Duramax LBZ Guide to Performance & Cold Air Intakes
If you had the 8.1 Vortec engine in your truck instead of a Duramax, I’d probably be telling you an intake is a waste of money. However, for turbo-diesel engines it’s one of the first mods we recommend for people just getting started. Outside of an upgraded intake being a building block to more power, it is probably one of the best bang-for-your-buck options.
While not overly important but worthwhile to mention, pretty much every LBZ intake option is called a cold air intake. However, none of these intake systems are truly designed in the same fashion as cold air intakes. A traditional CAI relocated the intake filter from the top of the engine bay to the bottom. The purposes is for the intake to suck air in from underneath the front bumper, as close to the ground as possible, therefore grabbing the coolest air possible.
LBZ intake systems all sit within the factory location in the top of the engine bay. The performance gains from an upgraded performance intake primarily come from additional air flow, not cooler intake temps.
Upgraded Intake Performance Benefit – LBZ Duramax
- Power gains upwards of 20hp and 50tq *(not peak power gains)*
- Increase intake sound that sounds really cool
- Increased turbo efficiency and faster spool
- Increased throttle response
- 50%+ increases in volumetric air flow
I put an asterisk after the power gains because quoted gains can be misleading. In turbo diesel engines, the majority of power gains will be realized at lower RPM’s, or at the lower end of the power and torque curves. Peak horsepower and torque gains from a cold air intake usually fall within the 5-10whp range. However, many intakes will claim 20hp+ and 50tq+. While these gains are true, they are not peak gains. They are gains over the stock intake at low RPM’s.
Let’s look at this dyno chart from aFe as an example. Peak horsepower increases by 3whp and peak torque increases by 7wtq. However, if you look at the lower end of the curve, around the 2,000rpm mark, power gains are in excess of 20whp and 50wtq. Upgraded intakes are great for low-end power which is good for towing, acceleration, etc.
LBZ Power Constraints
If you plan on excessively modifying your Duramax LBZ, keep in mind that the engine and transmission are power constrained. As we wrote on our LBZ Common Problems guide, 600whp is the approximate mark where cracking pistons becomes common.
However, you’re guaranteed to break your stock transmission long before you crack a piston. While the Allison 1000 is a highly reliable powertrain, it does not fair well with modifications. The Allison 1000 transmission will generally need to be built and upgraded around the 400whp mark.
Open-Air vs. Closed-Box Intakes
As you look at my highlighted intake options below, you’ll notice two styles of intakes. Open-air intakes, in which the filter is open to the engine bay and closed-box styles where the filter is protected within a box.
People will argue for days about which is better. Open-air intakes are claimed to result in higher intake temps because the filter is sucking in engine bay air while the closed-box systems aren’t open to the engine bay. However, intake air temps on closed vs. open systems really won’t matter. The LBZ has an intercooler so a degree or two won’t be a game changer.
The second consideration is that open-air systems usually increase volumetric air flow more than closed-box systems. On a closed box system, the air has to flow into the box and then through the intake and the boxes are space limiting, which therefore restricts the intake to a degree. You could say that the box increases pre-intake air pressure but increases airflow increases post-intake air pressure which is more important.
Overall, the differences between the two are minimal. Open-air systems will flow additional air, closed systems will flow colder air. The most popular and widely used intakes on the LBZ are closed-box systems. The reason being is that the LBZ stock intake draws its air from within the wheel fender, which naturally has colder air.
Whether open or closed, an upgraded intake will supply the engine with more air than the stock intake and that is the main purpose of upgrading.
Best LBZ Performance & Cold Air Intakes
We’re going to showcase three of the most popular and highly praised intakes for the LBZ Duramax. While all of these are closed-box systems there are a number of great open-air systems on the market. Banks tops my list as they have some compelling competitive data on their product page showing decreased air temps compared to the other aftermarket systems. But all-in-all, most of these systems will show similar performance gains and I don’t think you can go wrong with any intake.
Banks Power Ram Air LBZ Cold Air Intake
Similar to the other two options, the Banks Power intake is another closed box system mounting directly in the OEM intakes spot. One noticeable design difference is that the intake outlet piping has bellows on it which counteracts engine movement. While this is a nice feature, there aren’t enough claims of people breaking intakes from engine movement to give it much credit.
A second consideration is that this actually sucks are from the bottom of the intake as well as the side. The thought process being that the air from the bottom is cooler than the air from the factory location. This intake boasts a 57% increase in air flow over the OEM unit and has an increased outlet size of 7-1/8in. helping the intake deliver more air to the engine.
Another option on the Banks Power intake is adding the super scoop. The super scoop mounts to the bottom of the Banks Power intake and dips about a foot lower, sitting within the front bumper, grabbing colder air. This is more synonymous to a traditional cold air intake which is why Banks calls their product both a ram air and cold air intake.
S&B Filters LBZ Cold Air Intake
S&B Filters cold air intake for the LBZ is a closed-box design with a clear cover of the box to give your engine a cool look. This system draws air from the factory intake location and claims a 50.15% increased flow over the OEM intake system. At $299, this is one of our favorite intakes. S&B is widely considered one of the best filter manufacturers alongside K&N and aFe. As a matter-of-fact, a lot of the other aftermarket intake systems for the LBZ will actually use S&B filters on their intakes.
aFe Momentum HD – LBZ Intake
Similar to the S&B intake, this is another OEM location, closed-box performance intake. Outside of the lack of see-through cover on it, you will notice that the front of the intake has an extra air inlet. This extra inlet allows this aFe intake to flow 57% more air compared to S&B’s 50%.
The dyno chart I shared above is for this intake. While you are only increaing 3whp and 7wtq, power gains at low RPM’s are substantial and make this a great intake for those looking for some more towing power or faster acceleration.
Combining an Upgraded Intake with a Tune
At the beginning of this post, I called the intake a “building block to more power”. While a lot of folks say an intake is pointless with respect to peak power gains (which is sort of true) increased air flow is critical for high horsepower applications. While you can add a tune for mpg, the most common use of a tune is to increase power. On turbo vehicles, tunes do this by increasing the amount of boost or psi that the turbocharger is producing.
As boost or psi increases, the turbocharger has to compress more air. Compressing air to 30psi from 10psi requires 3x the amount of air. If you are running higher boost, you need more air entering into the engine to reduce lag and increase turbo efficiency. Additionally, the increased air flow also increases the pre-turbo air pressure, which improves turbo efficiency as the compressor wheel does not have to work as hard or spin as fast to create the increased boost pressure since the air is already more compressed.