The Myth: Resonance Tuning vs. BackPressure
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I was hoping to see some discussion on X-Pipe TYPES.
The basic two being the ones that are siamesed, but fairly parallel, and the ones that are crossed like the intersection of two roads.
I would assume that the "siamesed" X-Pipe works better, but I honestly don't know.
Does anyone have any thoughts on that subject?
The basic two being the ones that are siamesed, but fairly parallel, and the ones that are crossed like the intersection of two roads.
I would assume that the "siamesed" X-Pipe works better, but I honestly don't know.
Does anyone have any thoughts on that subject?
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Joined: Sep 2002
Posts: 655
I don't know too much about the dynamics of X-pipe design, but
using some information picked up from the book, I would think
an x-pipe which maintains the least amount of angle from entrance
to exit will flow best.
I wonder what the effect of having two pipes come together side
by side (parallel fashion) with a hole cut on each pipe sealed from
the outside world do for scavenging?
The fact that the pipes remain straighter and still have a channel
to equalize pressure must have some benefit. When compared
to an H-pipe design with a 90 degree angle between secondary
pipe and equalizer pipe, the result must be somewhere between
X and H design, if not more toward X?
Another wild stab makes me believe reducing pressure in the
mufflers and running a dual pipe without the X-pipe would yield
better results.
Now, onto my question (and the reason for digging up this dinosaur)
about the book and the term, "drumming".
In chapter 7, page 143, he uses the term "drumming". I don't recall reading
this term earlier in the text and I'm not sure what he means.
Is DRUMMING the fabrication of the muffler? In other words to
make a drum type device to act as the muffler.
Or...
Is DRUMMING an aspect of exhaust flow which improves/degrades
performance?
I'm thinking the first is true - just want to make sure.
Thanks!
using some information picked up from the book, I would think
an x-pipe which maintains the least amount of angle from entrance
to exit will flow best.
I wonder what the effect of having two pipes come together side
by side (parallel fashion) with a hole cut on each pipe sealed from
the outside world do for scavenging?
The fact that the pipes remain straighter and still have a channel
to equalize pressure must have some benefit. When compared
to an H-pipe design with a 90 degree angle between secondary
pipe and equalizer pipe, the result must be somewhere between
X and H design, if not more toward X?
Another wild stab makes me believe reducing pressure in the
mufflers and running a dual pipe without the X-pipe would yield
better results.
Now, onto my question (and the reason for digging up this dinosaur)
about the book and the term, "drumming".
In chapter 7, page 143, he uses the term "drumming". I don't recall reading
this term earlier in the text and I'm not sure what he means.
Is DRUMMING the fabrication of the muffler? In other words to
make a drum type device to act as the muffler.
Or...
Is DRUMMING an aspect of exhaust flow which improves/degrades
performance?
I'm thinking the first is true - just want to make sure.
Thanks!
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Joined: Nov 2001
Posts: 2,985
From: In a house by the bay
Tino, I can't (and I'm sure others) follow what you're saying.... much of it seems to be contradiction. So please clarify a few points.
Side by side, "parallel" but they come "together"?
Are you saying that the two pipes are in contact with each other? Then there is a hole cut into each pipe so gasses can exchange between the two??
Neat idea, basically like an "H" pipe without the pipe. Maybe creates a stronger pressure pulse? Or maybe I'm just misunderstanding your example.
No crossovers at all, just reduce restriction at the muffler(s)?
I have this book somewhere... but it's been probably 15 years since I read it. Don't remember the term but if you include it in the context it might be easier for someone familiar with the "lingo" to comprehend.
-Mindgame
Originally posted by Zero_to_69
I wonder what the effect of having two pipes come together side
by side (parallel fashion) with a hole cut on each pipe sealed from
the outside world do for scavenging?
The fact that the pipes remain straighter and still have a channel
to equalize pressure must have some benefit. When compared
to an H-pipe design with a 90 degree angle between secondary
pipe and equalizer pipe, the result must be somewhere between
X and H design, if not more toward X?
I wonder what the effect of having two pipes come together side
by side (parallel fashion) with a hole cut on each pipe sealed from
the outside world do for scavenging?
The fact that the pipes remain straighter and still have a channel
to equalize pressure must have some benefit. When compared
to an H-pipe design with a 90 degree angle between secondary
pipe and equalizer pipe, the result must be somewhere between
X and H design, if not more toward X?
Are you saying that the two pipes are in contact with each other? Then there is a hole cut into each pipe so gasses can exchange between the two??
Neat idea, basically like an "H" pipe without the pipe. Maybe creates a stronger pressure pulse? Or maybe I'm just misunderstanding your example.
Another wild stab makes me believe reducing pressure in the
mufflers and running a dual pipe without the X-pipe would yield
better results.
mufflers and running a dual pipe without the X-pipe would yield
better results.
