A trick that an old drag racing buddy taught me was to add an equal diameter tube onto that flange. say, 22 inches long. Paint it a light color with hi temp barbeque paint. After a few runs, cut the tube where the paint stopped burning up. It is now ideal length,
its good for finding where to put h pipe or x pipe too. but go in a little before the paint stopped burning as the pipe picks up some of the heat too and its not the exhaust gas burning it. a line in crayon or china marker works too.
As a 65 year-old hotrodder, you explained this well and correctly. However, I never uncorked headers to gain power. I only have raising hell and making noise on my mind. Is that bad?
Only if you do it at 3:00 am after s night if drinking and then do a burnout in of a friends driveway. Not a good way to score points with the friends parents. 🤷♂️
@@danmyers9372 I like your style! At 65 I still raise hell but none of the parents are still alive. Come to think of it, almost all of the real hotrodders in this area aren’t either. But your idea is solid!
I tried to make it easier to understand for the "New Guy" hence the channel name 😆 ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-1CzGFoXwrfo.html Did one for if you are running forced induction!
You are 100% correct. Back around 1974 I took my street driven 1970 Mach 1 to a test n tune. I uncapped my street headers and fought with the car all day. It definitely lost torque and was running a good 2-3 tenths slower than what it ran on the street. Being an ignorant kid I tried rejetting the carb, switching carbs and changing the timing all to no avail. It was a turd, especially down low. If only I had had some bolt on collector extensions!
Very good video. You are 100% correct about the scavenging effect and the power pulses. (Same goes for the intake, look at Chryslers ram induction). Our rule of thumb was to install a collector that was painted, run the engine at about 2500 rpm and see where the paint burned off on the collector. Then we would cut the collector at 3" past the paint burn off area. This was back in the '70's when we were doing this.
He's only saying half the story,! There are positive and negative pulses. One helps pull charge in during valve overlap and ex gas out. It also reflects, positive pulse to prevent charge being wasted out of exhaust. Shorter the pipe, sooner it occurs....ie high rpm I'm going to leave the chat now, can't teach old dogs etc, just do some reading.
Sorry mate. Same for my other comments, the things you describe must be quirks of such engines ....long header Vs shitty cast ex is obviously better( mostly) but it's not because they're longer it's cos they just flow better etc. Please research exhaust theory......I was going to say nowt else but it's so irritating...... you make your engine faster etc no doubt but you just guess why! Sorry.
@@peterjohn3180 i know there are math involve and the length for the pulses. there is a spoon civic that the runner itself cost more than the car itself. its so long that the entire engine bay need to be refitted to include the engine relocated so the exhaust runner could fit in. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-j9p24qIjWSQ.html
You are mostly correct but there is one part you're missing, scavenging occurs because of a pulse that is sent backwards whenever the exhaust pulse reaches the collector, think of it as a ripple in a pond bouncing back after hitting a dam. Basically you are trying to catch the vacuum on the bounce back, which pulls the air into the cylinder over exhaust and intake overlap, thus creating scavenging. This only happens over a short rpm band, and this rpm band is determined by the distance from the valve to to the collector, and the longer the header the higher up in the rpms you catch the scavenging effect. Now because it works like a wave there will probably be 4 or 5 peaks in torque that you will see in decreasing magnitude, but if you aren't running high enough rpm it is absolutely possible to have too long of headers and so you won't be catching the first and strongest pulse, instead youll be using the second, much weaker pulse. Anyway I hope this helps someone learn something.
Maybe people should give this a listen, each tube needs to be a specific length and diameter for a given cylinder, and horsepower/rpm range: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-f72BMpmoGMY.html
Dang, world of knowledge going on here, this is very interesting. Sounds very similar to the concept of 1st, 3rd, and 5th harmonics of a fundamental frequency where the 1st harmonic is larger in amplitude than the 3rd and 5th.
62 year old son of a former drag racer. I never ran open headers. I had a buddy of my Dad weld up a collector with a wedge to help scavenge an bolted a high flow glass pack to my 428 Cougar. Never noticed even a tenth at the track.
You should check out the old school Mickey Thompson Super Scavenger headers with the long racing style collectors and mounting flanges for street exhaust systems. The best of both worlds.
