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Old 03-31-2004, 01:13 AM   #1
wildbill99
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Default have ? on true duals

coming from a v8 background im figureing i could put true duals on the h4 and see gains and probably have a totally different sound. be fore anyone can ask the reason i want duals is that im wanting to build my little jap car with some american muscle flavor and nothing say that like chrome sidepipes. but i dont want to spend the money to do this and then not be happy or worse have it negatively affect my performance.

i know i could loose some low end umph but i dont spend much time down there. i have looked over previous posts and they were all pretty old. they speculated it would sounded like some strange two stroke hybred. there was also some talk about there being no scavenging effect on the first ignition per bank.

when i slaped the straight duals on my blazers 5.7 in conjunctin with big heades there was a big hp gain. shouldnt the same thing work on the subie engine or does does it work alot more different than the V8s than i thought. im really looking for someone who has or nows someone who has already done this.

thanks scott
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Old 03-31-2004, 01:22 AM   #2
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Well, depending on your muffler selection, it may sound like two v-twins next to each other, or it may sound like 4 lawnmowers next to each other. Not much displacement going through each pr of exhausts. Hi end will improve, but at what cost?

Try it with the cheapest tubing you can find, and see how it goes. If it seems okay to you, build a set in nice SS and roll on.

Jay Storm
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Old 03-31-2004, 04:30 AM   #3
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If you want to sound more like a v8 shoot for borla headers first.
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Old 03-31-2004, 08:37 AM   #4
pdlindor
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Quote:
Originally posted by Kostamojen
If you want to sound more like a v8 shoot for borla headers first.
Indeed. Check out the video clip in this thread:
http://forums.nasioc.com/forums/show...hreadid=516712

Borla headers + custom mid-pipe + ScoobySport muffler.

I played it for my Mustang owner friend and he LOVED the sound!

~Paul
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Old 03-31-2004, 02:12 PM   #5
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Is this a looks quest, or a performance quest? Looks - you're on your own. Performance - dual exhaust is an unlikely avenue to gains. The header is the main bottleneck, in any case. Adding the weight of the extra pipe, plus the weight of another muffler, and you'll probably lose performance. Aside from that, there's no place to fit a muffler on the right rear, and not much room to tuck twin pipes through the center of the car.

No 4 cylinder runs true duals, they aren't necessary and don't work. Honda S2000 has dual mufflers, but they branch off a single pipe, Camaro style.
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Old 04-02-2004, 01:06 PM   #6
wildbill99
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why dont true duals work? if i run both pipes through a 2in 2out muffler say a gibson with 2 in pipes it should eliminate the v twin or lawm mower sound.
scott
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Old 04-02-2004, 01:34 PM   #7
00RScoupe
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Please don't think of this as a flame. I completely respect people who do thier own thing and try to be different. But true Duallys seems way to impractical to me.

Have you even looked under your car yet? Take a gander and look at the your differentials and all the AWD stuff under the car. Then look at the channel subaru put there for the exhaust. Now try to imagine putting two pipes there instead of one, simply because that channel is the only place to put the exhaust unless you want it dragging the ground.

The more I think about it, it just seems like alot of work and expermentation. You actually have lots of choices on aftermarket exhaust. Most are proven to perform well, unlike a homemade dual setup which is questionable at this point.

When you were messing with 8 cylinders did you hook up an complete exhaust pipe from engine back for every two cylinders?

Have you thought about engine management and the rear O2 sensor and how you will handle that? The same fixes for aftermarket exhaust and teh P0420 CEL might not work on a true dually setup, because the rear 02 will only be able to see half of the "pulses".

Like I said, this post isn't a flame, just some things to really think about before you put alot of effort into it.
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Old 04-02-2004, 11:24 PM   #8
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duals = R1C3

it wont help at all and prob kill low end with all the extra piping.

and take a look under the car there is no room to run a second pipe
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Old 04-03-2004, 02:41 PM   #9
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If it made sense to use duel exhaust for 4 cylinders, then don't you think there whould be quad exhausts for an 8? Really, think about it, the 2.5L H4 is going to have the exact same displacement as one cylinder bank of a 5.0L Ford V8. If a single header and exhaust is so great for the V8, then shouldn't a single header and exhaust be good enough for the H4?
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Old 04-03-2004, 04:53 PM   #10
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if you want duals, do like i'm going to do this spring. i have a 2.2 with 1 exhaust port per head. take a pipe and just run it staight out the side. i've looked at it and i think that they will fit nicely in front of the front wheels, maybe bent upward (warthog style).
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Old 04-03-2004, 05:53 PM   #11
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i think i found a solution. talk to a gut who can make me custom headers and then im going to bolton a high flow cat to each side and then run it to a X or H pipe and i should eliminate exhaust pulse and firing order pressure differences then run them into either smithy mufflers or glass packs . and run them down the sides implace of the factory side skirts. since im in ga loudness doesnt matter. what ya all think.

