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For the V6 car, the exhaust is often one of the more prized components of any build given the fact that there's simply not that much power to be made out of tinkering under the hood; but the motor sounds pretty awesome once its opened up.
Headers Selection
We'll go from the cylinder head aft - first up are the headers. Building headers that actually allow for a performance net gain over stock is very difficult. For example, one manufacturer took over 30 revisions to their design of headers on a Corvette motor before they finally stopped losing power and gained some. As a general rule, short-run or "shorty" headers will typically offer the best combination of low-restriction gain without losing too much low-end torque. Bear in mind on a naturally-aspirated motor, exhaust system backpressure is actually a desirable thing as the motor is operating at atmospheric pressure. With a turbocharged/supercharged car, as little backpressure as possible is desirable because of the forced-induction appratus hanging off the car's motor.
Long-tube headers - meaning the runners extend from the head (generally in equal lengths per-cylinder) and meet in a collector far aft of the cylinder head - are the most difficult to design for power gains as things like runner diameter consistency & collector size/placement all affect exhaust gas flow etc. so on and so forth. In a nutshell what this means is that long-tube headers, if designed properly, can offer a better top end (lower restriction) power gain, but almost always cost you low-end torque. Given as the V6 motor is already fairly limp as torque performance is concerned (by most any standard) choosing long-tube headers will damage your already lackluster torque curve, and whether or not they will net you much horsepower is entirely up in the air depending on the design.
For a max of around 15-17whp gain and at most 10-12wtq gain, headers may seem like a monumental waste of money - but for a naturally aspirated motor, freely flowing headers are a supporting modification for other upgrades, not so much a power-added in and of themselves.
**NOTE** Many, if not all - aftermarket headers for your car will present fitment issues mating to aftermarket exhausts due to X-pipes not mating up and so forth. The ARK H-pipe for example (which is a piece of junk and you should use an X-pipe instead) will necessitate welding work be done to mate up to aftermarket exhausts.
Available Products
- CP-E (Custom Performance Engineering) Long Tube Headers - MSRP ~$1200-1300
See notes above regarding the dangers of long tube designs. In testing these headers actually lost both horsepower and torque, and required a PowerAXEL canned ECU flash tune to achieve a max total HP gain of 1whp on a DynoJet. See numbers in 2010 November/December/2011 January issues of DSport. I handled the 3.8L car being used in the tests and I can personally tell you the car lost a bunch of torque, sounded raspy as hell, the headers scraped all kinds of speedbumps (car wasnt even that low) and the only benefit was a tiny bit of max top end power gain and the car sounds like a Lamborghini up REALLY high in the RPM range right as you shift. Blow money on these at your own risk. Also Dmitri at CP-E wants me dead, so try not to tell him where I live or anything.
- DC Sports Headers (shorty) - MSRP $670-880
These are good, clean, affordable headers and they are available with ceramic coating - which is very cool because it means the stainless steel headers will survive longer, and contribute less to engine bay underhood temperatures while being used hard. Like many headers they are built to order and take up to 8 weeks to ship. Great value, good equal-length short header design, definitely recommended.
- NGM (Next Generation Motorsports) - MSRP $600
These are difficult to get ahold of at the time of this writing, and these are likely knockoffs of Korean products (if not Korean products themselves) given the history NGM has with KDM product development - these probably work just fine, though if it were me I'd spend the extra cash for DC Sports just for peace of mind.
- ARK R-Spec Headers (shorty) - MSRP ~$900
Believe it or not you can find these listed on a few sites as "Tiburon 3.8 V6 headers". While I hesitate to recommend any ARK produts given the way ARK does business overall and the hit-and-miss quality of their products (because they ripoff other products and even if they claim it, it's unlikely they design anything they sell) these are actually decent headers.
- System Upgrade (Korean import)
- MSRP $???
Simply put, don't buy them if you find them, the price you'll pay to get them here from Korea will be a waste compared to just grabbing a set of headers from a retailer that imports in bulk and sells here more commonly.
Exhaust Systems
Full exhaust systems for the V6 are plentiful, easily available, and as always simply taking the car to an exhaust shop and fabricating a shop exhaust is nearly always cheaper and easier than buying an off-the-shelf cat-back name brand exhaust, with the same results. Expect little in the way of gains on the car, maybe 10-15hp at the very most, but again an exhaust on an NA car is as much for sound enhancement as it is for power. An NA car requires backpressure to work well so opening the exhaust up too much is actually a bad thing.
- Available brands of note (there are others not listed here)
Magnaflow - My personal favorite in terms of sound, quality and cost. A nice, clean, sharp exhaust for a reasonable price. Very well designed overall.
ARK - A massive waste of money; hangs so low its likely to scrape a number of things on the road, and your wallet too. Looks very pretty but the little secondary cans
built into the exhaust they claim is "researched and designed to increase power" is nothing more than a pretty bauble to look cool.
Injen - Hangs very low to the ground, easy to damage on the road. A little on the loud side, especially if you have headers. Definitely on the expensive side. The blue tips look a bit ostentacious but that may be your thing.
MXP - Oddly expensive for what you get. VERY VERY loud, especially with headers. Like wake the farmers and the cows loud.
CNT Racing - Holy shit loud, holy shit cheap, does not sound GOOD per se but its LOUD. Do not use with a stock set of cats/downpipe. You'll have to drill stuff if you do.
CP-E - A true-dual setup. A bit on the expensive side. Sounds good. Beware that a true-dual (both exhaust tracts are completely separated) is actually counterproductive to generating more power, as one bank will inevitably evacuate exhaust gas faster than the other, leading to the car sounding like it's sharting its pants between every shift. Some people like this. I would not recommend this exhaust only because an X-pipe (the two exhaust tracts meet each other) allows whats called 'scavenging' to occur and one bank's flow to 'pull' the other bank's exhaust gas out when there is a backpressure differential.
Agency Power - Smartly designed, no-bullshit, good price, possibly a bit too loud for some people.
GReddy - Typical GReddy - we've forsaken the performance approach for a WOW THIS LOOKS RIDICULOUS approach. Uses an H-pipe arrangement to cross exhaust flow which is better than a true-dual, but is not as truly efficient as an X-pipe. Utilizes the massive blue-tip fart cans you typically only see one of on an old-school turbo JDM car. Very pricey. Titanium will not save you enough weight to justify the price so you've got to want the titanium to brag about it. GReddy offers an axle-back exhaust thats universal to both motors; don't waste your money.
DC Sports - As usual DC Sports comes through with a no-bullshit, good sound exhaust that doesn't cost a fortune. Great price, not a top-shelf premium product but a great buy. Designed very smartly with a great X-pipe arrangement and a good muffler that doesn't kill too much sound and its loud without being obnoxious.
Cat Deletes/Down Pipes
For the V6 your OEM cats can be easily replaced with simple test-pipes that any exhaust shop can cheaply fabricate, or if Road Race Motorsports still makes them, cat deletes (of mediocre but working quality) were/are available from them. Be careful not to confuse downpipe/cat deletes on the V6, they are one and the same when it comes to aftermarket modifications. If you delete your OEM cats do not join the pipes together as one assembly, just have two individual test pipes made, otherwise down the road you will have fitment issues attaching aftermarket headers to aftermarket exhausts and you'll just throw youself in front of a train.
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