Tech Data by Dezod Motorsports|| Topic: Collectors
09-30-2006, 03:55 PM
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Tech Data by Dezod Motorsports|| Topic: Collectors
Well, in light of some of the posts and discussion I have had with various forums recently, I beleive it's time to spread some info and give back some of the highly discussed items such as the collector of the header.
There are thousands of great articles out there regarding this subject and many others...Feel free to post up anything else you want us to cover.
Picture of a GREAT pyramid merge collector:
Picture of a not-so-great collector:
Originally Posted by burns stainless
Before we delve into the dark art of exhaust theory, let's take a quick journey through the exhaust system from the perspective of the exhaust gases.
As the piston approaches top dead center, the spark plug fires igniting a fireball just as the piston rocks over into the power stroke. The piston transfers the energy of the expanding gases to the crankshaft as the exhaust valve starts to open in the last part of the power stroke. The gas pressure is still high (70 to 90 p.s.i.) causing a rapid escape of the gases (blowdown). A pressure wave is generated as the valve continues to open. Gases can flow at an average speed of over 350 ft/sec, but the pressure wave travels at the speed of sound (and is dependent on gas temperature). Expanding exhaust gases rush into the port and down the primary header pipe. At the end of the pipe, the gases and waves converge at the collector. In the collector, the gases expand quickly as the waves propagate into all of the available orifices including the other primary tubes. The gases and some of thewave energy flow into the collector outlet and out the tail pipe.
Based on the above visualization, two basic phenomenon are at work in the exhaust system: gas particle movement and pressure wave activity. The absolute pressure differential between the cylinder and the atmosphere determines gas particle speed. As the gases travel down the pipe and expand, the speed decreases. The pressure waves, on the other hand, base their speed on the speed of sound. While the wave speed also decreases as they travel down the pipe due to gas cooling, the speed will increase again as the wave is reflected back up the pipe towards the cylinder. At all times, the speed of the wave action is much greater than the speed of the gas particles. Waves behave much differently than gas particles when a junction is encountered in the pipe. When two or more pipes come together, as in a collector for example, the waves travel into all of the available pipes - backwards as well as forwards. Waves are also reflected back up the original pipe, but with a negative pressure. The strength of the wave reflection is based on the area change compared to the area of the originating pipe.
This reflecting, negative pulse energy is the basis of wave action tuning. The basic idea is to time the negative wave pulse reflection to coincide with the period of overlap - this low pressure helps to pull in a fresh intake charge as the intake valve is opening and helps to remove the residual exhaust gases before the exhaust valve closes. Typically this phenomenon is controlled by the length of the primary header pipe. Due to the 'critical timing' aspect of this tuning technique, there may be parts of the power curve where more harm than good is done.
Gas speed is a double edged sword as well, too much gas speed indicates that that the system may be too restrictive hurting top end power, while too little gas speed tends to make the power curve excessively 'peaky' hurting low end torque. Larger diameter tubes allow the gases to expand; this cools the gases, slowing down both the gases and the waves.
Exhaust system design is a balancing act between all of these complex events and their timing. Even with the best compromise of exhaust pipe diameter and length, the collector outlet sizing can make or break the best design. The bottom line on any exhaust system design is to create the best, most useful power curve. All theory aside, the final judgement is how the engine likes the exhaust tuning on the dyno and on the track.
Various exhaust designs have evolved over the years from theory, but the majority are still being built from 'cut & try' experimenting. Only lately have computer programs like X-design or high end engine simulation programs been able to help in this process. Practical tools like adjustable length primary pipes and our B-TEC and DynoSYS adjustable collectors allow quicker design changes on the dyno or in the car. When considering a header design, the following points need to be considered:
*
1) Header primary pipe diameter (also whether constant size or stepped pipes).
*
2) Primary pipe overall length.
*
3) Collector package including the number of pipes per collector and the outlet sizing.
*
4) Megaphone/tailpipe package.