Now, onto my question (and the reason for digging up this dinosaur)
about the book and the term, "drumming".
In chapter 7, page 143, he uses the term "drumming". I don't recall reading
this term earlier in the text and I'm not sure what he means.
Is DRUMMING the fabrication of the muffler? In other words to
make a drum type device to act as the muffler.
Or...
Is DRUMMING an aspect of exhaust flow which improves/degrades
performance?
I'm thinking the first is true - just want to make sure.
Thanks!
about the book and the term, "drumming".
In chapter 7, page 143, he uses the term "drumming". I don't recall reading
this term earlier in the text and I'm not sure what he means.
Is DRUMMING the fabrication of the muffler? In other words to
make a drum type device to act as the muffler.
Or...
Is DRUMMING an aspect of exhaust flow which improves/degrades
performance?
I'm thinking the first is true - just want to make sure.
Thanks!
-Mindgame
Thread Starter
Registered User
Joined: Sep 2002
Posts: 655
>>Are you saying that the two pipes are in contact with each >>other? Then there is a hole cut into each pipe so gasses can >>exchange between the two??
>>Neat idea, basically like an "H" pipe without the pipe. Maybe >>creates a stronger pressure pulse?
Yes, that is the design I was imagining. I'm wondering if such a
setup might produce better results than an X, or Y pipe.
>>No crossovers at all, just reduce restriction at the muffler(s)?
Correct. Reduce (or eliminate) back pressure by removing the
muffler and run two individual pipes.
I would think the X and H pipe benefit most when there is
restriction at the exit of the exhaust system.
If the exhaust gas were to flow freely (without any restriction),
would it be necessary to include a cross-over? Would there be
any further benefit of adding a cross-over if the exhaust system was designed to flow the volume of exhaust gas produced at full
throttle.
As for the text, the quote reads:
"In any case, however, it is preferable for the box to be fairly narrow, with extra length, rather than vice-versa; this is from the
practical aspect of reducing drumming, rather than any significance
in regard to the flow of gases"
As first is seems like he's referring to efficiency in design, but later
in the quote it appears that drumming might be a term used to
describe pressure waves hitting a baffle in the muffler for instance.
Thanks in advance for the clarity Mindgame.
>>Neat idea, basically like an "H" pipe without the pipe. Maybe >>creates a stronger pressure pulse?
Yes, that is the design I was imagining. I'm wondering if such a
setup might produce better results than an X, or Y pipe.
>>No crossovers at all, just reduce restriction at the muffler(s)?
Correct. Reduce (or eliminate) back pressure by removing the
muffler and run two individual pipes.
I would think the X and H pipe benefit most when there is
restriction at the exit of the exhaust system.
If the exhaust gas were to flow freely (without any restriction),
would it be necessary to include a cross-over? Would there be
any further benefit of adding a cross-over if the exhaust system was designed to flow the volume of exhaust gas produced at full
throttle.
As for the text, the quote reads:
"In any case, however, it is preferable for the box to be fairly narrow, with extra length, rather than vice-versa; this is from the
practical aspect of reducing drumming, rather than any significance
in regard to the flow of gases"
As first is seems like he's referring to efficiency in design, but later
in the quote it appears that drumming might be a term used to
describe pressure waves hitting a baffle in the muffler for instance.
Thanks in advance for the clarity Mindgame.
Last edited by Zero_to_69; Jul 1, 2004 at 10:37 AM.
Registered User
Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Originally posted by Zero_to_69
I would think the X and H pipe benefit most when there is
restriction at the exit of the exhaust system.
If the exhaust gas were to flow freely (without any restriction),
would it be necessary to include a cross-over? Would there be
any further benefit of adding a cross-over if the exhaust system was designed to flow the volume of exhaust gas produced at full
throttle.
As for the text, the quote reads:
"In any case, however, it is preferable for the box to be fairly narrow, with extra length, rather than vice-versa; this is from the
practical aspect of reducing drumming, rather than any significance
in regard to the flow of gases"
As first is seems like he's referring to efficiency in design, but later
in the quote it appears that drumming might be a term used to
describe pressure waves hitting a baffle in the muffler for instance.
Thanks in advance for the clarity Mindgame.
I would think the X and H pipe benefit most when there is
restriction at the exit of the exhaust system.
If the exhaust gas were to flow freely (without any restriction),
would it be necessary to include a cross-over? Would there be
any further benefit of adding a cross-over if the exhaust system was designed to flow the volume of exhaust gas produced at full
throttle.
As for the text, the quote reads:
"In any case, however, it is preferable for the box to be fairly narrow, with extra length, rather than vice-versa; this is from the
practical aspect of reducing drumming, rather than any significance
in regard to the flow of gases"
As first is seems like he's referring to efficiency in design, but later
in the quote it appears that drumming might be a term used to
describe pressure waves hitting a baffle in the muffler for instance.
