need straight answer on the true dual setup??
11-03-04, 04:45 AM
#1
need straight answer on the true dual setup??
my setup is a s5 n/a with very mild porting on primaries and secondaries, aggressive porting on aux ports. mild port work on exhaust, reworked pineapple sleeves, electronic aux port actuation, fully port matched at all seams, 9.5# flywheel, typical intake, and e6k.
because of my decision to bring my car to school, i have to tame it down for a daily driver. the goal is to have very good driveability/low end power, access top end power when i want to, reliable, and reasonably quiet. emissions are not of concern. i need to know if a true dual setup is better in terms of low AND high end power in comparison to a rb collected header and presilencer into a y to dual exit setup...? i know the subject is beaten to death but i never have deciphered a final answer. at first my plan was to get a down pipe from stock manifold to rb presilencer to rb mufflers because i didn't want to worry about noise. i would like to run a header to promote flow, but i'm thinking it would be too loud with just rb presilencer and mufflers alone. my friend has the rb true dual setup (with header) and it's as loud as i want my car, no louder....of course, he has two presilencers to help his situation out. what should i do?
because of my decision to bring my car to school, i have to tame it down for a daily driver. the goal is to have very good driveability/low end power, access top end power when i want to, reliable, and reasonably quiet. emissions are not of concern. i need to know if a true dual setup is better in terms of low AND high end power in comparison to a rb collected header and presilencer into a y to dual exit setup...? i know the subject is beaten to death but i never have deciphered a final answer. at first my plan was to get a down pipe from stock manifold to rb presilencer to rb mufflers because i didn't want to worry about noise. i would like to run a header to promote flow, but i'm thinking it would be too loud with just rb presilencer and mufflers alone. my friend has the rb true dual setup (with header) and it's as loud as i want my car, no louder....of course, he has two presilencers to help his situation out. what should i do?
11-03-04, 06:33 AM
#2
Seduced by the DARK SIDE
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Full dual - with your setup - hell yes.
It's true a collected header can give slightly more power, but it requires careful tuning.
A full dual is a lot less fussy - it just works!
A side benefit - If you have a miss, you can tell which rotor is the problem.
BUT - you will need pre-silencers to tame the loud.
Mufflers alone can't quiet an NA with a header.
Link to stereo sound recording
My NA engine was stock except for the exhaust. Your ported setup should see way more gains than I got.
This video is pulling out a short on-ramp, from inside.
link to short 2MB video
It's true a collected header can give slightly more power, but it requires careful tuning.
A full dual is a lot less fussy - it just works!
A side benefit - If you have a miss, you can tell which rotor is the problem.
BUT - you will need pre-silencers to tame the loud.
Mufflers alone can't quiet an NA with a header.
Link to stereo sound recording
My NA engine was stock except for the exhaust. Your ported setup should see way more gains than I got.
This video is pulling out a short on-ramp, from inside.
link to short 2MB video
11-03-04, 08:08 AM
#3
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You'll get no straight answers here. It never hurts to ask the question but remember you'll be getting many replies from people that have no idea what they are talking about.
SureShots setup is easy to duplicate and will definetly be an improvement over the factory setup. You can build it with the unassembled header kit from racing beat or mazdatrix and use some of the factory pieces. If your not happy with it, luckily you don't have lots of money tied up in it.
I prefer a collected system that still uses two mufflers out back. But, to get the most out of it you do need to tune the collector length and size. Generally the longer the primary header the better but with two mufflers sitting out back its hard to get it much further than in front of the rear differential.
Having said that the true dual is the easiest way to go and still have good preformance with it. Good luck.
SureShots setup is easy to duplicate and will definetly be an improvement over the factory setup. You can build it with the unassembled header kit from racing beat or mazdatrix and use some of the factory pieces. If your not happy with it, luckily you don't have lots of money tied up in it.
I prefer a collected system that still uses two mufflers out back. But, to get the most out of it you do need to tune the collector length and size. Generally the longer the primary header the better but with two mufflers sitting out back its hard to get it much further than in front of the rear differential.
Having said that the true dual is the easiest way to go and still have good preformance with it. Good luck.
11-03-04, 08:44 PM
#4
MPM- i highly agree with your first statement and appreciate your contribution. the reason i posted this question is to sort out the pros and cons between a true dual setup and a rb collected header.(i know it's not the best but better than stock.) SO what's the deal with this scavenging effect or whatever i keep hearing?
