As many of you may know, we’ve recently been tackling a ton of neat products for the E46 3-series. This includes an aluminum radiator, aluminum coolant expansion tank, silicone coolant hose kit, and direct-fit electric fan kit. Along with all these cooling products, we also wanted to tackle an intake system that would bring out a more aggressive induction tone compared to the stock airbox and filter setup.

Our goal is to develop a system that sounds great, retains a stock-like appearance, and provides some safe power gains on the stock ECU tune.

Stock Intake System

Jumping right into the project, let’s take a look at the stock-equipped intake system.

In case that you are not entirely familiar with this system, here are some basic details. As you can see, ducting runs from the front kidneys to provide cold airflow to the airbox, which is located just behind the driver-side headlamp. The airbox contains a standard, flat paper filter that provides a barrier for dirt and debris attempting to enter your engine. Before the throttle body, a mass airflow (MAF) housing with sensor is in place to measure the volume of air entering the engine. This volume dictates the correct amount of fuel that is injected into the engine.

Below is a shot of the MAF housing, courtesy of realoem.com.

As you can see, the MAF housing is connected to the throttle body with a rubber inlet hose. This hose is prone to failure and cracking over time. We will be working to develop a silicone hose for this section to improve reliability.

The MAF portion of the intake for this vehicle is a sealed unit. It contains the sensor, the housing, and inlet and outlet screens. The mesh/screen promotes laminar (smooth) airflow across the sensor. This will provide more accurate readings from the sensor, which will result in a smoother running engine.

With other vehicles, we have developed our own MAF housing, as the sensors are typically removable. This is not the case with the E46, so we will be sticking with the stock housing and sensor assembly for our intake.

Here is a look at the rest of the intake system.

This detailed diagram shows the intake ducting, airbox, and filter. The air duct is a key component for providing cool air to the filter, so we will be working to retain this duct.

Initial Design

We will be using a Mishimoto cone filter that will provide reduced restrictions and greater surface area compared to the stock paper unit. Additionally, our filters are oiled and completely serviceable, so replacing them at regular intervals is not necessary.

Our filter is installed on the MAF housing in the image below.

Project done, right? Wrong. With an unprotected filter in a hot engine bay we have effectively created a hot-air intake system. This is not what we want. To enhance performance and reduce the chance of filter heat-soak, we would need to build some form of shrouding or box to defend against this heat.

So begins the design work on our prototype. First we mapped our design using a cardboard template.

Once we had a general idea of the plan, this template was converted to a steel prototype.

Weather stripping is added to the edges to provide a clean edge and to properly seal our shroud with the hood of the vehicle. Check it out!

As you can see, we are utilizing the stock air duct to pump cool air in from the kidneys. Our filter will be fully enclosed by the shroud, which seals against the hood of the vehicle. So far things are looking pretty good!

Coming Up!

Next time our prototype will be fully installed and we will be collecting dyno data to see if we can achieve any appreciable power gains. Check back next time for dyno images, video, and testing results!

After completing our initial prototype it was time to strap this E46 to the dyno and make a few pulls. We would be evaluating power output, monitoring vital engine sensors such as AFR, and collecting sound clips for comparison against the stock intake system.

Dyno Testing

Time to make some pulls! Check out the dyno video below.

Initial Impressions

The video shows the changes our setup made in  intake noise. This is likely a result of our open-element filter residing within the engine bay. Although closing the hood seals off the airbox portion of the intake, it is still more audible than the stock unit. The stock airbox is designed in a way to reduce noise and create a more drivable experience for non-enthusiasts. That said, this creates a numbness among car folk and leaves much to be desired.

Power Gains

So we’ve managed to improve engine sound with our intake system. How did we make out in the power department?

First up, our horsepower plot.

We were not expecting massive gains with this intake system. For our setup, we are using the stock MAF housing. Intake gains are typically achieved by modifying the diameter of the housing to lean the mixture slightly. If this is designed carefully, precisely, and properly tested it can be very beneficial.

The gains we are seeing with this vehicle are likely because of the improved airflow from our filter and lack of restriction. The stock airbox is likely impacting flow in a negative manner (although only slightly), so we are able to take advantage of this by removing it.

We saw maximum gains around 4,600 rpm to the note of around 4 whp and peak gains of 2 whp at 6,000 rpm. If you look at the plot, you will see that we make 1-3 whp throughout the entire rpm band, which is fantastic.

One additional note is in regards to the data we collect. Each plot represents an average of 3 consistent runs with each individual setup. We could easily select the highest Mishimoto run and lowest stock run to compare and promote bigger gains. We do not do that at Mishimoto. These are the results you can expect, they are not mind blowing, but we are pretty pleased with what we saw.

Next up, a look at torque output.

Although intake systems are generally characterized by horsepower gains, we should not forget torque as an equally important measurement of power. The plot above depicts the improvements we saw with our intake installed compared to the stock setup. Maximum gains were achieved at 3,500 rpm to the tune of nearly 5 wtq. Peak gains at 4,750 were right around 2 wtq. Both numbers are very respectable for an easy bolt-on intake system.

These gains aren’t comparable to strapping a Holset to your M54, but for a bolt-on intake system these gains are pretty respectable.

Intake Kit Information

Check out a few 3D models of our final intake setup!

The black portion of the model depicts our intake shroud that will be constructed from powder-coated black steel. We will also be using the weather-stripping noted earlier in this series to seal the box and reduce the chance of any vibrations on the edges.

The blue hose in these models is our silicone intake hose, which leads from the MAF housing to our air filter. We will also be using one of our oiled air filters, which is completely serviceable allowing for years of service.

What’s Next!

Now that we have completed the testing and full design of our intake, we need to construct a final prototype for an official test fit.

Final Intake Images

With successful testing data acquired from our first prototype, it was time to make a final prototype and perform our last test fit before producing a batch of final intake systems. Check out a shot of the shroud, intake hose, and filter!

The airbox is constructed of powder-coated steel, and we line the edges with weather stripping to prevent any vibrations or damage. The silicone coupler is a four-ply unit designed specifically for this kit.

The air filter shown above is the Mishimoto Oiled Air Filter. These filters are completely serviceable and can provide a lifetime of service if appropriately cleaned and maintained.

We also designed an internal CNC-machined connector that will allow the silicone intake hose to mate properly with our air filter. This setup can be seen in the image below.

All clamps and hardware needed for installation are included.

Fully Installed Images

This kit installs in less than 30 minutes,  soon we had the final kit in place and looking great! Check out a few shots.

Good news! Everything fit perfectly and this system looks great.