The Power of 2.5- vs. 3-Inch Exhaust - Engine Masters Ep. 9 

Even more so because the cam profile in a stock or mild engine will be effected much more by exhaust flow than a performance engine with little valve overlap and a sharp lobe profile.

Clay Thompkins but even simpler than that a 600 hp engine puts out so much exhaust gas compared to stock that of course 2.5 is gonna be too restrictive compared to 3

life dont begin till 600+ hp haha

Amen to that brother!! I have an 04’ F-150 and would love to see how much HP these guys can squeeze out that bad boy. 5.4 Triton all the way

That_Ford _Guy don't blow a spark plug now lol

LMAO

5 inch? They must be going small in your neighborhood.

Does it have VTEC bro?

@Stev Rex im not a republican, i dont live in Murica, im not white, im not a boxer, sooo, yea, fukwit.

Ask any ricer, Any real ricers

Nust look at the point of 350 hp on this motor. Makes no difference.

use that 2-1/2 " system with a x pipe and get the mufflers as far back as you can. If your engine is under 400 HP and you use an X pipe with 2-1/2" tubing, your loss would be less than same exhaust on a 620 HP engine for sure

not impressed- all the fast caddies have chevy motors in them.

Agreed.

+hueroski I would also love to see this comparison! Something a little more "real world."

yeah, thinking a 2.5 inch would lose hardly anything on a 300 hp average smallblock... would definately be cool to see

+hueroski Then run the test on those terrible buzzing pieces of trash the ricers put on their cars vs a real quality muffler. Not that ricers would care....

+hueroski A 2.5" exhaust on a 300-400hp smallblock is plenty. I have a good 2.5" mandrel bent system in my LS1 powered station wagon and love it - lots better than stock and a good note when you step on it but wont wake the neighbours when I go to work at 5:30am. I've heard the same car with a 3" setup from the same manufacturer and its obnoxious... might be necessary for over 400hp though.

Well done sir.

Mine too....good example of having the right actor play the right part...Duvall im convinced can play anything set in front of him one of the greats...got alot of laughs from this movie ..

+David Ridout I want you to go out there and hit the pace car... Hit the pace car? HIT. THE. PACE. CAR.

Watched Days of Thunder last night. Great film. Fuck Russs Wheeler.

+motorhead1964 Duvall could play Mandela and win an Oscar.

You blew the Plumber?

Sometimes we just settle for less....unless you are referencing your amazing girlfriend

Barely submerged as I drop the kids off at the beach

Ya ya did...one inch at a time. 🤣

Bruh you made my scrolling through comments waiting for the vid to load wayyyy less boring 🤣🤣🤣

Didn't they do a H pipe and X pipe hp test but it's under subscription & not free on Y.T.

I found with 2 cams, my 460 responded at low end with massive gains with an H pipe, but not so much with other cams...

+little billy Host people have 300 hp cars! Where do you live?

+Barış Çepni he lives in USA maybe?

raga1s Maybe he has a Camaro? I believe thise are like 300hp for the 3.6 litre v6 and 400hp for the 6.2 litre v8 model.

+Barış Çepni v6 11+camaro, mustang, charger, challenger, over 300 hp Plus v4 mustang and camaro has over 300hp too

Is there a v4 mustang? Are you sure that Its not I4?

lmao

Brilliant! Your 6" drain pipe is only good if ice cream doesn't have bones in it.... See? I can sound like Magnaflow, yet I don't charge double the price others do! (Like Magnaflow! Wait! If you're here, you're already confused)

Rok Gok nah bro, I did it and it was like 19 with a 3” pipe, you just gained like 50+

Is that at the flywheel, or the tires?

Plus no worries about flooding

the lower the less difference.

+Bill Panop With my first vehicle (96 Ford Bronco) I did this thing I called the *superpipe*, but it was really just *TWO pipes* going into *ONE pipe*, which then split into *TWO pipes* to the mufflers. And maybe it was just first car love or something, but it sounded badass, it was freakin perfect, moderate when daily driving, and loud when I wanted to be.