scott
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Old 04-03-2004, 06:08 PM   #12
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I think the idea is cool, dunno why no one else likes it.
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Old 04-03-2004, 06:37 PM   #13
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we all arent ricer rednecks
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Old 04-03-2004, 06:43 PM   #14
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what's ricer about it?
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Old 04-04-2004, 10:40 AM   #15
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Talking GO for it

WildBill
go for it dude i want to see pics if and when its get done and mabey a video. i think its a cool idea rice or not it will be different.just don't have 8 small pipes coming out the back, somebody posted a pic of a black wrx with 4 small pipes on each side of the rear bumper it was pretty lame.

GOOD LUCK dude
Donut

ow ya if you do the X or H pipe you could put the O2 sensor in there
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Old 04-04-2004, 04:44 PM   #16
wildbill99
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hey donut thinks for the incouragment. i should have it done in about 6 six weeks if i dont come across too many problems. will keep everyone up todate on my progress.

scott
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Old 04-04-2004, 06:01 PM   #17
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Sounds interesting..
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Old 04-04-2004, 06:18 PM   #18
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Comparing this to a dual exhaust V8 the way some of you are is apples to oranges. The idea is not to have 1 pipe per 2 cylinders as some people are saying, but to have a seperate header for each side of the engine, like a true dual V8 system. The reason no one does a 1 pipe per 2 cylinders is the space it would take up and why bother if the flow is good with the standard 4 pipe to one set up being used. How are you going to run 4 pipes from the engine back? So why bother trying. If this guy can fit a second pipe all the way back with a glasspack and a cat I say go for it. I'd probably reduce the pipe diameter a bit to make up for excessive loss of back pressure tho. Sounds like a cool project. If it can be done firly inexpensively go for it. If it doesn't work he can always go the traditional route. It would be something new.
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Old 04-04-2004, 09:33 PM   #19
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If I'm not mistaken, in order to get proper scavenging, you'd want to couple cylinders 1&4, and 2&3 which are 180 degrees apart in terms of firing angle. That's going to be a bit of a spaghetti nightmare under there...
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Old 04-04-2004, 11:46 PM   #20
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I'm fairly certain that's so, as well. I'm not sure of the extent of the benefit, if any, but if you go through with it, post some pics!
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Old 04-05-2004, 12:11 AM   #21
wildbill99
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the army is paying me $1325 per month for school and tuition is only $385 per quarter plus i work. i have nothing better to do with my money. im going through and auto tech corse so i have full access to a top of the line garage and the machine and body shops classes are always more than happy to help out on a project. i really hope it works.

scott
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Old 04-05-2004, 03:20 AM   #22
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Well, if I had the time and the facilities I would most likely be fabbing a system like MRT's, but have fun, and let us know how it goes!
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Old 04-05-2004, 01:55 PM   #23
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Aside from the space constraints(look at a BMW for nice routing of duals). There are reasons why the exhaust doesn't flow as duals already. Part of it is our funky firing order, part of it is the boxer design. I think you'll find that whatever you gain up top will be less than what you're going to lose in drivability. If VW and Porsche haven't decided on running duals over the past decades, I can't see where the Subaru is going to be much different.

Like I said before, make a set from cheap tubing and see how it goes. Ya never know......you may find something.

Personally, the MRT is probably as close as you'll ever need for dual exhaust. Though, I have contemplated lopping off our rattlebox of a MRT cat and fitting a Catco dual 2"in/dual 2"out and running some ovalized pipes out the side, just for sheetz&giggles. If I do decide to try this, I'll surely post results, no matter how wrong it ends up being.

Jay Storm
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Old 04-06-2004, 02:28 AM   #24
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I say nutts to everyone...

Do it if you want to. And if you do... be sure to document it and give us the photos/video clips of yer car running WOT...

Then again, its not my $$ getting ready to be spent.
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Old 04-06-2004, 08:47 AM   #25
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you know, on my hatchback I ran duals. some people run duals on their older 1.8s in the 80s body styles. And it sounds *good*! But, of course, there is no room under the newer soobs, and that's the only problem in my opinion.
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