GM 2.7 L3B Turbo Performance Upgrades Guide

Finally, a turbocharged engine option for GM trucks. The awesome thing about turbocharged engines is you can add a lot of extra power very easily with just a few basic bolt-on modifications like tuning, intakes, and exhaust systems.

In this guide we’re going to discuss how you can add up to 100whp to the 2.7 L3B turbo with only four upgrades: engine tuning, a cold air intake, a downpipe, and a cat-back exhaust system.

GM 2.7 Turbo Performance Upgrades

• JB4 for L3B
• Cold Air Intake
• Cat-back Exhaust
• Downpipe

Due to the L3B being a relatively new engine on the market, it does not have the most aftermarket support, yet. Still, there are a number of mods you can do to increase horsepower and torque and improve overall performance. While turbo swap kits are not yet available, you can still tune and open up both the intake and exhaust for some more power. 

If you would rather consume this content via a video, check out our How to Make Your Chevy/GM L3B Faster video below:

1) ECM Tuning 

By far, the best bang for your buck for 2.7 turbo performance upgrades is the JB4. Since flash tuning is not yet an option for the L3B, the next best thing is the JB4. The JB4 is quite popular across other brands and it works very well on the L3B in all applications. 

The JB4 works by plugging into the factory ECU and manipulating the electronic signals as they pass through and control the engine. This allows the JB4 to do things like crank up the boost, the fuel pressure, and the ignition/camshaft timing, increasing horsepower and torque. The JB4 is incredibly easy to install and virtually undetectable. 

There are several different maps that can be run off the JB4, and it takes real time info from the engine to mitigate things like detonation and overboosting. You can also monitor your engine in real time through various gauges and datalogging, and you can make adjustments too, through the JB4 smartphone app.

For the GM trucks, the JB4 adds an incredible 85 wheel-horsepower and 120 wheel-torque without any other hardware modifications. On the Cadillac CT4 and CT4-V, the improvements are 60 wheel-horsepower and 80 wheel-torque. That’s a pretty stunning increase from just a JB4 module, making it by far the best GM 2.7 turbo performance upgrade. 

JB4 Purchase Link: JB4 for the L3B

2) Cold Air Intake Upgrades

Next up on our list of GM 2.7 turbo performance upgrades is a cold air intake. To be fair, the factory intake is technically a “cold air intake” due to the placement of the filter. Aftermarket intakes essentially are beneficial for their improvement to airflow. Still, it’s one of the most popular mods for the L3B engine, and has shown some decent performance increases. 

The purpose of an upgraded air intake is to decrease the amount of restriction present in the factory intake system. This usually involves using larger diameter tubing, lighter weight and more efficient materials, and a cone-style filter instead of panel-style. All of these allow for superior flow over stock, allowing for more air to reach the engine faster, increasing combustion and adding power. Additionally, upgraded intakes generally look much sleeker than the OEM units and help liven up the engine bay.

As you can see from the dyno plot above, a cold air intake adds as much as 25 horsepower and 30 lb-ft of torque on an otherwise stock Sierra 1500. This is from a 12% increase in flow from the intake, and it’s a pretty significant improvement. But do keep in mind this is from aFe so the charts are likely juiced a bit in their favor.

3) Cat-Back Exhaust System

For our third GM 2.7 turbo performance upgrade, we’re looking at cat-back exhausts. Now, a cat-back won’t add nearly the performance of a JB4 or an intake, but they are one of the top aesthetic mods for the L3B engine. Horsepower and torque increases are probably limited to about 5 horsepower at the most, and most of the benefit comes from the increase in sound.

Typically, cat-backs will have 3 inch exhaust piping with high-flow mufflers, which allows for a big improvement in volume. They will usually bolt-up directly to the factory exhaust, and are often made from a high-quality steel like 304 stainless. Depending on your preference, there are single-exit, dual-exit, side-exit, or rear-exit options. Generally, a single-exit exhaust will sound louder than dual-exits, but a lot of it depends on the muffler.

4) Downpipe Upgrades

For our final GM 2.7 turbo performance upgrade, we suggest looking into a downpipe. The downpipe is the part of the exhaust system that connects directly to the exhaust housing on the turbocharger. It takes the excess exhaust gasses away from the engine and routes them into the cat-back. It’s probably the most restrictive part of the OEM exhaust system, and one of the most important parts to upgrade for serious power increases. 

Unfortunately, there are not many available downpipes for the L3B engine. Some of this has to do with the fact that the OEM downpipe contains a catalytic converter emissions system. Removing the cat is only an option for non-street vehicles, as it is a mandatory emissions system.

A downpipe is good for 10-15 horsepower/torque by itself, but will offer even more with tuning. It’s highly recommended you tune (or use the JB4) when adding a downpipe, as without it you are prone to running lean and potentially overboosting. 

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