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Old June 23rd, 2004, 04:18 PM   #1
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Dual Exhaust to Single?

I have a V6 coupe and I'm thinking about going to a single exhaust set up for that "sleeper" look. Will going to a single exhaust set up decrease performance? I'm probably gonna go with the greddy evo 2 with custom piping. What do you guys think?

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Old June 23rd, 2004, 05:39 PM   #2
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that is a great idea! but you'll have to increase the piping. i'd say about 3 inches would be good after the junction... and make sure the guy doing the exhaust makes the junction as smooth as possible.
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Old June 23rd, 2004, 06:22 PM   #3
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Our cars in all actuallity are single because the down pipe from the engine (front and rear) go into one, so its not really true dual. If you were to go to one muffler, I would opt for 2.5" piping at the most unless you plan on running turbo.

Wouldnt 3" lose a lot of backpressure so low end would be compinsated?
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Old June 23rd, 2004, 06:32 PM   #4
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Quote:
Originally posted by relentless
Wouldnt 3" lose a lot of backpressure so low end would be compinsated?
The good old backpressure myth. Modern cars with the ability to adjust fuel/air mixtures don't need backpressure to "increase torque." Reducing backpressure lets the engine breath better and put more power to the wheels instead of trying to push exhaust out the tailpipe.

Edit: forgot to add ... an exhaust pipe that is too large can reduce velocity which is bad. You want the right balance of flow and velocity with as little backpressure as possible.

Last edited by Swank; June 23rd, 2004 at 06:39 PM..
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Old June 23rd, 2004, 07:20 PM   #5
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Quote:
Originally posted by relentless
Our cars in all actuallity are single because the down pipe from the engine (front and rear) go into one, so its not really true dual. If you were to go to one muffler, I would opt for 2.5" piping at the most unless you plan on running turbo.

Wouldnt 3" lose a lot of backpressure so low end would be compinsated?
ya 3" is too big. i would get a 2.5". and its already been done. one of the member name Roy (forgot his user name) already done it. i think he got the greddy evo.
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Old June 27th, 2004, 12:07 AM   #6
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I did this, and I feel a little gain in torque but loos of high end from my former setup
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Old June 27th, 2004, 08:08 PM   #7
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What are you gonna do about the 2 exhaust cutouts in the rear bumper? Sure will look funny with 2 cutouts and only one pipe!
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Old June 27th, 2004, 10:34 PM   #8
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you can buy the cover at the dealership, like the i4 cars.
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Old June 28th, 2004, 05:17 AM   #9
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Does anyone know where I can get a universal thermal muffler. I was thinking about doing a custom single thermal muffler set up. Any help is much appreciated.
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Old June 28th, 2004, 02:48 PM   #10
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I think roy did this... Awsomnamja is his username i think
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Old June 29th, 2004, 02:25 PM   #11
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Quote:
Originally posted by Shadyguirguis on June 27th, 2004 at 02:07 AM

I did this, and I feel a little gain in torque but loos of high end from my former setup
That is expected when switching from a duel muffler (semi duel exhaust) to a single muffle setup (single exhaust). Back pressure helps with low end but will hurt top end power.

Quote:
Originally posted by Swank on June 23rd, 2004 at 08:32 PM

The good old backpressure myth. Modern cars with the ability to adjust fuel/air mixtures don't need backpressure to "increase torque." Reducing backpressure lets the engine breath better and put more power to the wheels instead of trying to push exhaust out the tailpipe.

Edit: forgot to add ... an exhaust pipe that is too large can reduce velocity which is bad. You want the right balance of flow and velocity with as little backpressure as possible.
Not true. The 5th gen Maxima used a duel stage muffler to help with backpressure. At low rpm the muffle would allow only so much exhaust pressure out. But at high rpm a valve opens up from the increased pressure and allow more exhaust out to help with high end power.

So having a car with a 2.5'' straight pipe (no catalytic converter(s), resonator(s) and muffler(s)) from the headers back would hurt overall performance of almost any car.



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Old June 29th, 2004, 02:27 PM   #12
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im actually gonna convert my car to a single exhaust as soon as i get that bolt out of my block and running again, all i have to do is go pick it up.
single Greddy EVO. dude said it sounded great too. i cant wait to do it, debadged with single EVO, this sleeper is just waiting to eat some food.
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Old June 29th, 2004, 03:16 PM   #13
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Quote:
Originally posted by Plumaccordcoupe
Not true. The 5th gen Maxima used a duel stage muffler to help with backpressure. At low rpm the muffle would allow only so much exhaust pressure out. But at high rpm a valve opens up from the increased pressure and allow more exhaust out to help with high end power.
This myth about backpressure keeps getting recirculated over and over so people keep thinking it is true. It is not. You don't want backpressure -- you want good exhaust velocity. Backpressure causes the engine to do more "useless" work. Useless, because energy is spent pushing exhaust out of the tail pipes instead of turning the wheels.

