Duramax LMM Cold Air Intake Guide
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The Duramax LMM was a monstrous 6.6 liter diesel V8 that General Motors/Chevrolet used in their heavy duty lineup from 2007–2010. Depending on the year and model it was in, the LMM put down 250-365 horsepower and 460–660 lb-ft of torque. Yet, with just a few mods you can seriously transform your truck and make it even more powerful. One of the most popular mods is a performance cold air intake. With a Duramax LMM cold air intake, you can gain 5-15 horsepower and 10-25 lb-ft of torque. With tuning, you can get up to 30 horsepower and 50 lb-ft of torque. Read on to find the top Duramax LMM intakes available today.
What is a Duramax LMM Performance Intake?
First, let’s start by talking about what a Duramax LMM performance intake is. The Duramax air intake is what delivers fresh air to the engine so it can function. OEM intakes pull in ambient air from outside and draw it through a panel filter, where it then travels into the turbocharger to be compressed.
The purpose of installing a performance intake is to increase the volume and velocity of airflow going into the engine. On a turbocharged engine like the Duramax LMM, the air intake connects to the compressor or cold-side of the turbocharger. The more air that can enter the turbo the more air that can be compressed and fed into the engine. The greater amount of air it takes in, the more power an engine can ultimately make.
Intakes increase the volume and velocity of the airflow by being larger than stock, using a freer flowing air filter, and having a more efficient design. This allows a greater amount of air to be sucked in through the intake, and it can move faster because of the decrease in restriction from the more efficient design. This results in increases of as much as 5-15 horsepower and 10-25 lb-ft of torque.
Short Ram vs Cold Air Intakes
For turbo-diesels there are two broad kinds of performance intakes: Either short ram intakes or cold air intakes. Both of them accomplish the same goal of increasing horsepower by maximizing air velocity and volume, but they do so in different ways and they have different results.
Short ram or ram-air intakes are the smaller of the two. The idea behind a short ram is that they are as small (or short) as possible to give the least amount of restriction. This allows air to fly through the intake without getting bogged down with lots of tubing and air turbulence. They use the least amount of tubing possible and draw in air directly from the engine bay.
On the other hand, cold air intakes operate under the principle of attracting the coldest air possible. Instead of the air filter being located as close to the turbo-inlet as possible, cold air intakes reroute the filter away from the engine bay and towards the fender or wheel-wells. This allows them to cut through the hot engine bay and take in colder air from the fenders/wheels. Colder air has more oxygen by volume, which allows it to make more horsepower.
On naturally aspirated engines the difference between a short ram and cold air intake is more important. But, on turbocharged engines the difference is generally much more minimal. This is because turbochargers themselves run off exhaust gasses and air heats up as it compresses. This means that no matter what the intake temperature of the air is, it’s going to get much hotter just going through the turbo. In addition, most turbo-diesels have intercoolers that cool down the charge air before it reaches the engine anyways. If you really want to improve cooling, a better intercooler is a better route.
Open vs Closed Airboxes
In addition to short ram vs cold air intakes, there is also the issue of open vs closed intakes. The stock Duramax LMM intake comes with an airbox, and most aftermarket intakes have one, too. The purpose of an airbox is to seal off the filter from the engine bay to improve cooling and longevity. It shields the filter from the engine bay heat, and also stops it from accumulating as much dust and debris.
One downside is that many people claim that airboxes can impede airflow by adding a restriction on the filter’s ability to suck in air. In addition, they are also more expensive, as sometimes just the airbox can add as much as $100 to an intake kit. Typically, we recommend using open box intakes, but the difference is pretty minimal.
Dry vs Oiled Air Filters
The final consideration for a Duramax LMM cold air intake is going to be the filter media itself: Either dry or oiled. Both of them have their pros and cons, but we definitely recommend going with a dry filter if possible. The liquid from the oiled filters often has a tendency to leak down the intake and interfere with the mass airflow sensor (MAF). This can cause it to malfunction and throw a check engine light and diagnostic trouble codes (DTCs). If you have the choice, definitely get a dry filter over an oiled one.
Benefits of Duramax LMM Cold Air Intake Upgrade
- +5–15 horsepower
- +10–25 lb-ft of torque
- Increased fuel economy
- Increased engine sounds
- Increased throttle response
For most people, the biggest benefit of a Duramax LMM cold air intake is the increase in power. With just an intake alone, the Duramax LMM can pick up 5-15 horsepower and 10–25 lb-ft of torque. While most intakes do not require a supplemental tuning solution, with a tune you will see as much as 30 horsepower and 50 lb-ft of torque in gains.