11-04-04, 02:32 AM
#5
I am going to be very long winded on this response go go get something to drink and use the restroom first.
First, understand that there are 2 types of scavenging that take place. Inertial exhaust scavenging refers to what happens in an exhaust when the one exhaust pulse itself uses it's air movement through the exhaust pipe to help pull on those of another pipe that join into it, aiding it in emptying the chamber. This type of scavenging can only take place on a collected system. People get this confused with acoustic scavenging which is a little different. This relies on a tuned frequency at a certain rpm to send a sound wave back to the exhaust port in the form of a low pressure wave at the same time the exhaust port is opening. This low pressure spot helps to pull the gasses out of the chamber. This is based on the total length of the exhaust pipe either to the end on an uncollected system or to the throat of a collector. While it does scavenge to a point, inertial scavenging more effectively helps to empty the chamber.
A true dual setup is only tuned to a certian rpm range based on it's total length. It is very important when designing these systems that both pipes are the exact same length. If not, one exhaust pipe will be tuned to a different frequency than the other. The shorter the pipes, the higher the rpm tuning. The longer the pipes, the lower the rpm tuning. A true dual setup ONLY relies on acoustic scavenging.
A collected system has some of the same rules. This time the engine is tuned based upon the length of the pipes up to the collector. Again, it is important that both pipes are equal length. If they aren't, the car will still run fine. You are just losing potential power. The farther back the collector and therefore longer the pipes, the lower the tuning frequency. The shorter the pipes and consequently closer the collector to the engine, the higher the tuning frequency. With a collected system, we now have an acoustically scavenging system, and an inertial scavenging system. We have 2 forces at work rather than 1, to help get gasses out of the engine faster.
From this simple explanation it would seem that the collected system would be the preferred choice. However, each system has it's advantages and disadvantages based on the porting of the engine as well as the desired powerband.
On this forum it is very divided as to which is better. The proponents of the dual system think that it is a better system under all situations and porting styles. The proponents of the collected systems think that theirs are the best under all porting styles. In truth, they are both wrong in this respect. One system has the advantage at certain times and the other system has advantages at other times. This is usually determined by the amount of porting.
First off just on the subject of noise, the farther back a rotary is collected, the harder it gets to effectively muffle. A true dual system is effectively a system that is collected at infinity. That is pretty far back and therefore harder to muffle than a collected system. I'm not going to get into the effect that mufflers have on the tone but they don effect it greatly. Also while mufflers have a large effect on the tone of a rotary, so does the collector or lack thereof point. The farther back a rotary is collected, the lower the tone. The farther forward, the higher the tone.
Back to which is better and when. An uncollected true dual system works good on low overlap engines. These include stock porting up to what I personally consider mild streetporting. Any streetporting templates from Racing Beat or Mazdatrix are to be considered mild. Mild streetporting within my definition are those intake ports which have only had their closing timing extended. The opening points are unchanged. The exhaust closings have not been altered but the opening may have been. This level of porting has not increase port overlap appreciably. At this level of porting, the tuning of an uncollected system that exits the rear of the car will tune the average powerband of the engine right within the center of the cars gear ratio. It will have very nice low end power and bring much improved gas mileage. The midrange will be much nicer and the top end is even improved. This type of porting does well utilizing only acoustic scavenging because there isn't alot of port overlap. Without alot of port overlap, there isn't alot of scavenging of the intake side that can take place through the exhaust. When you start to get into large streetporting which I define as porting less than a bridge but that has intake/exhaust port overlap increased, you really need to start looking at some form of collected system. I'll get into why next.
Collected systems should be considered at the large streetport level or above and are absolutely mandatory to get the most power from a bridge or peripheral port engine. The exhaust pulses of these engines have become much more significant. The increase in port overlap will cause much more of this exhaust to go back into the intake side during this overlap period. This is hotter air and it has less oxygen. That results in less room for cool, oxygen rich air and therefore is less potential power. By collecting the system, we are utilizing not only acoustics but also the inertia of the gasses traveling through the opposite pipes to help pull the other side's out. Using this method it is possible to have less exhaust pressure than intake pressure. This promotes better intake filling and less dilution. The inertial scavenging is directly proportionate to the speed of the exhaust gasses in the system. The acoustic scavenging is only proportionate to the speed of sound and may be above or below the rpm of the most effective inertial scavenging.
