I think the real reason the old timers told you to have back pressure is so that your car would be slower than theirs at the drag strip

@xemanuelli

Жыл бұрын

They said that and then hit the strip on open headers 😂

@markim5087

Жыл бұрын

Na, as a old timer I guess being 56 and wrenching since 88-89, the back pressure thing came around from heavier trucks ,or cars which need low end TQ at a lower RPM , for better TQ drivability, and what happens on say a blown supercharger D motor removing the back pressure will make it feel like the bottom end fell out of it, so that’s where it came from, plus dyno weren’t everywhere like today, to prove the facts, I’ve had plenty of supercharged motors which I regretted removing the factory mainfolds , granted it sounds better,and made more power overall, but since the power band was moved up , the drivability sucked it wasn’t as much fun why the vehicle was heavy , if I’d added a smaller pulley and retuned it ,then yes I’m pretty sure it would of felt better..

@Cjbarker2

Жыл бұрын

​@@markim5087 I've noticed that most headers are designed to perform best at higher-than-stock RPM, and if you follow the ecomodder guys, they'll go out of their way to build a manifold that produces the most optimized scavenging possible with the cam/port/displacement combination. This results in vacuum/max flow at peak design RPM, but it does produce a restriction for higher-RPM use

@robcarey4278

Жыл бұрын

An engine does need some back pressure for torque I know this for my own experience if you go to big of a pipe you lose low-end torque and they had to keep on going higher RPM to get any power why on God's green earth would he say something like this small engines do require backpressure not a lot mind you just a little

@bobtee7899

Жыл бұрын

🤣🤣

As an engineer who grew up working on my own cars, these types of videos are awesome. They bridge the gap between the book smart engineers and the street smart technicians with the hands on experience.

@januarioqueiroz3122

Жыл бұрын

👉😊👍

@johnalcala

Жыл бұрын

As I posted above, I've been in a Fox body mustang GT that lost a lot of torque after he added headers. It was sad actually

@j4ke2fl0w3

Жыл бұрын

@@johnalcala like he explains in the video, you still need proper tubing to create enough velocity without adding backpressure. too thin tubing restricts air flow and puts backpressure. too much air flow will not let the exhaust have enough speed

@agems56

Жыл бұрын

That's because like we used to say about souped up Fords is " But it's still a Ford"

@thecraftsman8133

Жыл бұрын

@@johnalcala lost a lot of torque? How did you measure that? Dyno? What about HP?? Did you gain or lose? Did it change the power curve up or down? I have never seen a Fox Body or any other "lose torque" from adding headers....& I have known a few. Wonder if you tuned? Or deleted the O2 sensors like I have seen a few bone heads do thinking they can delete and don't tune. Also your headers shorty, mid or long tube? Diameter of tubing? Its hard to believe you lost actual measurable torque. You didn't just "think" you lost torque and was just disappointed you didn't gain 35HP instantly like the advertisement on the Box said did you? And that lack of throwing you and pinning you to the back of your seat didn't happen so you just assumed or thought that was the outcome? Because gaining that "advertised" HP & torque on the box is supposed to include doing a handful of other mods to the engine to get that Maxed out HP gain from those "amazing" headers, such as tune for starters.... after freeing up the exhaust with headers, now your moving more exhaust and now its running lean and have to add more fuel. You are not running optimum air/fuel mixture. You aren't getting the most out of the headers if you don't do other mods, now your intake isn't keeping up, you need more fuel also.....tune tune tune tune after EVERY MOD YOU DO. if its a carburetor then make your adjustments add more fuel and free up the restriction at the intake to help the headers do what they are supposed to do, free up restriction

How can you not just feel totally comfortable with everything he’s saying. The wisdom spoken by a man that has obviously years under his belt. He reminds me of an old Hawaiian surfing dude sitting on the beach, describing the waves and how to surf.

@fattslapper1819

Жыл бұрын

Bro are you all out of drugs now? Or do you still think he’s jesus?

@dudesweetpro

9 ай бұрын

This guy is so knowledgeable and always chill. He’s OG with all the jdm stuff and his builds are amazing!

@RT22-pb2pp

9 ай бұрын

I believe engineers who really understand the science of things, call me crazy.

@danielsvamp

8 ай бұрын

@@RT22-pb2ppNo need to be an engineer to understand the science and physics of these things.

@nitramleinad9622

8 ай бұрын

Or Mr. Miagi...

My thought is that in the old days, people would go full flow exhaust without re-jetting the carb. It would run leaner and lose power. I know because of a 1983 thunderbird that I put a 351w in. I ran dual exhaust with a h-pipe. it had slowed down. Once I listened to a local garage friend of mine (running that garage since the 60s) I drilled out the jets slightly, corrected timing, and installed colder plugs. It made a huge difference.

@motoiq

3 ай бұрын

Bingo you get it!

I believe this myth mostly still persists from the fact that a lot of people don't realize that you need to retune the fueling on your engine once you make your exhaust more free flowing. People remove mufflers or install a new aftermarket exhaust and lose power because they just leaned out their engine. Happens in the motorcycle world I come from too.

@working2bselfsufficient724

Жыл бұрын

100% is the tuning. People didn't know needed retune when change pressure either way to more or less. Once returned less pressure is almost always better as far as performance goes. However if want a quiet motor/exhaust you'll end up with a lot pressure after adding everything on. Cats mufflers etc which are needed to run quietly and for some states inspections if your state has them.

@LifeInJambles

Жыл бұрын

I mean tuning is important when you're doing things that change your mixture obviously, but he literally explains the main issue with oversized tubing clearly in the video. Even properly tuned, the larger your tubing the higher the RPM your scavenging effect will be effective at. If you're running a track-only NA rig then you still need to pick the right size tubing, but it'll be larger than what you'd want for a street rig, especially a daily. Not getting any scavenging will result in imperfect exhaust clearing which means you can't pull as much fresh air in and can't squirt as much fuel. Basically as he explained it's a VE issue. No exhaust performs perfectly at every RPM so your tubing diameter should be tuned like anything else to the powerband you're looking for. Even if you tune the fuel to match, larger tubing raises your powerband and hurts your bottom end power.

