Duramax LLY Cold Air Intake Upgrade Guide
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Chandler is a leading content writer for 8020 Media. Outside of writing truck related GM content for Chevy Trucks he creates a lot of articles around LS engines over on TuningPro. Chandler is a gearhead with tons of hands-on experience. Furthermore, he has a masters degree in history that makes him invaluable in crafting high-quality, well-researched articles on both classic and modern Chevy trucks.
The factory intake on the Duramax LLY is really restrictive. As such, a cold air intake upgrade will add up to 15 horsepower and 25 torque while also providing benefits like lower EGTs, faster turbo spool and throttle response, and even 1-2mpg increases in fuel economy.
The performance benefits and overall efficiency improvements make a cold air intake one of the best performance mods for an LLY. We’ve been modifying Duramax’s and leveraging intake upgrades for years and are going to share all of the benefits and considerations in this article.
Duramax LLY Cold Air Intake Benefits
- +5–15 horsepower
- +10–25 lb-ft of torque
- Increased fuel economy
- Increased engine sounds
- Increased throttle response
There are a few benefits to upgrading the stock intake to a cold air or ram air intake, but the most important is the increase in horsepower and torque. With a cold air intake you can see increases of as much as 5-15 horsepower and 10-25 lb-ft of torque. To get the most out of your intake, tuning is recommended. Especially on a MAF based system like the LLY uses.
In addition to the performance increases, you’ll also notice the throttle is much more responsive whenever you hit the gas. You can also see increases to fuel economy from using a less restrictive and better breathing intake. Usually, it’s only 0.5-1.5 mpg, but it’s better than nothing and is a nice byproduct.
Finally, after installing your new performance intake you will definitely hear it from behind the wheel. Not only does the larger filter make more noise, but even intakes with airboxes are not nearly as insulated as the stock intake system. The new intake will be noticeable from the moment you step on the gas, and can really complement an upgraded exhaust.
Open vs Closed Airboxes
The biggest consideration when choosing an intake is open vs closed designs. Open intakes have the filters completely exposed to engine bay air, whereas closed systems keep the filter within a box, like the factory intake.
Open intakes usually outflow cold ones by around 20% so they are going to be the best for performance. The caveat is that they will draw in slightly warmer air, but this is mitigated by the intercooler so ultimately the IATs are going to be about the same.
Closed intakes will flow a bit less, but still a lot more than the factory intake. So closed systems are still good, just not recommended for those looking to maximize performance or shooting for high power levels. They will be less noisy if you don’t want cool induction sounds from the intake.
Overall, open intakes are what we install on the LLY’s in our shop since they offer better performance and that’s what we’re all about.