Fenris, GaryZ etc. further header discussion
03-12-2003, 11:40 PM
#1
Fenris, GaryZ etc. further header discussion You have probably heard words like: back pressure, scavenging, tuned length, merged collector, rotational firing order, compatible combination and many others that meant something, but how they relate to a header may be a little vague.
The first misconception that needs to be cleared up is that a header relieves backpressure, but a certain amount of backpressure is needed for optimum performance. Just the opposite is true. A good header not only relieves the backpressure, but goes one step further and creates a vacuum in the system. When the next cylinder's exhaust valve opens, the vacuum in the system pulls the exhaust out of the cylinder. This is what the term "Scavenging" means. (Stainless headers with a Goilet or "spike" help here)
The first consideration is the proper tube diameter. Many people think "Bigger is Better", but this is not the case. The smallest diameter that will flow enough air to handle the engine's c.c. at your desired Red Line R.P.M. should be used. This small diameter will generate the velocity (air speed) needed to "Scavenge" at low R.P.M.s. If too small a diameter is used the engine will pull hard at low R.P.M.s but at some point in the higher R.P.M.s the tube will not be able to flow as much air as the engine is pumping out, and the engine will "sign off" early, not reaching its potential peak R.P.M. This situation would require going one size larger in tube diameter.
The second consideration is the proper tube length. The length directly controls the power band in the R.P.M. range. Longer tube lengths pull the torque down to a lower R.P.M. range. Shorter tubes move the power band up into a higher R.P.M. range. Engines that Red Line at 10,000 R.P.M. would need short tube lengths about 26" long. Engines that are torquers and Red Line at 5,500 R.P.M.s would need a tube length of 36". This is what is meant by the term "Tuned Length". The tube length is tuned to make the engine operate at a desired R.P.M. range.
The third consideration is the collector outlet diameter and extension length. This is where major differences occur between four cylinder engines and V-8 engines. The optimum situation is the four cylinder because of it's firing cycle. Every 180 degree of crankshaft rotation there is one exhaust pulse entering the collector. This is ideal timing because, as one pulse exits the collector, the next exhaust valve is opening and the vacuum created in the system pulls the exhaust from the cylinder.
In the case of V-8 firing order, the five pulses fire alternately back and forth from left to right collector, giving the ideal 180 degree firing cycle. Then it fires two in succession into the left collector, then two in succession into the right collector. If the proper collector outlet diameter is being used (two sizes larger than primaries) the two pulses in succession load up the collector with more air than it can flow. This results in a very strong midrange torque, but causes the engine to "sign off" early, not reaching its potential peek R.P.M. The improper firing order on a V-8 engine results in the need to use large diameter collectors so the engine will perform well at high R.P.M.s. Unfortunately the large diameter collectors cause a tremendous drop in air velocity, resulting in less scavenging through the entire R.P.M. range.
Often cams are used with extended valve timing to help the exhaust cycling. This results in valve timing overlap (Intake and Exhaust valves both open at T.D.C.) which causes a "Reversion"cycle in the exhaust. When this happens, exhaust actually backs up into the cylinder causing intake air to be pushed back out the intake. This reversion causes "Standoff" (fuel blowing out of the Intake) at low R.P.M.s. This whole improper cycling has resulted in a number of "Cure Alls" to help stop this reversion and standoff.
The plentum intake was created to stop the fuel "Standoff". Then came "Anti Reversionary" Cones in the exhaust tubes, and stepped tube diameter in the header, extended collector lengths and even plentums in the exhaust tubes.
In this chain of events beginning with improper firing order, a series of cures has developed, each one causing a new problem.
The optimum cure to this whole problem is to correct the exhaust firing cycle. The two cylinders that fire in succession into each collector have to be separated. This can be done partially by a "Tri-Y" header, where the four primary tubes from each bank merge into two secondary tubes (separating the two pulses firing in succession) and finally collect into a single collector. This type of header helps, but the two pulses are still coming back together at the collector.
The second optimum cure is to cross the two center tubes from each bank, across the engine running them into the collector on the opposite side. This makes the firing cycle in each collector 180 degrees apart, the same as a four cylinder engine. Once this firing order is achieved, the small collector outlet diameter can be used and the "High Velocity Scavenging" at low R.P.M.s cures the reversion problems and eliminates the need for extreme cam duration.
This sounds so easy, you are probably asking why wasn't this done from the start?
