Test pipes have almost nothing to dislike. In addition to the affordability, they are incredibly easy to install. However, one thing I was skeptical about was whether this pipe would increase a car’s horsepower.
So I began using test pipes for a more thorough investigation. And guess what I discovered? The pipe indeed improves horsepower, even a great deal sometimes.
Test pipes add horsepower to your car through more efficient exhaust flow and reduced back pressure. The amount of horsepower they produce varies from 3 to 20.
In the article, I discuss how test pipes affect horsepower in different vehicles. I will also explain when it is appropriate to tune after installing a test pipe.

What Are Test Pipes?
Test pipes are aftermarket car parts fitted in place of catalytic converters. They are much like straight pipes, only flanged and unrestricted.
Now you might wonder why you would use this pipe instead of the converter. Here is the answer:
You see, a catalytic converter makes an exhaust system extremely restricted in an effort to neutralize harmful gasses. While the end result is a safer environment, the restriction limits the power of your automobile.
This is where a test pipe comes to the rescue. It replaces the cat and eliminates the restrictions in the exhaust system. As a result, exhaust gases begin to move more freely.
Moreover, test pipes also significantly lower back pressure if a car is turbocharged.
With less back pressure and enhanced exhaust flow, your car can reach its full potential. In other words, the test pipe boosts your vehicle’s horsepower.
How Much HP Do Test Pipes Add?
Test pipes generate horsepower at different rates according to the car. Here are the horsepower differences between turbo and non-turbo vehicles.

1. For Turbocharged Cars
First, you need to consider how restrictive your exhaust system is.
The majority of car owners never tamper with their OEM catalytic converter. All these OEM cats are notorious for putting severe restrictions on exhaust systems.
If you replace such converters with an entirely free-flowing 3-inch test pipe, you will likely gain 15-20 horsepower. Keep in mind that I am sharing this idea from the perspective of someone who owns a turbo car.
2. For Regular Cars
So how much horsepower do you get if your vehicle is not turbocharged?
Well, in that case, test pipes add 3-7 hp at most and, on rare occasions, even 10 hp.
Power Output of Different Cars Using Test Pipes
1. Do Test Pipes Add Horsepower 350Z?
A test pipe will certainly add more hp to a Nissan 350Z. Although users differ on the amount of horsepower, it should be between 6-10 hp.
Even a high-flow catalytic converter can easily bring 5 hp to the 350Z. So it is perfectly reasonable for a test pipe to increase horsepower from 6 to 10.
Suggested: Does Removing the Catalytic Converter Increase Horsepower?
2. Do Test Pipes Add Horsepower G35?
If you install a high-quality test pipe on your Infiniti G35, not only will the horsepower improve, but also the torque.
As for horsepower gains, it should be 8-10 hp assuming your car consists entirely of stock components.
The cats Infiniti G35 come with tend to be heavy. Since a test pipe is lightweight, it can save your car about 11 pounds. All of this contributes to better performance in the G35.
3. Do Test Pipes Increase Horsepower G37S?
Infiniti G37S owners who want to boost their horsepower can install a test pipe. However, you must re-tune it to get the maximum output, which is approximately 10 horsepower.
If you decide to continue on the stock tune, the hp gain will reduce to 2-5.
4. Do Test Pipes Add Horsepower 370Z?
A Nissan 370Z is capable of generating 10 horsepower with a test pipe. Remember, the more flow a test pipe has, the greater hp your 370Z will receive.
Related: Do Test Pipes Make Car Louder?
Do You Need a Tune After Installing Test Pipes?
It is not mandatory to tune test pipes. Having said that, tune-ups may be necessary for certain circumstances.
For example, test pipes must be tuned to maximize their performance.
Furthermore, if your vehicle is equipped with a mass airflow sensor, you may need to get a tune to prevent the check engine light from coming on.
Which Test Pipe Produces The Most Horsepower?
GTM resonated test pipes are highly rated by users for their impressive horsepower boosts. Nonetheless, the test pipes currently available on the market are all essentially the same.
You should still consider a few factors while buying a test pipe, such as:
- Make sure the welds are of good quality.
- The material must be metal.
- It is preferable to have extended bungs for o2 sensors. They prevent the check engine light from showing up.
- While most test pipes are the same, they sound very different from one another. For instance, resonated pipes produce a less buzzy sound.
Does a Test Pipe Make a Big Difference?
Yes, test pipes do make a big difference by making your car perform better.
I am sure many will point out how small the horsepower increase is. In reality, however, it is quite substantial. Here’s how:
When it comes to turbo vehicles, a test pipe can boost performance by 20 horsepower. For motorheads, 20 horsepower for a couple of hundred dollars is like winning the lottery.
On the other hand, installing the test pipe is a breeze. Compared to other exhaust pipes designed to improve performance, you won’t have to deal with complicated installation procedures.
Considering all factors, a test pipe does make a significant difference.
To Sum Up
The addition of test pipes to your vehicle will result in a decent increase in horsepower. Moreover, if you are ready to throw some cash on tuning, you can certainly expect to achieve more than just 3-5 hp.
Tuned or not, a test pipe is undeniably one of the most effective ways to improve your car’s performance on a budget.
Not sure how test pipes and downpipes differ? Click here to learn the differences.