I can confirm this information is 100% true. My engine on my 73 ford makes more torque with mufflers but lacks the top end power of open headers. When I tried just running open headers I had great top end power but horrible bottom end torque. When I ran 18 inch collector extensions on my headers I got the best of both worlds. With the extensions I seemed to have way more torque than I did with the mufflers and just as much top end power as open headers and a better throttle response. My car is definitely faster with the collector extensions!😁
Back in the day I put a big block in my 68 Camaro and I had to run header mufflers for a couple weeks until I could save up the money to get the exhaust system done. I swear the car had twice as much bottom end torque after I got the full exhaust system installed. Back then you had to bring it to a muffler shop and have the system custom bent. I ran two and a half inch pipe with a set of Turbo mufflers. I miss that car so much, I should have never sold it!
Still have my 69 Camaro convertible I bought in late 1983. Been bringing it back to life the last couple years. Grandson and I rebuilt the engine last year. We also put in a new transmission , disc brake conversion, new suspension front to back and a new moser 12 bolt posi. Starting to shape up nicely. Been off the road for several years. Understand about missing it. Glad I never sold it.
That was a lesson I learned in my late teens when I bought mine. ALL of the older guys back then all said that same thing. They all wished they still had their “???” car from when they were younger. I learned from the older generation and said I was not going to be that guy. Now I get to pass it on to my kids/grandkids.
Great video! You should make another header video that describes the physics how exhaust manufacturers & many authors concluded short collectors are favored for horsepower and longer for torque. Smokey Yunick mentioned in his book Power Secrets how tricky in his attempts with exhaust, He actually figured out ways to find natural low atmospheric pressures under the chassis of moving race cars and "dump" header pipes there. He was genius in many "waste not want not" hp gains.
Its alwase better to be to long than to short with collectors. The power lose from being to long is verry minimal but the power lose from being to short can kill all of your bottom end. Not to many cases were you would give up 50 foot pounds below tourqe peak to gain 10 hp at the top 😅
Thanks for this video. This gives me ammo in my arsenal to send my buds who are just not educated on the science dynamics behind what exhaust actually does to performance.
Thank you for this and it reassures that what they did at the garage where I got my open headers on my Chrysler 5th Avenue was the best set up! It's a very lean burning car with very little horsepower, but it just sounds amazing on the open road!
Excellent description. I've seen older bikers tuning their bikes with a sliding exhaust listening to the tone change. Take an exhaust off a two stroke it virtually stops.
Two strokes need back pressure and scavenging otherwise they're a mess I used to have a Suzuki 250 Hustler X6 1970 it was a fun little bike I'm surprised I lived through it have a great day
Scavenging effect goes all the way up to the next intake charge (camshaft overlap). Also, you can use white fingernail polish to draw a line on the collector extension. Make a few full throttle passes and cut where the white turns brown.
@@newguysgarage6802 Yes, I watched it. I simply added that those exhaust pulses also create a vacuum to pull the next intake charge into the cylinder. That's why camshafts are ground with "overlap" so that the exhaust valve and intake valve are open at the same time. The amount of overlap needed is dictated by the intended use. At the collector, pulses are merged from other cylinders to increase the "usefulness" of these pulses. However, as exhaust gas cools it slows down and becomes a restriction. Optimally we want to keep the fast/hot exhaust gasses and expell them quickly when they slow down. This is done by tuning the collector length. You can guess at optimal collector length or you can get a pretty good idea of optimal length my checking temps on the collector. Measuring temp on a long bare metal collector with FLIR would probably be the best method currently available. However, you can get close with white fingernail polish (the cheap stuff...not extended wear or anything) or you can use temp paint. It's not going to be a sharp line. Remember, even if you apply it on a dyno, we're seeing the result spanning across an RPM range. It'll be a gradient. So start at the beginning of the gradient and fine tune from there.
Yep i have other videos explaining overlap too lol. But my point was with the paint stripe actually not working to find optimal collector length. With the paint trick you will almost always cut it too short because exhaust dose not have to be hot enough to burn paint to still be hot enough to flow. Only time paint trick is close is when using large primary tube diameters, because they naturally want a shorter collector length so the paint is closer to optimal simply by coincidence 🤔
That's why I made longer collectors to my headers, tapering the pipe down to my exhaust pipes. Great breakdown and explanation of scavenging the exhaust pulses.
