In the previous post, I talked about the mandatory mods that needed to be added to the car in order to support any future modifications safely. Once the HPFP has upgraded internals and you have acquired the tuner device of your choice (Cobb Accessport or Versatuner), you can begin adding parts to your car!
One of the first modifications that owners add to the engine is replacing the stock turbo inlet pipe (which is sometimes referred to as TIP) with either a silicone turbo inlet hose (TIH) or an aluminum TIP. Other options include a short ram intake (SRI) and a cold air intake (CAI), which replaces the stock airbox. Aftermarket SRI’s and CAI’s come with a conical air filter and an aluminum mass air flow (MAF) sensor housing that replaces the airbox.
Most of the aftermarket intakes I will be talking about in this article will be of the 2.5″ pipe variety. The pipe diameter remains constant throughout the entire system all the way to the turbo inlet, where there is a coupler that will neck down from the 2.5″ diameter of the TIP/TIH to the 2.0″ diameter inlet on the stock k04 turbo. The MAF housings that come with the 2.5″ intakes are the same circumference as the MAF housing in the stock airbox lid (which is 2.63″ if you were wondering) so they will not require a tune to use.
There are aftermarket intakes that are 3″ and larger that have been shown to flow more air and increase turbo efficiency, but for the purpose of this article I decided to stick to just the 2.5″. Using one of the larger intakes will require a tune as the MAF housings are larger than stock and the increased airflow numbers will be incorrect for the stock ECU tuning, which can result in a car that will not run properly.
Now, I know I just threw a bunch of terms and acronyms at you, and you are probably wondering if this is still a beginner’s guide! Fear not, intrepid reader! I will go into detail about the various parts that make up the intake system from the turbo inlet to the air filter for both stock and aftermarket systems and it will all make sense by the end of this article.
The Stock Setup
The stock intake setup is comprised of three pieces. The turbo inlet pipe, the intake hose, and the airbox. When Mazda designed the system, their goal was not all out performance, but a system that would flow enough to support their stock horsepower goal and to keep engine noise as low as possible. While they succeeded in doing both, they also did a really good job of choking down and restricting the performance of the engine, as there isn’t enough air flow to support a higher state of tune.
If you are going to be tuning for performance, the first thing you are going to have to do is make sure that the turbo and engine are getting the air they require. The stock system is restrictive and features two bottlenecks that need to be replaced to allow the engine to breathe.
Turbo Inlet Pipe
The stock turbo inlet pipe is made of plastic. The largest end is connected to the turbo inlet by a rubber coupler (1), a small vacuum port (2) that is connected to the electronic boost control solenoid (EBCS), the outlet to the airbox (3), and the outlet (4) that runs to the recirculator/bypass valve.
This piece is very restrictive as it does not maintain the circumference of the turbo inlet all the way through the pipe and is one of the bigger bottlenecks in the intake setup. .
The stock airbox sits in front of the battery on the driver’s side of the car. It has a connection for the intake hose from the TIP and the Mass Air Flow (MAF) sensor housing on the lid. From the size of the airbox, you would think that it would flow a lot of air! But it is actually very restrictive.
See that tube that is on the side of the airbox? That is what the engine has to breathe through. The air inlet for the airbox is close to half the size of the turbo inlet! The stock airbox is designed more so to reduce induction noise (the reason why you can’t hear the turbo spool up on a stock Mazdaspeed 3) and meet fuel economy targets than to deliver all-out performance.
With the stock restrictive system in place, it is surprising that the car performs as well as it does. Good thing that there is performance to be unlocked with a few bolt-on parts!
The Performance Upgrades
Silicone Turbo Inlet Hose
Silicone Turbo Inlet Hoses (TIH) are constructed of multiple layers of silicone and reinforcement material with a wire skeleton to prevent collapse under vacuum (so they don’t collapse under high turbo spooling situations). They usually come with a set of metal couplers with bead rolled edges that help to secure connections for the intake and recirculator valve hoses. Prices range from $55.00 – $227.00 (I have seen some TIH’s on E-bay for $55 – buyer beware and do your homework – to $227 for a CP-e 4″ Nviscid TIH that you will not need unless you go big turbo) and can be had in a multitude of colors. As you can see in the picture, the silicone TIH removes the bottleneck of the stock TIP and is a more free flowing design. The benefit for the turbo is that airflow is increased, which helps with spool up, which should begin around 2500 rpm or when you hear the induction roar/hiss.
That’s right, you can hear it! YAY for turbo noises!
