Evo X Downpipe Upgrade

The Mitsubishi Evo X is one of the most legendary and sought out modern tuner cards in the world. It is the 10th generation of the iconic Lancer Evolution, and first made its debut in the 2008 model year. Unfortunately, Mitsubishi discontinued it after 2015, making it one of the hottest options on the used market. The Evolution X is powered by the 4B11 engine, a turbocharged 2.0 liter inline-4, which puts out 303 horsepower and 305 lb-ft of torque to all four wheels. However, the real fun with the 4B11 comes from modifying it and adding lots more power. 

One of the most popular mods for the Evolution X is a downpipe. An Evo X downpipe upgrade is a great way to boost horsepower, torque, and improve turbo spool and responsiveness. In the following guide, we will look at what benefits you can get from upgrading your downpipe, followed by a list of our recommendations for top downpipes on the market. Make sure to check out our other Evo content, including: Evo X coilover upgrades, Evo X intake upgrades, and the Top seven mods for the Evo X.

What is an Evo X Downpipe (DP)?

First, let’s start with what a downpipe is and why you would want to upgrade it. The downpipe is the part of the 4B11 exhaust system that connects directly to your turbocharger. It collects the gasses exiting the exhaust valves and pushes them through the rest of the exhaust. Upgrading to a larger downpipe reduces the back pressure in the exhaust system, which increases horsepower and exhaust scavenging. 

However, the Evo X exhaust system is a little different from most turbocharged cars. On most turbocharged cars, there is at least one catalytic converter in the downpipe. However, on the Evo X, Mitsubishi put the cat in the test pipe instead. The test pipe connects to the downpipe but is separate. 

What does this mean for an Evo X downpipe upgrade? You won’t see nearly the same gains as other downpipes. You will still see a small reduction in back pressure and improvement in exhaust scavenging, but not nearly compared to removing the catalytic converter. However, this does mean that Evo X downpipe upgrades are emissions compliant, which is a bonus.

A 4B11T downpipe upgrade will still free up exhaust flow and add both horsepower and torque. You will also see an increased and more aggressive sound from the exhaust after changing the downpipe. Most Evo X downpipes are 3” in diameter, which is larger than the stock 2.5” diameter. The larger piping is what produces more power and sound, as it moves a lot more air.

Widemouth vs Divorced Downpipes

For an Evo X downpipe upgrade there are two basic options: Either widemouth or divorced style. Both of them offer similar flow and performance as each other, and sound decibel-wise they are also similar. The difference between them is how they connect to the turbocharger.

A divorced style downpipe (see below) has two different tubes — one significantly narrower than the other — that both connect to the turbo. The larger tube covers the turbine outlet and the smaller tube (or “dump tube”) covers the wastegate outlet. They both eventually merge together towards the middle of the downpipe. This is compared with a widemouth style downpipe, which covers both the wastegate and turbine outlets with a single exit and only consists of one large tube.

The purpose behind a divorced style downpipe is to reduce boost creep and lessen potential turbulence in the exhaust flow. By allowing for two smaller exits instead of one larger one, the flow can be controlled better and more smoothly.

Widemouth designs have been known to be prone to boost creep, which is where the turbo continues to build boost even when it should be tapering down. This is problematic because the engine can run in a lean condition if boost can’t be controlled, causing detonation and pre-ignition. This winds up potentially leading to catastrophic engine failure. The boost creep effect gets exacerbated with catless test pipes.

Divorced Dump Tubes

On divorced downpipes, the smaller tube that covers the wastegate outlet is called the wastegate “dump tube.” On some downpipes, the dump tube is merged into the larger tube partway down the downpipe. However, there is also the option on some for the dump tube to be left open and not connected. This vastly increases the sound of the downpipe to epic proportions, but attracts a lot of attention. This option should really be reserved for track cars, as it is absolutely thunderous.

409 vs 304 Stainless Steel

When purchasing an 4B11T downpipe, typically there are two options: Either 409 stainless steel or 304 stainless steel. For the most part, high performance exhaust systems are made largely out of 409, because it presents a good balance of cost and corrosion resistance. It also polishes nicely, and is much cheaper than the next step up, 304. 

304 is the top dog for mass produced performance exhaust material without using titanium. It  looks sleek, polishes very nicely, and is even more corrosion resistant than 409 – hence the increased cost. Compared with 409, 304 has double the amount of chromium, and more than 20x the amount of nickel, which is what makes it so corrosion resistant. It’s often referred to as marine steel because it even holds up to repeated use in saltwater. 304 can turn gold after repeatedly being subjected to high heat. 

For most people, a 409 exhaust will be a good compromise of price and performance/longevity. In most climates, 409 will be more than fine for lasting several years without succumbing to any corrosion or rust.

Evo X Downpipe Upgrade Benefits

Most people looking at an Evo X downpipe upgrade are concerned with horsepower and torque gains, but there are several other benefits that come with it.

• +10-15 horsepower/torque
• Improved turbo efficiency
• Quicker turbo spool
• Louder and more aggressive exhaust tone
• Reduced backpressure
• Reduced EGT

An upgraded downpipe on the 4B11 will net between 10-15 horsepower and 10-15 lb-ft of torque. The gains would be more if a catalytic converter was being removed, but those are not a factor in these downpipes. Still, there are some noticeable power gains that will be had and the car will definitely feel livelier.