Currently collecting the parts to build a rat rod, I appreciate that you not only identified the problem but also offered the solution, that info will be put to use on the build, thank you 🤙🏻
That's why when I built my own 3 inch exhast system for my 340 Dart it picked up a very large amount of power. The combination of 3" header collectors and 3" exhaust pipes to the mufflers extended the scavenging effect. Mandrel bends and good mufflers lowered back pressure to increase the flow in the exhaust system at all rpms. My previous exhaust system when really examined at its bends was pretty bad.
My friend had a 1972 Dodge demon we had a lot of fun with that Mickey Thompson 14s up front and 15s L60 15s in the rear with Craig SS all the way around man that was a fun car we had a lot of good times took it to connecting highway if you're from the East Coast you'll know where that's at have a good day
I agree, I ran long tubes and 3' exhaust on my FE 390 and it really woke up compared to what previous owner had them dumping into 2" all the way back. The old Indy cars ran extra long headers, essentially a very long collector. But I also think cam duration has a lot to do with how the exhaust is tuned after the initial dump into a street length collector. The old school high lift cams were not as technical with full duration as engines of today. So I can see why they got the good results they were after by simply measuring where mass heat ended vs newer engines need the math formula. Of coarse we know math formulas can be reliable to get us close but still advisable to play around with different set-ups behind the collector. The small exhaust ports gripe my ass on the Vortec V6 heads. I wish someone would make some 202 style heads for that little engine that could. I hate depending on boost for power. Freaking vacuum cleaner sounding POS that won't last 100,000 miles if you drive them hard. Just my opinion.
It is all about your engine. There is a racing procedure to get the optimum collector pipe length. I actually read the real hand written instructions by Grumpy Jenkins.
Back in the day I ran my 69 Road Runner with full exhaust but where the headers met the collectors instead of a gasket I put a washer in between the bolts for a little gap. That seemed to work fine. A lot of Mopars in the Washington DC area back then ran like that.
Weird idea, but I think i can see how it works. Velocity of exhaust pulse jumps straight past the breather gap, and if the vacuum behind the pulse is too great it draws air from outside to keep the velocity up in the pipes I take it. Now if I'm right about that, that's bloody clever and I love the idea! However I'm no exhaust expert, I'm just trying to make sense of it with my limited knowledge of physics
@@YouNameItGaming how does introducing outside air into the system that goes back against the flow increase velocity? Further more at that point you lose the draw of the hot exhaust pulling the burned gasses out of the cylinders and the valve overlap ..when both vales are open at the same time drawing fuel and air loses some of its effect ..well actually what happens is the lower pressure that is created internally or vacuum from escaping exhaust leaves a void that the atmospheric pressure above the air intake tries to equalize it forces its way in and if you have x about of space that has air moving thru it and then the space is reduced the air behind continues to push meaning in order for the air volume to vmcontinue it has to speed up ..the velocity effect ...
@@jamesgibson5876 "how does introducing outside air into the system that goes back against the flow increase velocity?" It doesn't. Nobody said anything about increasing the velocity! Like I said, I'm not an expert in exhaust, I'm just trying to make sense of how it would work if indeed it does, and the way I speculate that it would work is if the exhaust pulse carries momentum down the exhaust tube and follows a similar principle to a bullet in an insanely long barrel (expansion completes whilst bullet is still in barrel, the momentum of the bullet creates a partial vacuum behind it, bullet loses velocity) and so allowing air to enter behind it in such an event would in theory reduce the the partial vacuum behind the pulse and reduce the potential for lost velocity. Now to be fair it could lead to a reduction in scavenging, but I simply do not know Now once again, I'm no expert and I could be and probably are wrong, but you're clearly not looking at it the same way I am
As long as those headers seem I’d guess they are for around 4500-5000rpm at that diameter, often will try to incorporate two pulse per runner before the collector for higher rpms in some theories but using theory and formulas only goes so far, as nothing beats making it and testing it, the best I’ve seen is 8-1 system with an adjustable length collector it makes an ol gm v8 sound like a formula 1 engine
Yeah I saw a mini modified puller tractor back in the mid '80s with an 8 into 1 that screamed but seemed to do better than the 2x 4 into 1 tractors with the same capacity SBC
Most of the tuning I've done internally on my engines is cheap free horsepower take your pistons and balance them take your sharp edges in your motor & chamfer allow for good air flow allow for good oil flow run high Volume oil pump but the price of the pump is worth it saves you from losing a motor and the main thing port and polish you're intake it's simple get your sanding rolls and a long extension polish it out match it to your heads with dicem blue and you'll get free horsepower also make shore your rotating assembly is well balanced and it's real simple have a good day
Port.....but not polish lol If you get the intake verry smooth then that lets the fuel come out of suspension and puddle up along the port walls. On a carburated engine anyway.
