Team SITH Puts Air Intakes to the Test

Over the past few months members of SITH Racing started to truly pay attention to temperatures under the hood of the Ford Focus ST. Not just intake and charge temps, but things like oil temperatures and fuel rail temperatures. We drive our cars in stop and go traffic every day and it's just as important to keep the temperatures under the hood in check while in traffic as it is to keep them in check on a track. One of our members  had the Custom Performance Engineering (CPE) intake for a long time and have  had numerous conversations with a few fellow enthusiasts about intake temperatures and how the CPE is handling these temperatures. For those who may not know, the CPE intake is a fully aluminum air box and intake tube assembly. While we at SITH have no bias towards any organization, given the CPE intake was representative of the most aluminum available in an intake setup on the market today, we decided to test its function against its form. We truly wanted to test and see if there were differences and/or if there was a high efficient setup. We noted that another ST with a nearly identical setup to this one (same hood, same FMIC, same charge pipes, same exhaust) but different intake (aftermarket tube with stock air box) saw lower/steadier charge temps than the one fitted with the CPE.

A small degree difference in intake temperatures isn't the most important thing to focus on, and understand that while moving the air temps stay where they should be (especially with a snorkel and the open bumper and hood vents), but this is about testing and we wanted to test to see if we could maximize the efficiency and minimize heat as best as possible. In stop and go traffic things change quite a bit. Just as they do in between autox heats where the car is sitting still for upwards of 10 minutes at a time. Challenge accepted.

The first few things we did all added airflow assistance: Opening the bumper allows the most air possible to flow into the engine bay from the front of the car. The snorkel directs air directly into the air box keeping intake temps down while moving. The vents in the hood allow hot air to flow out of the engine bay. Air now flows in from the front of the car, around the engine, and out the hood. No more trapped hot air!

Given what we observed between the two aforementioned STs, we started data logging drives home. What shocked us when we looked the daily drive home, were the spikes seen in intake temps. Below is a graph of intake, charge, fuel rail and oil temperatures on a 92* ambient day when running the CPE intake. When ever we came to a stop the intake temps spiked and the charge temps were slowly pulled up as well. Yes, it drops relatively quickly when we started moving, but it was just a bit concerning how things would start to heat up when coming to a stop. This was also observed after the car was warm, hence why the oil temp was already up to operating temperature. Notice how intake temps never really dropped below 100* on a 92* ambient day:

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We replaced the  CPE intake and gave the OEM intake (box and tube with an aftermarket open ended filter) a shot to see how it keeps temperatures down. Surprisingly (or perhaps not so) the temperature spikes were muted. Notice how the intake temps stayed below or at 100* for the most part except for one extended creep up closer to 120*. With the CPE intake we saw temperatures over 130*. Temperatures across the board were better, including fuel rail temperatures which rose above 150* with the CPE intake, and never rise above 120 with the OEM intake. Everything seemed to stay much cooler, even on similarly hot days stuck in traffic. We admit that this isn't a perfect test as the amount and length of stops varied between the two tests. We also know humidity can play a role as well, but it wasn't drastically different from log to log and we were able to get logs on days with nearly identical 92* average ambient temperatures for all 3 tests.

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We decided to stick with the OEM intake tube while developing a new intake.

Given the heat resistant properties of silicone, and the fact that you can purchase all sorts of angles, diameters, and lengths at ease, we decided to create a full silicone intake. The hypothesis was that it would minimize the metal in the intake path that could potentially absorb and transfer heat to intake air or allow displaced heat to remain longer under the hood.

We ordered the following parts:

One 2' x 3" Diameter Straight
Two 45 Degree 3" Couplers
Two 90 Degree 3" Couplers
One 3" to 2.5" Silicone Reducer
Twelve 3" T-Bolt clamps
Six 3" Aluminum Joiners
One Silicone Port System (Still waiting on it)

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After working with different configurations and various positions, we were able to install a full 3" diameter silicone intake tube. It doesn't rub anywhere, and its easy to install once all the lengths and angles are figured out. We will post the measurements so that you can create your own version of this, for now here's an installed picture:

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The line from the back of the intake tube to the valves still exists and we are awaiting the silicone port system to arrive to make that connection a much cleaner one. For now we have a barbed elbow cut into the silicone and sealed into place.

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We are still gathering a few more logs this week to confirm what is being seeing and to ensure this intake is holding up well, but all signs are positive at this point. When at a complete stop, the intake temps are following along with the OEM intake. They aren't rising above 100* that often. We admit that the drive this log was based on didn't have very many stops (which is why we are gathering a few more) but initial signs show that it's better than the CPE intake we had on hand, and at least as good as the OEM intake. Keep in mind we are still using the OEM air box and the same aftermarket open-ended filter used in other logs. The only thing changed was the OEM intake tube to this silicone intake tube. Given that the temperature sensor is part of the first MAP sensor right after the airbox this setup isn't really measuring the efficiency of the intake tube as it is more towards the efficiency of the air box itself. However we can see that this is an improvement in temperatures over the CPE box, and it's full 3" intake all the way to the turbo which maximizes airflow. We plan on continuing testing by adding a temp sensor pre turbo to truly measure the intake tube efficiency, but for now this will do.

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When moving, intake temps are at ambient. We have seen on multiple occasions where the intake temps displayed on the COBB Access Port are 4 degrees lower than the ambient temps displayed by the car, and stay that low for 15 min or more. It's interesting to see this large of a difference for an extended period of time. To date, we have yet to see -4 ambient temperatures. At most we have seen -2 on other intake setups not using aluminum intake tubes (i.e. Carbon Fiber). The data shows that this intake cools incredibly fast since it is not retaining any heat.

We will continue testing against other comparable intake setups but for now, we are pleased with the results.

On a side note, you have to admit it looks pretty sick 🙂

- Team SITH