@LifeInJambles

Жыл бұрын

This all basically goes out the window when you're dealing with a turbo. On a turbo application you basically want the least restriction possible post-turbine, so an open, oversized exhaust tube can only help performance if you can live with the sound.

@imoffendedthatyouareoffended

Жыл бұрын

Odd, after removing the mufflers off my wrx it felt better, it definitely didn’t lean out though. Not even slightly. Backfires like a mfer.

@lunoirxx

Жыл бұрын

@@imoffendedthatyouareoffended Do you know your AFR? Lean backfires can happen too. Could be that your ECU is able to compensate for the increase in flow. Not all fuel injection systems can do that though.

This man is a legend, and the fact that he’s out here sharing his knowledge and actually working on projects is awesome!

@skivijimmy

Жыл бұрын

He might be a legend but it's so irritating to watch him with that stupid smirk on his face

@powar7746

Жыл бұрын

​@@skivijimmy bro? 💀

@SAMPLETEXT285

11 ай бұрын

​@@skivijimmy then dont watch him its a pretty simple concept but i know that can be hard to comprehend for someone like you who might be a little IQ deficient or lacking in intelligence hence why instead of just clicking off you complain in the comments but i want you to try it at least once or twice i promise you that you'll be better off doing that. And also nobody asked for your opinion on him either just saying.

I remember finding a book in high school and i believe the title was "the design and building of the british sports car" and by sports car they really mean racing car. It was written by a pair of british mechanical engineers and what i found fascinating was that it was filled with formulas and tables that at first i was pretty sceptical about. For example and pertinent to this subject they had a formula that you could enter displacement, compression ratio, stroke and maybe rpm that you wanted to optimize and it would give you diameter and length for both intake and exhaust. Now this was 50+ years ago so i don't remember the formula or variables exactly but i was amazed that these formulas existed. As a gear head and at that time heading toward a career as a mechanical engineer it reinforced that math could be a handy tool to be utilized toward that goal.

@michaelhurley3333

4 ай бұрын

Probably David Vizards, he's pretty sharp!!!, Also on U tube!

@MrSilus2000

3 ай бұрын

The nerds try to forumulize what the real mechanics know by feel.

This guy has a smile on his while explaining engine stuff. Thats how u know he love what he is doing❤

@fredconnell2612

10 ай бұрын

Or he’s stoned doing it lol

@crawford323

9 ай бұрын

Gases have mass and moving gasses have inertia. Gasses have viscosity which means they will stick to each other and to other materials, in this case the exhaust pipes and components. Gasses are compressible. Gasses obey the laws of thermodynamics. These things can complicate design efficiency efforts. Why are expansion chambers necessary on some two cycle engine exhaust systems?

@danielsvamp

8 ай бұрын

@@crawford323Expansion chambers are for reflecting exhaust gases back towards the cylinder, the exhaust gases contain some fuel which got sucked all the way through the cylinder (which is good for cylinder filling). In an optimal situation the expansion chamber is tuned exactly for the exhaust port's dimensions to have the returning pulse enter the cylinder just before the piston closes the port. With increasing engine speed the returning pulses grow stronger and stronger until you overcome the "hill" on the powerband. After peak power the pulses return too late to get into the cylinder (because of the port closing too soon (piston moving too fast)). By having a shorter pipe the pulses return quicker and the power moves higher into the rpm-range which can greatly increase peak power, though this also significantly decreases torque at lower engine speeds. Sorry if this is hard to read or if I'm rambling, I know I am, I'm crazy about this stuff. Video from motoiq: kzread.infoqf9eFYPYXUY?feature=share, great video from 2stroke stuffing: kzread.info/dash/bejne/dY6k0Jdrl8SnXZM.html

@edwardmoreno9435

6 ай бұрын

And that’s why I love this man

@razor6888

3 ай бұрын

He has no idea what he is talking about...... this is a views and money video.. dont take advice from here. Any Tech worth his/her salt will tell you that. Pure Garbage.

I have been trying to explain this to people for years, now I can just send them your video. Awesome content!

@chestrockwell8328

Жыл бұрын

Same here... there are other videos as well but Mike has some "cred". Silly how even today people mention needing back pressure on a four stoke engine. On two stroke "back pressure" is really reversion pulse tuning otherwise two strokes don't need "back pressure" either.

@daviddntait

Жыл бұрын

Exactly the same thing I was gonna say! I always tell people, if back-pressure is a good thing, go tell the top fuel dragster guys to put mufflers on instead of zoomie headers only!

@frederickcook87

Жыл бұрын

Likewise, but there are folk out here still saying you need back pressure to make HP 😖

@ryurc3033

Жыл бұрын

But really , how many people think what he said was I need 3 inch straight pipe on my stock Honda Accord

@leftyo9589

Жыл бұрын

@@daviddntait and truthfully it is just a restriction, not back pressure, as you arent pumping air in from the other side.

He’s quite literally an Engine Guru.

@seansmith1725

Жыл бұрын

Engine Buddah

@PutsOnSneakers

Жыл бұрын

Smoke weeed erryday

@chrispitre2439

Жыл бұрын

Guru Mike

@shorty808100

Жыл бұрын

he's 1/2 right 1/2 wrong

@motoiq

Жыл бұрын

It will be hard, Smokey has been dead for some time now.

I am loving this series, Mike is hands down one of the greats in motorsports.

This is one of the best explanations of exhaust flow. I have always focused on keeping velocities high in the exhaust and intake. Usually my race cars and motorcycles have always run at the front of the pack as a result. It's counterintuitive sometimes - smaller intake runners often seems wrong - but the results are provable on the dyno and the track. Same goes for hot street cars and race cars exhaust.

@sahzhree7757

Жыл бұрын

Smaller intake runners always seem wrong, until you realise early race and rally cars (especially euro) often featured independ throttle bodies, with basically 1 - 2 inch runners.

@xxxxxxxxxx6903

Жыл бұрын

To be honest I didn't even watch this video. But based on the video's title, it seems he just wrote off the huge potential NA gaines from exhaust scavenging? No exhaust back pressure = little to no scavenging! Not to mention in anything less than max-effort combos, exhaust back pressure is a design tool to optimize compromises between performance, mileage, NVH, and emissions.