That's a great idea! I have always wondered what the difference really is.

Hopefully they see this comment. I'm interested in that as well.

I'd like to see this too. Is 3" a complete waste on a 350-400 hp small block.

+Bill Panop Also repeat with a longer muffler

LS vs Coyote vs 392

If they did a more practical test using an engine size most of us could relate to, the results would be less impressive and fewer mufflers that weren't needed in the first place would be sold. I don't consider a 454 a typical street/strip motor as they described it today.

Roger Carlin or a 250 I6

It makes about a 2-3 percent difference. If you had 300 HP with 2.5" exhaust, you would gain about 5-10 HP...might be enough to feel...about like flipping the air cleaner lid on the old Q-jets, but don't expect some miraculous difference.

@@qq-hk2sq I'm with you on this one. They seemed to be a more common street rod motor in the 90s

+Zackster698 That "joke" struck me as very callous. Stopped watching the video at that point.

+nippaaa To live your life trapped inside of a mind that betrays you, your own mind, because of a sickness in the form of a mental disorder that is debilitating and completely devoid of any kind of relief. A pain and agony that you can't physically run from, because its part of you, is detrimental. Every day normal things that most people take for granted are so far out of reach. It takes away every part of you that makes you able to live your life like you feel you should, like you know you could if you could only feel better, even for a little while. So you find a way to run away anyway, escape the trauma and the pain that eats away at you every second of your life, a tiny moment within your misery where you can have some peace of mind. But your illness isnt gone, only momentarily pushed so far down that you can no longer hear it's constant nagging. But down there it grows meaner and harsher than ever and that momentary relief from that drug of choice is no longer your release but now a part of the beast of burden that you so desperately wanted to escape. Every time you pushed it down, ignored it, it got stronger and more hateful, more hurtful, and more resistant to your pleading for it to go away. Its not so easy. Not everyone is born into this world with a mind made able.

+Frederick Horsman Ditto, boss. We'll also be unsubscribing too, if it isn't addressed or dealg with.

+revolutionday1 Did you post this somewhere?

.

haha omfg!

+cerealfamine1 brutal

+julien foss OMG, I'm ROLLING!!!!!!

+julien foss Savage

I'm not sure that's something to be really proud of. (The non-curve curve thing not the fact that the guy is dead, I didn't even know who the fuck this man was until he died)

3 inch to 2.5 tailpipes works great on mid 300 hp cars too.

@RAMBO JOHN J I strongly suggest you ditch the cats. Also, do some research. There are much better mufflers available. Borla Mufflers are OK. But there are better flowing mufflers on the market & they'll give you the "throaty" sound you're looking for; without sounding overly loud and like "gramps" old farm truck. Respectfully, Ben

Unless ur car is turbocharged then it's different

Thanks Ben, I am building a 6.0 with flat top pistons, 862 heads, a ss2 cam, and stock truck intake with slightly bigger injectors, I have 2.5 collectors off my variable headers, guessing about 425 is for a rock crawler. I was planning on just running 2.5 all the way out.......... you answered me up real nice.

@@patrickhickman8723 I sincerely appreciate your reply....sounds like an awesome build. I'm not being critical...but...why are you choosing to use a "stock truck intake"? In my...respectful...opinion, the characteristics of your "SS-2" cam profile and those 862 heads will demand more than that intake can deliver. My friendly advice is to speak to a Tech Adviser at the company who produced the camshaft. Most have a toll-free tech-line. When you call, have with you as much information about your build as possible. ie; camshaft info, flow numbers for your heads, piston info, etc. They'll ask several important questions & give you valuable information to help guide you to a more beneficial intake. About your exhaust system: Trust me, you won't be disappointed by staying with 2.5''. There are 2 logical enhancements to your chosen 2.5" exhaust: 1.) An X pipe...not too far downstream from the collectors. 2.) Opt for oval 2.5'' pipes...rather than the standard round. The X pipe will balance the turbulent exhaust pulses on both banks of your V-8 engine...GREATLY improving torque throughout the RPM range. An X pipe will also allow you to take better advantage of the useable horsepower produced...by placing that HP in a more effective RPM range. Oval exhaust pipes GREATLY enhance scavenging from the combustion chambers & provide a beneficial increase in exhaust velocity. Also, the oval shape allows more ground clearance. Regardless Patrick, I hope ALL works-out well for ya'. Best regards, Ben

Keep rockin on brother

know exactly what u r talking about .