Do a google search and see for yourself. In case you can't find any good links, here is one from a Nissan rag:

Link to Nissanperformancemag.com

The valve you speak about most likely opens at high rpm because gas velocity is restricted and backpressure is greater with the single stage. At low rpms, the velocity would be reduced too much if both valves were open. It has nothing to do with backpressure.
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Old June 29th, 2004, 04:37 PM   #14
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Quote:
Originally posted by Swank on June 29th, 2004 at 05:16 PM

This myth about backpressure keeps getting recirculated over and over so people keep thinking it is true. It is not. You don't want backpressure -- you want good exhaust velocity. Backpressure causes the engine to do more "useless" work. Useless, because energy is spent pushing exhaust out of the tail pipes instead of turning the wheels.
Then explain this guys quote:

Quote:
Originally posted by Shadyguirguis on June 27th, 2004 at 02:07 AM

I did this, and I feel a little gain in torque but loos of high end from my former setup
I know excessive backpressure isn't good but removing backpressure altogether isn't good either. It all depends on the car and how much exhaust gas is exiting out of the engine.



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Old June 29th, 2004, 05:06 PM   #15
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Plumaccordcoupe: It probably has to do with the exhaust velocity and not because of backpressure.

You will most always have/need some backpressure, especially in FI applications. Many times folks who lose power blame it on the loss of backpressure, but it is really due to the lower exhaust velocity and flow. In addition, who knows what happened to backpressure in that person's exhaust setup. Going from two small exhausts to a single big exhaust could possibly keep backpressure somewhat constant, but reduce velocity at high rpms and cause the performance characteristics they saw. This could be similar to the 6th gen Maxima exhaust someone brought up. The Maxima needs the dual-stage exhaust to increase velocity at high rpms much like how the J30A4 has the dual-stage intake. More air is sucked in at high RPMs = more air expulsed. Just because your exhaust is sufficient for low rpms doesn't mean it is for high rpms. (Does the Maxima in question have a dual stage intake as well?)

Like I said before -- you want low backpressure and the right balance of flow and velocity. From the article I linked earlier: "If the exhaust pipe is too large, the flow will be sluggish with low velocity and the scavenging will not be good. Remember that a good exhaust has low backpressure and high velocity."

(edited to fix my reading comprehension problems )

Last edited by Swank; June 29th, 2004 at 05:15 PM..
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Old June 29th, 2004, 11:38 PM   #16
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my original setup was 2.25 from the cat till the Y, and 2.5 for the Y pipe.. and the torque gain isnt notciable, so pretty much the new stup just made me lose a very tiny bit of high end
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Old June 29th, 2004, 11:51 PM   #17
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Quote:
Originally posted by Shadyguirguis on June 30th, 2004 at 01:38 AM

my original setup was 2.25 from the cat till the Y, and 2.5 for the Y pipe.. and the torque gain isnt notciable, so pretty much the new stup just made me lose a very tiny bit of high end
So you noticed no low end gain from switching from a semi duel to a single? Thatís not what you said about unless you are wording it differently between which setup had which gain/loss.



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Old June 30th, 2004, 01:18 AM   #18
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Plum, you need to listen to Swank. He's correct.

Backpressure bad, scavenging the cylinders good. That takes velocity and correctly timed exaust pulses. When velocity drops, the exaust will actually over scavenge the cylinder and pull out the fresh air/fuel charge like a vaccum.
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Old June 30th, 2004, 01:59 AM   #19
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Quote:
Originally posted by bored&stroked on June 30th, 2004 at 03:18 AM

Plum, you need to listen to Swank. He's correct.

Backpressure bad, scavenging the cylinders good. That takes velocity and correctly timed exaust pulses. When velocity drops, the exaust will actually over scavenge the cylinder and pull out the fresh air/fuel charge like a vaccum.
Ok, that makes more sense to me. I'm still learning about this type of stuff . I think there are a few threads he with misleading info. That is where I got the idea that a certain amount of backpressure was good and that removing it was a bad thing to do.



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Old July 3rd, 2004, 01:18 PM   #20
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Quote:
Originally posted by Swank on June 29th, 2004 at 06:06 PM

Plumaccordcoupe: It probably has to do with the exhaust velocity and not because of backpressure.

You will most always have/need some backpressure, especially in FI applications. Many times folks who lose power blame it on the loss of backpressure, but it is really due to the lower exhaust velocity and flow. In addition, who knows what happened to backpressure in that person's exhaust setup. Going from two small exhausts to a single big exhaust could possibly keep backpressure somewhat constant, but reduce velocity at high rpms and cause the performance characteristics they saw. This could be similar to the 6th gen Maxima exhaust someone brought up. The Maxima needs the dual-stage exhaust to increase velocity at high rpms much like how the J30A4 has the dual-stage intake. More air is sucked in at high RPMs = more air expulsed. Just because your exhaust is sufficient for low rpms doesn't mean it is for high rpms. (Does the Maxima in question have a dual stage intake as well?)