Thanks in advance for the clarity Mindgame.
Thoughts:
I think you might be referring to Smith's Brooklands silencer or even muffler design. The drumming is because of the flat sides "oilcanning" due to pressure pulses. By making it more oval like a modern mufler or with a crease or bead rolled nto the surace you could pretty much eliminate this.
IMO, it's not anything to do with tuning, just NVH as heard/felt by the occupants.
As far as your "narrow X pipe" with almost parallel pipe, just bend them a few degrees out then back to create a bulge. Slice thru the bulges where they touch and get an oval. Weld all around. Someone already does such in production, I believe.
You will probably get the tuning or pressure results of an H but not much shared flow like you may get in an X. IMO the extra bends used in many X cross-overs can cause more restriction to flow than a simple H. So, if anything the "bulged X" might work better than an X, and if your chassis layout brings the header pipes pretty close to gether. Think C5 Vette, but not Camaro.
I'v never seen any testing that took into account the extra bends (often four 45's) often used to get an X. The old rule of thumb is every 90 degree bend has the flow restriction of about 10 feet of straight pipe.
Generally any big restriction at the end of an exhaust system is a rear-mounted muffler. Almost anything you do upstream is negated by muffler restriction. Shouldn't the first step be to minimize the larger restrictons like restrictive mufflers? Often that's enough unless you are modding the engine.
My $.02
edited for spelling, not content
Last edited by OldSStroker; Jul 1, 2004 at 09:08 PM.
Thread Starter
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Joined: Sep 2002
Posts: 655
From what you've posted SS, the "drumming" is an acoustic annoyance
created by pressure pulses bouncing off the ends of the muffler.
This is simply an aural issue, and not something that concerns
performance.
Thanks for clearing that up.
"Shouldn't the first step be to minimize the larger restrictons like restrictive mufflers? "
That's been my plan of attack. My current exhaust system consists
of long tube headers with straight through mufflers bolted directly
to the collector.
It's a dual system that side exits just before the rear tires. Overall
length of muffler and pipe after the collector is about 2.5 feet.
http://members.rogers.com/tdese739/i..._muff_copy.JPG
http://members.rogers.com/tdese739/i..._pipe_copy.JPG
When I race, I drop the exhaust after the collector, so that's
not an issue.
On the street, would inserting an H pipe before the mufflers
(at the collector) be of any significance to justify cost and effort?
I know that's a subjective question, but I'm thinking the little
restriction I have doesn't warrant the installation of an H-pipe...
Anyone with a similar setup have dyno/track data to backup my
assumption?
created by pressure pulses bouncing off the ends of the muffler.
This is simply an aural issue, and not something that concerns
performance.
Thanks for clearing that up.
"Shouldn't the first step be to minimize the larger restrictons like restrictive mufflers? "
That's been my plan of attack. My current exhaust system consists
of long tube headers with straight through mufflers bolted directly
to the collector.
It's a dual system that side exits just before the rear tires. Overall
length of muffler and pipe after the collector is about 2.5 feet.
http://members.rogers.com/tdese739/i..._muff_copy.JPG
http://members.rogers.com/tdese739/i..._pipe_copy.JPG
When I race, I drop the exhaust after the collector, so that's
not an issue.
On the street, would inserting an H pipe before the mufflers
(at the collector) be of any significance to justify cost and effort?
I know that's a subjective question, but I'm thinking the little
restriction I have doesn't warrant the installation of an H-pipe...
Anyone with a similar setup have dyno/track data to backup my
assumption?
Last edited by Zero_to_69; Jul 2, 2004 at 09:04 AM.
Registered User
Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Originally posted by Zero_to_69
... My current exhaust system consists
of long tube headers with straight through mufflers bolted directly
to the collector.
It's a dual system that side exits just before the rear tires. Overall
length of muffler and pipe after the collector is about 2.5 feet.
When I race, I drop the exhaust after the collector, so that's
not an issue.
On the street, would inserting an H pipe before the mufflers
(at the collector) be of any significance to justify cost and effort?
I know that's a subjective question, but I'm thinking the little
restriction I have doesn't warrant the installation of an H-pipe...
... My current exhaust system consists
of long tube headers with straight through mufflers bolted directly
to the collector.
It's a dual system that side exits just before the rear tires. Overall
length of muffler and pipe after the collector is about 2.5 feet.
When I race, I drop the exhaust after the collector, so that's
not an issue.
On the street, would inserting an H pipe before the mufflers
(at the collector) be of any significance to justify cost and effort?
I know that's a subjective question, but I'm thinking the little
restriction I have doesn't warrant the installation of an H-pipe...
I'll bet your system is LOUD on the street.