If you have ever seen a set of 180 degree headers you would understand.
On today's cars, with space virtually nonexistent, crossing four tubes either under the oil pan or around the front or rear of the engine presents major problems. On racing applications where it is possible, there is still the problem of keeping the tube length down to a reasonable 32" long. If that's not enough challenge, then try to arrange the tubes into each collector so they fire in a "Rotational Firing" pattern. Then you have, what has been called "A Bundle of Snakes".
Arranging the tubes to fire rotationally adds to the scavenging capabilities. The exhaust gas exiting one tube, passing across the opening of the tube directly beside it, creates more suction on that tube than it would on a tube on the opposite side of the collector.
The next problem is "Turbulence" in the collector. When four round tubes are grouped together in a square pattern, so a collector can be attached, you notice a gapping hole in the center of the four tubes. The standard method in manufacturing headers is to cap this hole off with a square plate. This plate in the center of the four tubes creates dead air space, or turbulence, disrupting the high velocity in the collector. This problem is solved by using a "Merge Collector". This collector is formed from four tubes, cut at approximately an 8 degree angle on two sides. When the tubes are all fitted together they form a collector with a "Pyramid" in the center. This has eliminated the need for the square plate and has taken up some of the volume inside the collector, speeding up the air velocity.
Other methods of curing this problem are: fabricating a pyramid out of sheet metal and welding it over the hole between the tubes, or squaring the tubes on two sides so they fit together forming a "+" weld in the center eliminating the hole all together...(Heres the spike Barry and a few others have)
You can see that there are a great many factors that go into making a good header. When the header, intake system, and cam timing are all designed to operate to their maximum in the same R.P.M. range, then you have a "Compatible Combination". This combination can be tuned to deliver maximum power at any desired R.P.M. range.
Thanks to Loren Barnes for the great info.
This should answer Fenris's question as to why, perhaps, the perfect header is a difficult design to manufacture... kudos' to Fenris for knowing when something ain't perfect! Thanks for being out there to keep us laymen studying. <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />
The first misconception that needs to be cleared up is that a header relieves backpressure, but a certain amount of backpressure is needed for optimum performance. Just the opposite is true. A good header not only relieves the backpressure, but goes one step further and creates a vacuum in the system. When the next cylinder's exhaust valve opens, the vacuum in the system pulls the exhaust out of the cylinder. This is what the term "Scavenging" means. (Stainless headers with a Goilet or "spike" help here)
The first consideration is the proper tube diameter. Many people think "Bigger is Better", but this is not the case. The smallest diameter that will flow enough air to handle the engine's c.c. at your desired Red Line R.P.M. should be used. This small diameter will generate the velocity (air speed) needed to "Scavenge" at low R.P.M.s. If too small a diameter is used the engine will pull hard at low R.P.M.s but at some point in the higher R.P.M.s the tube will not be able to flow as much air as the engine is pumping out, and the engine will "sign off" early, not reaching its potential peak R.P.M. This situation would require going one size larger in tube diameter.
The second consideration is the proper tube length. The length directly controls the power band in the R.P.M. range. Longer tube lengths pull the torque down to a lower R.P.M. range. Shorter tubes move the power band up into a higher R.P.M. range. Engines that Red Line at 10,000 R.P.M. would need short tube lengths about 26" long. Engines that are torquers and Red Line at 5,500 R.P.M.s would need a tube length of 36". This is what is meant by the term "Tuned Length". The tube length is tuned to make the engine operate at a desired R.P.M. range.
The third consideration is the collector outlet diameter and extension length. This is where major differences occur between four cylinder engines and V-8 engines. The optimum situation is the four cylinder because of it's firing cycle. Every 180 degree of crankshaft rotation there is one exhaust pulse entering the collector. This is ideal timing because, as one pulse exits the collector, the next exhaust valve is opening and the vacuum created in the system pulls the exhaust from the cylinder.
In the case of V-8 firing order, the five pulses fire alternately back and forth from left to right collector, giving the ideal 180 degree firing cycle. Then it fires two in succession into the left collector, then two in succession into the right collector. If the proper collector outlet diameter is being used (two sizes larger than primaries) the two pulses in succession load up the collector with more air than it can flow. This results in a very strong midrange torque, but causes the engine to "sign off" early, not reaching its potential peek R.P.M. The improper firing order on a V-8 engine results in the need to use large diameter collectors so the engine will perform well at high R.P.M.s. Unfortunately the large diameter collectors cause a tremendous drop in air velocity, resulting in less scavenging through the entire R.P.M. range.