There are many ideas about header pipe sizing. Usually the primary pipe sizing is related to exhaust valve and port size. Header pipe length is dependent on wave tuning (or lack of it). Typically, longer pipes tune for lower r.p.m. power and the shorter pipes favor high r.p.m. power. The collector package is dependent on the number of cylinders, the engine configuration (V-8, inline 6, etc.), firing order and the basic design objectives (interference or independence). The collector outlet size is determined by primary pipe size and exhaust cam timing.
As the piston approaches top dead center, the spark plug fires igniting a fireball just as the piston rocks over into the power stroke. The piston transfers the energy of the expanding gases to the crankshaft as the exhaust valve starts to open in the last part of the power stroke. The gas pressure is still high (70 to 90 p.s.i.) causing a rapid escape of the gases (blowdown). A pressure wave is generated as the valve continues to open. Gases can flow at an average speed of over 350 ft/sec, but the pressure wave travels at the speed of sound (and is dependent on gas temperature). Expanding exhaust gases rush into the port and down the primary header pipe. At the end of the pipe, the gases and waves converge at the collector. In the collector, the gases expand quickly as the waves propagate into all of the available orifices including the other primary tubes. The gases and some of thewave energy flow into the collector outlet and out the tail pipe.
Based on the above visualization, two basic phenomenon are at work in the exhaust system: gas particle movement and pressure wave activity. The absolute pressure differential between the cylinder and the atmosphere determines gas particle speed. As the gases travel down the pipe and expand, the speed decreases. The pressure waves, on the other hand, base their speed on the speed of sound. While the wave speed also decreases as they travel down the pipe due to gas cooling, the speed will increase again as the wave is reflected back up the pipe towards the cylinder. At all times, the speed of the wave action is much greater than the speed of the gas particles. Waves behave much differently than gas particles when a junction is encountered in the pipe. When two or more pipes come together, as in a collector for example, the waves travel into all of the available pipes - backwards as well as forwards. Waves are also reflected back up the original pipe, but with a negative pressure. The strength of the wave reflection is based on the area change compared to the area of the originating pipe.
This reflecting, negative pulse energy is the basis of wave action tuning. The basic idea is to time the negative wave pulse reflection to coincide with the period of overlap - this low pressure helps to pull in a fresh intake charge as the intake valve is opening and helps to remove the residual exhaust gases before the exhaust valve closes. Typically this phenomenon is controlled by the length of the primary header pipe. Due to the 'critical timing' aspect of this tuning technique, there may be parts of the power curve where more harm than good is done.
Gas speed is a double edged sword as well, too much gas speed indicates that that the system may be too restrictive hurting top end power, while too little gas speed tends to make the power curve excessively 'peaky' hurting low end torque. Larger diameter tubes allow the gases to expand; this cools the gases, slowing down both the gases and the waves.
Exhaust system design is a balancing act between all of these complex events and their timing. Even with the best compromise of exhaust pipe diameter and length, the collector outlet sizing can make or break the best design. The bottom line on any exhaust system design is to create the best, most useful power curve. All theory aside, the final judgement is how the engine likes the exhaust tuning on the dyno and on the track.
Various exhaust designs have evolved over the years from theory, but the majority are still being built from 'cut & try' experimenting. Only lately have computer programs like X-design or high end engine simulation programs been able to help in this process. Practical tools like adjustable length primary pipes and our B-TEC and DynoSYS adjustable collectors allow quicker design changes on the dyno or in the car. When considering a header design, the following points need to be considered:
*
1) Header primary pipe diameter (also whether constant size or stepped pipes).
*
2) Primary pipe overall length.
*
3) Collector package including the number of pipes per collector and the outlet sizing.
*
4) Megaphone/tailpipe package.
There are many ideas about header pipe sizing. Usually the primary pipe sizing is related to exhaust valve and port size. Header pipe length is dependent on wave tuning (or lack of it). Typically, longer pipes tune for lower r.p.m. power and the shorter pipes favor high r.p.m. power. The collector package is dependent on the number of cylinders, the engine configuration (V-8, inline 6, etc.), firing order and the basic design objectives (interference or independence). The collector outlet size is determined by primary pipe size and exhaust cam timing.
