View Poll Results: 1987 N/A Dual or Single Exhuast?
Dual
32
68.09%
Single
15
31.91%
Voters: 47. You may not vote on this poll
Single Or Double Exhast
06-28-02, 10:55 AM
#26
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[QUOTE]Originally posted by NEED4SPEED'88
[B]I personally think that a single exhaust system would perform much better for a few reasons.... 1) a single exhaust is much lighter [QUOTE]
True, it is lighter!
[QUOTE]2) it would flow more exhaust through by pressure [QUOTE]
Huh? Just what is this supposed to mean?
I can not vouch for scavenging effects of a somewhat smaller exhaust, nor the "benefits" of back pressure, for example, the backpressure on an NA.
If we are talking NA cars here, a somewhat smaller exhaust can be beneficial.
If we are talking Turbo cars, there is no way anyone can convince me backpressure is a benefit! When it comes to turbos, the better the exhaust flows, the more power you are going to make, period!
It would be interesting to see some dyno results of a car with a good aftermarket dual exhaust against the same car with an aftermarket single exhaust.
The weight argument is a decent one, but there are alot of other factors involved.
[B]I personally think that a single exhaust system would perform much better for a few reasons.... 1) a single exhaust is much lighter [QUOTE]
True, it is lighter!
[QUOTE]2) it would flow more exhaust through by pressure [QUOTE]
Huh? Just what is this supposed to mean?
I can not vouch for scavenging effects of a somewhat smaller exhaust, nor the "benefits" of back pressure, for example, the backpressure on an NA.
If we are talking NA cars here, a somewhat smaller exhaust can be beneficial.
If we are talking Turbo cars, there is no way anyone can convince me backpressure is a benefit! When it comes to turbos, the better the exhaust flows, the more power you are going to make, period!
It would be interesting to see some dyno results of a car with a good aftermarket dual exhaust against the same car with an aftermarket single exhaust.
The weight argument is a decent one, but there are alot of other factors involved.
06-28-02, 01:57 PM
#27
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Originally posted by TeamWireRacing
Bill H is correct in that a true dual exhaust has more area of exhaust pipe. The problem may be that the rotary may not be able to use all that area, so it probably acts as a negative more than a positive.
A trend that is showing in some of the race cars I see, and an idea that I have experimented in my mind about, is to run the dual 2" pipes from the Motorsport header, then Y them into a single 3" pipe. Sounds pretty conventional, huh? Well, the key is to create a "merge collector" prior to going to the 3" pipe. A merge collector is a necked-down piece of pipe, say down to 2.25 or 2.5", just before expanding it to the 3".
This accomplishes a couple of things. First, it acts as a venturi for the gases and will actually speed them up coming out of the header. Second, it creates a scavenging effect as the sped-up gases create a low pressure area behind the pulses to aid the next pulse coming down the tube. Third, it combines the gases from each header tube in the 3" pipe, and the gases will "heat each other up". And we all know that hot gases move more quickly than cooler gases.
I guess my concerns with a dual system would be that a) the gases are never encouraged to speed up, they just get pushed along, b) there is no scavenging effect whatsoever, and c) the additional weight from 2 mufflers instead of one, plus the extra piping to make it work.
I would like to see someone do a back-to-back set of dyno runs and post the results. It may clear up a few misconceptions and save people some money too!
Bill H is correct in that a true dual exhaust has more area of exhaust pipe. The problem may be that the rotary may not be able to use all that area, so it probably acts as a negative more than a positive.
A trend that is showing in some of the race cars I see, and an idea that I have experimented in my mind about, is to run the dual 2" pipes from the Motorsport header, then Y them into a single 3" pipe. Sounds pretty conventional, huh? Well, the key is to create a "merge collector" prior to going to the 3" pipe. A merge collector is a necked-down piece of pipe, say down to 2.25 or 2.5", just before expanding it to the 3".
This accomplishes a couple of things. First, it acts as a venturi for the gases and will actually speed them up coming out of the header. Second, it creates a scavenging effect as the sped-up gases create a low pressure area behind the pulses to aid the next pulse coming down the tube. Third, it combines the gases from each header tube in the 3" pipe, and the gases will "heat each other up". And we all know that hot gases move more quickly than cooler gases.