Perhaps the short collectors at the track isn't your best bet.
"Purple Hornies" or similar glass packs are sometimes more restrictive than a Magnaflow or Dynomax UltraFlow style muffler.
Putting the mufflers farther away from the headers helps on the street because the flow is less the farther you get away from the engine due to rapid cooling.
An H-pipe will help quiet it down a little, and probably will help street power. IMO, that, and Magnaflow/UltraFlows back a ways might just give you more power (street or strip) than you have now.
Have you run back-to-back strip runs with the mufflers connected and then dropped? What were the mph results?
I'll bet your system is LOUD on the street.
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Joined: Sep 2002
Posts: 655
My system IS LOUD on the street. I'm debating whether I should
chance my luck, or quiet the beast before I get pulled over.
I've done bench mark runs with "street trim" and managed an average
of 2 tenth better by dropping the exhaust after the collectors.
It's possible that I might gain by sticking on a tube of certain length
rather than open headers when I race. I never really knew better
until reading the book which happened in the off season.
There isn't much of an exit pipe out of the muffler. Just enough
to channel the gas out the side. Maybe 16 inches of 2 1/4" pipe.
Are you thinking I have too much exit pipe and too much diameter
after the cooling and attenuation occurs?
It's a 3" collector reduced down to 2 1/4" for the muffs and exit
pipes.
Thanks so much for the help guys!
chance my luck, or quiet the beast before I get pulled over.
I've done bench mark runs with "street trim" and managed an average
of 2 tenth better by dropping the exhaust after the collectors.
It's possible that I might gain by sticking on a tube of certain length
rather than open headers when I race. I never really knew better
until reading the book which happened in the off season.
There isn't much of an exit pipe out of the muffler. Just enough
to channel the gas out the side. Maybe 16 inches of 2 1/4" pipe.
Are you thinking I have too much exit pipe and too much diameter
after the cooling and attenuation occurs?
It's a 3" collector reduced down to 2 1/4" for the muffs and exit
pipes.
Thanks so much for the help guys!
Registered User
Joined: Aug 1998
Posts: 520
From: Perryopolis, Pa
To take this one step further.......
Would a pair of collectors connected back to back such as dual 3" into single 4" & back to dual 3" produce the best results vs. an x-pipe or h-pipe. This would create a total integration of the 2 pulses & then split them back apart.
With this being said, is there a benefit to split them back to duals instead of running a big single exhaust (aka Mufflex)? Maybe the dual mufflers would flow better than a bigger single?
Since some type of equalizing means will help.... this would also imply that it should be before any restrictions like mufflers, cats etc. (x-pipes are after the cats on the typical c5 systems.... not the best location I presume) Typical configuration (transmission interference) generally prevents an x-pipe from be closer than 2 ft. from the collectors (roughly 50-55" from the exhaust port). So, would it be better to use an h-pipe closer to the collectors.
Locating mufflers at the rear of the car would be good (as previously discussed), but unfortunately cats likely will not get hot enough to work properly too far from the engine. Would cats effectively diminish the x-pipes function maybe other than altering sound?
Anyone care to comment on these scenerios?
Take a typical LT1 Vette that uses dual exhaust.
1. Use (2) 3" pipes into an x-pipe or merge collector right behind the trans, splitting back to duals (these cars already run the duals about 3" apart). Mufflers are at the extreme rear of the car.
2. Would an h-pipe right behind the collectors provide better results?
3. Would a single 4" work better (effectively a very long x-pipe) just splitting at the rear of the car?
4. Now add cats to the equation. They have to be very close to the collectors so they function. Would the system work better with an h-pipe in front of the cats (more ideal location but less effective pressure equalization) or a merge or x-pipe behind
them... or both?
Hope to keep this discussion going as I feel too many people end up choosing exhaust by sound.
Would a pair of collectors connected back to back such as dual 3" into single 4" & back to dual 3" produce the best results vs. an x-pipe or h-pipe. This would create a total integration of the 2 pulses & then split them back apart.
With this being said, is there a benefit to split them back to duals instead of running a big single exhaust (aka Mufflex)? Maybe the dual mufflers would flow better than a bigger single?
Since some type of equalizing means will help.... this would also imply that it should be before any restrictions like mufflers, cats etc. (x-pipes are after the cats on the typical c5 systems.... not the best location I presume) Typical configuration (transmission interference) generally prevents an x-pipe from be closer than 2 ft. from the collectors (roughly 50-55" from the exhaust port). So, would it be better to use an h-pipe closer to the collectors.
Locating mufflers at the rear of the car would be good (as previously discussed), but unfortunately cats likely will not get hot enough to work properly too far from the engine. Would cats effectively diminish the x-pipes function maybe other than altering sound?
Anyone care to comment on these scenerios?
