Cold air intakes vs. warm air intakes
Many arguments have erupted over which is better, a cold air intake (CAI) or a warm air intake (WAI, also known as short ram or SRI). There isn't an easy answer, and it really comes down to what fits in with your price range and preference.
Cold air intakes have longer tubing, which goes outside of the engine bay to get "cold air" compared to the warm air in the engine bay. Stock intake systems are in fact cold-air intakes, but suffer from poor flow due to many restrictions. Aftermarket cold-air intakes smooth out the airflow and provide excellent performance and sound. The cost of cold-air intakes is usually higher because of the amount of piping required. One downside, due to the longer piping of a CAI, is the delay in throttle reponse compared to a WAI or SRI.
Warm air, or short ram, intakes are much smaller, with a shorter length for the air to flow. As a result, they provide better throttle response and are generally louder than cold air intakes. However, they use air from inside the engine bay which is almost always warmer than a cold-air intake. Some people have experienced temperature differences of up to 30 degrees F, but this can vary depending on speed and your local climate.
Other JBO members have found the best of both worlds, by using a warm air intake coupled with a cold air duct to bring colder air into the engine bay.
The bottom line is... colder air is denser, containing more oxygen molecules, and therefore has the ability to burn more fuel. Exactly how much colder is the key, but without measuring your vehicle you will never know exactly how great or small the temperature difference is.
Other issues you may need to consider... cold air intakes are more susceptible to sucking water into the engine. Hydrolock is bad, no matter how it happens. If you live in an area that floods often, or experiences heavy rain, you may want to evaluate exactly where your air filter is placed or consider using a filter bypass in case of water ingestion.
