We enlisted the help of Doug MacMillan from Hondata, a man who has more experience with the RSX's brain than anybody outside of Honda itself. He informed us of two things. First, the car is very sensitive to temperature, and will switch programs if it detects just a slight variance in the engine's temperature. Second, the car will rapidly change its long-term fuel correction, pulling out fuel (and reducing power) as intake temperatures rise.
Our handy OBD-II reader came to the rescue again. We were able to monitor the engine's coolant temperature down to the degree, and ran all of our tests with the computer reading 204F. In addition, Doug showed us the easy way to reset the long-term correction by unplugging that part of the computer briefly. By doing that, we were able to achieve repeatable dyno pulls, with numbers within a horsepower or so.
Our on-road temperature testing taught us another thing: Dyno tests need to be done hood-open to achieve anything like real-world conditions. Although the engine compartment doesn't get nearly as cool as the outside air, it does benefit from underhood circulation. Unless your dyno is in a wind tunnel, it's impossible to replicate high-speed airflow on a chassis dyno, even with fans blowing all over the place. However, opening the hood cools off the engine bay temperature to about the same levels as they would be on the road, and this is how we conducted our tests.
However, we also conducted tests with the hood closed. This gave us a chance to see how the different systems reacted to heat soak. With the hood closed, all of the intakes suffered a tremendous drop off in power, with intake temperatures skyrocketing quickly. Even the cold-air systems were seriously affected. This means that in the real world, you would want to open your hood and let the engine cool for a while if you're trying to get consistent quarter-mile times.
A word about some of the photos. You will notice that the AEM and DC Sports cold air intakes were tested with the filter sticking out of the hood, not mounted near the ground. We did this for the sake of convenience, since removing and replacing the cold-air systems was quite difficult. Although this would seem to be an unfair advantage, we checked to make sure the intake air temperature was the same at the nose of the car as was the ambient temperature where the filter was placed. They were identical. Also, note that the intake air temperature numbers for the dyno test match the numbers from our on-road tests. In other words, despite the strange positioning, having the filter mounted in this way made no difference in our temperature reading, and we conclude it didn't make a difference in our final testing.
So, how'd they do? The only modification that didn't make any power was the K&N drop-in filter, which in fact lost a statistically insignificant 0.1 hp. Considering the low flow numbers from the flowbench testing we conducted, we didn't have very high hopes for the drop-in anyhow. As a money saver, it's worthwhile since you'll never have to replace it. Just don't expect much power from a drop-in.
On the other hand, all of the short-ram and cold-air intakes made power. Of the short-ram intakes, Injen came out on top, bumping power up 9.2 hp to 166.9. This tied DC Sports' short-ram in power, but Injen had a slight edge in torque. However, we were shocked by the numbers produced by the cold-air intakes. We're going to call it a draw between AEM's system and DC Sports. AEM's CAI added a whopping 20.7 hp, 1 horse more than DC Sports. However, DC's system added a statistically similar amount of torque.
ConclusionsYou can't go wrong with any of the systems. All of the new pipes made power, to varying degrees. The short-rams are generally much easier to install, less expensive, and will provide a good dose of horsepower. The cold-air systems are much more difficult to install, but the extra effort is well worth it considering the tremendous power gain. Read the individual tests to see our impressions of each system. Finally, note that the prices listed are MSRP; shop around and you'll be able to find almost all of them for less.