Take a typical LT1 Vette that uses dual exhaust.
1. Use (2) 3" pipes into an x-pipe or merge collector right behind the trans, splitting back to duals (these cars already run the duals about 3" apart). Mufflers are at the extreme rear of the car.
2. Would an h-pipe right behind the collectors provide better results?
3. Would a single 4" work better (effectively a very long x-pipe) just splitting at the rear of the car?
4. Now add cats to the equation. They have to be very close to the collectors so they function. Would the system work better with an h-pipe in front of the cats (more ideal location but less effective pressure equalization) or a merge or x-pipe behind
them... or both?
Hope to keep this discussion going as I feel too many people end up choosing exhaust by sound.
Registered User
Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Originally posted by Zero_to_69
My system IS LOUD on the street. I've done bench mark runs with "street trim" and managed an average
of 2 tenth better by dropping the exhaust after the collectors.
It's a 3" collector reduced down to 2 1/4" for the muffs and exit
pipes.
My system IS LOUD on the street. I've done bench mark runs with "street trim" and managed an average
of 2 tenth better by dropping the exhaust after the collectors.
It's a 3" collector reduced down to 2 1/4" for the muffs and exit
pipes.
Forget the rocket science for now and just get some free-flowing stuff on there. While you are at it, an H-pipe kit from Dynomax or Summit (SUM-642025 for 2-1/2 inch or SUM-642030 for 3 inch) wouldn't hurt. If you are going to reduce headers to 2-1/2 inch, which shoud be ok for maybe 375 RWHP, try Flowmaster 8 inch long header reducer cones (FLO-R3025). IMO forget Flowmaster mufflers.
My $.02
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Joined: Nov 2001
Posts: 2,985
From: In a house by the bay
Originally posted by Lonnie Pavtis
To take this one step further.......
Would a pair of collectors connected back to back such as dual 3" into single 4" & back to dual 3" produce the best results vs. an x-pipe or h-pipe. This would create a total integration of the 2 pulses & then split them back apart.
To take this one step further.......
Would a pair of collectors connected back to back such as dual 3" into single 4" & back to dual 3" produce the best results vs. an x-pipe or h-pipe. This would create a total integration of the 2 pulses & then split them back apart.
What about having the collectors terminate in some type of resonance chamber (like a hollow muffler) with a crossover between each side?
If the chambers were large enough, it'd be like using open headers. Everything downstream of that setup (with a high flow muffler) would basically be invisible.
The problem I see with something like that is getting a large enough volume for the resonance chambers, plus the weight. Plus... what is the ideal volume?
But it seems that it'd work nicely in theory.
You're doing that with your example but the volume of the area change is much smaller, thus the return wave will have less intensity. Just thinking out loud here and I could be off base. Anyone??
With this being said, is there a benefit to split them back to duals instead of running a big single exhaust (aka Mufflex)? Maybe the dual mufflers would flow better than a bigger single?
So a 600hp small block (with duals) would need a muffler capable of flowing 660cfm (1320/2) to render itself no restriction. Seems to me that splitting the exhaust duty to two mufflers would be a better bet.
Since some type of equalizing means will help.... this would also imply that it should be before any restrictions like mufflers, cats etc. (x-pipes are after the cats on the typical c5 systems.... not the best location I presume) Typical configuration (transmission interference) generally prevents an x-pipe from be closer than 2 ft. from the collectors (roughly 50-55" from the exhaust port). So, would it be better to use an h-pipe closer to the collectors.
This is a little off topic but have you cut apart the C5's "crossover"? The hole between the two pipes is so small you'd have a hard time getting a kidney bean through there. Sorry, didn't mean to go tangent but I remember this from playing with my C5's exhaust.
That H-pipe up-close thing warrants experimentation though. I dunno about that one.
Locating mufflers at the rear of the car would be good (as previously discussed), but unfortunately cats likely will not get hot enough to work properly too far from the engine. Would cats effectively diminish the x-pipes function maybe other than altering sound?
Good points though. Hopefully we can get some more input on this.
-Mindgame
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Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Originally posted by Mindgame
Not a bad idea. Seems that it would create two scavenging waves of different magnitudes kinda like a tri-y.
Perhaps the 2 into 1 would be the only significant reflection point. If you are putting mufflers in the system, the 2>1>2 packaging gets tough.
What about having the collectors terminate in some type of resonance chamber (like a hollow muffler) with a crossover between each side?
If the chambers were large enough, it'd be like using open headers. Everything downstream of that setup (with a high flow muffler) would basically be invisible.
The problem I see with something like that is getting a large enough volume for the resonance chambers, plus the weight. Plus... what is the ideal volume?
But it seems that it'd work nicely in theory.
You're doing that with your example but the volume of the area change is much smaller, thus the return wave will have less intensity. Just thinking out loud here and I could be off base. Anyone??
