What Are Test Pipes On The 350Z?

The Nissan 350Z (also known as the Fairlady Z if looking at the Japanese Domestic Market/JDM version) is one of our favorite Japanese sports cars of all time.

Considering how much Japanese ‘hero cars’ have shot up in price in recent years, the 350Z still offers excellent value for money and is part of that rapidly dying breed of analogue, old school, naturally-aspirated sports cars.

We have written a number of articles on this site about the Nissan 350Z, including what we believe is the most comprehensive and detailed 350Z buyer’s guide. We have also looked at whether the 350Z is a good first car, as well as why 350Zs are considered dangerous cars.

In today’s article we are looking at what test pipes are on the 350Z.

Someone might have told you to install test pipes on your 350Z to improve power and the exhaust note, or you might have just purchased a 350Z where the owner had test pipes fitted. 

Please note that we have written this article to be a “101” guide to test pipes on the Nissan 350Z – we don’t go into specific reviews on the best test pipes for your 350Z.

What Are 350Z Test Pipes?

Long story short, a test pipe is a piece of exhaust pipe that replaces your catalytic converter in the exhaust system.

The reason some people install test pipes on their 350Z (or other cars) is because swapping out the catalytic converter allows for a freer-flowing exhaust system. As you’re probably aware, the catalytic converter system in your exhaust strips some of the power and noise from your car, in exchange for reducing emissions.

Swapping to test pipes can result in modest horsepower gains as well as a louder exhaust note, if that’s your thing.

As far as how much horsepower you can gain? This is something that is heavily debated, but we have seen claims of gains ranging from 5-15hp; we would be inclined to think that actual hp gains would sit on the lower end of that range.

Considering that test pipes generally aren’t all that expensive, this can be a good option if you are looking to gain a bit of extra power.

One thing to note is that installing test pipes has the effect of worsening the emissions from your car – we will talk about that more later in this article. Test pipes are not the eco-friendly solution to making your 350Z more powerful!

Why Are They Called ‘Test Pipes’?

The term test pipe is used as it is meant to denote that the pipe in question is intended for “testing” whether or not you have a catalytic converter issue.

Basically, the original purpose of test pipes was to allow for easier isolation of catalytic converter issues – you could swap out to a test pipe and see if the issue you were having with your car/exhaust system was solved.

Test pipes are meant to be a temporary solution to test if your exhaust flow is being restricted excessively by the catalytic converter, or if there is some other catalytic converter-related issues.

However, some owners like to keep test pipes on permanently due to the increased exhaust flow, louder noise and potential for more power.

Are Test Pipes Legal?

This is one of those “your mileage may vary” questions – it all depends on the jurisdiction in where you live, and what is permissible in terms of car emissions controls, noise limits etc.

Being based in New Zealand we are not so well versed in American road law, but our research indicates that test pipes on a 350Z aren’t likely to pass emissions checks in states that require emissions testing – we go into more detail on this topic further on in the article.

Furthermore, test pipes have a tendency to increase the volume and noise coming from your exhaust (this is part of the reason people want them, after all). In some jurisdictions there may be restrictions on how loud your exhaust can be.

This isn’t always set by government or local authorities – we have heard of people installing test pipes on their cars and then being told by the HOA in their area that they need to quieten their car down, or else!

A good place to start is by doing a Google search to see what the relevant legislation is in your area. Look at requirements in terms of catalytic converter installation, emissions control, and noise control.

If the legislation in your local area looks challenging for test pipe use, then another option in installing high flow cats on your 350Z – we will cover this in another article, but basically you get much of the benefit of test pipes but also avoid the potential legal issues with your car.

If you are intending on using test pipes on your 350Z for track use only, then you probably don’t have to worry about the legal side of things.

The most important thing is to check your local rules and regulations with regards to modified cars, exhaust emissions and noise etc and then decide the best course of action from there.

Can Test Pipes Cause A Check Engine Light On A 350Z?

Installing test pipes can have the unwanted side effect of causing a check engine light on your 350Z.

This is basically because the ECU of the car is programmed to operate with the car having a fully functioning catalytic converter system with the relevant sensors etc (that is an oversimplification, but hopefully gets the point across)

When you remove the catalytic converter system and swap in the test pipes, the car’s “brain” is now not receiving the right signals and so it can throw a check engine light.

However, there are steps that can be taken to prevent/eliminate CEL issues after installing test pipes on your 350Z, such as correctly installing non-foulers/de-foulers. You can get non-foulers for this purpose here on Amazon.

Here’s a quick video guide on how to do this that we found on YouTube:

Will My 350Z Fail Emissions/Smog Testing With Test Pipes Installed?

This is entirely possible, and comes down to how thorough the test requirements are in your area (and the extent to which the inspecting garage/workshop follows these requirements).

For example, if your emissions check just involves hooking your car up to a scanner to see if there is a check engine light on, then you can probably pass the test fine. There are ways you can “trick” your 350z’s ECU into thinking there are still catalytic converters installed, or you could use an OBD2 scanner to clear any codes before going in for a test – although we cannot comment on just how legal this is in your area so please don’t come knocking if you get into trouble!

However, if your check involves a “sniffer test” for actual emissions output and/or having a physical inspection of the catalytic converter system while the car is up on a hoist, then you almost certainly will not pass.

Recap – What Are Test Pipes For The Nissan 350Z?

Test pipes are exhaust components that effectively replace the catalytic converter.

To recap, the name “test pipe” comes from the fact that these pipes were originally intended to be used to test and isolate issues with the catalytic converter that might be causing problems with the proper running of your car.

However, due to the increased flow, louder noise, higher horsepower etc some people like to install test pipes permanently on their cars.

If you are thinking about test pipes for your 350Z, then it’s important to consider local rules and regulations in your area.

For example, you will probably find that your car will no longer pass emissions control tests, if these are a thing where you live.

There are a number of 350Z enthusiast forums and blogs where owners with test pipes discuss strategies for passing emissions/smog checks – so if you are really sold on the idea of test pipes you can look at threads like this as a starting point.

Please note that test pipes aren’t really road legal in many jurisdictions – so if you install them on your 350Z and then get hit up by the cops or other enforcement officials, don’t come complaining to us!

If you are interested in the power and noise gains that come with having test pipes but want something more road legal, then we recommend you look at high flow cats instead.

Don’t forget to read our Nissan 350Z buying guide for more information on this great car.