Like I said before -- you want low backpressure and the right balance of flow and velocity. From the article I linked earlier: "If the exhaust pipe is too large, the flow will be sluggish with low velocity and the scavenging will not be good. Remember that a good exhaust has low backpressure and high velocity."

(edited to fix my reading comprehension problems )
Hmm, your starting to sound like me Plummy

The Maxima has a dual-resonance intake manifold. The flaps switch at 5,000rpms (5,200rpms on the tach). The Muffler in the Maxima is back-pressure actuated. In stock form, the flap opens at 2,000rpms, and you can hear a change in muffler note (louder tone). Once you open up the exhaust, the flap opens at a lower rpm. The main advantage of the flap is to decrease noise at low-rpms while still maintaining excellent flow-rates (heated exhaust gases) once the revs move up the scale. The flap itself is set to low to enhance any low-rpm flow rates, but aftermarket rear-sections are proven to add nill to an N/A VQ30DE-K engine so the muffler itself is well-matched to the flow rates of the exhaust system.

Ideally, you want a diameter of the piping to keep the exhaust gases hot all the way through, which in turn increases velocity of exiting gases. Running 2.5" header->downpipe on the JA30 isn't out of the question, but running 2.5" catback is pushing it. Its still a 3.0L engine, running 2.25" single set-up (or duals, since its a fakAr dual) would be good enough before going FI.

Last edited by Max on This; July 3rd, 2004 at 01:27 PM..
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Old July 3rd, 2004, 08:49 PM   #21
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It has to do with the scavenging effect. You want the exhaust pulses to be timed so that exiting exhaust will "pull" behind it, making the engine work less. Saying a 2.5" or 3" is better is just guessing. Size, muffler efficiency, and routing has to be taken into consideration. That's the whole point of R&D. You have to go through several exhaust models until you find the right one.

I've seen headers that make only 3hp, and I've seen dyno's of cars with open headers making just 3hp more than a stock exhaust.

For all we know, the size of the piping matters little and it could be all in the mandrel bends and a less restrictive muffler.
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Old July 3rd, 2004, 11:08 PM   #22
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Quote:
Originally posted by Genius6Spd
For all we know, the size of the piping matters little and it could be all in the mandrel bends and a less restrictive muffler.
No, we know for a fact the diameter of the piping matters
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Old July 6th, 2004, 12:43 AM   #23
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Quote:
Originally posted by bored&stroked
No, we know for a fact the diameter of the piping matters
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Old July 13th, 2004, 02:06 PM   #24
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I don't know if anyone else has ever tried this, but I just took my mufflers off of my 98 v6. I had pipe run to the back from where the old mufflers connected and had the same style tips put on the back. It works well in 3 ways. It looks stock, so make a good sleeper, It sounds pretty close to stock at low rpm speeds but roars when you get on it, and it performs better than having the mufflers on there. I still have the two resenators underneith and i went from a 16.3 to a 16.0 by using a 20$ intake off ebay, and 16.0 to 15.7 by taking off the mufflers and using the pipes. Budget performance worked for me :-)
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Old July 13th, 2004, 03:05 PM   #25
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Quote:
Originally Posted by BConly
I think roy did this... Awsomnamja is his username i think
hello...yeah that is what i did....power wise...ill be honest..i didnt feel n e more torque...nor hp...maybe a lil bit more top end...but thats about it....nothing to a point where everyone should do it....but i love the look when silly civic si people are behind me....but yeah....great sleeper....looks decent...and plus dont forget to get the rear bumper cover...its only 5 bucks from the dealer.

www.cardomain.com/id/accord03

o yeah...i dunno y but my account is gone or something...can mods help me and see if my account is still there?
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Old December 10th, 2004, 07:20 PM   #26
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So the person the did true duals had a lot of gains.. does that suggest that a single exahsut is actually restricting our cars??
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Old December 10th, 2004, 11:00 PM   #27
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for a single greddy, are u gonna buy the greddy for the i4 and make it fit on the v6 or wat?
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Old December 11th, 2004, 09:48 PM   #28
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No i already did custom piping.. but till this day I wasn't sure if I had lost or gained power.. becasue I never did a dyno... but according to the person who did true duals.... By allowing MUCH more airflow.. he gained a bunch of power.. so my question is.. should I go back to duals because the car performs better with the more airflow.. espicially that I just bough a V2.. so i might be limiting its gains.. I need opinions guys??



Also if I keep single exahaust waht would be the recommended width of the piping.. I currently have 2.5... but I feel that might not be enough.. I know with too wide Ill loose torque.. but that seems like a myth right now.. because again with the true duals he actually gained a little torque??
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Old December 13th, 2004, 04:43 PM   #29
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I'm interested in doing this too. Here is my plan. S2000 oval style tip, single right side exit. I played around with some pictures of my car and here is what it might look like if and when I do it.

Stock dual exhaust setup.


Dual exhaust with S2000 Tips.


Single Exhaust with S2000 tip.
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Old December 13th, 2004, 04:57 PM   #30
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Hey if any of u v6 7th gens want a single exhaust, ill trade with you or buy your oem exhaust
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