That's a rare car

I found out that I had to have spinal cord surgery C5 and C6 fused together because of my balance and loss of feeling all over my body. I found that my hobby seeing that working with the justice department was not safe anymore. So I pulled the trigger and they told me I am not supposed to life anything heavy stand or sit for long times. I said what can I do! They said you will have to figure it out. So again I had gone back to my hobby fixing cars and renovating my house and planning to build my own shop and start my own business! Never give up always do what you love. Also a doctor can only give you a suggestion he is going to say what will keep him safe from malpractice. He will not say yes you can do your old job if it is heavy and dusty dirty. Just be smart about it. People like everything can brake down.

get some work done and keep on going

Lmao

Lol a mopar guy worried about weight? What a joke

Het said sort of stock bottom end that means only high compression pistons

Was thinking the same thing. And throw in an EFI system that would compensate for changes in AFR on each config.

They've done tests comparing exhaust patterns before, if not on RU-vid it's probably been moved to MTOD thanks to Discovery.

X pipe all the way bro. :)

@@angelgjr1999 Depends on the car. On my 2v I have long tubes o/r x and spintech super pro streets. I had lm1, couldn't stand the rasp, so I gave it a muscle car sound, not some junky raspy car.

Karl Hopkins Mine has staggered wheels (285) x pipe and cold air intake. What should I do next? Coils? I don’t want to lower suspension because roads are trash here and I need my spine intact. )

W

+Andrius Čičirka its stupid, thats just the tip, u need the whole exhaust or open headers i hate honda idiots

jose sanchez I hate too. It's just a prank

W... Wait? Did you say that evey honda owner is idiot? Fuck you

+Andrius Čičirka 5 inch dumper ftw

for sure

lmao. definitely the 4 inch

open header for sure lol

+Brian O'Connor Imagine how much power that engine could make with DOHC and VTEC heads? 650hp @ 5200 rpms and/or 930hp @7500 rpms assuming relatively the same flat torque curve afforded by the bottom end, and the much higher rev range due to the different cam profiles. Def need 4 inch exhaust for anything above 5k though as evidenced by the tq dive at 5.1k. Is that because of the cams, valves, or carbs?

+Marcus Taber what the hell did I just read you just asked a theoretical question basically just said "imagine if honda v-tec engines had DOHC ".... they do but then you go on to assume doing this will put out silly numbers at random rpm points and then advise a 4 inch exhaust but then ask why it needs it? are you ok? unless you mean on the 454 in which case its make a bit more power v-tec isn't some magical thing it basically just makes a cam with low lift have increased lift when activated by lowering the cams. which it otherwise has high lift honda has v-tec for efficiency not power

lmfao

While driving around town I saw a jetta TDI with a stock exhaust but he had an "aftermarket" exhaust as well....dryer hose right out from under his fender and up the side of the car...little plumes of black. Made my day

lmao

Does the catalytic converter do a good job of catching the lint?

@@DavidG-vq3bk nah! Thats the cabin filters job. Hehe

Yeah boy

@@davelowets Wouldn't a quieter, hence more restrictive muffler defeat the purpose of going 3" anyway? You only flow as much as your most restrictive piece can allow. Quieter mufflers usually have more baffles and restrict flow accordingly.

@@BigfootUnibrowMan The big 5x11 MagnaFlow muffs quiet things down pretty good without hurting power but bottom line is the more power it makes, the louder it is, unless it has some hair dryers on it to kill the pulse! LOL My 409 small block isn't bad with 2, 12" glass packs with good turndowns hangin on the end of the headers isn't terribly loud, until I hit the loud pedal!! Will finish the real exhaust one of these days with dual 2.5s running into a MagnaFlow with internal Y pipe & a single 3.5" out! Will still be loud but way quieter than now with zero loss of power.