@ALOSOOON

Жыл бұрын

The venturi effect. A liquid or gas gains velocity after transitioning from a small opening into a larger one.

@ALOSOOON

Жыл бұрын

​@Xxxxx Xxxxx Watch the vid. You can have scavenging without back pressure. When the exhaust leaves the tailpipe it pulls.

@truth4reel

Жыл бұрын

Resonance tuning?

How would a person not like this guy? He gives great information in a manner that anyone can understand plus he is cheerful!

Great explanation! You are so correct! The whole purpose of cam overlap is to let the air/fuel charge begin flowing into the combustion chamber while the exhaust valve is open, creating a negative pressure due to the exhaust pulse velocity leaving the header pipe. AF can begin filling the chamber an eternity of time, with respect to crank position, before the downward piston movement can pull the AF charge. Proper fluid dynamics is paramount to VE absolutely.

@geemy9675

Жыл бұрын

sounds a lot like how 2 strokes scavenge exhaust gases with fresh gases. it might benefit from pressure waves bouncing off changing diameter in the pipe, but obviously only at certain rpms. might work if you're tuning your engine only for top end power

@j.thomas7128

Жыл бұрын

And ya don't get negative pressure without scavaging. To have scavaging, there must be some backpressure even if it is as minimal as a 4 into 1 header; as opposed to a true open pipe for each cylinder. Run any motor on a dyno stand with a header and short collector or down pipe vs no header at all as in zero backpressure... tell me your results.

@geemy9675

Жыл бұрын

​@@j.thomas7128 first, remember this is especially about tuned engine with valve overlap . you're right its negative pressure that can help scavenging, but you cant generate negative pressure with positive pressure( back pressure). back pressure does the opposite of what you want for scavenging. It's exhaust gas velocity/inertia that keeps pulling fresh air in the cylinder during valve overlap when intake valve just opened even though exhaust gas still has more pressure than intake. The exhaust gas "wants" to go back to the lower pressure (intake), but because its already going fast towards the exhaust, it only slows down, but keeps moving through the pipe, and sucks gas behind it. with no header, exhaust velocity is lost because gas expands in every direction, so during valve overlap, the exhaust gas will probably go backward in the intake. if you have no valve overlap, open headers shouldn't have such a big impact, but still, inertial scavenging can help squeeze the most gasses out of the cylinder before intake opens. In fact, velocity is not the only parameter that can affect power, if you want a very complete explanation why back pressure is not good, watch kzread.info/dash/bejne/nJ6Ex7KYftGYcpc.html maybe what you meant is that back pressure is needed as a by-product of velocity, but the best compromise is still highest velocity with lowest back pressure

@j.thomas7128

Жыл бұрын

@@geemy9675 i understand your explanation. I think the point was missed. You don't have scavaging or boosted exhaust gas velocity unless you have a collective header or collector pipe. Any collecting header or pipe will add some, even if very minimal, backpressure. You won't have the same gas velocity or scavenging without a collector where the just fired cylinder helps to evac the exhaust from the previously fired cylinder. An engine with no header or exhaust manifold will have no as in zero backpressure. Adding a collective header will add some, if minimal, backpressure and some amount of backpressure is needed to create these scenarios. Do you think this reasoning is faulty?

@fishandgameman

Жыл бұрын

@@j.thomas7128 Yes maybe, but barely measurable and for an almost immeasurable amount of time, as some of the exhaust pulse from another cylinder may dam a header pipe at the collector. I think if that were to become measurable or rob performance it would be related to post collector downstream exhaust piping-too small, too large, or turbulent flow. When you consider how many times a valve opens or a piston moves one stroke at 3000 RPM in seconds, there are going to be variables in velocity causing different flow dynamics. I installed a WM8-22XE cam in my M8 107 Harley. It made a huge difference over stock performance with a good tune. I thought it was great and at peak performance, but I never could seem to get the engine to spin up achieving RPM over ~4500-5000 and it took a while. I didn’t know until later it was sluggish as hell. This back pressure myth is huge amongst Harley peeps, and they all parrot the same shit they hear. It didn’t make sense to me, so I rid the factory exhaust of a great big engineered restriction upstream from where it goes from one back into two before the Tab Performance mufflers. The change was unbelievable! Not a little or placebo effect, incredibly better. Immediate taps on the rev limiter in in the first 4 or 5 gears and the only thing preventing it in higher gears is my sense for self-preservation. Speed kills, 😆. That cam has a lot of overlap. Unequivocally, the M8 doesn’t need back pressure. It destroys performance at least in my case. Take it for what it’s worth, this was my own experience. ✌️

Just found this channel and you’re honestly one of the best car channels on KZread thank you for your content

Mike, I really appreciate you sharing your tuning knowledge, some of what you said went over my head. Please can you make an in depth course on different tuning topics like exhaust fabrication for highest power, engine building, suspension set up. That would be awesome!

@motoiq

Жыл бұрын

check out some of the stuff we have already done, here and on motoiq.com

I got to say how incredibly well you are at explaining things .. the right information well said piece after piece .. a rare gift.. one thing you could of put down with your explanation is to briefly cover overlap and that would have made your explanation flawless..

I've never seen anyone look so happy when talking about exhaust gasses 😅

Loved your write up on project Tundra. I read it many times when I got mine and went with the TRD exhaust. Thank you for all the pics and info!

This man's cadence and demeanor do not seem naturally aspirated and I'm all here for it. Thanks for dropping this one I've been curious about this for years!

I just watch the video because I felt happy watching this guy explain something complicated yet so chill.

Gained a new subscriber, love when you supply information in a simple effective manner for everyone to understand. This is the perfect video to send someone when they start talking about back pressure.

Love his explanation so chilled and easy to understand and he’s right too.

Had exhaust work done on my Toyota a while back and I was worried that they cut out all the flanges and welded the whole pipe front to back. Thought the engine needed back pressure but I noticed a huge power increase (with the small motor) after that repair. Thanks for the reassurance.

What an amazingly well done explanation. Probably the best I've seen.

A lot of folks confuse the return shock wave of a tuned exhaust with back pressure.