Both systems, while improving power also both hurt in their own ways too. You can't have gains without a loss somewhere else. This is regardless of if the system is collected or not. Remember that any pressure waves present in the system have a high and a low spot. We are trying to get our lengths so that the low pressure spots are arriving back at the exhaust ports as the open at the rpm we want them to hep us at. However the high pressure waves are also going to arrive back at the ports in their own time. These will take place at different rpms. This is why tuning only affects a certain rpm range effectively. This happens in collected systesm of any length as well as uncollected systems of any length. You can't avoid it.
Now since I covered which systems work best and why, let's also show how the wrong system can hurt you. Typically you hear people referring to a long primary or a short primary collected system. This is because there are 2 lengths (that fit under a car) where a collected system benefit the powerband really well. The larger the porting, the shorter the primary pipe length. You want a short primary system to be less than 24 inches long and a long primary sysem to be less than about 120 inches long. These numbers are highly dependent on port timing and are only an example. What happens if we collect the system halfway under the car at 50 inches? Yes the car will still make power. It will probably make it's peak power where we don't want it/can't use it effectively and the car is actually slower than a properly designed system that is longer or shorter. This all goes back to when I said there are also harmful pressure waves present in all systems. In this scenario, they would be more dominant than the good waves. A vehicle with a header may not seem all that impressive if the wrong length one is used. If someone had only experienced the wrong length collected header, they could also get a very negative oppinion on them based solely on their only experience with them.
A true dual system on a higher overlap car is something that people here still recommend but isn't the best system. It has it's place. Just not here. You absolutely need the wave of the other rotor to help pull the gasses out of the other side. If you use an uncollected system with a high overlap engine, yes it will work. Nobody is saying that it won't. But, it won't make as much power as a properly collected system. Since there is not another rotor trying to help pull it's gasses down the pipe, these gasses eventually back up in the system. You now have several high and low pulses in the pipe. All of these are constantly reflecting back to the port. More will hurt than help at this point.
Whatever system you choose will most certainly be better that the stock system so at least be encouraged there. Understand that most of the people here that claim one system is absolutely better over the other have usually only had experience with only one system or are going by what others have told them. I have had all 3 systems on my cars. The short primary system was an improvement over stock. The long primary system was better yet, especially on the low end. It pulled everywhere. The true dual system was fantasic on the low end which is contrary to what others will say here. I'm only telling you what happened on my car and that is how it was. The ultimate top end suffered compared to the others though. This however was only such a small area that the collected system had the advantage that the car was still faster with the duals. It is average and not peak power that make a car fast. Peak numbers which everyone is fond of quoting mean absolutely nothing important. All of these examples were on my bone stock '88 RX-7 using only 1 ugly wrong looking muffler. Also, as the collector got farther back, I got less and less fond of the sound. I personally hated the dual sound but that is just my opinion. Others love it.
When I streetported it, I again tried all 3 combos. Things changed a bit. The duals were tried first since I liked them best on the stock motor. It felt OK and I certainly wouldn't have complained if I hadn't have tried the other systems. Next I went to a short primary system. The first thing I noticed was that all of my low end power was gone. It wasn't even close. My top end power was fantastic though. In a drag race it was faster but in traffic it wouldn't be. These results led me to once again try a long primary system. The low end was back and the top end was there too. This system was by far the nicest for the streetport and definitely the fastest. That car is now gone but the long primary and a streetported engine are what I am currently using in my GSL-SE. Thank god this car only came with one muffler and actually looks good with only 1 muffler.
Based on this short book I have now written and on your description of yow your porting is done, I would say go with the dual exhaust. It doesn't sound like that extreme of porting to me. Be very picky about which mufflers you go with. The stock ones will sound terrible. The ricer style cans or those with inserts should be avoided. They are going to be very loud and the tone won't be very nice. Look for a larger muffler such as an oval shaped one. The type of muffler you use on your type of porting won't have much affect in power despite what people say. You could use a couple of Dynomax Super Turbo mufflers. Don't dare use them on a brideport or peripheral port though. For a streetport you won't feel a difference but they will be fairly quiet and sound good.
There are probably going to be a thousand replies to this telling me why I am wrong. That's fine. This is after all just my opinion and what I have personally found to work. Most people have no experience with every system just keep that in mind. If others disagree, that's OK. Make up your own mind but in the end remember, anything is better than stock.