@@newguysgarage6802 yeah it’s a complicated topic and it’s different for different parts of the port, and can be counter productive in the wrong place causing more fuel to come out of suspension than a completely polished port Eric weingartener has excellent porting videos and has done some testing with golf ball ports from memory should not be done on the port short side
Excellent video, I put header insert mufflers in my 3.5 collectors and got an extra 4 inches of length on a 3 inch system netting 18" before the bend and boosted low torque.
You are partially right ! The fuel/air mixture enters thru the intake valves scavanges the burned gasses, passes thru the exhaust valve and cools the exhaust valve on the way out. Valve overlap duration, header diameter and length, intake diameter and length needs to be all in tune. A portion of that fuel/air mix that is now partially in the exhaust reverses direction by the pulse of the next cylinder exhaust. That pushes back thru the exhaust valve and back into the cylinder along with the incoming fuel/air from the intake and will increase the cylinder volumetric efficiency. An open header will reduce the double charge efficiency of all the cylinder. Some back pressure is necessary to improve torque and hp.
I want a cold intake. Please use water to cool the stem and seat of the exhaust valve. Scavenging is to suck out the heat early and to suck on the piston surface while it moves up.
You can also add a High Flow Catalytic Convertor at the flange on the headers, they give the hot gases somewhere to expand in to in a similar way to the expansion volume on properly Tuned Headers, without restricting gas flow, and clean up the cancer causing gases in the exhaust.
I did this on my GTO and unfortunately that theory doesn't hold true. The car was completely gutless on the bottom without the catback. The converters are about 20-24 inches in length past the collector. Kooks 1 7/8 headers with Hi Flo cats. Put a 3 inch stainless works exhaust on with x pipe and it runs awesome.
@@prowler10393 'GTO,.. brain went 'what model GTO from the '60's/70's had cats,.... then went 'Ohhh, Commodores,...' Yeah, removing the Cats from the DunnyDoor is a bad idea, back to those Aromatic Organic molecules in the exhaust making people sick who breath them. As for performance, 'gutless without the catback',.. So it had power with the cats in place? High Flow cats have that funnel shape at both ends to expose the whole front face of the honeycomb to the incoming hot gases, which transfer a lot of heat in to the honeycomb, by the time the gases leave the cat they can fit down a pipe easier as they have been cooled by that heat transfer.
In 76 I built a 390 4 barrel for a friend with a 66 mustang fastback and stuffed it in with headers for the exhaust i had a muffler shop where a friend of mine worked make up a custom dump gate aimed down and out you could either run standard duel exhaust or uncap the turn outs so he could make a LOT of noise .his neighbors hated that car but at night the fire coming out of those pipes and hitting the pavement at the local car hang out was something to see . O to be 18 again .
This is very well explained. Another thing here, when the exhaust (gas) scavenging is less efficient, so is the heat scavenging from the head (Referred to as waste heat, QC, in determining thermal efficiency of a heat source, n(efficiency)=W/Qn, or, (W/Qn)=((Qn-Qc)/Qn), or said, Work in Joules over Resevoir Heat (in) (Engine) (Joules) equals Resevoir Heat (in)(Engine)(Joules) minus Resevoir Cold (Header outlet)(Joules) over Resevoir Heat (in)(Engine)(Joules). Increasing exhaust efficiency with the longer header add on also increases heat transfer efficiency and therefore contributes to added power/torque. By increasing thermal efficiency, we can increase the Work (W) produced, and if we produce more Work in Watts...then we create more HP. 746Watts is approximately 1 horsepower.