@thomaslabrum8182

Жыл бұрын

I can see why, if an engineer using the lingo is explaining exhaust pulse resonance to some average joe that just puts gas in the tank, I can see the takeaway being “more back pressure”

@daynasmum529

Жыл бұрын

Perfect example is the expansion chamber on a 2 stroke - it does give an amount of back-pulse if tuned right to the engine - preventing fresh incoming charge going out the exhaust port increasing efficiency.

Thanks for the details on this. I've always wondered how much back pressure is good, and how much is bad

This guy speaks so fluently and makes everything very digestable. All excellent information. Cheers!

Great explanation, it's pertinent to mention that the knock characteristics change with the flow of the exhaust. I've noticed a major change in my CL9 project when I increased the DC header collector size from 2 1/4 to 3". The tune actually works now ;). makes power all the way to 7600.

@tiles3458

Жыл бұрын

I cant wait to install my weapon r header and 3 inch single exit exhaust! I have hondata so I know it'll change the characteristics quite a bit.

@pepperfish_

Жыл бұрын

@@tiles3458 make sure to either disable or adjust the knock sensitivity, headers are "noisier" than oem manifolds and can still fool the knock sensor into cutting back on timing. FYI.

I absolutely love your content, there are many who will not understand how you are explaining it but I do one hundred percent, Master tech for Ford Motor Company of Canada for about twenty years now. I appreciate your knowledge and how you explain it as it rings out crystal clear to me and you have helped tremendously on multiple builds my son and I are doing currently as they require different exhaust requirements. (North American race motor big and small blocks in vehicles way too small to JDM cars all over the map) Keep up the great work and thank you.

As alway I learn so much from this channel. It’s easily my favorite. Thank you for explaining this so it’s easy to understand

One thing I heard from an old guy made a lot of sense to me. He said, why build the baddest set of heads that flow the most, just to restrict them?

Good to hear this after gutting the dpf on my van, was worried it had lost boost as it felt less punchy but it seems to just spool earlier and smoother so feels less aggressive but more efficient, great explanation!

@Patrick-857

Жыл бұрын

Hope you got a tune afterwards. Any change to a modern engine setup needs to be compensated for in the ECU, otherwise it screws up mixtures ect.

@monkeyportions1722

Жыл бұрын

@@Patrick-857 yeah first test drive was to be reprogrammed. The dpf done a regen on the way and got smokey but it was alright to drive there.

thanks mike! this has helped me finalize the exhaust design and piping diameter for my e92 m3 with a 4.4L stroker. since the factory piping is around 2.5" iirc, so with that said, the design would utilize a slightly larger diameter piping off the headers, to a smooth Y merge, to a larger single pipe all the way back. this should be the ticket here but I'll know when it comes down to meeting with my tuner again. with many revisions of course :)

@kopronko

9 ай бұрын

People Must be aware of what a Terrible Idiotic Deception is the catalytic converter !!! ! !!! And even Worse is the Egr valve. !!! ! !!!

the real claim is that you need a little back pressure to prevent burning your valves, valve technology has since changed that for the most part

I like the multiple camera , great production for the chillest dude on earth!!

I could listen to this man for days. He's a definite virtuoso of the auto engine.

@rockman4699

8 ай бұрын

The torque factor needs to enter the equation. Depending on the application back pressure can help with mid range torque. Drag racing and road racing applications don’t require mid range to work but motocross and Enduro application certainly do

Great video!!! As an engineer this was very interesting. I had heard the addage about back pressure, but never really thought about it until now. A friend of mine works on exhausts for a major OEM. I am going to quiz him on some of your points next time we catch up.

@kevinedwards7206

4 ай бұрын

what did he say bro?

I know this to be absolutely 100 percent true as I would have weird stumble in acceleration with my exhaust setup that is free flowing on OBX Long Tubes , Y pipe and test pipe but kept the OEM muffler on my 93 6 Speed Coupe Acura Legend. Until I finally change that huge OEM muffler out for a Free flowing but chambered Super HK5 Dual 3 inch Burned tips muffler that definitely took care of that stumble in acceleration at the cost of being just a little louder then stock. I love your videos and awesome explanations for your content, thank you for making super informative vids!!

Wonderful explanations making complex stuff seem obvious with a smile. I will never get exhausted listening to somebody at the top of their game who obviously has such a passion for what they do. Thank you for such a to the point explanation, politicians need to more like you sir 👍

To be fair to the back pressure idea, I think it's more of a misattribution than just a malicious lie. The proper flow of the exhaust system through adequately sized tubing (as you described) is probably what a lot of those people have in mind, but how it's expressed can get lost in the weeds to the average layman.

@WhalerGA

Жыл бұрын

Yes, definitely. With naturally-aspirated engines, effective exhaust scavenging (ex: through the use of appropriately-sized long tube headers) is helpful in the generation of a healthy power curve. Forced-induction engines are a different story: With forced induction, the bigger and more open the exhaust, the better.

@AdamantineAxe

Жыл бұрын

Probably the thought that no headers=no back pressure=worse low end

@thomaslabrum8182

Жыл бұрын

I would say it probably had to do with exhaust pulse resonance, old headers were designed with fit over anything else, and a bigger tube on a shit header probably caused turbulence in the exhaust. A mis-timed exhaust pulse will actually prevent scavenging (the vacuum effect) from pulling the remaining exhaust gasses from the cylinder. Nowadays your stock or even aftermarket headers are already formed with exhaust resonance in mind, so everything is different than it used to be.

@pablovargas2778

Жыл бұрын

I recently did a muffler delete on my 2007 v6 mustang (which has kit h-pipe with dual tips) After the delete, i noticed some loss of power (not that I had much anyways😂) like in Hp and torque and thought it was because I didn’t have enough back pressure. So would the actual logical explanation maybe be that my exhaust pipe may be to thick in diameter that it’s not flowing at a fast velocity? Thus reduction in power? My car engine is basically stock btw.

@flowmastaflam

Жыл бұрын

It's true. The theories were always correct, but the jargon was slightly misrepresenting.

Love this one Mike, thank you.