In addition, you may also see a slight bump in fuel economy. Usually, the difference is only around 0.5–1.5 mpg, but over several tanks it can definitely add up to some good savings. With the larger air filter you will also hear an increase in the engine sounds. The stock airbox does a good job of deafening the intake sound, but aftermarket ones really let you hear it.
The final noticeable benefit will be overall better throttle response. Not only does a cold air intake add peak gains of 15 horsepower and 25 lb-ft of torque, they also improve the entire power band. This means that the car will feel faster even when you are not going wide-open-throttle, and you will also notice towing gets easier, too.
Best Duramax LMM Cold Air Intakes
The top 3 Duramax LMM cold air intakes are:
- S&B Cold Air Intake
- Banks Power Ram-Air Intake
- aFe Magnum Force Cold Air Intake
1) Duramax LMM S&B Cold Air Intake
Starting off our list is the Duramax LMM S&B Intake. S&B is one of the top turbo-diesel intake manufacturers in the industry. They are known not only for their individual kits, like this one for the Duramax, but their filters themselves are widely used by a huge number of companies. They are very comparable to K&N brand filters – which is a pretty big complement.
According to S&B, their Duramax cold air intake will add 10-15 horsepower and 20-25 lb-ft of torque by itself. It is capable of outflowing the stock intake by 53% and comes with high-quality polyethylene and silicone construction for the best flow, heat reduction, and cost effectiveness. The S&B Duramax intake is also unique because it has two different airflow configurations, due to an optional block-off section near the front.
The S&B intake has a closed airbox with a clear cover on top. While we have stated open intakes usually perform better, the airbox in this case is not too big of a deal. The extra block-off section can also be left open for improved airflow. You can get either a dry or oiled filter, and we recommend the dry version. Overall, the S&B is probably the most popular Duramax intake on the market, and it is a very solid unit.
2) Duramax LMM Banks Power Intake
Second on our list is the Duramax LMM Banks Power ram-air intake. Banks Power is another well known name in the turbo-diesel industry, and they have been making products for more than 60 years. They had several Duramax intakes, including for the LBZ Duramax – the LMM’s predecessor.
The Banks Power Duramax LMM intake is a ram-air (or short ram) style of intake. It offers the smallest distance from filter to turbo for the least amount of restriction. Compared with the stock unit, Banks Power claims their intake can flow 47% better. The tubing is made from polyurethane and silicone to help heat reduction and for the best flow. Power gains can be as much as 15 horsepower and 25 lb-ft with the Banks unit.
Banks offers their Duramax LMM intake with either an oiled or dry media filter. As we stated above, we pretty much always recommend dry filters over oiled ones, as they perform the same but are not as susceptible to problems from leaking oil. Compared with the S&B unit, the Banks Power is not quite as popular but performs just as well. It is more expensive, somewhat due to the materials, but you are getting a solid intake.
3) Duramax LMM aFe Magnum Force Intake
Our final suggestion is the Duramax LMM aFe Magnum Force cold air intake. AFe is one of the top intake companies out there, and they make products for a wide variety of trucks and cars, including more than just turbo-diesels. They are pretty well known as somewhat of a budget option, as they don’t have the best quality control but offer decent products.
The aFe Magnum Force Duramax intake is a good piece that claims to outflow the factory intake by as much as 40%. They claim pretty astonishing improvements of 30 horsepower and 60 lb-ft of torque, which are pretty dubious on their face. Most likely, this intake will perform as well as the others, at about 10-15 horsepower and 20-25 lb-ft of torque without a tune at the most. The aFe uses an airbox, but it is open and not closed.
You also have your choice of a dry or oiled filter, with the oiled version running around $100 more. We definitely recommend the dry filter option of the two. Overall, the aFe Magnum Force Duramax LMM intake is a good piece, but the manufacturer’s claims are a little far-fetched. Still, it should perform just as well as the others on our list, and is a good budget option.
Duramax LMM Intake Upgrade Summary
Upgrading your stock intake on the Duramax LMM is one of the most popular and easiest mods to do on your truck/SUV/van. The install is pretty straightforward and does not require a ton of time or technical know-how. The gains you can see are as much as 15 horsepower and 25 lb-ft of torque with just the intake, or 30 horsepower and 50 lb-ft of torque with tuning.
We recommend three options for the Duramax LMM: The S&B, Banks Power, or aFe Magnum Force. Of them, the S&B is the most popular and will probably perform the best. The Banks Power is a little more expensive due to upgraded materials, but probably won’t outperform the S&B unit. The aFe Magnum Force is a good budget option that should perform as well as the others.
Which Duramax LMM intake are you considering? Let us know in the comments below!