Often cams are used with extended valve timing to help the exhaust cycling. This results in valve timing overlap (Intake and Exhaust valves both open at T.D.C.) which causes a "Reversion"cycle in the exhaust. When this happens, exhaust actually backs up into the cylinder causing intake air to be pushed back out the intake. This reversion causes "Standoff" (fuel blowing out of the Intake) at low R.P.M.s. This whole improper cycling has resulted in a number of "Cure Alls" to help stop this reversion and standoff.
The plentum intake was created to stop the fuel "Standoff". Then came "Anti Reversionary" Cones in the exhaust tubes, and stepped tube diameter in the header, extended collector lengths and even plentums in the exhaust tubes.
In this chain of events beginning with improper firing order, a series of cures has developed, each one causing a new problem.
The optimum cure to this whole problem is to correct the exhaust firing cycle. The two cylinders that fire in succession into each collector have to be separated. This can be done partially by a "Tri-Y" header, where the four primary tubes from each bank merge into two secondary tubes (separating the two pulses firing in succession) and finally collect into a single collector. This type of header helps, but the two pulses are still coming back together at the collector.
The second optimum cure is to cross the two center tubes from each bank, across the engine running them into the collector on the opposite side. This makes the firing cycle in each collector 180 degrees apart, the same as a four cylinder engine. Once this firing order is achieved, the small collector outlet diameter can be used and the "High Velocity Scavenging" at low R.P.M.s cures the reversion problems and eliminates the need for extreme cam duration.
This sounds so easy, you are probably asking why wasn't this done from the start?
If you have ever seen a set of 180 degree headers you would understand.
On today's cars, with space virtually nonexistent, crossing four tubes either under the oil pan or around the front or rear of the engine presents major problems. On racing applications where it is possible, there is still the problem of keeping the tube length down to a reasonable 32" long. If that's not enough challenge, then try to arrange the tubes into each collector so they fire in a "Rotational Firing" pattern. Then you have, what has been called "A Bundle of Snakes".
Arranging the tubes to fire rotationally adds to the scavenging capabilities. The exhaust gas exiting one tube, passing across the opening of the tube directly beside it, creates more suction on that tube than it would on a tube on the opposite side of the collector.
The next problem is "Turbulence" in the collector. When four round tubes are grouped together in a square pattern, so a collector can be attached, you notice a gapping hole in the center of the four tubes. The standard method in manufacturing headers is to cap this hole off with a square plate. This plate in the center of the four tubes creates dead air space, or turbulence, disrupting the high velocity in the collector. This problem is solved by using a "Merge Collector". This collector is formed from four tubes, cut at approximately an 8 degree angle on two sides. When the tubes are all fitted together they form a collector with a "Pyramid" in the center. This has eliminated the need for the square plate and has taken up some of the volume inside the collector, speeding up the air velocity.
Other methods of curing this problem are: fabricating a pyramid out of sheet metal and welding it over the hole between the tubes, or squaring the tubes on two sides so they fit together forming a "+" weld in the center eliminating the hole all together...(Heres the spike Barry and a few others have)
You can see that there are a great many factors that go into making a good header. When the header, intake system, and cam timing are all designed to operate to their maximum in the same R.P.M. range, then you have a "Compatible Combination". This combination can be tuned to deliver maximum power at any desired R.P.M. range.
Thanks to Loren Barnes for the great info.
This should answer Fenris's question as to why, perhaps, the perfect header is a difficult design to manufacture... kudos' to Fenris for knowing when something ain't perfect! Thanks for being out there to keep us laymen studying. <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />
03-13-2003, 12:26 AM
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Re: Fenris, GaryZ etc. further header discussion Amazing! You can cut and paste! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
hmmm...
Do you want me to critique that article or what?
hmmm...
Do you want me to critique that article or what?