One of the biggest improvements an aftermarket downpipe will give is reduced backpressure, which aids in both turbo efficiency and spool. Your turbo will spool noticeably quicker after an Evo X downpipe upgrade, due to the ability to push exhaust gas through quicker and easier. This also reduces exhaust gas temperature (EGT), and overall makes the engine and turbo work more efficiently. 

In addition, you will also see an increase in sound from an 4B11 downpipe upgrade. The tone will be deeper, more aggressive, and much louder. This is even more apparent when paired with an aftermarket test pipe and cat back. Especially if there is an open dump tube.

Tuning Considerations

Tuning is not necessary after upgrading to a new downpipe on the Evo X, but it is always recommended for the biggest gains. Tuners can take advantage of the reduced backpressure and greater flow by increasing boost. This gives more power throughout the powerband and makes the car stronger and quicker everywhere.

Best Evo X Downpipes

Now that we understand the benefits and reasoning for the 4B11 downpipe upgrade, let’s get into the recommendations. Instead of a comprehensive list, we will instead look at the top-four Evo X downpipe upgrades based on price, quality, reputation, and performance.

1) AMS Performance Evo X Widemouth DP

Price: $529.95

Design: Widemouth

First up on our list is the AMS Evo X Widemouth Downpipe. It is a widemouth design and one of the most sought out and recommended downpipes on the market. The Evo X AMS downpipe is a fantastic combination of price and performance, with fitment and quality being top-notch. AMS makes them entirely from 304 stainless steel and they are full 3” throughout, allowing for maximum gains.

The Lancer Evolution X will see power increases of 10-15 horsepower and torque after installing the AMS downpipe. You should also notice much improved turbo spool, too. It is one of the better flowing downpipes on the market and has been used on some really big horsepower builds. The AMS Evo X downpipe features direct OEM fitment to the turbo and test pipe, making it a great first mod for many enthusiasts.

2) ETS Evo X Divorced Downpipe

Price: $695.00 – $795.00

Design: Divorced

The next entry on our list is the Extreme Turbo Systems (ETS) Divorced Dump Downpipe. It is a divorced style downpipe and the dump tube has two options – recirculated or open. The recirculated option merges the dump tube back into the larger tube, whereas the open version lets it vent to the atmosphere. The open option is much, much louder, and is really meant for dedicated track or show cars.

The Lancer Evolution X will see power increases of 10-15 horsepower and torque with the ETS divorced downpipe. Both versions of the dump tube offer the same power, with the difference being sound. As usual for ETS, their downpipe has been used on some pretty iconic builds, including some 7 second Evo Xs.

Like the AMS Performance DP, the ETS tube also offers direct OEM fitment to the test pipe and turbo. Fitment and quality are exceptional on the ETS downpipe, and users can’t go wrong installing it on their 4B11.

3) MAPerformance Evo X O2 Eliminator Downpipe

Price: $793.49 – $811.89

Design: Divorced

The MAPerformance Evo X Eliminator Downpipe is one of the most tried and tested downpipes on the market. It is known for being a fantastically engineered and fabricated downpipe, and is capable of 10-15 horsepower and torque gains. The MAPerformance Eliminator downpipe is also available with ceramic coating for a very reasonable price.

The MAPerformance Eliminator is a solid Evo X DP upgrade choice. It is divorced style with a recirculated dump tube. The dump tube helps to reduce boost creep, and it has the option of a CNC 3D contoured flange for those with larger turbos. The O2 Eliminator name comes from the integrated O2 sensor housing, which not all downpipes have. 

4) Tomei Evo X Widemouth Downpipe

Price: $531.00

Design: Widemouth

The final entry on our list is the Tomei Evo X 3” Widemouth Downpipe. It is a widemouth style downpipe, and like the AMS is full 3” throughout. It is a great option for the 4B11, and Tomei is widely known for their excellent quality and fitment.

Installing this downpipe on the Evo X will net 10-15 horsepower and torque, and should significantly reduce spool time and backpressure. The Tomei is known for being one of the louder options on the market. It also comes with exhaust heat wrap included which aids with flow.

Evo X Downpipe Upgrade Summary

As far as Evo X modding goes, an Evo X downpipe upgrade is one of the best choices. It keeps the car emissions compliant while still unlocking some horsepower and torque. The volume increase is also nice and adds a distinct and aggressive tone to the exhaust.

Not only are the power gains great, but the reduced back pressure and EGTs are also great benefits. Reduced back pressure means the turbo will spool faster and work more efficiently, greatly increasing the power band.

This guide looked at four top options for Lancer Evo X downpipe upgrades, including both divorced and widemouth styles. The ETS and MAPerformance are both great divorced style options at a similar price. Both are manufactured in the USA, with the ETS having the option for the open dump tube. Likewise, both the AMS Performance and Tomei downpipes are great widemouth options. Quality and price wise they are nearly identical, with AMS getting the nod due to its reputation within the community.

What’s your experience with Lancer Evo X downpipe upgrades? Are you considering one?

Leave a comment and let us know!

Evo X Downpipe FAQ