First, understand that there are 2 types of scavenging that take place. Inertial exhaust scavenging refers to what happens in an exhaust when the one exhaust pulse itself uses it's air movement through the exhaust pipe to help pull on those of another pipe that join into it, aiding it in emptying the chamber. This type of scavenging can only take place on a collected system. People get this confused with acoustic scavenging which is a little different. This relies on a tuned frequency at a certain rpm to send a sound wave back to the exhaust port in the form of a low pressure wave at the same time the exhaust port is opening. This low pressure spot helps to pull the gasses out of the chamber. This is based on the total length of the exhaust pipe either to the end on an uncollected system or to the throat of a collector. While it does scavenge to a point, inertial scavenging more effectively helps to empty the chamber.
A true dual setup is only tuned to a certian rpm range based on it's total length. It is very important when designing these systems that both pipes are the exact same length. If not, one exhaust pipe will be tuned to a different frequency than the other. The shorter the pipes, the higher the rpm tuning. The longer the pipes, the lower the rpm tuning. A true dual setup ONLY relies on acoustic scavenging.
A collected system has some of the same rules. This time the engine is tuned based upon the length of the pipes up to the collector. Again, it is important that both pipes are equal length. If they aren't, the car will still run fine. You are just losing potential power. The farther back the collector and therefore longer the pipes, the lower the tuning frequency. The shorter the pipes and consequently closer the collector to the engine, the higher the tuning frequency. With a collected system, we now have an acoustically scavenging system, and an inertial scavenging system. We have 2 forces at work rather than 1, to help get gasses out of the engine faster.
From this simple explanation it would seem that the collected system would be the preferred choice. However, each system has it's advantages and disadvantages based on the porting of the engine as well as the desired powerband.
On this forum it is very divided as to which is better. The proponents of the dual system think that it is a better system under all situations and porting styles. The proponents of the collected systems think that theirs are the best under all porting styles. In truth, they are both wrong in this respect. One system has the advantage at certain times and the other system has advantages at other times. This is usually determined by the amount of porting.
First off just on the subject of noise, the farther back a rotary is collected, the harder it gets to effectively muffle. A true dual system is effectively a system that is collected at infinity. That is pretty far back and therefore harder to muffle than a collected system. I'm not going to get into the effect that mufflers have on the tone but they don effect it greatly. Also while mufflers have a large effect on the tone of a rotary, so does the collector or lack thereof point. The farther back a rotary is collected, the lower the tone. The farther forward, the higher the tone.
Back to which is better and when. An uncollected true dual system works good on low overlap engines. These include stock porting up to what I personally consider mild streetporting. Any streetporting templates from Racing Beat or Mazdatrix are to be considered mild. Mild streetporting within my definition are those intake ports which have only had their closing timing extended. The opening points are unchanged. The exhaust closings have not been altered but the opening may have been. This level of porting has not increase port overlap appreciably. At this level of porting, the tuning of an uncollected system that exits the rear of the car will tune the average powerband of the engine right within the center of the cars gear ratio. It will have very nice low end power and bring much improved gas mileage. The midrange will be much nicer and the top end is even improved. This type of porting does well utilizing only acoustic scavenging because there isn't alot of port overlap. Without alot of port overlap, there isn't alot of scavenging of the intake side that can take place through the exhaust. When you start to get into large streetporting which I define as porting less than a bridge but that has intake/exhaust port overlap increased, you really need to start looking at some form of collected system. I'll get into why next.
Collected systems should be considered at the large streetport level or above and are absolutely mandatory to get the most power from a bridge or peripheral port engine. The exhaust pulses of these engines have become much more significant. The increase in port overlap will cause much more of this exhaust to go back into the intake side during this overlap period. This is hotter air and it has less oxygen. That results in less room for cool, oxygen rich air and therefore is less potential power. By collecting the system, we are utilizing not only acoustics but also the inertia of the gasses traveling through the opposite pipes to help pull the other side's out. Using this method it is possible to have less exhaust pressure than intake pressure. This promotes better intake filling and less dilution. The inertial scavenging is directly proportionate to the speed of the exhaust gasses in the system. The acoustic scavenging is only proportionate to the speed of sound and may be above or below the rpm of the most effective inertial scavenging.