@@newguysgarage6802 Dragsters and funny cars have short, stubby individual pipes because they REALLY make power. Same for airplanes in WWII if they didn't turbos. *The KEY is matching the flow rates of the intake **_with the exhaust_** AT the most operated RPM.* Think about this - how often is a street driven hot rod operated at wide open throttle? Not too much, most of it is at cruising speed with some hard acceleration now and then. How often is a legit race car driven at half throttle? Almost never if it's a top fueler. For a V8 street car the _best_ option is not a '4-into-1' but a tuned crossover OR 'tri-Y' header with a dual plane intake because it has the best wide range of RPM flow characteristics ... unless you're literally drag racing from stop light to stop light but that's going to get you arrested.
.......you are misunderstanding why dragsters use zoomies. They are supercharged and running a high volume fuel. On supercharged engines air is getting forced into the combustion chamber and during overlap pushing the exhaust out. The reason scavenging makes power is because it is helping pull the intake charge into the cylinder during overlap. On a supercharged application that is not necessary and as such exhaust scavenging is less important. At a dragsters level were they are also running a high volume fuel along with that all they need is to get as much out as possible AKA zoomies. Now radial engines, they do not use headers as we in the car world would recognize because of packaging restraints in the airplane itself. They make about 1,200hp which seems like a lot until you realize they are 1,800 cubic inches..... thats like a 302 making 250hp....stock manifold territory....
I like your explanation dont forget size of the collector extension too small reduces/minimizing the scavenger effect , hence keep the larger size like 2.5-4” size like the header came with !. Great video buddy
A guy giving me advice and insight on header and scavenging technology.......on a header.....on a motor.....on an engine stand in his kitchen. Thats pretty much a ''must subscribe'' in any gearheads book. In subbed.
That was actually one of the better explanations I´ve heard on the issue. Nice, very nice. If I may I would like to add something that might help. The pressure wave that is provoked by the escaping gas out of the exhaust port is just that, it´s a wave. Meaning there are peaks and valleys. Simple so far. If you have an open exhaust those peaks and valleys help scavenging but only a little bit, i.e. you do not generate as much power as you could be. By extending the collector and/or reducing the actual exhaust tip you provide a reflection point for that wave. This new wave has more restriction for the gas flow so the AVERAGE pressure of this wave is actually higher than an open header. But, BUT, this new wave has higher peaks and valleys. The valleys are actually a slight vacuum and as the new wave has a LOWER valley it´s pressure is actually lower than the valley of the open header. It is this lower pressure (valley) of the restricted wave that provides more of a pressure differential during valve overlap. This higher differential forces out more of the remaining spent gases and that leaves more room for a fresh charge of air/fuel mixture. In other words, if you want more power you need more air/fuel in the cylinder BUT before that can happen you must first evacuate the spent air/fuel from the last power cycle. Provoking a higher amplitude wave by restricting it a bit gives you higher peaks and valleys and that equates to more room in the cylinder, i.e. more power. So if you say you need back-pressure you are correct and wrong at the same time. There is no one, single pressure in an exhaust system at any one time. Rather, they are full of waves (peaks and valleys) and it just so happens that the wave with the HIGHER AVERAGE PRESSURE provides the LOWEST pressure. Hopefully that makes sense.
Good video. A heart murmur is similar and for similar reasons. If the flow becomes turbulent at the heart valve (exhausting), the result is poor flow. Poor flow robs efficiency and creates a loss of power and a suffering of output. Engines from air induction (air cleaner/filter housing/or air horn/hat etc) to the end of the exhaust pipe and everything in between needs to be built around each and the total. Not doing so is a crap shoot and ends up being mostly chance that you are not leaving power on the garage floor/workbench. It's a fine line between the art and science. It takes science, and the true artist, knows how to use the science to the fullest. Those are the folks that win consistently over time.