That's a good description of a "terminator box" as Vizard calls it. Using one for each side and connecting them with an H-pipe is a good idea.
One of the advantages is you can tune the header collector length to what the engine needs and still package the complete exhaust system in a vehicle. This might be the best use for a "box".
Another advantage is that the large area of the "box" radiates a lot of exhaust heat so the outlet could be smaller than the inlet with minimal flow restriction. So with 3-1/2 in. header collectors, you could use 3 in. "Box" outlets into your 3 inch mufflers. Of course the heat radiaton requires some insulation for vehicle packaging. There's still no free lunch.
I think 10-15 times the volume of a cylinder (per bank) is close for the volume. 14" x 9.5" x 4.5" boxes would be pretty close for a 355, and it's about the size of some mufflers.
A "Brookland's Silencer" of the 20's was pretty much a terminator box. FWIW they don't do much silencing.
I remember reading something about 2.2cfm per hp. That was the number derived from dyno tests on various engine combinations where hp gains due to restrictive mufflers basically leveled off. I believe that was Vizard but it could have been McFarland... I'm not sure.
So a 600hp small block (with duals) would need a muffler capable of flowing 660cfm (1320/2) to render itself no restriction. Seems to me that splitting the exhaust duty to two mufflers would be a better bet.
This is a little off topic but have you cut apart the C5's "crossover"? The hole between the two pipes is so small you'd have a hard time getting a kidney bean through there. Sorry, didn't mean to go tangent but I remember this from playing with my C5's exhaust.
I think the size of that port changed from early C5 production to later. IMO, it's not a flow thing but a tuning thing for the C5. I think my early '97 has the opening about the size of the joined area.
I guess it depends on the cat. I have never seen a cross section of one so the question for me is, "What does the flow path look like?". If it is basically the same cross section as the collector then it will just act as another length of pipe. If the area is large (a chamber) then it probably reflects a pulse. I think the balance pipe is still effective though... maybe just to a smaller magnitude?
Cats flow the air thru many hundreds of small straight, often square holes a couple mm across to expose the exhaust to a large area of the catalyst. The chamber is pretty much full of the ceramic core, so if it reflects it's probably due to a restriction. My thought is the flow sees it as just another piece of pipe.
Good points though. Hopefully we can get some more input on this.
My $.02
-Mindgame
Not a bad idea. Seems that it would create two scavenging waves of different magnitudes kinda like a tri-y.
Perhaps the 2 into 1 would be the only significant reflection point. If you are putting mufflers in the system, the 2>1>2 packaging gets tough.
What about having the collectors terminate in some type of resonance chamber (like a hollow muffler) with a crossover between each side?
If the chambers were large enough, it'd be like using open headers. Everything downstream of that setup (with a high flow muffler) would basically be invisible.
The problem I see with something like that is getting a large enough volume for the resonance chambers, plus the weight. Plus... what is the ideal volume?
But it seems that it'd work nicely in theory.
You're doing that with your example but the volume of the area change is much smaller, thus the return wave will have less intensity. Just thinking out loud here and I could be off base. Anyone??
That's a good description of a "terminator box" as Vizard calls it. Using one for each side and connecting them with an H-pipe is a good idea.
One of the advantages is you can tune the header collector length to what the engine needs and still package the complete exhaust system in a vehicle. This might be the best use for a "box".
Another advantage is that the large area of the "box" radiates a lot of exhaust heat so the outlet could be smaller than the inlet with minimal flow restriction. So with 3-1/2 in. header collectors, you could use 3 in. "Box" outlets into your 3 inch mufflers. Of course the heat radiaton requires some insulation for vehicle packaging. There's still no free lunch.
I think 10-15 times the volume of a cylinder (per bank) is close for the volume. 14" x 9.5" x 4.5" boxes would be pretty close for a 355, and it's about the size of some mufflers.
A "Brookland's Silencer" of the 20's was pretty much a terminator box. FWIW they don't do much silencing.
I remember reading something about 2.2cfm per hp. That was the number derived from dyno tests on various engine combinations where hp gains due to restrictive mufflers basically leveled off. I believe that was Vizard but it could have been McFarland... I'm not sure.
So a 600hp small block (with duals) would need a muffler capable of flowing 660cfm (1320/2) to render itself no restriction. Seems to me that splitting the exhaust duty to two mufflers would be a better bet.
This is a little off topic but have you cut apart the C5's "crossover"? The hole between the two pipes is so small you'd have a hard time getting a kidney bean through there. Sorry, didn't mean to go tangent but I remember this from playing with my C5's exhaust.
I think the size of that port changed from early C5 production to later. IMO, it's not a flow thing but a tuning thing for the C5. I think my early '97 has the opening about the size of the joined area.