Both systems, while improving power also both hurt in their own ways too. You can't have gains without a loss somewhere else. This is regardless of if the system is collected or not. Remember that any pressure waves present in the system have a high and a low spot. We are trying to get our lengths so that the low pressure spots are arriving back at the exhaust ports as the open at the rpm we want them to hep us at. However the high pressure waves are also going to arrive back at the ports in their own time. These will take place at different rpms. This is why tuning only affects a certain rpm range effectively. This happens in collected systesm of any length as well as uncollected systems of any length. You can't avoid it.
Now since I covered which systems work best and why, let's also show how the wrong system can hurt you. Typically you hear people referring to a long primary or a short primary collected system. This is because there are 2 lengths (that fit under a car) where a collected system benefit the powerband really well. The larger the porting, the shorter the primary pipe length. You want a short primary system to be less than 24 inches long and a long primary sysem to be less than about 120 inches long. These numbers are highly dependent on port timing and are only an example. What happens if we collect the system halfway under the car at 50 inches? Yes the car will still make power. It will probably make it's peak power where we don't want it/can't use it effectively and the car is actually slower than a properly designed system that is longer or shorter. This all goes back to when I said there are also harmful pressure waves present in all systems. In this scenario, they would be more dominant than the good waves. A vehicle with a header may not seem all that impressive if the wrong length one is used. If someone had only experienced the wrong length collected header, they could also get a very negative oppinion on them based solely on their only experience with them.
A true dual system on a higher overlap car is something that people here still recommend but isn't the best system. It has it's place. Just not here. You absolutely need the wave of the other rotor to help pull the gasses out of the other side. If you use an uncollected system with a high overlap engine, yes it will work. Nobody is saying that it won't. But, it won't make as much power as a properly collected system. Since there is not another rotor trying to help pull it's gasses down the pipe, these gasses eventually back up in the system. You now have several high and low pulses in the pipe. All of these are constantly reflecting back to the port. More will hurt than help at this point.
Whatever system you choose will most certainly be better that the stock system so at least be encouraged there. Understand that most of the people here that claim one system is absolutely better over the other have usually only had experience with only one system or are going by what others have told them. I have had all 3 systems on my cars. The short primary system was an improvement over stock. The long primary system was better yet, especially on the low end. It pulled everywhere. The true dual system was fantasic on the low end which is contrary to what others will say here. I'm only telling you what happened on my car and that is how it was. The ultimate top end suffered compared to the others though. This however was only such a small area that the collected system had the advantage that the car was still faster with the duals. It is average and not peak power that make a car fast. Peak numbers which everyone is fond of quoting mean absolutely nothing important. All of these examples were on my bone stock '88 RX-7 using only 1 ugly wrong looking muffler. Also, as the collector got farther back, I got less and less fond of the sound. I personally hated the dual sound but that is just my opinion. Others love it.
When I streetported it, I again tried all 3 combos. Things changed a bit. The duals were tried first since I liked them best on the stock motor. It felt OK and I certainly wouldn't have complained if I hadn't have tried the other systems. Next I went to a short primary system. The first thing I noticed was that all of my low end power was gone. It wasn't even close. My top end power was fantastic though. In a drag race it was faster but in traffic it wouldn't be. These results led me to once again try a long primary system. The low end was back and the top end was there too. This system was by far the nicest for the streetport and definitely the fastest. That car is now gone but the long primary and a streetported engine are what I am currently using in my GSL-SE. Thank god this car only came with one muffler and actually looks good with only 1 muffler.
Based on this short book I have now written and on your description of yow your porting is done, I would say go with the dual exhaust. It doesn't sound like that extreme of porting to me. Be very picky about which mufflers you go with. The stock ones will sound terrible. The ricer style cans or those with inserts should be avoided. They are going to be very loud and the tone won't be very nice. Look for a larger muffler such as an oval shaped one. The type of muffler you use on your type of porting won't have much affect in power despite what people say. You could use a couple of Dynomax Super Turbo mufflers. Don't dare use them on a brideport or peripheral port though. For a streetport you won't feel a difference but they will be fairly quiet and sound good.
There are probably going to be a thousand replies to this telling me why I am wrong. That's fine. This is after all just my opinion and what I have personally found to work. Most people have no experience with every system just keep that in mind. If others disagree, that's OK. Make up your own mind but in the end remember, anything is better than stock.
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11-04-04, 02:50 AM
#8
...94% correct.
11-04-04, 03:45 AM
#9
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goodness gracious. i showed that to a friend and they said "i couldnt write that much about.. myself." and that was all knowledge. thank you rotarygod... so for a stock NA motor, would you say that the difference between an RB downpipe and an RB collected header is negligable?
