Looking at the features of test pipes and downpipes, you would assume they are the same. One of my neighbors had similar thoughts and bought a downpipe without thinking twice about it.
Now he regrets the decision as a test pipe would have served his purpose far better.
Test pipes and downpipes differ primarily in terms of their placement, performance, sound, and impact on turbos. There is also an enormous price difference between them.
In the article, I will discuss downpipes and test pipes separately, then dive into their differences. I will suggest a specific product based on what they have to offer at the end.
Let’s jump in!
What Are Test Pipes?
Test pipes, also known as straight pipes, are one of the most popular automobile modifications.
They are designed to replace your car’s stock catalytic converter and allow exhaust gasses to flow more freely. This will increase horsepower and lead to better engine performance.
Undoubtedly, the cat plays a crucial role in reducing emissions. However, the same converter also creates back pressure that limits your vehicle’s power.
This is exactly where a test pipe excels. It removes the catalytic converter to eliminate back pressure. The removal of the device also results in less restriction in the exhaust system.
All of that contributes to a higher level of performance.
What Are Downpipes?
Downpipes are similar to test pipes, but they are designed to fit between your car’s catalytic converter and muffler.
Like test pipes, downpipes can also help improve engine performance by increasing exhaust gas flow. However, they provide slightly less power than test pipes.
You can greatly improve turbo efficiency if you can afford a high-quality aftermarket downpipe. These pipes are ideal for minimizing turbo lag too.
Some people install downpipes on their cars even when they perform well. As soon as they observe poor performance, regret sets in.
It happens due to certain downpipes limiting the power your vehicle generates.
Comparison Table of Downpipe Vs. Test Pipe
It is time to figure out what the differences between the pipes are. Before elaborating on the differences, I will provide a brief overview in the following table.
| Key Factor | Test Pipe | Downpipe |
|---|---|---|
| Horsepower | Provides more horsepower. | Slightly increases horsepower. |
| Sound | Has a louder sound. | Produces a quieter sound. |
| Turbo Performance | Does not affect turbo. | Enhances turbo performance. |
| Placement | Replaces the catalytic converter. | Placed between the muffler and the catalytic converter. |
| Tuning | Does not require tuning. | Needs tuning for optimal performance. |
| Installation | Easy to install. | Can be a hassle to install. |
| Cost | Affordable | Expensive |
Differences Between Test Pipe and Downpipe
There are several major differences between test pipes and downpipes that distinguish them. Let’s see those.
Placement: Test Pipe
Test pipes are designed to replace your car’s catalytic converter. And as you might have guessed from the name, these pipes run tests to determine whether your cat is working correctly.
To verify the condition thoroughly, it replaces the converter.
Placement: Downpipe
Downpipes are designed to fit between the catalytic converter and muffler. This means test pipes remove the catalytic converter from your car while downpipes keep it.
That being said, bear in mind that a catless downpipe does not contain a cat.
Horsepower: Test Pipe
Test pipes usually offer a greater increase in power than downpipes. This is because exhaust gasses can pass more freely, resulting in more horsepower.
Horsepower: Downpipe
If maximizing your vehicle’s power is your top priority, a downpipe may not meet your expectations.
These pipes are not as effective as test pipes for facilitating the free passage of gas. As a result, they provide only moderate power gains.
Noise: Test Pipe
You are probably aware that test pipes ensure maximum exhaust gas flow. While this can yield more horsepower, it also causes more engine noise.
It is also important to understand that test pipes will remove the cat, the same device responsible for muffling your car’s sound.
In light of all this, adding a test pipe will certainly enhance your vehicle’s sound. Those who do not prefer loud noise may find it irritating.
Noise: Downpipe
Catted downpipes are abundant on the market. With such pipes, you won’t have to worry about your car making too much noise.
Regarding the catless downpipe, I should warn you that it can be noisy, almost as loud as one could expect from a test pipe.
Installation: Test Pipe
Many folks wish to gain additional power through exhaust pipes. Unfortunately, not every one of them has experience installing such pipes.
The test pipe is ideal for them because of its ease of installation. What’s even better is that it does not require any modifications to an existing exhaust system.
Installation: Downpipe
Those who are unfamiliar with exhaust pipe installation should not consider a downpipe. It must be cut and welded properly in order to be installed. If you lack experience with these tasks, installing the pipe will be incredibly challenging.
Nevertheless, you can always have a mechanic install the downpipe, which may be time-consuming and costly.
Tuning: Test Pipe
After putting the test pipe into place, you will notice an immediate increase in horsepower. You don’t need to perform any fancy tuning to make it run well.
Tuning: Downpipe
As I mentioned earlier, downpipes will only provide a slight boost in power. And even for that power, you may need to re-tune your car’s engine management system.