hi, i used to race on the Atacama desert with my nice patrol v8 and i always used long headers (not that long as in the video, because they didnt fit), but i did run a tube between both sides, joining left and right after the collector and the torque gain was huge. I think the old nascar cars made this too :) (im not an expert, but read that in an old hot rodders forum). That compensate both sides of the engine and it was very smooth, considering the cams i did use. Im kinda old school. :). it was a 2 main bolts 350, bored to 355 with 10.5 compresion, arp bolts, alu intake, rods, flat pistons , crower cam, lifters and a small edelbrock carb ( i thing it was between 500 and 600 or something like that) with an offroad kit (this kit was awesome). Very nice video explaining the scavenging effect. At the end it comes down to where do you need torque/hp in the powerband. I could bash 40 degrees dunes without having fuel issues and i didnt died, so i think it was a good combo :D.
Yep! Connecting both sides of the engine together is essentially a second collector allowing pulses from one side to help pull out the pulses from the other 😁
Er..... 5 inches over bore? I've never heard of such a thing on a small block ...hell you could get five inches with a hone...as for 500 or 600 ..what ? Horsepower? On a naturally aspirated engine your going to work very hard to do slightly better than one horse per inch and it won't be cheap. So 500 or 600 seems sorta uikley ..
@@jamesgibson5876 Hi, CFM, these numbers comes after Carb... :), the engine was .030 overbored. The engine was used and not in the best condition initially and the pistons where a gift from a friend :D. That was in Chile, where we cannot buy easy a v8. It was very difficult to get that motor. hp... well, 5 here, 5 there, at the end i wanted reliability and 320+ hp, from an engine that was originally 210 hp and the most important thing, it cannot die in the middle of the dessert with hi temps. Found an old video :D. Carb and suspension wasnt set yet. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-5Fyns2gXMl0.html found other video :) ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-0Jr8GKtPXoQ.html
I used to run a 383 stroker motor dome Pistons basically a 350 with a 400 crank man great little motor get a lot of horsepower for the whole deal with basically stock parts you modifications but it was worth it I'm 69 years old & old school I worked in a machine but did most of my modification in my garage with simple hand tools have a good day
@@jamesgibson5876 I think he was saying .005 or .006 so before we used to run our bores a little bit loose not quite that loose we went more like three or four just to get the motor to run good without too much resistance on the cylinders have a good day
All engine combinations are different. My old supercharged sbc hated exhaust of any kind and didn't care about any length of extension on the headers. But I also know guys who pick up a tenth or so with extensions. Experiment to see what your motor likes.
I have a boss 302 engine in my 68 F 100. Makes plenty of torque with 5 inch diameter collectors made from a dodge drive line. Like you said. Every engine is different.
@@jesse75 Lol to let you know how crazy overkill that probably is the downpipe on my 600hp turbo Coyote is one 5in pipe and it's probably still overkill. But whatever turns your crank.
They used a cutout, which came close, but, they didn't test a 12 to 18 inch extention designed for scavenging...true extensions would have made the most torque...
They did an entire episode on extensions, ,conclusion, at least 18 inch stub. After 24 inches ,no significant gain on hp/torque, or backpressure increase. Need to rewatch. I do know this my 427 AFR Headed SB stroker, 60 fts a little quicker with stubs, as opposed to open headers. as well as a slightly better ET.
Excellent video and explanation! I do agree this to my surprise is still filled with misconceptions and your video explains a lot real well :) length = helps scavenge I did a drawing w/ animation pertaining to Volumetric efficiency and stated that as soon as the exhaust column exits the tip of the exhaust? The length itself “pulls” the newer oncoming exhaust from the head hence helping “scavenge” Your words are perfect “you’re not taking advantage of what the header is capable of” Thank you for this love it!
And I do agree with Mr Meyer on the comments on the intake it’s the same but inverse or the opposite… prolly why “stacking” was used in the term “velocity stack”
ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-1CzGFoXwrfo.html Thank you for watching! Also when you add forced induction into the mix everything changes lol 😆
I agree with the comments below that say it depends on the setup, and also that long tube headers don't always make more power, thats why high rpm engines use short pipes and no collector. Long tubes are usually for low end torque... And I would also like to say that some engines do need back pressure if that is how they were tuned from the factory. Many engines will run too rich or too lean if you just change the exhaust and get rid of the back pressure. Just ask the people who've burned holes in their pistons shortly after getting rid of their back pressure.