03-13-2003, 01:10 AM
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Re: Fenris, GaryZ etc. further header discussion <strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">This should answer Fenris's question as to why, perhaps, the perfect header is a difficult design to manufacture... kudos' to Fenris for knowing when something ain't perfect! Thanks for being out there to keep us laymen studying. <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I understand why the design won't be changed. It is not a difficult change to make, but the party in question will not change the design because they believe the cost in retooling the jigs is not worth it since people are willing to buy the headers as is. Guess I am going to have to dust off the ol' tig and take a shot at it <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
That entire article neglected to mention how exhaust pulses aid in scavenging by increasing the momentum of the subsequent exhaust charge, and how the length of the primaries affects these pulses. Tuning a header for a proper RPM range involves timing the pulse oscillations (which are actually traveling at near the speed of sound, much faster than the exhaust gasses!) to help bring in the next charge. This gets even more complicated when using several steps in a header design to amplify (or negate) this effect, but that is a whole 'nother mess. I am rambling now, sorry...
<small>[ March 13, 2003, 02:35 AM: Message edited by: Fenris Ulf ]</small>
That entire article neglected to mention how exhaust pulses aid in scavenging by increasing the momentum of the subsequent exhaust charge, and how the length of the primaries affects these pulses. Tuning a header for a proper RPM range involves timing the pulse oscillations (which are actually traveling at near the speed of sound, much faster than the exhaust gasses!) to help bring in the next charge. This gets even more complicated when using several steps in a header design to amplify (or negate) this effect, but that is a whole 'nother mess. I am rambling now, sorry...
<small>[ March 13, 2003, 02:35 AM: Message edited by: Fenris Ulf ]</small>
03-13-2003, 01:47 PM
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Re: Fenris, GaryZ etc. further header discussion </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">What kind of power gains do you estimate LS1's would see, if the header was re-designed? </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Excellent question, Ian. My estimate, based upon ignorant intuition, is no measurable change.
<small>[ March 13, 2003, 02:00 PM: Message edited by: Gary Z ]</small>
<small>[ March 13, 2003, 02:00 PM: Message edited by: Gary Z ]</small>
03-13-2003, 02:48 PM
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Re: Fenris, GaryZ etc. further header discussion Ok, another question. I believe I read that the driver side header was already properly setup (primaries in the proper location, for those that want a design change), and it's the passenger side header in question. Why do you guys think whoever designed these headers DID NOT design the passenger side the same way as the drivers side? They obviously knew how to design one header. Fitment issues?
No one take me as an expert, or as someone taking a side, I'm just trying to learn. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
No one take me as an expert, or as someone taking a side, I'm just trying to learn. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
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03-13-2003, 07:39 PM
#8
Re: Fenris, GaryZ etc. further header discussion Fenris...of course its a cut and paste... dont for a minute think i can write that well without spelling errors and theory inconsistancies. Just bringing info to the board and have no idea to create a "link". There is much info out there for anyone looking. Fenris... Go for it... I'll meet ya in the garage with some beer and a welder...you bring the pipe and the mandrel!
03-13-2003, 11:53 PM
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Re: Fenris, GaryZ etc. further header discussion Let me put that first post (or cut and paste) in redneck terms.
I have a shot gun pointed at your head with a 26 inch long barrel and fire it might put a 2 inch diameter hole through your skull. The long barrel will contain the explosion longer and nothing but velocity is gained. Now lets saw off 20 inches off that shot gun and put a new head on ya and fire again. Well this time I blew your head off! The explosion is not contained and therefore nothing but torque is gained <img border="0" title="" alt="[Razz]" src="gr_images/icons/tongue.gif" />
Sean
I have a shot gun pointed at your head with a 26 inch long barrel and fire it might put a 2 inch diameter hole through your skull. The long barrel will contain the explosion longer and nothing but velocity is gained. Now lets saw off 20 inches off that shot gun and put a new head on ya and fire again. Well this time I blew your head off! The explosion is not contained and therefore nothing but torque is gained <img border="0" title="" alt="[Razz]" src="gr_images/icons/tongue.gif" />
Sean
03-14-2003, 01:50 AM
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Re: Fenris, GaryZ etc. further header discussion </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Gustin:
<strong> Let me put that first post (or cut and paste) in redneck terms.
I have a shot gun pointed at your head with a 26 inch long barrel and fire it might put a 2 inch diameter hole through your skull. The long barrel will contain the explosion longer and nothing but velocity is gained. Now lets saw off 20 inches off that shot gun and put a new head on ya and fire again. Well this time I blew your head off! The explosion is not contained and therefore nothing but torque is gained <img border="0" title="" alt="[Razz]" src="gr_images/icons/tongue.gif" />
Sean </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">ROFLMAO
Hey Sean when you coming back down to Houston? Do you have the camaro back together so I can give you a good *** whoopin?