I guess my concerns with a dual system would be that a) the gases are never encouraged to speed up, they just get pushed along, b) there is no scavenging effect whatsoever, and c) the additional weight from 2 mufflers instead of one, plus the extra piping to make it work.
I would like to see someone do a back-to-back set of dyno runs and post the results. It may clear up a few misconceptions and save people some money too!
http://www.burnsstainless.com/2into1with_trans.jpg
06-28-02, 10:20 PM
#28
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That is exactly the piece. However, I don't think that an off-the-shelf Y pipe/merge collector will have the proper center-to-center distance to mate right up to the Mazda header. I believe it will have to be fabricated. I will probably do a version or two, test them first, then have it replicated in stainless. Too expensive to do any other way.
06-29-02, 05:54 AM
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I spoke with Vinnie @ Burns last week about this very issue. They are very will versed in BOINGER engines but were honest when it came down to Rotaries that they didn't have much experience. Still they do know their product and can do the welding and custom length merge collectors. Chris, what are your plans for testing? Some dyno runs? Has SAS already incorporated this into their exhaust design? You are already running the MAZDA sports header, correct?
06-29-02, 08:44 AM
#30
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Having seen a few of these exhausts already, I think that I can have one or two put together for testing before committing to the final stainless product. I have the Mazda header, but since the car is not completed yet, we are a bit far from any dyno testing.
I will be experimenting with the location of the Y collector relative to the header exit flange, the configuration of the collector itself (round, oval), and the length of transition to the 3" pipe, and finally, muffler length, sound, and type. That should produce some pretty interesting data to analyze, and I am looking forward to it. Thing is, gotta get the unit running first!
I do not have any specific info about the SAS project. However, I have always found Carl very up front and informative when it comes to the services he provides. While some info needs to be a secret to protect his customers, Carl is usually happy to discuss what items he thinks will yield results for your setup. Compared to SpeedSource, Carl is an open book!!!
I will be experimenting with the location of the Y collector relative to the header exit flange, the configuration of the collector itself (round, oval), and the length of transition to the 3" pipe, and finally, muffler length, sound, and type. That should produce some pretty interesting data to analyze, and I am looking forward to it. Thing is, gotta get the unit running first!
I do not have any specific info about the SAS project. However, I have always found Carl very up front and informative when it comes to the services he provides. While some info needs to be a secret to protect his customers, Carl is usually happy to discuss what items he thinks will yield results for your setup. Compared to SpeedSource, Carl is an open book!!!
07-02-02, 11:09 AM
#31
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sooo
on my 86 i also thought one pipe back
how does this sound
after cat 2.5 inch single all the way back to single muffler with 2.5 in or the racing beat muffer??
does racing beat have a dual header set up with dual pipes and presilencers to duals in the back. on my old 85 gls-se i had that set up where it was dual all teh way back to dual muffler in and out?
its a 86 with 31000 orig miles. has recaro seats, short shifter, intake, and body kit. im just wondering how much the header, taking out the cats getting presilencer and cat back single or dual would give me hp wise??
on my 86 i also thought one pipe back
how does this sound
after cat 2.5 inch single all the way back to single muffler with 2.5 in or the racing beat muffer??
does racing beat have a dual header set up with dual pipes and presilencers to duals in the back. on my old 85 gls-se i had that set up where it was dual all teh way back to dual muffler in and out?
its a 86 with 31000 orig miles. has recaro seats, short shifter, intake, and body kit. im just wondering how much the header, taking out the cats getting presilencer and cat back single or dual would give me hp wise??
07-02-02, 11:37 AM
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7 Dreams, it does make a statement for YOU. I am of the opinion that the best performance gain for COMPETIION at auto-x or Solo I is with a PROPERLY DESIGNED single. The only thing I see with MOST duals is XTRA weight.
07-02-02, 03:01 PM
#34
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Originally posted by 98 SS ON NOS
how does this sound
after cat 2.5 inch single all the way back to single muffler with 2.5 in or the racing beat muffer??
how does this sound
after cat 2.5 inch single all the way back to single muffler with 2.5 in or the racing beat muffer??
