Breathing Fresh Air – Intake R&D, Part 3: Design

We often say that engines are just air pumps. The more air you can get in and out of them, the more efficient they are, and the more power they make. While that’s true for any engine at its core, computers and electronic controls tend to complicate the equation. As cars and trucks become more complex and efficient, the computers controlling them have a hand in almost every aspect of how they run. Most of those controls focus on how the engine breathes in through the intake and out through the exhaust.

So, what does that mean for our 2018+ JL 2.0T intake? It means that “good enough” isn’t an option. The sensors attached to the Hurricane’s stock intake and its complex design require precision along every step of development. It may seem like we’re dragging our feet by looking so closely at the stock intake, but every feature of every component plays a major role in how the intake functions.

Our first two posts focused solely on the JL’s stock intake and at the end of the last post, I said we’d look at our design next. And we will, but first we must take one more look at the stock part. Our study of the stock intake up until now has focused on the outside. We’ve looked at its overall design and scanned every detail of its shape and home in the engine bay with our 3D scanner. The only remaining facet of the stock intake to study is arguably the most important: how air flows through it.

To measure how air flows through a part, we turn to our flow bench. This machine is essentially a giant vacuum that pulls air through a part at a fixed rate. Knowing that flow rate, we can then read the pressure created by the part. We can then compare the pressure at the inlet and outlet to calculate pressure drop across the part. Since pressure is the measure of restriction, less pressure means less restriction and a lower pressure drop across the part. It sounds counterintuitive, but a lower pressure drop means higher flow.

We attached the stock Hurricane intake to our flow bench and fired it up. Our main goal was to get a reading across the entire intake system so that we had something to compare our intake to. We also wanted to take this test a step farther. To do that, our engineer, Ye, placed test ports on the airbox and before the muffler. These ports would let us measure the pressure drop across each component to see exactly how they affect flow.

We wanted to test the muffler and the airbox specifically for one simple reason: they’re complicated. The muffler incorporates a mount for the PCV pressure sensor. We’ve seen on our F-150 catch can projects that these pressure sensors can be extremely sensitive to even the slightest change in flow. The coupler between the muffler and the turbo also houses a heater for the PCV system. Recreating these two components would be extremely costly, so if their impact on flow is minimal, we don’t want to charge our customers more money for extra parts that don’t benefit them.

The same applies for the airbox. We’ve found in past projects that modern engine airboxes are typically over-engineered and often don’t restrict flow enough to warrant changing. We’ve also found that intakes without airboxes tend to perform worse than those with airboxes. Without an airbox, the intake draws in air from the surrounding engine bay. Some of that air is cold, some is very hot. That inconsistent flow makes it difficult for the computer overlords to figure out how the engine should be fueled, and performance suffers. That inconsistent flow can easily trigger a check engine light as well.

The lower box plays a role in the JL’s water fording ability. A dense filter material over a large opening in the lower airbox allows a lot of air into the intake when the JL is driving normally. Once the Wrangler starts fording water, this screen acts as a barrier to keep water out of the intake. We want to keep the JL’s off-road ability intact while letting in as much cold air as possible. If we can keep the lower airbox without sacrificing flow, we will.

After running the flow bench a few times, we had pressure drop data for the entire intake as well as the muffler and airbox. While the overall data isn’t very useful to us until we have a prototype to compare, the data from the muffler and the airbox was useful. Our flow bench test showed that neither the airbox nor the muffler caused a major restriction in the intake. Using this data, we were finally able to design our intake. Our engineer started with a 3D model.

Most of the flow increase for our intake will come from simplifying and smoothing the main tube of the intake. Removing the three resonators and increasing the volume of the pipe will help bring more air into the engine and bring it in faster. To draw in as much clean, cold air as possible, we’ll replace the panel filter with a large, custom-designed performance filter. The lower box will remain stock and our upper box will bolt right up to keep the water-fording ability of the stock intake.

You might also notice that the mount for the PCV pressure sensor is present on the end of the pipe. Even though the muffler didn’t restrict flow, we want to try replacing it to get some more sound out of the turbocharged Hurricane. We’ll test designs with and without a muffler to see how they perform and sound.

With our initial design finally created, we can begin prototyping. In the next post, we’ll start the long process of creating components using our 3D printers and old-fashioned hand tools. The sensors will make rapid prototyping challenging, but with a little patience, our intake should be a big improvement over stock.

Thanks for reading,
-Steve

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