Picture of a GREAT pyramid merge collector:
Picture of a not-so-great collector:
09-30-2006, 04:05 PM
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Originally Posted by SS33
Do you guys have any pics of the 4-2-1 header you have listed on your site?
You're the first I've seen to list one for the SS
You're the first I've seen to list one for the SS
09-30-2006, 04:07 PM
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I may be waiting til then to do mine then, Closest to long tube for us so far.
Can you tell us what size collector, and if that B/pipe w/ cat will bolt
up to the typical catback?
Also which header is that in the first pic?
Can you tell us what size collector, and if that B/pipe w/ cat will bolt
up to the typical catback?
Also which header is that in the first pic?
09-30-2006, 04:08 PM
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Originally Posted by SS33
I may be waiting til then to do mine then.
Can you tell us what size collector, and if that B/pipe w/ cat will bolt
up to the typical catback?
Can you tell us what size collector, and if that B/pipe w/ cat will bolt
up to the typical catback?
The 1st, great looking one is the collector pictured above is a Burns Stainless 4-1 pyramid collector.
The 2nd, not-so-good one is the Pacesetter header.
09-30-2006, 04:12 PM
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Solid info, but you're teasing us with pics of a collector we can't even get on our cars yet, lol
Do you guys have plans on selling any Burns products? Or do you know of any upcoming LSJ headers that will feature such a nice collector?
I think the Hahn and CTI are probably the only ones that come close currently
Do you guys have plans on selling any Burns products? Or do you know of any upcoming LSJ headers that will feature such a nice collector?
I think the Hahn and CTI are probably the only ones that come close currently
09-30-2006, 04:14 PM
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Originally Posted by SS33
Solid info, but you're teasing us with pics of a collector we can't even get on our cars yet, lol
Do you guys have plans on selling any Burns products? Or do you know of any upcoming LSJ headers that will feature such a nice collector?
I think the Hahn and CTI are probably the only ones that come close currently
Do you guys have plans on selling any Burns products? Or do you know of any upcoming LSJ headers that will feature such a nice collector?
I think the Hahn and CTI are probably the only ones that come close currently
09-30-2006, 04:24 PM
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No offense man, but showing us that collector is like going into the 2.4 forums and posting pics of a turbo kit they can't have.
I agree the pacesetter header is garbage, but at least show us pics of a better product that is available, and I'd imagine it in your best interest for it to be pics of a product that you carry.
just my .02
I agree the pacesetter header is garbage, but at least show us pics of a better product that is available, and I'd imagine it in your best interest for it to be pics of a product that you carry.
just my .02
09-30-2006, 04:28 PM
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Originally Posted by SS33
No offense man, but showing us that collector is like going into the 2.4 forums and posting pics of a turbo kit they can't have.
I agree the pacesetter header is garbage, but at least show us pics of a better product that is available, and I'd imagine it in your best interest for it to be pics of a product that you carry.
just my .02
I agree the pacesetter header is garbage, but at least show us pics of a better product that is available, and I'd imagine it in your best interest for it to be pics of a product that you carry.
just my .02
09-30-2006, 04:29 PM
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So do large steps in diameter.
Like going from a 2.25 header to a 2.5 or larger DP
And I agree about this being an educational discussion.
I didn't mean any offense, just pointing out that I felt teased with pics of that sexy collector
my bad
Like going from a 2.25 header to a 2.5 or larger DP
And I agree about this being an educational discussion.
I didn't mean any offense, just pointing out that I felt teased with pics of that sexy collector
my bad
09-30-2006, 04:46 PM
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Originally Posted by SS33
So do large steps in diameter.
Like going from a 2.25 header to a 2.5 or larger DP
And I agree about this being an educational discussion.
I didn't mean any offense, just pointing out that I felt teased with pics of that sexy collector
my bad
Like going from a 2.25 header to a 2.5 or larger DP
And I agree about this being an educational discussion.