This is gold content in the time of bite size and dumbed down yt clips. I love it that is unpolished, presenter makes mistakes like looking into the wrong camera, but the content and info is spot on.

Man this guy is super chill and he looks happy to be wherever he is

I think too many people equate back pressure with scavenging. You do not need to add back pressure for scavenging. Excessive back pressure will actually harm scavenging...

@duanebailey6253

Жыл бұрын

It's more for low end power. The higher the power band the less you want. Also turbos don't need any scavenging making this more complex. Might car mods did a dis service with that potato years back.

Thank you so much. I had always misunderstood this concept. I've noticed lower engine response at low rpms on small NA engines with huge exhausts. I always attributed that to lack of back pressure. I'm really thankful that you've cleared that up

@LifeInJambles

Жыл бұрын

I've got a lot of respect for you just now tbh. Not often you'll see somebody say "looks like I was wrong about how things worked, thanks for correcting me" on the internet.... especially about this specific topic.

"Pulsating hot gas generator"! Sounds like a job for Tums! I started driving in '69 and would hear the "back pressure" argument. First time I've ever heard it explained! Thank you.

Don't understand it all but love listening, Thanks Mike.

I love this guy. He'd make a phenomenal teacher/instructor.

@kopronko

9 ай бұрын

Yes, But, People Must be aware of what a Terrible Idiotic Deception is the catalytic converter , and even much worse is the Egr valve. !!! ! !!!

I've often wondered if there would be an advantage to slowly increasing the diameter of the exhaust down the temperature gradient.

@charlesmyers9765

6 ай бұрын

No, not only would it have a negative effect on gas velocity but exhaust gas, though miniscule, cools as it travels down the pipe. So what your thinking is counter intuitive.

Thank you so much for your time and information! It helps people like me building cars in their garage!

I was told that the back pressure thing started in NHRA when they were trying to make power with flat head Ford V8s. If they ran no pipes they made less power than headers. Then it kind of got out of hand with people not really understanding what was going on, but they understood just enough to make it work. Granted this was told to me from an old NHRA crew chief about 30 years ago, so I am sure he knew what he was talking about, but maybe I don't remember so well. Good video.

@motoiq

9 ай бұрын

He is probably right.

Thank you so much for this video. I have been explaining this to folks since the 80s. I am still surprised how many people (even in the industry) don't know this.

@pipedynamics116

Жыл бұрын

Many in the industry still believe the back pressure myth, it can be frustrating debating with them

@Comet-hn3gm

Жыл бұрын

@@pipedynamics116 Don't bother. Make more power and go faster, while they perpetuate a lie.

@dormantmenace

Жыл бұрын

Cause it's bullshit.. open pipes get you more peak numbers. But back pressure puts the torque curve were it's usuable for average spirited driver. Not all on top like a you on the track or drag strip

@willbeasy2898

Жыл бұрын

Same here. Seems to fall on deaf ears.

@AdmiralRustyShackleford

Жыл бұрын

@@dormantmenace learn the difference between backpressure and optimal velocity

Reminds me of the old Drive network Exhaust Myth video with the engineer from Magnaflow. It was too long for the average Joe to tune in and learn anything lol.

Good explanation. There are still haters of velocity and back pressure, before the internet and still after. Another myth is you lose mpg. But that's baloney too, they just have a heavy foot. I am so glad you understand it right and explain it.

Totally agree and have always believed that but was afraid to say it thank you for the boost in confidence now

In defense of the old timers I think what they meant was exactly the fact it needed some resistance for gas velocity. .it probably got misconstrued with time that you needed lots of back pressure instead of the right size to allow the gas to escape smoothly

@JorgeHernandez-lu1mi

Жыл бұрын

In defense of all the engineers who I went to school with, the old-timers were wrong. You don't need back pressure in a four-cycle, multicylinder engine's exhaust system, you need backflow prevention between cylinders that coincide on intake and exhaust. The way to do that is to tune acoustics into the system to do that. Back pressure defeats the effect of pulse acoustics.

@codyharney2997

10 ай бұрын

You want each exhaust pulse pulled by the pulse in front of it. You don't want to have to shove the pulse into a tube that's already filled with other pulses that haven't left the tube yet. Pull>push

@neiliewheeliebin

10 ай бұрын

What you just said doesn't even make sense back pressure does not equal velocity whatsoever

@clintvosloo7694

10 ай бұрын

@@neiliewheeliebin it does to lamens. .my point exactly .

@neiliewheeliebin

10 ай бұрын

@@clintvosloo7694 It needs adequate diameter pipes to maintain velocity not back pressure, in some instances it can be literally sucking gasses out of the next cylinder in naturally aspirated engines with over 100% volumetric efficiency

I remember reading a Hot Rod article from back in the 80's or early 90's they did a dyno test using different exhaust. With H pipe, X pipe and true duals as well. The true duals ( one pipe from the header to tail pipe for each side) made to most hp and torque.

@lLpars

5 ай бұрын

This is also the reason why dragsters have one individual (very short) exhaust pipe per cylinder.

A great explanation and very well presented. Thank you!

Thank you very grateful I learn something new everyday and I learned a lot of learning about exhaust explain it very well

Finally a well thought out and explained video. So tired of people saying they need back pressure.

@Widowmaker2828

Жыл бұрын

A lot of guys like me say that it is true, you do in fact need a certain amount of back pressure. The guy actually states this in the video. You need the exact amount of back pressure to maximize velocity through the motor of any given aspiration. 🥂

@mrman1536

Жыл бұрын

@@Widowmaker2828 true that. It also reduces burnt valves.

Depends on what you refer to as back pressure. The harmonic of the exhaust pulse is used in conjunction with valve timing so the pulse arrives back in the exhaust port to keep the incoming charge from leaking into the exhaust port just before the valve shuts. If the action of the gas flowing out of the cylinder is being pulled by momentum or the flow of exhaust from the previous cylinder's exhaust, the incoming charge will be at risk of following the exhaust gas out. The exhaust note changes because of theses pulses especially when the engine is "on cam". Back pressure in this sense doesn't effect overall volumetric efficiency, because it's not an overall restriction in gas movement, just a pulse at the right time.

