I know that we all see the same questions over and over concerning CAI's and SRI's. So I will do my best to explain the difference (in laymans terms) between a CAI and an SRI, as well as the difference between different brand CAI's. This is going to be a VERY simplistic explanation, so veterans steer clear...
We are dealing with internal combustion engines. This means that air is mixed with fuel, ignited, causing combustion (duh). There are a few factors that play into how well (or poorly) that combustion is executed.
Number one, the more air the engine has access to in order to mix with fuel, the more energy can be produced. This is also the basic logic behind turbo- and superchargers, but I'll leave that to the REAL tuners on this board (i.e. - not me). But back to the subject. An engine needs oxygen to combust with fuel, which creates the power to turn the wheels. The two main factors at play here are:
1) Volume of air (O2). More air to combust, more power.
2) Temperature of air (O2) Colder air is DENSER (i.e. - more O2 (oxygen) per cubic inch of air) than HOT air, and therefore the engine has even MORE oxygen to combust.
MOST stock intake systems are constructed of a thick plastic, have many bends and turns, use HIGHLY restrictive filters, and pull air from inside the HOT engine bay. Look at your stock Tiburon intake...HORRIBLE. But, Hyundai did this is for two reasons:
1) To keep the engine quieter, as most drivers (not tuners like us
) prefer a quiet ride. CAI's and SRI's make MUCH more noise than stock, as the air is being taken in MUCH faster, and is resonating off of METAL piping. Loud.
2) To keep the engine flood safe (if the vehicle is submerged, it will continue to run). CAI's suck from near the curb. If you run into a deep puddle, your engine will hydrolock and sieze. Not good. Some may talk of "bypass valves", but I really question thier integrity (experiments have shown that, in some circumstances, water can reach the engine bay anyway.)
But these minor pluses come at the expense of a MAJOR minus: POWER. In a perfect situation, our engines would have unlimited access to a LARGE volume of COLD air. This is impossible, but alternative intake systems offer better solutions....
SO...
An SRI (Short Ram Intake) is simply a short piece of metal (or plastic) that comes off the Throttle Body (that piece with the little flap that opens and shuts when you accelerate, i.e. - the "butterfly") and sucks air directly into the intake manifold. This is a BIG improvement over the stock system, as it...
1) eliminates all of the bends and turns of the stock intake, allowing for a greater, unrestricted VOLUME of air (O2) to enter the intake manifold.
2) is also relatively inexpensive and EASY to install. $80 and you're done in most circumstances.
It looks like this:
NOW....
A CAI (Cold Air Intake) is based on the same premise, but takes it one step further.
A CAI is a LONGER piece (or more than one piece) of stainless steel piping that extends from the Intake Manifold (IM) all the way down to a point FAR AWAY from the heat producing engine. This is usually a spot near the curb, infront of the wheels. When your car is traveling at 60 MPH, and the outside temperature is 70 degrees, the temperature of the air hitting your engine will be SIGNIFICANTLY colder than the air inside your HOT engine bay (where your stock intake used to pull air from).
It looks like this:
See how the pipe "disappears" near a spot infront of the front wheel??? That's where it's pulling its air from; near the street, infront of the wheel, where the air is RUSHING past the air filter.
Pro's and Con's to SRI and CAI...
EITHER system will be an improvement over stock. It all depends on what you're looking for, and what your budget is. A good SRI will run about $80. You will see
about 1/3 of the horsepower gains of a CAI, but that 1/3 will be available to you LOW in the RPM band (around 3K RPM). This is because the air doesn't have to travel very far to reach the intake manifold. When you mash the gas pedal, you will see more power. But this power is COMPROMISED as the engine heats up, because the hot air that the SRI is pulling will be progressively LESS DENSE, because the air around the engine will be hotter the longer the engine runs. This is not good for continuous power.
A CAI is more expensive, around $220, depending on brand. This will yield MUCH more horsepower than an SRI, because
the engine is getting COLDER (read DENSER) air and MORE of it). But the air has to travel a farther distance and takes longer to reach the engine. This power is available to you at 5K to 6K RPM). If you are racing, you should be spending most of your race time in the high RPM's anyway. This is why you want a CAI.
DOWN TO THE NITTY GRITTY.
All CAI's are basically the SAME. It is a STAINLESS STEEL pipe with SILICON or RUBBER connectors, that connects your intake manifold to a position infront of your front driver side wheel, where it pulls the air that the engine needs to make power.
1) They all produce about the same horsepower gain (~12-15 WHP, depending on your car and the ambient temperature). Some companies claim more HP than others; this is BUNK. Different test cars, different dynos, different claims, different air temperature conditions. ONE CAI IS NOT SIGNIFICANTLY BETTER THAN THE OTHER.
2) They make slightly different noises when you open the throttle, depending on how the pipe is bent. On each different CAI, the air resonates off the metal piping slightly differently, producing a different sound. But the physics are the same.
So what's the difference???
SOUND AND STYLE. Some like red pipes, some like chrome, some like blue. You may pay more for one color over the other. INJEN makes a different sound than AEM, which makes a different sound than COMPANY X. You pick what you like; you may think it's worth paying extra for one sound over another. Someone else may not think so. If you are going for a "show" engine bay, you may want the fancy powder-coated piping. There are some AWESOME looking intakes out there, and there are some very plain chrome looking ones. They both achieve the same goal.
I hope this helps clear up the SRI vs. CAI issue, as well as the "is Brand X CAI better than Brand Y"...any other questions, feel free to ask em...that's why the forums here!