Aluminum Turbo Inlet Pipe
Another option is an aluminum Turbo Inlet Pipe (TIP), like the one in the image above from Corksport. This aluminum pipe has some of the same characteristics of the silicone pipe, but is lighter in weight and is about the same price-wise, the Corksport TIP is $129.99. The pipe doesn’t neck down in any areas and is mandrel bent to maintain the same diameter throughout. Induction roar/hiss is slightly louder with the TIP over the TIH, so if that is an issue (What?! You don’t like the spool sound? Everybody loves the spool sound!!!) you may want to keep that in mind. Another item to note is that this pipe is aluminum, which may have some issues with heat soak (it is a debate that is neither yes or no) but since the air is going into a hot turbo, I think that it really doesn’t matter. We will save Intake Air Temperatures (IAT’s) and Boost Air Temperatures (BAT’s) for another discussion.
The Turbo Inlet Pipe is but one part of the intake system and what I consider to be one of the bottlenecks of the stock setup. Once the TIP has been upgraded, you will need to move on to the next bottleneck, which is going to be the stock airbox. Now that you have increased the airflow to the turbo inlet you are going to want to feed as much air as you can to it. To do that you are going to want to upgrade to what is known as a Short Ram Intake.
Short Ram Intake
The Short Ram Intake (SRI) replaces the factory intake hose and the airbox. Most kits will include a silicone inlet hose (this connects the SRI to the TIH/TIP), a new aluminum MAF housing (most of these come with air straighteners to improve flow and accurate MAF readings), a high flow filter, and clamps. Prices range from $170.00 – $341.00 (K&N) and can be had in multiple colors.
The SRI is the more commonly seen intake on a lot of Mazdaspeeds, as they take up less space than a CAI (I will explain in a minute). SRI’s due to their design can run into issues with higher intake temps due to the hotter under hood temperatures of a turbocharged car, but this can be mitigated by isolating the filter from the rest of the car with a heat shield made from aluminum.
Cold Air Intake
Cold Air Intakes (CAI) are basically the TIP, the MAF housing, and an extra tube that extends down lower to the splash pan of the car. The benefit of the CAI over the SRI is that the filter is down lower in the engine compartment where it has the chance to pull in colder air. Cold air is more dense than hot air. The more dense the air is, the more fuel you can pack into it. The more fuel you pack into the air, the bigger bang you get when the spark ignites it, and the bigger the bang, the more power you make.
Those are the upsides. Yes, there are downsides.
CAI’s, since they sit lower in the engine bay, can sometimes inhale water (if you for some reason aren’t running a splash pan or get stuck in a flooded area) that is bad juju for any engine. The main drawback to running a CAI on a Mazdaspeed 3 is that if you upgrade to a front mounted intercooler (FMIC, we will talk about these in another article), you will not have the space to run the intercooler piping AND have the CAI. The cooler intake temps may have some benefit, but the gains from using the FMIC outweigh anything that the CAI can provide. From a cost standpoint, the CAI is more expensive than the SRI ($30.00 – $120.00 more, depending on manufacturer), so keep that in mind if you decide to go this route.
The Best Choice for the Money
The best choice is whatever works for your build and your budget. I would highly recommend replacing the TIP at least to get you started, as that will allow the turbo to ingest more air, increase turbo and throttle response, as well as letting you experience the glorious noise of turbo induction/spool!
But What About Stage I, II, III..etc?
I get asked this a lot and I will tell you, it is just a marketing gimmick! Once you do the homework, you will see that all that upgrade stage nonsense is just buzz words to impress. Let me decipher the marketing speak and help you out:
- Stage 1 = Short Ram Intake. Basically this replaces the stock airbox.
- Stage 2 = Short Ram Intake with a Turbo Inlet Pipe/Hose. Replaces the airbox and the stock TIP.
- Stage 3 = Cold Air Intake.
Now, with that said, there are deals to be had here. Take for instance a silicone TIP may cost $165.00, so you buy that first. Later on, you pick up the SRI for $170.00. Total cost is $335.00 if you buy them separately at different times, unless you find them on sale.
But, if you buy the stage 2 setup from that same manufacturer, you get the SRI and the TIP and it costs you $250.00! You just saved yourself $85.00! That’s money that can be used for more parts! It pays to do the homework!
In a Nutshell
I hope this article helped explain why the stock intake system is a good place to start improving the engine’s performance. There are some slight gains to be made with installing one on its own, but there will be bigger gains later as this modification will help support the ones to come!
I will post some links to a couple of blog posts I read to help in your research.
Until next time!
Aftermarket Intake Manufacturers
AEM Induction Systems – http://www.aemintakes.com
ATP Turbo – http://www.atpturbo.com
Cobb Tuning – http://www.cobbtuning.com
Competition Engineering Performance (cp-e) – http://www.cp-e.com
Corksport Performance – http://www.corksport.com
HKS – http://www.hks-power-co.jp
HPS Performance Products – http://www.hpsperformancesystems.com
Injen Technology – http://www.injen.com
James Barone Racing – http://www.jamesbaroneracing.com
K&N Filters – http://www.knfilters.com
SURE Motorsports – http://www.suremotorsports.com