FAQ: Genesis Coupe 3.8V6 Exhaust

[KevinD]

The primary use of an exhaust on a vehicle is funnel away ignited air/fuel mixtures from the cylinders. Exhaust design is complicated and outside the scope of this FAQ, so for the rest of this article, we'll focus on the Genesis Coupe's exhaust components and their function, along with information regarding aftermarket replacement options.

Genesis Coupe Exhaust Layout:
[Source: HMAService.com]




*Note: Not included in the picture are the 2 exhaust manifolds containing the Warm Up Catalytic Converters.

Item # and Description:
1a. Exhaust Manifolds
1b. Front Muffler
2. Catalytic Converter
3. Center Muffler
4. Main Muffler

These 5 components make up the exhaust system of the 3.8V6 engine. A "Catback" system encompass the components starting at the Catalytic Converter back. All 5 of these components can be altered to increase engine output and alter the exhaust not characteristics of the vehicle.

Expected gains between the catback are still being researched. Historically, a Catback Exhaust nets 5-15 Wheel Horse Power (whp). As of the writing of this FAQ, the Genesis Coupe is too new on the market for definitive numbers.

Which manufacturer is best?
This is highly debatable. Your best bet is to check out the construction on the exhaust components and it's resulting sound, ease of installation, and power gains while researching an aftermarket exhaust. Determine what is best for you.

What exhaust material is best?
Exhausts are typically made with mild steel, but some are also made out of titanium. Aside from a difference in weight, there is no descernable evidence that suggests one material is better than the other. Corrosion is higher with mild steel than coated exhausts.

What exhaust diameter is best?
This all depends on your goals. Naturally aspirated cars typically have smaller exhaust diameters than turbo cars due to the lack of restriction on the exhaust. Below is general guideline on exhaust diameters and possible power gains: All numbers are approximate, other supporting mods may be required to meet numbers.

1. 2.25": Good for 300-350 HP
2. 2.5"-2.75": Good for 400-500 HP
3. 3.0": Good for 500HP +

There is a slight drop in low end torque when using a larger diameter exhaust than is necessary, so it is important to get the right size exhaust diameter for your needs.

Which exhaust as the best sound?
This is highly subjective and left up to personal taste. Evaluate exhaust sound videos and clips before deciding.

How hard is to install an exhaust?
Installation should take about an hour. You will need ramps, or a jack and jack stands, and various assorted sockets and wrenches. If you exhaust has seen a salt winter, like those in the Northern part of the country, you'll want to have some penetrating spray. I like PB Blaster, but any will do. Professional installation varies and typically costs around $75 dollars. This is a very simple installation and can be done by anyone. No experience necessary.

What about manifolds vs. headers?
The stock exhaust manifolds are very efficient and normally do not need to be replaced. Replacing the manifolds with headers is a matter of personal preference. Installing headers typically nets 5-10 Wheel Horsepower with additional supporting exhaust modifications. Headers by themselves will show negligible gain. Manifolds reduce exhaust noise and increase fuel economy. Headers increase exhaust flow, producing more power, but at the cost of some increased NVH (Noise Vibration and Hum). Be sure to weigh all factors before making any purchases.

Do I need Engine Management with a new exhaust?
For Catback systems, no. The stock ECU should be able to handle the slight change in exhaust flow. When replacing the exhaust manifolds with different manifolds or headers, engine management is recommended, but may not be required depending on the type of exhaust, catalytic converter replacement and O2 sensor housings. If your exhaust removes any catalytic converters, you will throw a CEL code. This can prevent your car from passing local vehicle inspections, where applicable, and can be just generally annoying. Also, without engine management, you will not get the maximum benefit from the new manifolds/headers added to the exhaust system. Invest wisely. If you are considering new manifolds/headers, factor in engine management and tuning to get the full benefit of your new exhaust system.

What about emissions and/or local inspection tests?
Removal of catalytic converters is a violation of section 203 of the Clean Air Act. Each state has their own laws and procedures regarding vehicle emissions and safety. All modern OBDII cars monitor all emissions components. Changing or altering these components may cause a Check Engine Light (CEL) to be thrown. These codes may prevent you from passing any vehicle checks. If you plan on using the vehicle as an "off-road" vehicle only, ie, a race car, emissions laws do not apply. But if you plan on registering your car and using it on public road ways, please be advised.


Editors Note:
This FAQ compiles a lot of information from various sources. It is here out of convenience for our members. If you have any suggestions for this FAQ, please respond below.