically the flow should be balanced. If your exhaust is sucking raw fuel out of the cylinder before the valve closes you might consider changing the flow of the exhaust. Valve timing sometimes overlap incorrectly. Also the expansion chamber of the 2 stroke doesn't create back pressure.

I disconnected my cat from my old 90 4runner once and it felt 10-20% slower.

r2dxhate that makes no sense a high flow exhaust wouldn’t change that much you might get a gain of like 1.5 to 3 horse power not much

@@zippyoya I'm not talking about a hp gain, I said my 4runner got slower. Someone suggest my cat might be clogged, so I disconnected my bolt-on cat to see if it ran better with no exhaust at all besides headers, and it was way slower instead. I'm not saying that proves engines need back pressure, but for some reason it wasn't running as good when it was allowed to breath better.

Michael DeJong seriously. Ive been trying to get this misconception out of peoples heads for years now.

coscorrodrift I believe he learned some of the basics through classes-thermodynamics, design, etc and then did self study outside the curriculum

Most of this is from online research - there were a few well researched papers and articles I found on the subject for bits and pieces. As is generally the case, there's a lot of good (and bad) information floating around on the internet, just needs to be sorted down to the facts. That's my goal! As far as my degree, I just did a bunch of challenging math problems for four years haha. Not a huge amount of practical knowledge, but definitely problem solving skills.

Yes, the sphincter has a smaller diameter than the colon. This could be the reason for two toots sometimes.

In your case yes. It causes brain damage.

No. That's scavenging.

Are you wearing spandex or cotton?

If the smell gets passed your underwear and jeans to people's noses than you don't have enough back pressure !

Nounours2627 you want that pressure wave to be as consistent as possible drawing maximum air out of the engine as possible. Ie maximum velocity with minimal resistance to keep the turbo spooled higher.

+ Bushcraft North of 60 : Well, it's not so much that they do more R&D per se... It's more that as you age, you realize that daily driver vehicle functionality and reliability are far more important than a little extra horsepower or torque. Typically, when a person starts "screwing" with any engine outside of the OEM settings, you will find more power, IF and ONLY IF you have a clue what you are doing. That said, typically the engine becomes less reliable and more expensive to operate. It's really just common sense. (Sadly, something that many folks lack.) That said, there are always some exceptions to the rule. For example, most modern emissions controls are literally "choking" the longevity, economy, and power outta the modern ICE's, both gas and diesel. That too is a proven fact.

You'd be amazed how many people I've come across that think they are smarter than a department of German engineers.

I quickly swapped my Urethane Transmission Mount back to a stock mount after being vibrated to death in my LT1 Pontiac Formula, the OEM people really do their homework/testing about components & conditions.

After a HiPo build they recommend running the pipes off the headers right out the side, wind up the engine until white hot, cut pipes where they change to red and you have a race car exhaust.

But, as TurboDiesel said, a daily driver is usually better off without screwing with it. The tuned exhaust (and I don't mean "tuner exhaust" on ricer cars) is tuned for a specific purpose - whether it's drag racing, circle track, or whatever, but it's not ideal for daily driving - unless you tend to drive stoplight to stoplight in 12.0 seconds or less.

Sounds like a fun activity - for you. Unfortunately, it is a skill that is becoming less and less valuable each day and he might not even have the opportunity to use it much if our roads go the way of autonomously driven electric cars when he's an adult. I think your fears are correct. Maybe learning to make his own PCBs to hack a Tesla would be more useful . . . I grew up in the '70s & '80s and I remember when dad got an electric weed-eater, then an electric leaf-blower and slowly, our garage went from lots of small ICEs to extension cord racks.

Less so than ICEs disappearing, I fear loosing a more accessible and tangible technology to learn. A young child getting hooked on ICEs might later realize them as a gateway to Physics, ME, or AeroE (or environmental conservation.) Who knows their trajectory. Modern electronics are pretty highly integrated, so mostly serial protocols, software, data sheets and integration. Early on it's more about creating experiences, especially sensory, and the ability to adapt. I spent a lot of time at university and every time a topic was completely dropped the students suffered. The argument was always the same... "computers can do this for them, they will not need this in 10 years." BTW: You guys were way ahead of everyone else. Today, I only know one person with an electric mower and two (high income) people with electric cars. Might be regional thing. Have a good one!

I don't understand older generations sometimes, look at car engine progression over the last 20-30yrs gone from a mechanically operated engine that was time consuming to diagnose or fix. now to having inputs that a very impressive that are processed at the speed of light, even looking at fuel trims can give easy idea of where to diagnose the problem, it was only easier back the ole days cause u did'nt have to worry about catalyict convertors or evap codes u could vent the engine crankcase straight into the atomsphere( a no no in todays world) and the fact its easier for the modern joe to keep his car serviced, or u gotta do change the oil,no more replacing contacts on dizzy. if u know how to read a relay diagram u know to diagnose problems for electrical theres alot of good channels out there. engine still use the same princepal air/fuel compression spark, just different way to operate.

back pressure will severely harm the performance of a 2-stroke here again you are confusing back pressure with the reflective sound waves as it works the same way in a two stroke.... reflective sound waves are much more critical for the performance of a two-stroke to keep the intake from escaping the exhaust port. these are not my words but the words of Pop Yoshimura the greatest tuner of all 2-stroke engines there ever was and the inventor and designer of Honda's first two stroke engine

@@donniebaker5984 edited it to be correct :)

Generally for turbocharged applications, you simply want low restriction after the turbo, because you're no longer going to gain the benefits of scavenging from exhaust pulses. Leading up to the turbo, you want to keep routing short, and hot, so that little energy is lost from the exhaust valve to the exhaust turbine.