@@BigfootUnibrowMan they are mufflers that actually increase air flow BUT they are 800+ a peice

I did 2.25" true dual exhaust with 8"glass packs on 2000 chevy silverado with 3" tips haven't noticed any power loss at all if anything it got more because I put 285/75/16 and it will smoke the tires like nothing when before I had 265/75/16 and they wouldn't smoke at all with stock pipes

+devils garage yup.. because basically your 1.3 engine has to be at full, high revs all the time to do a proper speed.. ; )

How could this be applied to a common Briggs and Stratton?

Jonathan Banta lmao

I have twin 3"pipes on my 96 Geo Metro, what a difference that makes, 3 banger with an unbelievable 1000 ccs of raw power.

I like u

I hope u have a brother named John

No

How about a test of a stock 350 from the early 90,s pickup ,headers ,y pipe (2.5 ) ,3 inch cat in +out , magnaflow 3 in +out ,3 inch side pipe exit ,single ,especialy at a modest 3500 rpm, u know , where most pickups operate maybe with an MSD package ? These dino tests wind up so fast to max throtle , ignoring cruising speeds, where u can actually smell the roses and check out the sites ,cruisen' Just sayin'

the power change figures are not really the point of this video, more just debunking the "calculated back pressure = higher performance" myth

@@justmechanicthings Just wanted to let you know that there is at least one other person out there that understands like you do. DF even said "these tests are done at WOT and not the way you would typically drive on the street". They joked about the myth several times which was another ample hint as to what the video was about. Keep on teaching on!

@@justmechanicthingsa pipe system can be caculated but not to make back pressure but to use the velocity and weight of the exhaust system to use it to "suck" in air while the overlap is occuring

they really should start talking as a percentage loss, its 3%! is that seat of the pants percevable.

+Roland Ocomen really funny punk!

+Roland Ocomen you never know with mustang driver lol

all last gen stock mustangs I beat no problem with my 4 cylinder.....I'm trying to figure out if a 3 inch exhaust would help make my domination be even easier.

+Motor Trend Channel *can you guys do an episode where u put a performance crankshaft on a European turbo v8 or v12 thanks*

+Roland Ocomen thats way to big..hahaha you need like a 2in full

+yuck fou Brutal.

+yuck fou hes been drug free for like a year now.

+Albion Laster dude hes dead

urmomsayswhat dumbass

+urmomsayswhat that's the joke

Y those mufflers are the same

Cherry Bombs? might well use Tuna Cans.

+1

A turbo charger wouldn't really work on this indoor Dino test. A turbo relies on extra airflow into the turbo turbines. But a supercharger would be fun to see

+Ryan Devid that's makes no sense. You clearly don't know how a turbo works

+Ant M it's okay that you're a ricer and don't know how turbos work. You need increase airflow into the turbo to increase the power. In a room with static air you won't get a big increase in power. Yes you'll see an increase in power but not that much

+Ryan Devid turbos use the exhaust gas to turn a turbine which is connected to a compressor wheel which sucks air into the turbo them compresses it to create boost. You are referring to ram air effect which doesn't effect a turbo engine that much

This is the real question.

If it was set up properly for the open headers, which is probably the case as Brule is one of the best carb tuning guys in the industry, it's not that hard to calculate. You have to remember the fact that while you can tune it for better AFR, it does not change the fact that the system as a whole moves less volume. The amount the AFR goes down, is basically the same as the amount of air flow lost. In this case, you would not see much by tuning the carb - maybe 5-6 hp at best.

+ABOisen69X Agreed, if the carb was set up for the longtubes with the 18" collector extensions, recalibrating the engine would be beneficial when adding any sort of full exhaust. Gains/losses from tuneup between swapping between the 2-1/2" and 3" would be minimal.

the longer the exhaust is, the more restriction it has........ maybe this needs to be explained in this video as well, drag on the walls etc. some engineering calcs need to be run.

