Fake dual exhaust vs. single, what is the general concensus?
#1
Full Member
Thread Starter
Fake dual exhaust vs. single, what is the general concensus?
I am seeing that a few RX7s with aftermarket exhausts just use one large pipe with one muffler, vs. the fake dual exhaust the cars had stock. Is this a typical thing to do w/ these cars? I'm guessing that the Y split in the stock exhaust probably disrupts flow and that a good single exhaust probably flows better?
#4
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Thread Starter
I am used to working on American V8 rwd stuff with two pipes all the way from the front to the back. Hence "fake" dual exhaust w/ the Y. I like the way the RX7 dual exits look but if the Y is a flow impediment and I do have to replace the exhaust anyway, I might do a single.
What size tubing should I use for an NA car single exhaust, 2.25"? I am going to build it with mandrel bends.
What size tubing should I use for an NA car single exhaust, 2.25"? I am going to build it with mandrel bends.
#5
Rotary Freak
iTrader: (16)
If you want to make you own I'd look at racing beats for design.
http://www.racingbeat.com/FRmazda2.htm
If it was my time and money...I'd buy the RB header, a flange, and gasket and fabricate the rest from some 321.
http://www.racingbeat.com/FRmazda2.htm
If it was my time and money...I'd buy the RB header, a flange, and gasket and fabricate the rest from some 321.
#6
Top Down, Boost Up
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Please, the y-pipe being an impediment to flow? It's going to be a tiny one at most, so don't worry about it. Most people go with a single exhaust system when using aftermarket parts because they're too cheap to buy 2 mufflers. Rotaries are loud as hell, so 2 mufflers are a must for any street car.
#7
No money. No love.
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Na true duals are pretty dope and sound amazing. The turbo guys usually always go single for the weight and what everyone else said...my old duals were quiet though which is why I liked them. That and it just looked right on the car. I'm single now Saved a good amount of weight and a few headaches putting the exhaust on.
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#8
Rotary Freak
iTrader: (3)
I have a single 2.25" no cats to magna flow muffler on my NA, and it sounds nice, not too loud at all. However I don't have headers on, with headers my car would be sooooo freakin' loud it would suck.
So if you are going to do a 2.25" single with headers and no cats, you gotta get a resonator in their plus muffler if you have any sort of laws against loud cars.
But yeah the single is lighter and performs better than the dual. The dual looks nicer and its quieter so less attention from cops, but thats about it.
So if you are going to do a 2.25" single with headers and no cats, you gotta get a resonator in their plus muffler if you have any sort of laws against loud cars.
But yeah the single is lighter and performs better than the dual. The dual looks nicer and its quieter so less attention from cops, but thats about it.
#9
Rotary Freak
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Please, the y-pipe being an impediment to flow? It's going to be a tiny one at most, so don't worry about it. Most people go with a single exhaust system when using aftermarket parts because they're too cheap to buy 2 mufflers. Rotaries are loud as hell, so 2 mufflers are a must for any street car.
#10
needs more track time
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If your going to think like that then I'll take it a step farther and point out that "it's a street driven normally aspirated rx-7 so why add an exhaust at all? You will have a few dollars less, a few hours less, and a 20 year old car that's annoyingly louder and a little less slow."
You have a good point with that comment. The exhaust really doesn't add much 'power' and will add sound. Mine got tiring after a few years.
#11
Get Twenty Beeeeee
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are you guys crazy? adding exhaust to a rotary ads a **** ton of horsepower! When I did the exhaust on my car it was like a night and day difference in throttle response.
The noise level was a bit annoying though (I didn't mind it, but the police did)
The noise level was a bit annoying though (I didn't mind it, but the police did)
#13
Rotary Freak
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I think the most significant increase in HP I have obtained is by replacing my exhaust starting at the exhaust manifold with 2.25" (non mandrel lol)with no cats to a magna flow muffler. My throttle response increased so dramatically it gave me an erection. I can keep up with KA 240s in the low end now which is awesome for an NA FC, and of course roast em' in the high end.