Engineering Explained To me that sounds like a short and fat turbo manifold leading into the turbine side of the turbo with a high flow cat right after it, and the absolute lowest possible restriction muffler after the cat to keep noise humanly acceptable. I am simply not psychopathic enough to needlessly pollute. Droning exhaust notes get old real quick.

my mustang needed back pressure because thats how ford designed it without it i lost a lot of torque i could feel i lost power in the gas pedal high flow mufflers and huge h pipe yeah my motor revved higher easier but when it came down to putting power on the ground hell no....explain with diagrams and whiteboards all you want i bolted the part on and felt the difference so you cant say all engines dont need back pressure new variable cam engines are being designed to use the exhaust gases to reduce displacement so how does this apply to that

I've heard very similar things, at least in the case of bikes. I know with fuel injected bikes getting a free flowing exhaust will do very little without a fueling retune, maybe that's what your thinking about? IDK I'm just some guy on the internet

Xantho - Correct. Matching intake with exhaust is the whole idea. In the example, we do have back pressure. That creates the velocity to generate the vacuum wave at the end of the exhaust valve opening? Here again, balance is critical.

Theonlylee1984 your forgetting the fact that without any upgrades to require more exhaust flow you won’t get any power gain from it If someone buts a blower and cam on their mustang they will prob want to open up the exhaust

But with stock motor and bigger exhaust you do loose torque and power

No back pressure you lose power because fuel is going out of the chamber... What does the backpressure is to keep the fuel inside the chamber before the piston goes up.

BrianNC81 Quite an antisocial adjustment though, as the dpf is designed to reduce small dust particles from your exhaust gasses by up to 90%. These days almost everyone has a member of their immediate family that has died due to cancer; I just don't see why anyone would decide delete the dpf. And even be proud of it...

Niels Onderbeke I'm glad my truck was never equipped in the first place with DPF due to it's age. Better reliability, mpg, and power. A diesel without a DPF should not smoke if tuned well but there are idiots out there that dump a lot more fuel than needed to put out more smoke on purpose. With an optimal tune it should be fairly clean without DPF.

Not even close.There is a reason the dpf exists or all diesels would be still be made the way you claim.Its called progress......

Its called government regulation.

I think a turbo dampens out some of the pulsations that are important in a non turbo system making post-turbo more about big cross section and less about "scavenging"

Generally you're tuning for a specific RPM window - for example in racing when you know RPM will remain high, you tune for peak torque at higher RPM (and thus also peak power). For passenger cars it's difficult to do, because a wider torque range is more favorable (turbochargers can generally accomplish this well).

Engineering Explained My field is biology based, so I am not far above caveman level on this. When you add boost, by supercharger (wider RPM) or turbocharger (narrower band) you increase flow through the exhaust system. Should you expect to leave a stock exhaust and catalyst system stay in line without blowing the stock converter? I am thinking about the Edelbrock SC CARB system for the MX-5 ND (and aftermarket CARB turbo systems) that require the dual catalyst stock exhaust. Great video thanks for the education! Turbo and supercharger system next?

Haha, no time for vacation! But nah vacation is important.

Negligible unless you’re running serious drag car power That said top fuel cars create about 5-600 lb of downforce from their exhaust just because they move so much air Same reason pro mod drag cars will run bull horn style exhaust. Every little bit counts. But honestly in passenger cars you’re more worried about the physical exhaust route than you are the gasses coming from it. Same goes for “low” hp cars

It makes a difference on motorcycles as their aerodynamics are crap. For example changing the direction of the exhaust tip can mean that you increase back pressure and harm horsepower by trying to make the gas escape into a high pressure zone. Or moving it a little bit can mean having the exhaust gases exit into a low pressure zone and helping with the scavenging effect. They can't be measured on a dyno. Unless your dyno is also in a wind tunnel

Thank you, what you have are a bunch of people trying to eliminate the word back pressure when if you have to much pressure in the exhaust system you kill exhaust gas velocity and it you have to little pressure you kill exhaust gas velocity. It is all about finding the right sized pipe for the highest exhaust gas velocity. Where all the misinformation and confusion comes in is an exhaust system is not designed with back pressure, an exhaust system is designed by maximizing exhaust gas velocity. John Lingenfelter built 600 horse power Corvettes and Borla worked with him on the exhaust systems, John Lingenfelter used 2 1/2 inch exhaust systems because that is what provided the best exhaust gas velocity to make the most power, as Borla says if a bigger pipe would have made John Lingenfelter go faster he would have used it.