@@AB-80X at what rpm? WOT?

yeah that was a bit fucked up

agreed. they didn't check to see how much leaner you can run the carb before you start getting into overtemp/knock and how much power would come back. that would have been too scientific.

+John Klatt surely it's worth noting that the AFR never really went wildly outside of an ideal range.

+M3rVsT4H kind of. I mean look at the flip side of this. if they had that tuned to the 2.5" and then switched to 3" and then just open headers with that little extension would it have not been running way lean? there were some spikes of leanness there. yes it's clear you are going to lose some power but it seemed that this was more of a 2.5" sucks video.

+John Klatt I think the comparison was that the carb was tuned for open pipes ie: max possible power output, and then they were going off of that tune to see how much power was lost by adding pipes.

+Numinous A chart to make choosing easier, courtesy of Dynomax;-) www.qsl.net/ya5t/techchart.jpg

JerseyMikeP It's a little different for me, since I'm forced induction (2.3 DI Turbo running 25psi). 3" serves me great at my power level, ~380whp.

Exhaust is always better when it's bigger. Your not looking for back pressure. Your looking for Exhaust scavenging. An x pipe on a 3 inch set up will always out perform an 2.5 set up or h pipe. But 2.5 inch pipe will give you gains with an x pipe. It's really all about making one exhoust pulse into a vacuum for the next pulse

@@rednecksworld2649 what about on a turbo motor? Would a 4 inch exhaust be better then a 3 inch exhaust on a stock turbocharged motor?

@@jackdaniels2657 that would be interesting. With a turbo, your not looking for exhoust scavenging. We already know a muffler on a turbo is restrictive. 3 inch exhoust is nice for exhoust flow but how big is to big. What problems will a 4 inch axhoust couse if any.

@@rednecksworld2649 like I said u need the restrictive backpressure cus without back pressure no spool and turbos work under load meaning backpressure

Big exhaust on a stock engine wont do anythingexcept make it louder

Philip Ball was thinking same thing, this engine is no where near stock. Therefore more air wants to exit and 2.5 restricts this

If the engine only 150hp what size that optimal?

John Lingenfelter (RIP) and Borla would disagree with you. Lingenfelter built over 600 horse power Corvettes using Borla 2.5 inch exhaust systems.

@@mustangecoboosthpp3869 I don't think you understood my statement. You can still make 600hp with. 2.5 inch system. But you'll be missing out on a few extra hp while you do it. Lots of times people stick with a smaller size to help get the pipes to fit under the car - especially with low slung corner carvers. Going bigger doesn't yield benefits but you are of course free to NOT optimize the system and miss out on some performance all you like.

+Brian C Same. I don't think I'd notice a 15-20hp loss on a 600hp motor, but it'd be nice to have a the option of quiet power. Semper Fi.

+Brian C Yeah would have been nice to get a number on that to compare too

+NoBrakes23 they make y pipes that you can open with a servo operated switch and cable operated versions too, or the old school type that you unbolt to dump the exhaus

Check out the new Cuthroat Exhaust Systems, DirectFlow Exhaust Cutout! Only true pure, full flowing, non turbulent design available. cuthroatflow.com

+Jalmarification I was thinking that too. Really should have re-tuned it after putting the 2.5 on and then gotten some better results

Not splitting hairs at all. Your point is valid.

Precisely. Whenever any changes are made to an engine's volumetric efficiency, the fuel and ignition really need to be re-optimized for those changes to make it fully worthwhile. This applies to anything from carb+dizzy to fully electronic fuel+ignition. I would also like to see how the power on this test engine looks with the 2.5" exhaust and a re-tune of, at least, the fueling.

It's virtually the same result.

WHAT why test something a normal,average ,everyday guy or girl might have in their car or truck? they need to test more top fuel and 700-800 horsepower unicorns none of us will ever own so we have useless data regarding parts we cant afford.

