Dual Exhaust on a 4dr

[Kuro3]

Hey guys, I saw this kit (http://www.msprotege.com/forum/showthread.php?t=75237&highlight=dual) on the mazda3 5dr that has the dual exhaust and all that. I love the look of a dual exhaust, but has anyone ever done that on their 4dr? or heard of any kits that have the rear bumber with a spot for another exhaust pipe coming out the right side? I think that would look so sick

 

[JRH1]

Unfortunately, if you're in the States, you can't change the number exhaust pipes on your car unless it was offered as an option on your model car that year.
For instance, if you've got a Mzd3 and every 3 only came with a single exhaust, EPA regs make you keep a single pipe even if you replace your stock pipe. However, if you've got a Mzd6 and one model comes with single exhaust and another comes with dual, you can replace a single pipe with a dual, even if the engines are different.

Or so I've heard.

You COULD run just a non-functioning pipe and tip to create the appearance of dual exhaust.

 

[Kuro3]

meh, a non functional exhaust is probably even worse than a non functional hood scoop. Kinda like what's the point, right? Oh well. I guess if it's illegal I won't think about it too too much. But it still would be interesting. I wonder if anyone has done double exhaust tips on one side ona 4dr.

 

[keleko]

dual exhaust on a 4 cyl. engine.....

yeah, that won't look like rice at all

 

[Kuro3]

what's the difference if it's a 4 or 6cyl for a dual exhaust?

or what about just having a double exhaust tip on the one side?

 

[JRH1]

The double tip might look pretty fly. Some VW Golfs/GTIs have the double tip.
You can put a double tip on anything, legally. It's changing the number of whole pipes that might get you into some trouble.

Also, just practically speaking, you'll start to run into problems regarding backpressure if you double the amount of pipe that the engine needs to pump exhaust through. Ideally, the exhaust sytem is tuned to help accelerate the exhaust gasses out of the system while causing the least flow resistance. That is, there's an ideal pressure for each engine. If you add a whole bunch of pipe, you'll alter that balance and actually decrease performace. For instance, if I want to upgrade my stock exhaust from 1.75 inches (wide) to 2.24, I'm positively increasing flow and decreasing restriction. But if I size up to far to 3 inches, the flow of exhaust will become sluggish and I'll lose power. An engine will have to work just as hard to move all of the exhaust and dead, momentum-less air through a gaping pipe as it would have to work to push that same volume of exhaust through a narrow restrictive pipe.

 

[RENE063]

There is yet another suggestion. My Camaro Z28 that I traded in for the 3 had a single exhaust going to the muffler, yet the muffler had two outlets. This gave the illusion of having dual exhaust when in actuality it was a single. Both outlets out of the muffler let out exhaust, therefore both tailpipes were "functional." Personally, I don't feel there will be enough back pressure with a true dual setup on a 4 cyl. engine to justify the money spent. Find a muffler with a single inlet and dual outlet if appearance is what you are after.

 

[thebeansoldier]

Unfortunately, if you're in the States, you can't change the number exhaust pipes on your car unless it was offered as an option on your model car that year.

what states? United States? Never heard that before. It's JUST an aesthetic mod that has nothing to do with emissions. You're not modifying any of the cats.

Nope, doesn't look ricey at all.

 

[StealthWyvern]

dual exhaust on a 4 cyl. engine.....

yeah, that won't look like rice at all

um... so your saying my gf stock 6 is ricey because it has dual tips on the back on a 4 banger... am I understanding you correctly?

 

[JRH1]

what states? United States? Never heard that before. It's JUST an aesthetic mod that has nothing to do with emissions. You're not modifying any of the cats.

Right. I suppose it's fine if you run two pipes from the cat or have a double-tipped muffler but you couldn't connect a second pipe at the header, bypassing one of the cats (or changing the number of cats).

But the point is kind of mute because the double tipped muffler is really the only way to go on a small NA engine because a true dual exhaust will create too much backpressure. I'd say that double the amount of exhaust pipe from the cat-back will start to cause problems.