I didn't mean any offense, just pointing out that I felt teased with pics of that sexy collector
my bad
Any sharp change is gonna make a difference. The smoother the surface, the smoother the air/gas will travel. Think of it this way, is it easier to ride your bike up and down a set of stairs or a ramp of same size and angle?
10-01-2006, 10:09 AM
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Originally Posted by SS33
No offense man, but showing us that collector is like going into the 2.4 forums and posting pics of a turbo kit they can't have.
http://www.burnsstainless.com/MergeC...ollectors.html
10-01-2006, 04:49 PM
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Originally Posted by SilverSS/SC
But you can have it , you would just need to weld the new collector on the existing header
http://www.burnsstainless.com/MergeC...ollectors.html
http://www.burnsstainless.com/MergeC...ollectors.html
10-02-2006, 09:26 AM
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Originally Posted by Dezod
Thanks everyone for the comments!
what? someone had to say something negative LOL. Nice readup dude! Ive heard of the burns collector but ive never seen em, looks like sex IMO
10-02-2006, 10:22 AM
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Originally Posted by Dezod
He will want to do that until he finds out the price of it, and then the labor to replace the existing one.
10-02-2006, 10:33 AM
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There's a third alternative.
Buy an inexpensive header that is a little rough, but has potential, like the CA equal length, stainless model that I bought. There are other good ones out there, but for $199 close out, I felt I couldn't go wrong. Then get out the porting tools and go to town.
Of course you have to know what you are doing - can't grind through a weld or make it too thin. But given a little time you can greatly improve the flow of an inexpensive product. I wish I had photographed my work before I bolted it up, but alas, I didn't anticipate this thread.
In a nutshell, all you have to do is get some mounted stones with 4-6" shafts in various diameters and grits and buy/make a flap wheel. Carbide augors are nice (a great time saver,) but they are primo expensive and can remove too much metal too quick, so if you don't know what you are doing, stay away.
They can't run in reverse and put the metal back. A die grinder or a porting tool with a flexible shaft works best, but a high speed drill can also be used. It's a little cumbersome, so give yourself plenty of time. Dremel tools should be avoided, as they don't have enough torque to do a good job.
I like to start at the cylinder head end and imagine I'm the exiting exhaust gasses. Make sure the openings on the header line up with the ports on the cylinder head. The most accurate way is to use prussian blue on the head to mark the header and vica-versa, but you have to have the head off to do a true port match. The next best method is to use the old manifold gasket to check for allignment, as it should have markings where it mated to the head. They did a pretty good job of alligning the ports on my header flange, so I just concentrated on flatening the center of the floor and ceiling of the rectangular header flange ports.
Next, feel with your fingers for the seams inside the primarys and check for small welding beads that penetrated through to the inside of the tubes. A header is usually made by jig-welding short sections of tubing together to create complex bends. These seams never mate perfectly, creating imperfections that should be smoothed out using stones and later a flap wheel. Make your own improvised flap wheel by cutting a 1 1/8" slit lengthwise in a 1/4" metal rod or bolt with a hacksaw or thin cut-off wheel. Insert a 1 1/2" strip of coarse grit emry cloth and about wrap it around the shaft so that it wears away as you polish.
After you're satisfied with your job, spin the header around and work on the collector. Most collectors have a ring welded in the flange end that needs to be radiused to smooth the airflow. Remember the pressure waves are reflecting around inside the collector, so don't create a flat, conical surface, make your surface bell out like a velocity stack. Do the same, as best you can, for each primary tube outlet into the collector. You won't be able to get it looking anything like the above picture of the "Great Pyramid" unless you add metal - easily accomplished by your local welder. Don't try to braze it yourself, or use any type of filler such as jb-weld or 1800 degree port filler, because even if it survived the high temperatures, the expanding and contracting of the dissimilar metals will cause it to crack, rattle and eventually fall out.
