2012 Nissan Altima 2.5 mod gone wrong!

Welcome back to the blog!

Today, I’m excited to share the first modification I made to my 2012 Nissan Altima—a classic beginner’s upgrade: the cat-back exhaust swap. Before diving into the details, let me give you some context. My Altima was powered by a 2.5-liter inline 4-cylinder engine, rated at 175 horsepower. What made it unique was its exhaust setup: it channeled all exhaust gases from the manifold into a single catalytic converter, followed by a Y-shaped split, resulting in dual cat-back exhausts. Pretty uncommon for a 4-cylinder car, right? 😎

Below, you’ll find a diagram of the 2012 Nissan Altima’s exhaust system to help visualize the setup. Let’s get into the details!

This exhaust setup is great for fuel efficiency and likely does well with emissions (perfect for keeping things under the radar 😁). However, when it comes to producing a satisfying engine sound, it falls flat. Paired with the CVT transmission, even the most high-end exhaust systems struggle to deliver a deep or appealing sound. Instead, the note ends up being disappointingly low and unpleasant to the ears. 😞

Choice of Catback.

Magnaflow straight through 4' street series.

Custom down-piping required for catback only setup.

Here is my Altima on the rails for the stock catback and down-piping removal.

Here's the car with catback removed, new catback with extra piping is visible on the right.

In case of only catback, make sure to align the catback before modifying the down pipes.

Voilà! After installing the cat-back exhaust and taking it for a test run, let’s address the big question: where did it all go wrong? Truthfully, the entire project turned out to be a disaster. There was no noticeable increase in power—at least nothing I could feel 😏. The exhaust note sounded like a starving hippo 😒, and the constant humming nose inside the cabin was unbearable, pushing my patience to its limits 👽. I kept the modification for about six months, but eventually, the noise became so overwhelming that I started to worry about my sanity—and my hearing!

The problem with Altima exhaust note is that the exhaust air gets divided between two catbacks which reduce the air pressure significantly and hence, the sound note become low in magnitude. Another reason is the CVT transmission that does not let the car rev to its limit and hence the sound-note is not very charming. 

Below is the eye-to-eye comparison of before and after.

Let me have your thoughts about this and let me know your experiences about cat-back mod. 

See you next time around.