@fppro1679

Жыл бұрын

Nope. Just plain old back pressure. That would be pumping loss. These are not harmonic shock waves traveling at the speed of sound. This is just plain old gas holding up the piston from coming up freely! Purely arcane pneumatics and a little bit of physics about expanding gases!

@yodab.at1746

Жыл бұрын

@@fppro1679 lol. Not the speed of sound. Its resonance. Its part of why you get a power band. And I don't mean Led Zeppelin

@fppro1679

Жыл бұрын

@@yodab.at1746 the resonance you're referring to, is it related to an acoustic event going through the gas, not the gas itself flowing out of the tube. The event itself is like sound or it is sound itself. Essentially traveling through the gas. What I'm talking to you about is pumping loss which is completely different because pumping loss is about the volume of gas being restricted and causing pumping loss, two distinctly different things i. E. Gas volume and flow, and shockwave.

@whiteoakproud7882

9 ай бұрын

We are all dumber for having read the above nonsense

I’ve got a mate telling me to not get an exhaust cut out on my diesel ute. When I heard him say that, I was for sure thinking ‘wtf is he saying’. I always thought that you’d want a good escape route for fumes so you don’t cause blockages etc. This vid just helps me make my case 🎉🎉

Thank you for the knowledge, what a great video!

Love this dude !!!!! Absolutely legend ! Much love from South Africa 🇿🇦 Thank you for all the amazing info

Those pulses happen in the intake manifold as well. Richard Holdener explains the concepts very well.

@RaceMentally

Жыл бұрын

Doesn’t he prove back pressure is good depending on what you’re trying to accomplish?

@calvinevans8305

Жыл бұрын

@@RaceMentally low to no back pressure is ideal. The pipe diameter needs to be big enough to flow with no back pressure but not to big because the exhaust will lose velocity. The idea is to give the combustion chamber and cylinder the most efficient airflow during the intake and exhaust strokes especially with overlap from a performance camshaft. When both intake and exhaust valves are open briefly the exhaust flowing out of the combustion chamber helps draw fresh air from the intake valve. This is called scavenging. Back pressure counteracts this effect. It's like the difference between coasting down hill and riding uphill on a bicycle.

I can listen to Mike all day long, make it so easy for the lay guy to follow. Thanks.. from the UK..

@motoiq

Жыл бұрын

Thanks for listening

There's a simpler, more intuitive explanation. It's pumping loses. If there is pressure in the exhaust, the crankshaft has to push the piston upwards to force that exhaust out, which steals power from the crank.

@motoiq

Жыл бұрын

actually if you look at the Otto cycle PV diagram most of the energy is used during blowdown.

@SpecialEDy

Жыл бұрын

@@motoiq blowdown is power lost, when the valve opens before BDC, this means some of the heat/pressure is not able to drive the piston to BDC and some energy is lost rather than extracted. If we look at the intake side of the engine, there is probably 85-95% volumetric efficiency on most production head designs. The exhaust side usually has smaller valves, inferior porting, and inferior manifold design, though a shorter dynamic head(mathematical pump head, not physical cylinder head), and a higher speed of sound(probably 2-3 times if I had to guess). So, though exhaust is much easier to expell than intake is to draw, there is still restriction which the piston must drive against. There will always be a loss on a real world engine during the exhaust stroke, scavenging helps at the expense of blowdown. This is especially true of Turbocharged engines. The exhaust turbine is essentially being driven by the crankshaft via the exhaust stroke. The higher the backpressure, the more force required to drive the piston against it. Which is why exhaust is so important. Backpressure creates pumping loses, scavenging reduces loses, theoretically scavenging below crankcase pressure could actually pull the piston upwards and add power to the crankshaft.

There is also the BIG problem of adjustability. If you remove the back pressure from an engine and assuming it can get enough fuel from the carbs to prevent it from running too lean the ignition timing may need to change extremely. You must size your pipes accordingly and remember the the limitations of the rest of your components. It's horses for courses. Newer engines are very different with fuel injection and electronic ignition being much cheaper and easier to tune to your requirements.

Great video! Concise and easy to digest.

I used to believe the same from my days of going from straight hedders to full exhaust. Now I understand.. Thank you sir for educating me on what I didn't understand.

The issue with oem exhausts are they're made for noise and emission standards, and not for the performance of the engine it self. Take a Nissan Patrol in Australia, by upgrading exhaust after the cats to a 3inch mandrel bent one you gain torque and a bit of hp. The standard exhaust has a section which is flat and a diameter of 1.9 inches, which for a 5.6l V8 is nuts, it also has hard bends and the mufflers has sharp bends and a value in it. Went after market with a good 3 inch and I've gained 30nm and 6kw and fuel usage dropped a bit as well. Yes, the car has a nice V8 note to it now, it's not overlay loud and it's made of 2mm thick 304 grade stainless steel which will last the life of the car.

You are spot on, in the past I have made stainless steel exhaust pipes kept them as straight as possible, built the silencer boxes with straight through perforated tube surrounded with fiberglass wool, and found the engines run smoother due to no back pressure in the exhaust system.

@razor6888

3 ай бұрын

LMAO

@Starscream8896

3 ай бұрын

@@razor6888whats funny

Solid knowledge session 🤝 rock on my man!

This dude is just always smiling while he's doing his videos. You can tell he loves what he does.

I’m a ECM designer, this all makes sense, this is a perfect explanation that doesn’t dig into the thermodynamics and compressible flow so deeply as to be intimidating. A lot of work I do is on turbocharged engines and it’s quite a lot different as you mentioned, especially if the ECM has control of boost and if you’re lucky enough to have access to the full calibration tools like I do. The one time I actually want exhaust restriction with a turbo is when I want to balance pressures with an EGR system… imagine balancing boost pressure, manifold pressure, wastegate flow, turbine flow, EGR flow, and exhaust pre-turbine pressure. That software is tricky to tune, in this case I’m using EGR to manage exhaust temperature at WOT. One thing I’m always amazed at is the low restriction and conversion efficiency of modern catalytic converters. I remember those old pebble bed converters… they were awful. One thing to not forget when calculating exhaust system flows, restrictions, or pressures is that the temperature is high enough to affect the calculations a lot. Thanks for a great video.