.......change the jets in the carburetor then!? Running too rich or too lean is not a flow issue its a tuning issue! That is the worst excuse ive heard 😆 🤣 😂 Your talking about zoomies on NHRA drag cars they are supercharged. Supercharged engines do not rely on scavenging and vaccum to get exhust out and help pull fresh intake air into the cylinder on overlap. Long tube headers are for high rpm not low. Shortie headers and cast manifolds are for low end around town everyday driving, thats why they are short from the manufacturer.
@@newguysgarage6802 If you say so, I'm just really glad you're not tuning my motors. My 468 BBC at 8500 rpm told me it like shorties, and as a bonus we get to make snow cones with the frost from the tunnel ram.
@@newguysgarage6802 Then I guess you're running straight out of the block if that's your mentality we don't need any back pressure we don't need any collecting we don't need any stinking badges
Thank you for making this video. I hate explaining exhaust pulse scavenging to people. It drives me insane that my friends won’t take my advice and always do stupid shit with their exhaust. They think changing mufflers will hurt the engine in a 90’s mustang.
That's right 👍 I told a few guys about how they think they gained power after goin long tube with an extension only gives you louder exhaust until u add the missing piece
This also has a lot to do with pulling a vacuum on your carburetor and manifold and distributor getting timing set right is crucial you can come up with a variable to fix your exhaust problem by going and pulling vacuum and setting the timing to the right dimensions of the motor thank you
I went through this with my wife's Mach 1 Mustang and Flowmasters vs Magnaflow and I can tell you there was a seat feel difference. The Flowmasters had more seat feel than the Magnaflow. We think it was from the back pressure from the baffles in Flowmasters. 🤔
That feeling that you were getting. Are you sure it wasn't that drone that Flowmasters are known for? Especially in a Mustang where they placed the muffler. Depending on the year I've seen many in the middle of the exhaust pipe. Normally we would expect to see them at the end. Not in the Mustangs that I've worked on back in 2002, 2003.
This makes sence I have longtube headers on my 87 4Runner and they always come with that collector extension I figured it was just so you can bolt and unbolt the rest of your exhaust more easily it’s nice to know it actually helps scavenge the exhaust the headers alone with a 22re you can definitely feel every hp gain
That one I had is just for coupling the rest of the exhaust together 😅 You would want one that is 18" long (that seems to be the best average length) and have it the same diameter as your collector 🙂
Sculpted collector also does this. Sand blast the collector & the header of paint when brand new. Cut it to follow the heat temper on the steel when fired up on the first time. @ collector end. Makes a different sound @ full throttle. Does give a little on a Dino. Full race only.
Awesome video love it all and I learned a lot about the collective length. One thing I was told a long time ago on exhausted and can't let it go is using the word back pressure instead of resistance to flow. it's Petty I know but every time I hear it I always think of my head resistance to flow
Resistance to flow is a better term for sure. But backpressure is a wider known term unfortunately so in order to get my point across i need to use the better known term 😅
@@newguysgarage6802 so cool you replied! It is a nitpicky thing I know it is. sometimes not even worth explaining but something in my 🧠 won't unlearn it. Thanks for the reply! Great video too
Yes you're 100% right my son and I used to race a Z28 1976 circle track that made a difference that little piece of pipe have a great day thank you very much
I replaced the factory shorties on my 93 ford Lightning with long tubes .With a 16 inch collector I always had my best 60's and ETs. With out collectors I always had my best trap speeds but slightly slower ETs.