I guess it depends on the cat. I have never seen a cross section of one so the question for me is, "What does the flow path look like?". If it is basically the same cross section as the collector then it will just act as another length of pipe. If the area is large (a chamber) then it probably reflects a pulse. I think the balance pipe is still effective though... maybe just to a smaller magnitude?
Cats flow the air thru many hundreds of small straight, often square holes a couple mm across to expose the exhaust to a large area of the catalyst. The chamber is pretty much full of the ceramic core, so if it reflects it's probably due to a restriction. My thought is the flow sees it as just another piece of pipe.
Good points though. Hopefully we can get some more input on this.
My $.02
-Mindgame
Registered User
Joined: Aug 1998
Posts: 520
From: Perryopolis, Pa
Mindgame..... Glad to see your perspective as well.
Figured the C5 Vette x-pipe had more of a connection between the 2 sides. Probably done more for sound instead of performance.
OldSStroker.... the "terminator box" would be similar to the "powerchamber" that MAC used on some Mustang kits.
Currently working on a customers '94 Vette. It is getting a new engine build (Procharged LT1) & thought I would throw out a few ideas as there is little made for serious HP efforts on these cars. Planning on TPIS longtubes w/ dual 3” cats w/ an h-pipe in front. After the cats, thinking about merging this into a 4” oval for about 4 feet then splitting back to twin 3” exhaust & mufflers at the rear. Any thoughts if this would be of benefit over keeping 2 separate 3" pipes?
I don’t like the single 3” version offered for the L98 cars or the twin 2.5” used by most others…. Especially for 600hp.
I'm also very interested in this technology for my own use as I currently have a set of stainless 3" duals on my Z28 with no “h” or “x” pipe and straight through mufflers at the rear bumper. The mufflers offer basically no restriction & almost no sound reduction as well. Essentially they are 10ft. header collectors. The new laws in my area require cats (to pass visual) so I have to cut up my expensive exhaust & I want to do it right the first time. Getting a 1 piece mandrel bent stainless exhaust was not easy & I don’t want to rebuild it from a bunch of small pieces.
Any thoughts would be appreciated.
Figured the C5 Vette x-pipe had more of a connection between the 2 sides. Probably done more for sound instead of performance.
OldSStroker.... the "terminator box" would be similar to the "powerchamber" that MAC used on some Mustang kits.
Currently working on a customers '94 Vette. It is getting a new engine build (Procharged LT1) & thought I would throw out a few ideas as there is little made for serious HP efforts on these cars. Planning on TPIS longtubes w/ dual 3” cats w/ an h-pipe in front. After the cats, thinking about merging this into a 4” oval for about 4 feet then splitting back to twin 3” exhaust & mufflers at the rear. Any thoughts if this would be of benefit over keeping 2 separate 3" pipes?
I don’t like the single 3” version offered for the L98 cars or the twin 2.5” used by most others…. Especially for 600hp.
I'm also very interested in this technology for my own use as I currently have a set of stainless 3" duals on my Z28 with no “h” or “x” pipe and straight through mufflers at the rear bumper. The mufflers offer basically no restriction & almost no sound reduction as well. Essentially they are 10ft. header collectors. The new laws in my area require cats (to pass visual) so I have to cut up my expensive exhaust & I want to do it right the first time. Getting a 1 piece mandrel bent stainless exhaust was not easy & I don’t want to rebuild it from a bunch of small pieces.
Any thoughts would be appreciated.
Registered User
Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Originally posted by Lonnie Pavtis
Currently working on a customers '94 Vette. It is getting a new engine build (Procharged LT1) & thought I would throw out a few ideas as there is little made for serious HP efforts on these cars. Planning on TPIS longtubes w/ dual 3” cats w/ an h-pipe in front. After the cats, thinking about merging this into a 4” oval for about 4 feet then splitting back to twin 3” exhaust & mufflers at the rear. Any thoughts if this would be of benefit over keeping 2 separate 3" pipes?
I don’t like the single 3” version offered for the L98 cars or the twin 2.5” used by most others…. Especially for 600hp.
I favor the twin 3 in pipes over the 4 inch oval. You give up some flow area with the 4 in. especially if you are ovalizing a 4 inch tube to 3 inch ends.
For 600 hp the 2 X 3 inch is needed, IMO.
I'm also very interested in this technology for my own use as I currently have a set of stainless 3" duals on my Z28 with no “h” or “x” pipe and straight through mufflers at the rear bumper. The mufflers offer basically no restriction & almost no sound reduction as well. Essentially they are 10ft. header collectors. The new laws in my area require cats (to pass visual) so I have to cut up my expensive exhaust & I want to do it right the first time. Getting a 1 piece mandrel bent stainless exhaust was not easy & I don’t want to rebuild it from a bunch of small pieces.