@motoiq

Жыл бұрын

Who do you work for? I curious thing I have found that was not intuitive is how EGR can help control detonation on a turbo car. The other thing I found interesting is how much a cat hurts power on a highly tuned naturally aspirated engine with a lot of overlap, more than what the backpressure gains would suggest. I think an out-of-phase-reflected wave is generated by the face of the brick and causes reversion. I think I am going to do a more scholarly version of the video based on all the idiotic comments this video gets.

@panicow6005

7 ай бұрын

So are y’all saying straight pipe is better or worse for turbo cars

@jimbrown3720

5 ай бұрын

What would you consider a modern catalytic converter ?

@dale116dot7

5 ай бұрын

@@jimbrown3720 After roughly 1998, when the chemistry and oxygen storage was optimized for dual loop feedback and active oxygen purge after a lean excursion or fuel cut event.

@dale116dot7

5 ай бұрын

@@motoiq I can’t really say for legal reasons who I work for but there was a SAE paper by Cummins that considered this. EGR was needed more to limit exhaust system temperature, but the combination of EGR and spark timing allowed enough margin from detonation and overheated exhaust valves at the target torque/boost. Keep in mind that these are truck/bus engines that go for half a million miles.

Dude is the Bobby Lee of mechanics. His whole vibe is spot on 😂

Best explanation I’ve heard on this subject!

Great video! Is tuff to explain things like this sometimes to people who "know everything" already! Back pressure is so useless that extreme performance vehicles have the exhaust on the highest vacuum area of the vehicle not only having zero back pressure but in reality "sucking" the gases out of the engine! Thanks for the video! ✌

@GonzoDonzo

Жыл бұрын

Ferrari 488?

@guzforce

Жыл бұрын

@@GonzoDonzo Not sure about that model specific, but if you look for the most powerful engines in the world (Top-Fuel Dragster) the pipes have no restriction or back pressure at all and as far as I know, the point up as the exhaust pressure creates more downforce also. Many different examples and applications, such as thin wall thickness with springs to create a resonance effect basically (peristaltic effect self-propelling the gases out)... everything is kind of exaggerated, but that is what makes the difference in the end!

@GonzoDonzo

Жыл бұрын

@@guzforce yeah old piston driven planes did the same thing but used the exhaust gases to propel the plane forward. Its something like 10% of a p-51's thrust at full power comes from the exhaust. Its a very complex problem and were starting to figure things out thanks to our computer modeling. So we design for the application

Sending this to my roommate (a jeep owner) who just two days ago made this claim and even went so far as to say that without back pressure "you lose 100 lb-ft real quick" in a Jeep 😂 Thanks for coming in with the right information.

@thecraftsman8133

Жыл бұрын

Only in a jeep??? Lol...kick your roommate out! Lol...its funny how a lot of people go off of superstition also. There must be some kind of curse with jeeps. If you do something like whatever they lose 100ftlbs instantly or in his case "real quick"! Where do some of these people gain their info? Tell your roommate he needs to crack a book and stop listening to idiots. Kinda shows how Naive he is...good luck. Hey, now that you know he believes he will loose 100ftlbs of torque REAL QUICK and belives in angels and unicorns, you know he is naive. he definitely needs to get his info from somewhere else. You never know a person till you live with them.

@isaacgarcia8686

Жыл бұрын

@@thecraftsman8133 Idiots are everywhere.

I agree, to explain why, my son had a 2002 Ford Escape with a rattling cat in one of 2 cats built into the exhaust manifolds which had the v6 3.0 lit. The downstream cat was rattling also. At that time replacement cats were insanely expensive, so I decided to remove the cat material out of each component. On the manifolds I zip cut a square opening and removed the cat material and wielded the tops back on, did the same on the downstream cat and installed a performance muffler with a 2.5 in and 2.5 out and kept the back resonator muffler and all other tubing in-between I used 2 1/4. Granted I got a check engine light doing this stuff but that wasn't the concern at this point, it was to keep the costs down for my son and emissions inspection was removed at that time. Now did we feel any difference in performance, you bet. I personally had a 2008 ford escape v6 in top running condition and hands down his escape ran faster off the line Reved up quicker, it would even light up the front tires a bit of the line. So the point of this is the back pressure was removed, the volumetric efficiency of the air pump (engine) increased dramatically! Nothing like a actual experience to prove the point and support the video shop talk on this topic 😎

@smokincooks7661

9 ай бұрын

You just admitted to breaking US federal law, if that's a road-going vehicle. Enforcement is lax, but it's a jerk move to selfishly pollute to save money.

I gotta have whatever strain he smokes.. just so chill.. so knowledgeable

Not sure how my algorithm led me here for the second time BUT Im sold. Mike is one cool cucumber - I don't know what's better his knowledge and ease of delivery or the super informative content?!! Im a subscriber. 🤙🤙💯💯

Interesting about turbo exhausts. On my VW 1.8t you could change shift the power up and down with exhaust size. a 2 to 2.5" had more low-mid torque, and a 3" had more up top. For a street driven car I preferred the middle sized options. Not sure why the turbo spooled faster with the smaller exhaust. I didn't notice much of a difference in fuel efficiency, maybe slightly more on the smaller stock exhaust.

@nicksmith4808

Жыл бұрын

It spooled faster because smaller exhaust same volume of air means more pressure making the turbo to have more pressure to spool it faster. Imagine blowing on a fan and then doing it with a straw, which one makes it spin up faster. And for the torque and HP you mentioned. It's a turbo engine it's not gonna make power unless the turbo is spooling. The larger exhaust just caused it to spool a little slower which could result in less bottom end torque but is less restrictive for better turbo efficiency on higher rpm ranges

@zzzzzsleeping

Жыл бұрын

likewise, I have a 2020 Acura NSX with just JB4 piggy back ecu (nothing else). My friend has JB4 too, cat deleted and muffler deleted (after market exhaust system). At the drag strip, I constantly getting 10.8 and a few times I got 10.6 where as he get 10.9. Seem my turbo like the way it is while making exhaust bigger piping gain horsepower but lost turbo spool time. My turbo spool faster.