Contrary. I actually lost power running an exhaust over open headers. Fair. That being said, I run a supercharged motor. And Scavenging on a N/A motor is so much more important it can be considered second-nature at this point, to the end of Scavenging and Backpressure being used interchangeably, as in order to get scavenging, you need channeled/directed flow through a restrict or that creates fluid adhesion to create a vacuum. Additional. “Backpressure” in the 4-stroke world doesn’t mean the same thing as “Backpressure” in the 2-Stroke world, as 2-strokes need specialized exhausts that create actual restriction to create enough vacuum for scavenging to take place. Backpressure (referred to correctly), in both applications is just a way of directing and funneling flow to create a scavenging effect. I could go on all day about Camshafts and Lobe Separation/Overlap, but I’ll leave that for everyone to research into and make their own conclusions on. It’s real simple, the information is out there and it’s the sorta information that wins races when the finish line is determined by 1/10th of a second of acceleration, and it’s decades-old knowledge as well. Conclusive. The confusion comes from a mix of fundamental misunderstanding of fluid dynamics, a fundamental misunderstanding of 2-stroke motor operating principles conflated with 4-stroke motor operating principles, ego (on both sides to some degree), and the absolute fuckup that is the English Language.
Thanks for a great video.....This explanation is about the extent of my understanding. I'm told there's a lot more.....cam overlap....primary tube size....length to rpm range.... varying primary tube length to compensate for the firing order ....collector diameter.... Most of this makes my eyes cross and gives me a headache
The exhaust system is a very complex part of the entire package! And it can make even more of a difference than your intake side of things in terms of power production 😃
I designed headers for a few years for Hendricks Motorsports. Tube diameters and lengths are a complex problem and depend on cylinder heads , cam timing and desired hp and torque goals.
I didn't really understand the wording but I understood that the manifold actually works collectively with the engine to pull the exhaust out. So I knew long tubes with longer straights after them worked better than short tubes or street long tubes with no extension. Couldn't explain it well to my friends so this video is going to them for the science!
The tube length is a frequency thing. The length can determine if you get a 2nd order harmonic, 3rd order, etc... (imagine stretching out a slinky between your hands, then twitching one side. You'll see a tight spot go back and forth until it runs out of energy and fizzles out. Same thing) The reason you need is collector extension, is because the collector can't do it's job, if an inch or so later, it dumps to atmospheric pressure. When that happens you no longer have a low pressure area at the other 3 tubes. When you have around 18" after the collector, that gives you about a foot of area to have a 'stretched spring' of air in there. And that 'stretched spring' is there pulling on the primary tubes.
Tomorrow my Cutlass is finally going to the shop to get longtube headers installed, thanks for all the help and for checking out my video to see if they’d fit. You are awesome! ✌️
Next you should teach everyone how to get the optimal collector pipe length for power & torque. When I was in high school I read the hand written notes on how to do the procedure from Grumpy Jenkins. All engines are different and have different lengths.New sub. I’m old school and been a mechanic for 40 years and work on big trucks for a living.
The only true way is just trial and error lol Start long and chop a little off until you run your best ET The old paint trick dosnt work...so that is basically the best way of doing it is just by going out there and making runs 😅
I owned an exhaust shop in Tn. For 17 years. You are exactly right. I use to tell people to run atleast a 12 inch extension off the collector. On our drag car we also scavenged off the valve cover to the backside of the collector.
Velocity management, simplified. This reminds me... need to make some bolt on collector extensions. Can't weld them on the headers or I will be stuck needing a lift to drop them to do other simple maintenance.
Well described and beneficial for noobs but I have to partially disagree. You have two sonic waves occurring, one at the end of the long pipe where the wave bounces back to the valve, and then returns, and a second sonic wave bouncing back form the rear of the collectors next opening. That's why the collector (or expansion chamber) also benefits from being tuned length to the pipe diameter/volume, speed of sound and the required Nominal RPM. Obviously the length (tuned RPM) of stock long pipes cant be changed so you need to match the collector either to a short dump (Large longer pipe), or a long tuned exhaust at the end of the next stage usually at a muffler using the short adapter (in this case the second sound wave bounces off the tuned location of a muffler. The pipe size is also important as you need to time how much exhaust gas can be drawn through the pipe before the next sonic wave and vacuum cycle.. A full tuned exhaust will have multiple sound renascence points. A muffler will also act as an expansion chamber or resonance point. It's all about the sound length and total volume of each stage which is matched to the desired RPM. You can have 1 x resonance length, 2 x resonance length and so on. Long resonance length usually smaller diameter pipe, larger diameter pipe = shorter resonance length, but its all a balancing act. > It's complex stuff to work out but Phil Irvin(Engineer) describes all the formulas quite well. I think it was in "Tuning for speed".