Regards
Trace
<strong> Let me put that first post (or cut and paste) in redneck terms.
I have a shot gun pointed at your head with a 26 inch long barrel and fire it might put a 2 inch diameter hole through your skull. The long barrel will contain the explosion longer and nothing but velocity is gained. Now lets saw off 20 inches off that shot gun and put a new head on ya and fire again. Well this time I blew your head off! The explosion is not contained and therefore nothing but torque is gained <img border="0" title="" alt="[Razz]" src="gr_images/icons/tongue.gif" />
Sean </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">ROFLMAO
Hey Sean when you coming back down to Houston? Do you have the camaro back together so I can give you a good *** whoopin?
Regards
Trace
03-14-2003, 02:30 AM
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Re: Fenris, GaryZ etc. further header discussion </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Gustin:
<strong> Let me put that first post (or cut and paste) in redneck terms.
I have a shot gun pointed at your head with a 26 inch long barrel and fire it might put a 2 inch diameter hole through your skull. The long barrel will contain the explosion longer and nothing but velocity is gained. Now lets saw off 20 inches off that shot gun and put a new head on ya and fire again. Well this time I blew your head off! The explosion is not contained and therefore nothing but torque is gained <img border="0" title="" alt="[Razz]" src="gr_images/icons/tongue.gif" />
Sean </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">??? <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
<strong> Let me put that first post (or cut and paste) in redneck terms.
I have a shot gun pointed at your head with a 26 inch long barrel and fire it might put a 2 inch diameter hole through your skull. The long barrel will contain the explosion longer and nothing but velocity is gained. Now lets saw off 20 inches off that shot gun and put a new head on ya and fire again. Well this time I blew your head off! The explosion is not contained and therefore nothing but torque is gained <img border="0" title="" alt="[Razz]" src="gr_images/icons/tongue.gif" />
Sean </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">??? <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
03-14-2003, 10:00 AM
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Re: Fenris, GaryZ etc. further header discussion </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Ian:
<strong> What kind of power gains do you estimate LS1's would see, if the header was re-designed? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">He is my take, THESE ARE MY OPINIONS.
I don't think that correcting one detail on any STREET header will make an enormous difference unless the problem is off by more than a small margin. I do however feel that a header that is correctly designed in all aspects will show HUGE gains in performance, tune-ability and efficiency.
One major problem that I have is that so many people (businesses) claim that their headers are equal length, but I have measured or been given the measurements by all LS1 header manufacturers and NONE of them are equal length. I was told by one of the manufactures that they did try for equal length but the chassis constraints and cost prohibited it (which I feel was truthful). Most manufactures tried to tell me that it was not important for a header to be equal length!? Why not? I would ask them if they had any experience with camshafts. When they said yes I would ask if they would run different duration on each lobe? Also if a 24 inch tube is used to scavenge at 10,000 rpm then why would we need that length on our 6500 rpm LS1?
The reason I am so hung up on length (besides owning a *****) is that I think that it is the most overlooked aspect of header design. If you have a header that has a tubes that vary by say ten inches (which most LS1 headers do) then it can never scavenge properly because the header is working in different rpm ranges, (especially if a header has a shorter tube that would need a higher rpm than the engine could actually attain). If all header lengths were correct (correct length and equal length) then the car would also be easier to tune because the all the tubes would be working together to balance the fuel and air distribution to each cylinder through the scavenging effect.
Also if your exhaust system is matched with the rest of the engines components then you could end up using a more street friendly cam and make more power in the lower rpm band and loose nothing in the upper rpm band because of the proper scavenging effect.
There is no one size fits all header.
PS I would love Mr. Kook to jump in on this subject because I think he is the most knowledgeable about exhaust systems on this site.
Later,
Bart
<strong> What kind of power gains do you estimate LS1's would see, if the header was re-designed? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">He is my take, THESE ARE MY OPINIONS.
I don't think that correcting one detail on any STREET header will make an enormous difference unless the problem is off by more than a small margin. I do however feel that a header that is correctly designed in all aspects will show HUGE gains in performance, tune-ability and efficiency.
One major problem that I have is that so many people (businesses) claim that their headers are equal length, but I have measured or been given the measurements by all LS1 header manufacturers and NONE of them are equal length. I was told by one of the manufactures that they did try for equal length but the chassis constraints and cost prohibited it (which I feel was truthful). Most manufactures tried to tell me that it was not important for a header to be equal length!? Why not? I would ask them if they had any experience with camshafts. When they said yes I would ask if they would run different duration on each lobe? Also if a 24 inch tube is used to scavenge at 10,000 rpm then why would we need that length on our 6500 rpm LS1?