@midnight347

Жыл бұрын

​@Nick Smith that isn't how it works. A larger exhaust actually make the turbo spool quicker. I noticed this on my fbo hybrid turbo fiesta st which is my daily. I had a 3 inch free flow downpipe and stock 2 1/4 catback with resonator delete and stock restrictive muffler. I went to a full 3 inch cpe catback with no neck down and it spools up quicker now and the guy in this video even backed this up saying a largere exhaust will spool a turbo quicker. It isn't the same as an na setup

This one video has answered all my questions about exhaust systems in one go, thank you.

This was an EXCELLENT video! Answers all the questions with intelligent descriptions reflective of known principles in physics. It's Mello easy to sit though and you want to share it with friends.... nice job! Can you talk a little about X and H pipes?

@motoiq

Жыл бұрын

We are probably going to do a more comprehensive video in the future and will cover that.

Good information and easily understood. Thanks

I have read so many articles, even sketchy forum posts about backpressure and none of them explain to me exactly why it is needed. I understand what it does, just couldn't understand why people say you need it. Thank you for finally explaining it to me.

@williamdawson3792

Жыл бұрын

Definitely need it

@gwot

Жыл бұрын

@@williamdawson3792 You are prime example of what I read online, just a statement of "need it" no explanation as to why and reasoning.

Would love to hear his thoughts on the valves that put exhaust in the intake

@josh817

Жыл бұрын

EGR valves are for emissions

Brilliant explanation

Great explanation! And it's cool to see a guy with a permanent smile on his face!

Man learned so much in just a few minutes from this guy. Love how he explains everything!

His guidance is consistent with what any chemical engineer would learn in a fluid flow class. Subscribed.

@valkman761

9 ай бұрын

Chemical engineer in a fluid flow class, LMAO

@JacopoSkydweller

9 ай бұрын

@@valkman761 What? They take 2-4 Thermodynamics classes, and multiple fluids classes. What do you think air and steam are if not a fluid?

@valkman761

9 ай бұрын

@@JacopoSkydweller fluid dynamics is what's relevant here and presentation isn't really consistent with what someone would learn in a "fluid flow class". The premise of less is more here is really not consistent with anything other than wide open throttle scenario

You nailed it the reverberating exhaust compression wave really helps scavenging during over lap we tested a bunch of exhaust and pipe dia combo's on our dyno with a healthy LS1 and the single exhaust wit 3" diameter made the most power with the correct mufflers of course we used a Streight thru Bullet muffler and got more HP and TQ than duel 2.5 ex however when we put the turbo type muffler on the single 3" we lost almost 80 HP wow what a difference. it's like you said back pressure is bad I've been teaching that for 20 years you need really good flow but you also need the correct resistance to flow in the form of an ex pipe to keep the velocity of that gas high and hot

@motoiq

11 ай бұрын

It's amazing how much a Turbo muffler or a chambered Flowmaster can kill the power. No one belies me until they actually do some dyno testing on a healthy engine.

Because of my illiteracy I call it back pressure but I've always understood the exhaust needs to be calculated just as efficiently as the intake and fuel metering. Thank You for using proper terms. You are in my prayers Hoka Hey

Great info. I always rebuild my exhausts in my cars, and even make my own resonator pipes and muffler systems. I was a sound engineer and a firearm supressor designer for years so its a good background.

@motoiq

11 ай бұрын

What company did you work for?

@razor6888

3 ай бұрын

LMAO

It is true for two strokes, the back pressure created by the exhaust cone sends back fresh mixture in the cylinder while the exhaust port is still open. The length and cone shape of the exhaust can be used to determine at what rpm the back pressure is most effective.

@jeffreystroman2811

Жыл бұрын

Excellent point, although the effect is only for a short duration of any piston cycle, the rest of the time the above is applicable, I imagine.

@wernerxldata

Жыл бұрын

@@jeffreystroman2811 It is at the part of the compression stroke, when the exhaust port is still open, the piston pushes fresh mixture out of the port and the pulse wave from the exhaust pushes it back into the cylinder.

@brettturner7057

Жыл бұрын

Sorry, not true for 2-strokes either. What a properly "tuned" exhaust for a 2 stroke does is create reflected pressure waves that when timed correctly, hit the exhaust port to reduce the amount of incoming mixture that escapes during port overlap. This is resonant tuning, NOT backpressure. I think the issue here is exactly as Mike explains in the video - backpressure is the wrong word, or at least conjures up the wrong image in people's minds. On 4 strokes, a slight amount of backpressure is a byproduct of creating velocity. You can create backpressure with a crappy manifold or restrictive mufflers, but that doesn't create velocity. The same is true in the argument for 2-strokes. Backpressure is the wrong word. Sure, the reflected wave in a 2 stroke exhaust is a pressure wave, but that's not the same as "backpressure".

@wernerxldata

Жыл бұрын

@@brettturner7057 You're right, back pressure is the wrong term here.

Hey! Bruh. I just stumbled on your channel and pretty cool! You are very knowledgeable about your stuff. You know your shit, pretty straight forward and no BS I like people like you. What would you recommend on 2001 Merdecedes benz S600? Car is all stock right now with 55k on it babied and garage. I wanna hear your thoughts about it. Thank you very much for sharing a very important matter regarding this subject as you may know a lot of people out there doesn't know much of this thing they just talk out of their ass. I'll be watching more of your videos and more power to you.

You are so right about the back pressure I have been saying that for decades but on a 5 or 6 hundred horse engine there is almost no difference in mandrel bent pipes or any others in fact I heard so many inconsistencies in your examples now you are right about the correct size pipe but no difference in the straight thru or the routed mufflers.I have seen dyno actually being done on the same engine with several different exhaust with no more than 3 hp difference spend your money on something besides mandrel bent pipe and 300 dollar straight through mufflers

@motoiq

Жыл бұрын

I have actually tested chambered mufflers vs straight through and have seen huge gains. More that I thought actually. Sometimes 50-60 hp on an engine producing 450 or so hp.

I'll have to say it plays a factor somewhat. My big block wouldn't start until I hooked up my exhaust. Never would have believed it. But it happened