11-04-04, 04:05 AM
#10
...94% correct.
Originally Posted by mycarisolderthanme
goodness gracious. i showed that to a friend and they said "i couldnt write that much about.. myself." and that was all knowledge. thank you rotarygod... so for a stock NA motor, would you say that the difference between an RB downpipe and an RB collected header is negligable?
But, when it comes down to it, a propperly designed system will be the best, reguardless of it's configuration. If a true dual was designed to achieve a specific goal with a specific motor, a collected system, if designed propperly, could meet the same goal with the same motor...but that gets into a whole other chapter of the story...
11-04-04, 08:45 AM
#12
Seduced by the DARK SIDE
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Post #5 - is definately the full explanation.
The short answer is - "Yes".
The low end "growl" from a full dual seems strange at first, but you get to like it quickly.
It's nice not to need as much throttle to accelerate in traffic.
The short answer is - "Yes".
The low end "growl" from a full dual seems strange at first, but you get to like it quickly.
It's nice not to need as much throttle to accelerate in traffic.
11-04-04, 09:09 AM
#13
rotarygod, That was awesome. 
I've personally driven the RB collected header with magnaflow cans(loud as **** but nice power), true duals(I love the sound personally and the power is great), Race piped stock exhaust(no cats) pretty nice low end..., And only one setup on a turbo so far which was Bonez 2.5" DP/MP to N1 duals(obviously I was impressed by boost but...) the sound quality and the rice look I hated. Hopefully in a couple of weeks I can drive the RB 3" turbo back
Santiago
oh yea I also drove race piped with cherry bomb mufflers at the end(sounds kinda like a toyota pick-up) lol
I've personally driven the RB collected header with magnaflow cans(loud as **** but nice power), true duals(I love the sound personally and the power is great), Race piped stock exhaust(no cats) pretty nice low end..., And only one setup on a turbo so far which was Bonez 2.5" DP/MP to N1 duals(obviously I was impressed by boost but...) the sound quality and the rice look I hated. Hopefully in a couple of weeks I can drive the RB 3" turbo back
Santiago
oh yea I also drove race piped with cherry bomb mufflers at the end(sounds kinda like a toyota pick-up) lol
Last edited by 1987RX7guy; 11-04-04 at 09:12 AM.
11-04-04, 05:59 PM
#14
thanks rotarygod for the in depth post. Santiago brings up another point i was sort of wondering about. i've been mostly set on buying rb products and it seems to me that a 3in OD turbo back system would be getting kinda small if you were pushing your ported engine to higher flow numbers.
11-04-04, 07:48 PM
#15
For a turbo, 3" is large enough for over 500 hp so "higher flow numbers" must be really high. The muffler design is going to have a larger effect on flow than the exhaust piping will. This assumes that you aren't just running a pathetically small exhaust pipe. Don't bother with a 3" pipe on a nonturbo unless you are getting into a bridge or peripheral port. 2.5" is fine.
11-04-04, 09:13 PM
#16
Banned. I got OWNED!!!
Let me impose my ignorance here...
You say 2.5" is good for the N/A. What sizes in different areas? Headers... y pipe (assuming you use one) ... etc.
You say 2.5" is good for the N/A. What sizes in different areas? Headers... y pipe (assuming you use one) ... etc.
11-04-04, 09:28 PM
#17
...94% correct.
the header's runners would be good for 2" ID to merge into a 2.5" straight exhaust. By the time that it gets back to the "Y" there's not really a lot that can be achieved my tubing size (as long as you don't get ridiculously small or big) so you could probably stick with 2.5" through to the mufflers. I personally use 2" or 2.25" on the "Y" to try and keep the consistancy a little closer.
11-04-04, 09:41 PM
#18
I'm building a bridgeported 12a. I have short and long headers available. If I am understanding this correctly, I should run the short style header and then collect there into a 2-1/4 or 2-1/2" system?
Any suggestions for resonators and mufflers. This will be a single system in a 1st gen. And RB is not an option. If the engine works well, it may get turboed.
Any suggestions for resonators and mufflers. This will be a single system in a 1st gen. And RB is not an option. If the engine works well, it may get turboed.