Any thoughts would be appreciated.
10 ft. header collectors might be costing you some power. Maybe not, but that's difficult to simulate accurately, IMO. You might consider and H-pipe someplace before the front u-joint. It doesn't have to be 3 in. and it could be flattened for clearance. The problem is you can't really test it without cutting your nice pipes
To pass visual you could cut apart some cats, remove the innerds then fit them back over your pipes without ever cutting the pipes. It might take some work, but it should work. Or...you could make them into terminator boxes.
My $.02
Currently working on a customers '94 Vette. It is getting a new engine build (Procharged LT1) & thought I would throw out a few ideas as there is little made for serious HP efforts on these cars. Planning on TPIS longtubes w/ dual 3” cats w/ an h-pipe in front. After the cats, thinking about merging this into a 4” oval for about 4 feet then splitting back to twin 3” exhaust & mufflers at the rear. Any thoughts if this would be of benefit over keeping 2 separate 3" pipes?
I don’t like the single 3” version offered for the L98 cars or the twin 2.5” used by most others…. Especially for 600hp.
I favor the twin 3 in pipes over the 4 inch oval. You give up some flow area with the 4 in. especially if you are ovalizing a 4 inch tube to 3 inch ends.
For 600 hp the 2 X 3 inch is needed, IMO.
I'm also very interested in this technology for my own use as I currently have a set of stainless 3" duals on my Z28 with no “h” or “x” pipe and straight through mufflers at the rear bumper. The mufflers offer basically no restriction & almost no sound reduction as well. Essentially they are 10ft. header collectors. The new laws in my area require cats (to pass visual) so I have to cut up my expensive exhaust & I want to do it right the first time. Getting a 1 piece mandrel bent stainless exhaust was not easy & I don’t want to rebuild it from a bunch of small pieces.
Any thoughts would be appreciated.
10 ft. header collectors might be costing you some power. Maybe not, but that's difficult to simulate accurately, IMO. You might consider and H-pipe someplace before the front u-joint. It doesn't have to be 3 in. and it could be flattened for clearance. The problem is you can't really test it without cutting your nice pipes
To pass visual you could cut apart some cats, remove the innerds then fit them back over your pipes without ever cutting the pipes. It might take some work, but it should work. Or...you could make them into terminator boxes.
My $.02
Registered User
Joined: Aug 1998
Posts: 520
From: Perryopolis, Pa
OldSStroker, thanks for the reply.
On the 'Vette, the 4" oval pipe could be substituted with a 5" oval. A 5" oval is only 3-1/4" tall for that matter so virtually no ground clearance will be sacrificed.
As for the dual 3" pipes on my Camaro being 10ft. collectors.... It's not what I consider good, but better than smaller pipes & I'm not sure bigger ones will even fit. I do not want to terminate the pipes under the car for noise considerations. I occasionally still drive it 30mi. each way to work. Building a dual purpose car can be a pain.
The car is currently in the 800hp range, but will be undergoing another transformation w/ bigger 220cc LT4 heads & more cam w/ over 20# boost. At this time, I plan to go to a 1-7/8" or 1-7/8" to 2" stepped units w/ 3-1/2" collectors. I will then go with 3-1/2" cats. I would like to use a 2-1/2" or larger h-pipe before them, but it would be much more convenient after the cats as the 3" pipes are already very close together behind the trans. Not sure of the performance sacrifice with the rear crossover as I thought the crossover would be better before the restriction of the converters. Obviously either is better than none.
The hollow slip on converters were already a consideration, but I thought I would try the legal approach just to avoid the hassles.
On the 'Vette, the 4" oval pipe could be substituted with a 5" oval. A 5" oval is only 3-1/4" tall for that matter so virtually no ground clearance will be sacrificed.
As for the dual 3" pipes on my Camaro being 10ft. collectors.... It's not what I consider good, but better than smaller pipes & I'm not sure bigger ones will even fit. I do not want to terminate the pipes under the car for noise considerations. I occasionally still drive it 30mi. each way to work. Building a dual purpose car can be a pain.
The car is currently in the 800hp range, but will be undergoing another transformation w/ bigger 220cc LT4 heads & more cam w/ over 20# boost. At this time, I plan to go to a 1-7/8" or 1-7/8" to 2" stepped units w/ 3-1/2" collectors. I will then go with 3-1/2" cats. I would like to use a 2-1/2" or larger h-pipe before them, but it would be much more convenient after the cats as the 3" pipes are already very close together behind the trans. Not sure of the performance sacrifice with the rear crossover as I thought the crossover would be better before the restriction of the converters. Obviously either is better than none.
The hollow slip on converters were already a consideration, but I thought I would try the legal approach just to avoid the hassles.
Last edited by Lonnie Pavtis; Jul 5, 2004 at 10:12 PM.