 

[keleko]

...
or what about just having a double exhaust tip on the one side?

now that might not be so bad, at least it's not trying to look like it's something it's not

 

[keleko]

um... so your saying my gf stock 6 is ricey because it has dual tips on the back on a 4 banger... am I understanding you correctly?

there's no clear way to tell if the 6 has a 4 or 6 banger in it, so if there's dual exhaust, it's conceivable that it's a 6cyl

the 3 doesn't have the option of a 6cyl, so yes, dual exhaust is rice on it

 

[Kuro3]

well if a dual causes too much back pressure, then why does the mazda6 have the 2.3liter 4cyl with a dual exhaust? Would that mess with backpressure too?

 

[orangezoom]

what states? United States? Never heard that before. It's JUST an aesthetic mod that has nothing to do with emissions. You're not modifying any of the cats.

Nope, doesn't look ricey at all.

I think this looks pretty good, I like it.
The CX-7 has a nice looking exhaust.

 

[keleko]

well if a dual causes too much back pressure, then why does the mazda6 have the 2.3liter 4cyl with a dual exhaust? Would that mess with backpressure too?

because it was designed for it

the 6's 4cyl engine, while basically the same as for the 3, HAS been tuned slightly different

 

[Hughes412]

There is NO law keeping you from putting duals or TRUE duals on a car. However the is an emitions rule that if do put on true duals it has to mirror the original exhaust system. So if you have
a pre cat
2 cat
res
and muffler
you will have to double it.
2 pre cats
a second cat for both sides
2 res
and 2 mufflers.

And having a 4banger and dauls is not rice. I don't think you would call the s2000 rice, or the up coming Solstice GXP and I'm sure if I took the time I could come up with more.

 

[flat_black]

Wow... Uuh... Wow. There's a lot of misinformation in this thread:

A cat back is not illegal, federally. Your state/county laws may dictate that your exhaust is too loud, however.

Putting one pipe off to one side of a dual exit header for an open exhaust back, while leaving the other exhaust on would be extremely pointless, and very un-functional. It would cause more issues than it solved.

The number of exhaust outlets in no way determines how many cylinders/what displacement a car runs.

Having a high flowing dual exhaust with twin properly sized runners, and a properly sized cross pipe, and/or Y-pipe will NOT reduce exhaust velocity, and two mufflers or one cross-flow muffler will not be any more resistant to velocity than any other equally baffled muffler.

The above, however, will be heavier, which lends itself to worse performance. However, if the above exhaust were done only for the reason of efficiency, then you would have NO cars that had a dual exhaust. Why? Most cars have a cross pipe or a Y pipe, as it allows for resonating exhaust pulses to create a more substantial scavenging effect further down the exhaust, and this is on six, eight, twelve cylinder cars. Furthermore, turbocharged cars would, or SHOULD, by the above beleif, never have a dual exhaust. Since a turbocharger collects all the exhaust gasses in one place, and pushes them out from yet another single source. So, insofar as dual exhausts are 'ricey', they should be considered ricey on ANY car.

Velocity is NOT the same thing as backpressure. Backpressure is, essentially, bad by definition. Port velocity, which can be lost by a) Having too large of an exhaust, b) having ports that are too large on a ported out head, c) having an intake system of such a diameter that you're gaining no velocity from having a tract (exception: velocity stacks just want air, and work on the Venturi Effect.)

And please, please, please, people... 'The point is mute' is not only not the proper saying, it makes little sense... The word is 'moot', which means to bring up a topic for a discussion or debate, for SPECIFICALLY that purpose, and heretofore, one means by saying; 'The point is moot,' you are trying to convey the fact that it's pointless arguing a point that was specifically brought up for the point of argument.

Whew. Sorry about the rambling. =)

 

[tsunami]

LOL^^^^ thanks for clearing some of that mess up flat black... also as he said about the y pipe or some one else said about a muffler with dual outlets is how the mazda6 and srt4 have a dual exhaust on a 4cyl they don't have two headers etc...

as far as looks go i think it looks good and balances out the ass end of the hatch especially but is there that much room under the car?? if you look the exhuast piping is in a tunnel under the car almost like a drive shaft would be in a rwd car. to custom make a y pipe or a dual outlet muffler i think is more trouble then its worth...

 

[awsmp5]

that looks bad ass
how about the racing beat miaters eh? i wouldn't call that rice

 

[JRH1]

....errr, like I said...



/sheepish