@@trillrifaxegrindor4411 if you test the lower hp cars the results would be minimal. The results already were minimal. 13 hp would not be seen on a track time. too many variables come in to play with that. My car is tuned properly for the 2.5 exhaust. I am willing to bet a 3 inch would make it a little louder, but minimal if any true gains.

@@johnscudellari3314 You really think 13 Horsepower is minimal?? Seriously?? 13 extra Horeapower is not minimal.

When they have already proven a 614hp engine would only lose 2.8% of its power if you dropped to 2.5" and totally forgot to tune the engine for the new exhaust... I'm pretty sure you have your answer.

+jonnda It should do a little something. When the exhaust gases passes through to the higher volume section, that lower pressure area difference theoretically increases the flow velocity of the tighter area. Obviously I am no dyno but if the old theory is true it should at least increase and help flatten your torque band.

I'd say they proved that you do need back-pressure. The idea has always been that it's only needed at low RPM's. The 2 1/2" out performed the other 2 setups below 3500 RPM @WOT.

+HvyMetal4Ever That is ideal for vehicles with EFI and multiple maps that can switched but carbs may suffer because of the difference in fuel requirements to make maximum power under either condition.

+HvyMetal4Ever a lot of manufacturers like BMW or audi actually do that. Take a look next time when you are by one of the newer models, if it has more than 1 exhaust, usually, only 1 will actually be open at idle. The general role is that for low RPM, you want a more restrictive exahust, and for high RPM, you want a more free flowing one :P

Karolis Nosevičius I know there are Corvette models that offer the option as well

what about turbocharged? no back pressure right?

Gonzo's Garden any setup needs to have an optimized exhaust. an exhaust that is to short or to long will let in atmosferic pressure in to the exhaust, that will create back pressure in a way. imagine it as a wave. as the exhaust clears it self of all the gasses, the vacume in the exhaust will suck in atmosferic pressure, and than, the next "charge" of exhaust gasses comming from the engine will need extra effort to push the atmosferic gasses out again.

LIKE THE ONE GUY SAID- try with a stock motor

That's the real test.

Friday

+David Freiburger whoop whoop! heck yeah.

+David Freiburger thanks burger n fries

on motortrend on demand. lmao

+MrAcelock1124 Furburger*

+James Godwin So? I get it if he was your friend, but chances are you never met the guy so what difference does it make? Personally I say more dead celebrity jokes!

+James Godwin dat torque curve comparatively doe

+James Godwin He was saying the torque curve was FLAT. Your point is correct, I guess you just didn't get the joke.

except when he's on coke. Then its flat, just higher

+ryan reed How about you go ahead and off yourself, and we'll all "joke" about it afterwards....even though you're basically a total nobody?

Camaro is GM and it's garbage boy, should of had a man's car with a Big Block Dodge under the hood.

+Daveros Garrett if only i could fulfill the sound

Lol I thought I was the only one that did that

i didn't... instead i went straight to cursing at my old muffler while trying to get it off and eventually going the screw it route and had a shop put it on... it was worth the $40 to read car magazines from 5+ years ago for a half an hour while someone else does it...

I was once a closet muffler screamer. Thanks to you, I can come out.

Guilty myself. Gotta test it. :)

sound is complety objective.

Dual 2.75 with tuning for the win

Yep.. I see 2.5 for small blocks vs 2.25.

Probably because you obviously own a lemon of a motor lol. Our 383 shift at 7.800rpm lol

​@@k.y.s_performace7038 That's his point. Most people rarely exceed the 4500 fpm piston speed threshold on stock, or one step up, parts. Do you turn your 383 at 7.800 rpm with a breaker bar, or by hand? I'd be fairly impressed with the latter....

K.Y.S_performace fr man I wanna see that. And to respond to the OP on this comment, my stock 345 hemi shifts at 6200.

@@thelikebutton4405 exactly, alot of people that run hemi's at the strip are spinning past 7000rpm with stock bottom ends. The original 426 hemi with a 727 torqueflight would shift at around 7250rpm and thats a bigblock lol

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