Turbo Performance: Test Pipe
The biggest problem I have with the test pipe is that it has absolutely no impact on the turbocharger.
If your ride has a turbo engine, a test pipe is not going to improve it. Instead, it focuses on enhancing gas flow.
Turbo Performance: Downpipe
For owners of turbocharged cars, downpipes are a treasure trove. This pipe makes your turbo engine way more efficient than ever before. Hence, your vehicle will experience a boost in turbo performance.
Moreover, downpipes improve turbo response by reducing turbo lag.
Price: Test Pipe
A test pipe makes the most sense if your budget is limited, but you still intend to improve your vehicle’s performance. You can get it for a fairly reasonable price.
Due to the fact that it is easy to install, separate installation fees are not necessary.
Price: Downpipe
Downpipes tend to be more expensive than test pipes as they require more complex installation. They have compatibility issues as well.
It implies that even if you manage to find a cheap downpipe, it may not fit your vehicle. The compatible one probably costs a lot.
Similarities Between Test Pipe and Downpipe
Okay, enough about the differences. Now let’s take a closer look at what test pipes and downpipes have in common.
1. Better Performance
Both test pipes and downpipes are intended to improve exhaust gas flow and increase power. Although the test pipe is better at it, they both achieve power by eliminating restrictions in the exhaust system.
2. Solid Build
While there is a massive difference in their prices, test pipes and downpipes are both usually constructed from stainless steel or another high-quality metal. This helps to ensure durability and resistance to corrosion.
3. Easy Setup
Yes, I know that I said downpipes could be tricky to install. This is true only when you have to cut or weld during installation.
However, if you are lucky, you may come across a downpipe that saves you from such hassles. In that case, both test pipes and downpipes will be relatively easy to install.
4. Environmentally Harmful
Whether it is a catless downpipe or a test pipe, you won’t find any catalytic converter in it. The test pipe even replaces the catalytic converter entirely.
Without the cat, an exhaust system will have no device for converting harmful gasses into less harmful ones. This toxic gas escapes into the environment, causing severe damage.
5. Against the Law
As I stated in the previous section, both test pipes and downpipes pose an environmental risk. This is one of the biggest reasons they are both illegal in most American states.
Among the other reasons are loud noises and cars emitting excessive black smoke.
Related: J-Pipe Vs. Downpipe
What Makes Test Pipes Superior?
Here are some of the reasons I consider test pipes to be the better option.
1. Performance
I cannot express enough how impressive the increase in power from a test pipe is. It does so by ensuring perhaps the smoothest exhaust gas flow.
Most people interested in buying exhaust pipes want more power. The test pipe does that better than a downpipe.
2. Quick Installation
Another benefit of test pipes is that they are generally much easier to install than downpipes. There is no need to make changes to your car’s exhaust system in order to install them.
3. Budget-friendly
Last but not least, test pipes are inexpensive, unlike downpipes. You are getting a ton of power and a stronger exhaust sound without blowing your budget.
You can also save a bit of money since a test pipe does not require any special installation and is often compatible with a wider range of vehicles.
What Makes Downpipes Superior?
Hearing so many positive things about test pipes may lead you to believe that downpipes are inferior. It is most definitely not true.
There are multiple reasons you might favor downpipes over test pipes. Let’s check them out.
1. Turbo Boost
If you desperately desire a turbo boost and want to keep your catalytic converter, a downpipe is a suitable option.
2. Less Noise
Another benefit of downpipes is that they are less likely to cause increased engine noise compared to test pipes. A downpipe will deliver a quieter sound that won’t irritate you as much.
Thanks to the cat’s noise-muffling abilities, there is significantly less sound emanating from the downpipe.
3. Lower Emissions
Most car enthusiasts are familiar with catted downpipes. The use of catalytic converters, dramatically reduces emissions. Moreover, catted pipes have a well-known capability to increase fuel economy.
Also Know: Bellmouth Vs. Divorced Downpipe
So What’s the Better Choice, Test Pipe or Downpipe?
Downpipes could be the ideal upgrade for those who are satisfied with a moderate increase in power but do not want a lot of noise. Additionally, you can opt for the downpipe if your vehicle is turbocharged.
However, I would strongly recommend grabbing a test pipe. It simply checks all those boxes with excellent performance gains, and that too at a reasonable price.
Whichever route you choose, do your research and make an informed decision before making any modifications to your car.
To Sum Up
Despite having plenty of similarities, the article makes it pretty clear how different downpipes and test pipes are. If your car is lacking performance, I believe you cannot do better than a test pipe.
Another factor to consider is how simple a test pipe is to use. You won’t need any tuning with it, which saves a great deal of money.
On the other hand, if you own a turbocharged vehicle, a downpipe will be most beneficial to you.
Exhaust pipe broke off the catalytic converter? Here’s how to fix it.