If you don't want to add metal, just do the best job you can with what you've got, being careful not to weaken the collector by removing too much metal. If you do make a mistake, take a trip to the welder and pick up where you left off. Do as little or as much as you feel comfortable with - even a little will help smooth the flow.
Have fun and good luck.
Buy an inexpensive header that is a little rough, but has potential, like the CA equal length, stainless model that I bought. There are other good ones out there, but for $199 close out, I felt I couldn't go wrong. Then get out the porting tools and go to town.
Of course you have to know what you are doing - can't grind through a weld or make it too thin. But given a little time you can greatly improve the flow of an inexpensive product. I wish I had photographed my work before I bolted it up, but alas, I didn't anticipate this thread.
In a nutshell, all you have to do is get some mounted stones with 4-6" shafts in various diameters and grits and buy/make a flap wheel. Carbide augors are nice (a great time saver,) but they are primo expensive and can remove too much metal too quick, so if you don't know what you are doing, stay away.
They can't run in reverse and put the metal back. A die grinder or a porting tool with a flexible shaft works best, but a high speed drill can also be used. It's a little cumbersome, so give yourself plenty of time. Dremel tools should be avoided, as they don't have enough torque to do a good job. I like to start at the cylinder head end and imagine I'm the exiting exhaust gasses. Make sure the openings on the header line up with the ports on the cylinder head. The most accurate way is to use prussian blue on the head to mark the header and vica-versa, but you have to have the head off to do a true port match. The next best method is to use the old manifold gasket to check for allignment, as it should have markings where it mated to the head. They did a pretty good job of alligning the ports on my header flange, so I just concentrated on flatening the center of the floor and ceiling of the rectangular header flange ports.
Next, feel with your fingers for the seams inside the primarys and check for small welding beads that penetrated through to the inside of the tubes. A header is usually made by jig-welding short sections of tubing together to create complex bends. These seams never mate perfectly, creating imperfections that should be smoothed out using stones and later a flap wheel. Make your own improvised flap wheel by cutting a 1 1/8" slit lengthwise in a 1/4" metal rod or bolt with a hacksaw or thin cut-off wheel. Insert a 1 1/2" strip of coarse grit emry cloth and about wrap it around the shaft so that it wears away as you polish.
After you're satisfied with your job, spin the header around and work on the collector. Most collectors have a ring welded in the flange end that needs to be radiused to smooth the airflow. Remember the pressure waves are reflecting around inside the collector, so don't create a flat, conical surface, make your surface bell out like a velocity stack. Do the same, as best you can, for each primary tube outlet into the collector. You won't be able to get it looking anything like the above picture of the "Great Pyramid" unless you add metal - easily accomplished by your local welder. Don't try to braze it yourself, or use any type of filler such as jb-weld or 1800 degree port filler, because even if it survived the high temperatures, the expanding and contracting of the dissimilar metals will cause it to crack, rattle and eventually fall out.
If you don't want to add metal, just do the best job you can with what you've got, being careful not to weaken the collector by removing too much metal. If you do make a mistake, take a trip to the welder and pick up where you left off. Do as little or as much as you feel comfortable with - even a little will help smooth the flow.
Have fun and good luck.
10-03-2006, 01:10 AM
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^^ Great info. I was thinking you could use a welder to add metal to create the pyramid. That's a bit more work than I would be willing to do, but good advice. Perhaps some could perform that kinda work on a stock manifold and see how well it responds. Last I heard the GMPP Extruded/Honed is only smoothed at the start of the primaries and the end of the collector.
10-03-2006, 03:37 AM
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I have not bout a header yet for this reason. Most have a cheaply costructed colector and dont look like they will make any more power then the GMP manafold. But there 1.5-2X the prices to save what 4lb in weaght and make almost the same power.
Good info though.
Later
Good info though.
Later
10-03-2006, 04:00 AM
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Its funny me and my dad are good friends of Jack Burns of burns stainless and I was thinking of having him make me a really nice merge collector and and making my own header and down pipe.