The reason I am so hung up on length (besides owning a *****) is that I think that it is the most overlooked aspect of header design. If you have a header that has a tubes that vary by say ten inches (which most LS1 headers do) then it can never scavenge properly because the header is working in different rpm ranges, (especially if a header has a shorter tube that would need a higher rpm than the engine could actually attain). If all header lengths were correct (correct length and equal length) then the car would also be easier to tune because the all the tubes would be working together to balance the fuel and air distribution to each cylinder through the scavenging effect.
Also if your exhaust system is matched with the rest of the engines components then you could end up using a more street friendly cam and make more power in the lower rpm band and loose nothing in the upper rpm band because of the proper scavenging effect.
There is no one size fits all header.
PS I would love Mr. Kook to jump in on this subject because I think he is the most knowledgeable about exhaust systems on this site.
Later,
Bart
03-14-2003, 01:17 PM
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Re: Fenris, GaryZ etc. further header discussion </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Colonel:
<strong>
Gas, like any other moving object, likes to go straight. Any bend in a pipe is going to rob *some* power. This power robbed goes up proabably in a somewhat exponential fashion as the bend gets steeper. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Very true Colonel. The loss goes up not quite exponentially as separation of the flow from the wall occurs as a function of fluid velocity, tube diameter, bend angle and radius of curvature.
<strong>
Gas, like any other moving object, likes to go straight. Any bend in a pipe is going to rob *some* power. This power robbed goes up proabably in a somewhat exponential fashion as the bend gets steeper. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Very true Colonel. The loss goes up not quite exponentially as separation of the flow from the wall occurs as a function of fluid velocity, tube diameter, bend angle and radius of curvature.
03-14-2003, 01:41 PM
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Re: Fenris, GaryZ etc. further header discussion And now we see why header design is no exact science! Lot's a variables...many of which are pretty much incalculable.
When it gets right down to it, the only way to know what really works best it try many, many, many different things and let the results speak for themselves. We can sit here and theorize all day but actual real world testing is where it's at.
BTW, just to pick on you about something. <img border="0" alt="[evil]" title="" src="graemlins/gr_devil.gif" /> Try that 2 liter bottle experiment with a descent sized hole in the other end of the bottom for the air to enter as the water exits. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
When it gets right down to it, the only way to know what really works best it try many, many, many different things and let the results speak for themselves. We can sit here and theorize all day but actual real world testing is where it's at.
BTW, just to pick on you about something. <img border="0" alt="[evil]" title="" src="graemlins/gr_devil.gif" /> Try that 2 liter bottle experiment with a descent sized hole in the other end of the bottom for the air to enter as the water exits. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
03-14-2003, 02:08 PM
#15
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Re: Fenris, GaryZ etc. further header discussion Good Post guys.
There are a lot of factors in designing a good header. Then with the choices out there, deciding which one is right for your application. Equal length, shorty, mid, tuned tube, coated ect....
I have a 2000 SS Camaro M6. Most of the bolt ons. I am ordering a cam and headers. The cam I choose is Comp 218/224 562/567 114. The car is mostly street. Heads a little later down the line will be added. The choice in headers is my next problem. My first choice was SLP. But since my car is lowered that lets that out due to clearance issues. I thought about the Hooker Lt's but think I like the QTP's better.
Any recomendations?
There are a lot of factors in designing a good header. Then with the choices out there, deciding which one is right for your application. Equal length, shorty, mid, tuned tube, coated ect....
I have a 2000 SS Camaro M6. Most of the bolt ons. I am ordering a cam and headers. The cam I choose is Comp 218/224 562/567 114. The car is mostly street. Heads a little later down the line will be added. The choice in headers is my next problem. My first choice was SLP. But since my car is lowered that lets that out due to clearance issues. I thought about the Hooker Lt's but think I like the QTP's better.
Any recomendations?