11-04-04, 09:58 PM
#19
Originally Posted by trochoid
I'm building a bridgeported 12a. I have short and long headers available. If I am understanding this correctly, I should run the short style header and then collect there into a 2-1/4 or 2-1/2" system?
Any suggestions for resonators and mufflers. This will be a single system in a 1st gen. And RB is not an option. If the engine works well, it may get turboed.
Any suggestions for resonators and mufflers. This will be a single system in a 1st gen. And RB is not an option. If the engine works well, it may get turboed.
For muffling on a bridgeport, you're going to have to keep it fairly loud to keep most of your power. Do not use any chambered mufflers. Straight through designs are about your only practical choice. I assume since you are using a bridgeport that you want to get all the power out of it that you can. If you restrict the exhaust too much with a quiet chambered style muffler, you'd probably get no more power than an average streetport. Use a nice presilencer. Racinb Beat is a little expensive but they are very nice units. You do not have to buy a complete system, just the pieces that you need. For a muffler or mufflers I personally recommend the Dynomax Ultraflow Oval series. They flow very well and are fairly cheap. The ovals while still pretty loud, are much quieter than the smaller round mufflers that most people use. They don't restrict any more though. They aren't fancy chrome and don't look all that impressive but they are just as functional as any others out there. If you want looks, you'll pay for it. FWIW: Magnaflow is the same company. Just remember that as a general rule, by the time you get enough muffling on a bridge or peripheral port engine to make it quiet enough to be a comfortable street car (this is subject to opinion), it is generally going to be so restricted that you are no faster than a mild streetport. If it is only a track car, who cares!
11-05-04, 12:35 AM
#21
Originally Posted by rotarygod
For a turbo, 3" is large enough for over 500 hp so "higher flow numbers" must be really high. The muffler design is going to have a larger effect on flow than the exhaust piping will. This assumes that you aren't just running a pathetically small exhaust pipe. Don't bother with a 3" pipe on a nonturbo unless you are getting into a bridge or peripheral port. 2.5" is fine.
i see what you are saying, what i observed was that rb offers a 3in OD downpipe and a 2.5 ID presilencer. is the differences of OD and ID a matter of 1/4 of an inch or???? so do clarify,,, you recommend 2 inch OD piping all the way back for the dual setup on an n/a correct?
11-05-04, 12:41 AM
#22
Generally it is 2" OD tubing. Racing Beat uses thick wall tubing but I have used thin wall with no issues. 2" ID might be a bit much though. The physical area of the actual exhaust ports (not the sleeves) is closer to the area of about a 1.6" port. Since the exhaust sleeves expand in area in such a short distance, it makes the pipe size look much bigger. Regardless of what type of 2" tubing you use, don't worry about restricting the flow. You won't.
11-05-04, 01:10 AM
#23
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Originally Posted by rotarygod
For a turbo, 3" is large enough for over 500 hp so "higher flow numbers" must be really high. The muffler design is going to have a larger effect on flow than the exhaust piping will. This assumes that you aren't just running a pathetically small exhaust pipe. Don't bother with a 3" pipe on a nonturbo unless you are getting into a bridge or peripheral port. 2.5" is fine.
This made me think about something. People say its fine that its 3" for up to 500horse, but just curious, does length of the pipe matter for the turbo? I mean just cause its 3" in diameter is great for flow at like 1' of pipe. But after like 10 feet of it, the exhaust gases have more surface area to flow through, thus the most resistance.
Like when you blow into a straw, if its only 2" in length, its easy, but if you hook up 3 straws its much more difficult to blow through. Im just curious as to when this is applied to cars, I mean a 3" downpipe is good, but would it get more flow if say it were 5" all the way through to the back of the car?
In no ways am I saying that this is practical, I mean fitting 5" is crazy, but im just curious thats all..
11-05-04, 01:50 AM
#24
Your way of thinking is valid but you do need to consider one thing. The farther the exhaust travels through the pipe, the cooler it gets. It loses alot of heat really fast. The cooler it gets, the denser it gets. The denser it gets, the less space in the pipe it takes up. This is why a muffler is less of a restriction at the back of a car than it is at the front. All of this is only true to a point but typically a car isn't long enough to really affect it in this manner. There would eventually come a point where you are correct though.
11-05-04, 02:30 AM
#25
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hmm, that makes perfect sense. I knew that what I said wasn't correct, or else everyone would be running 5" regardless the size/installation. Really I was asking why I was 'not' right, and you told me! thx!
heh..
heh..
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