Just gutting the 2 pre cats gave me such a dramatic increase in power that it stopped me from selling the car like I had originally planned when I first got it. A year later is when I did the rest of the exhaust work.
Just gutting the 2 pre cats gave me such a dramatic increase in power that it stopped me from selling the car like I had originally planned when I first got it. A year later is when I did the rest of the exhaust work.
#15
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That stock dual catback was used by Mazda to allow them enough flow, while keeping the noise down. A single muffler would either be too loud, or not flow well enough. This is well documented (ie. Yamaguchi books).
OEMs have different concerns then enthusiasts.
OEMs have different concerns then enthusiasts.
#16
needs more track time
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The header did help a lot more than the cat back. The cat back alone on my 88 GTU didn't add a lot of power.
Everything helps a little so it depends what your goals are and what your tolerance for sound is. At first, I was quite happy with the full RB exhaust - headers back. It got old after a couple of years.
I defer to Aaron for actual numbers and accurate technicals since I've been out of the FC scene for a long time.
Everything helps a little so it depends what your goals are and what your tolerance for sound is. At first, I was quite happy with the full RB exhaust - headers back. It got old after a couple of years.
I defer to Aaron for actual numbers and accurate technicals since I've been out of the FC scene for a long time.
#17
In a Bucket
iTrader: (8)
I got the stock duals on a base model and it was pretty quiet until I blew out the manifold to what would be the 1st pre cat gasket... its straight piped... (bought it that way..)
On the flip side.. My friend has an 88 gxl with a 2.5 inch long tube header to 2.5 all the way back to a single his is hella loud!!
On the flip side.. My friend has an 88 gxl with a 2.5 inch long tube header to 2.5 all the way back to a single his is hella loud!!
#19
Rotary Freak
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^^
Racing beat sells a dual that is popular and gives you a little horse power I suppose.
Honestly a single pipe cat-back exhaust system is not loud at all.
Even a straight pipe single exhaust system is not terribly loud. Its when you combine that setup with headers does it get crazy loud.
I can post a vid of my NA if you want me too. I have stock exhaust manifold -> single 2.25" straight pipe -> magnaflow muffler. Heck you are so close to me you can just stop by my smog shop and hear it yourself.
3inch downpipe to nothing but a muffler like I have on my TII? NOW THAT IS LOUD. Got pulled over the first day I drove it to work.
Racing beat sells a dual that is popular and gives you a little horse power I suppose.
Honestly a single pipe cat-back exhaust system is not loud at all.
Even a straight pipe single exhaust system is not terribly loud. Its when you combine that setup with headers does it get crazy loud.
I can post a vid of my NA if you want me too. I have stock exhaust manifold -> single 2.25" straight pipe -> magnaflow muffler. Heck you are so close to me you can just stop by my smog shop and hear it yourself.
3inch downpipe to nothing but a muffler like I have on my TII? NOW THAT IS LOUD. Got pulled over the first day I drove it to work.
#20
Rotary Freak
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I am seeing that a few RX7s with aftermarket exhausts just use one large pipe with one muffler, vs. the fake dual exhaust the cars had stock. Is this a typical thing to do w/ these cars? I'm guessing that the Y split in the stock exhaust probably disrupts flow and that a good single exhaust probably flows better?
If you're trying to decide which one to go with, it's basically going to come down to those 4 points.
Personally, I have a stock or near-stock header (which will be replaced someday,) a straight pipe/test pipe in place of catalytics, and a Borla catback dual exhaust. I'm quite fond of my own setup; it's good at keeping the noise to a reasonable level while having a nice tone, didn't cost an absurd amount, and I think it looks nice.
I am used to working on American V8 rwd stuff with two pipes all the way from the front to the back. Hence "fake" dual exhaust w/ the Y. I like the way the RX7 dual exits look but if the Y is a flow impediment and I do have to replace the exhaust anyway, I might do a single.
What size tubing should I use for an NA car single exhaust, 2.25"? I am going to build it with mandrel bends.
What size tubing should I use for an NA car single exhaust, 2.25"? I am going to build it with mandrel bends.