03-14-2003, 08:11 PM
#16
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Re: Fenris, GaryZ etc. further header discussion My take on headers:
A good LS1 header would have
-about 1 3/4" primary diameter for 346s
-26" or longer tubes, Whisper headers are as short as I would go
-As few bends as possible (I would rule out SLP on this one)
-Smooth transition from primary to collector (FLP gets cut here, QTP and Dynatechs will shine in this category)
-Fully welded construction (leaky Dynatechs are not my cup of tea)
-Stainless Steel would be my top choice but I will take coated
-Properly phased design
-As equal length primary tubes as possible
Under these stipulations the QTPs or other Grotyohann-clones would be my top choice and the reason I run them in my car <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
A good LS1 header would have
-about 1 3/4" primary diameter for 346s
-26" or longer tubes, Whisper headers are as short as I would go
-As few bends as possible (I would rule out SLP on this one)
-Smooth transition from primary to collector (FLP gets cut here, QTP and Dynatechs will shine in this category)
-Fully welded construction (leaky Dynatechs are not my cup of tea)
-Stainless Steel would be my top choice but I will take coated
-Properly phased design
-As equal length primary tubes as possible
Under these stipulations the QTPs or other Grotyohann-clones would be my top choice and the reason I run them in my car <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
03-15-2003, 12:25 AM
#17
TECH Senior Member
Re: Fenris, GaryZ etc. further header discussion My opinion is that if you truly made it equal length your gains would be VERY small (in part due to the already discussed fact that the firing order is out of wack for any major tuning effect to take place) and only at certain RPMS....that is IF you could physically do it while keeping the tubes fairly free of any more radical bends than what the QTP design has. If, for some reason, more bends or steeper bends have to be made, then you just lost your gains and probably then some. This is why I chose the QTPs over the SLPs.
The same goes for having the tubes firing in a rotational manner. If you have to make the tubes signifigantly more mismatched in length, and especially if you have to add more bends or steeper bends, you can throw all that theory out the window.
Gas, like any other moving object, likes to go straight. Any bend in a pipe is going to rob *some* power. This power robbed goes up proabably in a somewhat exponential fashion as the bend gets steeper.
<small>[ March 14, 2003, 12:34 PM: Message edited by: Colonel ]</small>
The same goes for having the tubes firing in a rotational manner. If you have to make the tubes signifigantly more mismatched in length, and especially if you have to add more bends or steeper bends, you can throw all that theory out the window.
Gas, like any other moving object, likes to go straight. Any bend in a pipe is going to rob *some* power. This power robbed goes up proabably in a somewhat exponential fashion as the bend gets steeper.
<small>[ March 14, 2003, 12:34 PM: Message edited by: Colonel ]</small>
03-15-2003, 02:26 AM
#18
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Re: Fenris, GaryZ etc. further header discussion Fenis,
Wouldn't a stepped header be better for producing low end torque than a "straight" header? What is your take on this?
Wouldn't a stepped header be better for producing low end torque than a "straight" header? What is your take on this?
03-15-2003, 04:16 AM
#19
Re: Fenris, GaryZ etc. further header discussion The funny part of all this is that while this discussion looks in depth, we haven't yet begun in so many ways. Theres still the discussion and point to make about the differences in the energy wave (1300+fps) and spent exhaust gases (300+fps) and how they react with differing designs. The associated reversion waves, wave harmonics, amplification and cancellation. These factors can cause us to look more seriously at the desire for the equal length headers(which of course, aren't to be had in the retail market for the most part), properly sized merge collectors(to large a merge and we lose scavenging, to small a merge and we get too much back pressure), and every facet from whats after the merge to the grind of the camshaft. The complex nature of this discussion will only lead to more inaccuracies and mistakes as each variable of the discussion is added. I would venture a guess that no matter how much we study, read and learn about different exhaust theory, were venturing into rocket science. When Just buy the damn grotts, preferablly stainless ones...in fact, ceramic coated stainless ones, but not SLP's.
On that note: I would think that if I had stainless QTP's (which I do, was one of the 1st few obviously) and I wanted to coat them (which I do) I should coat the inside...others say do the outside...most say do both....but if I was only to do one of the two, which would you guys choose, and why. Fenris...Colonel???
On that note: I would think that if I had stainless QTP's (which I do, was one of the 1st few obviously) and I wanted to coat them (which I do) I should coat the inside...others say do the outside...most say do both....but if I was only to do one of the two, which would you guys choose, and why. Fenris...Colonel???
03-15-2003, 05:06 AM
#20
TECH Addict
Re: Fenris, GaryZ etc. further header discussion Any reason that we leave the TTS headers out of the fray? They have most of the features you describe for a good header and the shorter collector makes for a more manageable Y pipe system if you need (or want) to use cats.