How do I choose the right intake system for my project car?

Getting a new project car is exciting but where do you start… the intake is a great place to start for several reasons; low cost ($150 - $500), high impact (5 – 20 hp gains), easy on the motor. So the next question is what intake should you get? Well this question will come back like many other questions you will face during your project with, “For what purpose are you building your car?” So now is the time to think, why are you building your vehicle; is it for rally, drag racing, circuit… All projects should start with the question, what is the purpose of this build. As this article is intended to cover how to choose the right intake upgrade for your project we are going to move forward to descriptions of the main two types of intake systems and there benefits.

Cold Air Intake

The cold air intake is a great option for quick performance gains. A cold air intake replaces the stock intake tubing and filter while moving the filter to a location that offers cooler surrounding air i.e. away from radiant heat generated by the motor. The move of the intake often places the filter insider the fender or behind the bumper cover. The location of the filter, while reducing intake temperature creates some problems; difficulty installing, filters get dirtied more quickly, and an increased risk of hydrolock. Hydrolock is not a problem in most cases and has a workaround, let’s first take a look at what hydrolock is. Hydrolock is when the motor ingests water through the intake; this in turn causes the motor to stop functioning due to inability to ignite fuel. The main way to avoid this of course would be to not drive through deep standing water but when this is not possible (like in the Dallas Texas aria where I live) a bypass valve can be used. A bypass valve functions by allowing air to flow through the bypass valve that is located further up the intake in the case where the intake is fully submerged in water. It is important to note that not all cold air intakes are susceptible to hydrolock; here is an example of the aFe Power intake on my 370z.

 Nissan 370z Cold Air Intake aFe Power

As you can see the intake is positioned in front of the engine where cold air is available, it is also positioned high enough to where it should never be submerged, if it is your problems are much bigger than hydrolock. This is not the case however with all designs, local climate and the use of a bypass valve should be considered in the decision making process.

While these risks can cause problems in some environments the benefits generally outweigh the drawbacks. Here are the main benefits and drawbacks:

Benefits

  • Greatest power gains
  • Greatest torque gains

Drawbacks

  • Difficult to install and maintain
  • Higher cost
  • Increased risk of hydrolock

Short Ram Intake

The short ram intake is the quicker, easier to install and often cheaper option when it comes to intake upgrades. While this option does not generally produce as much of a power gain as a cold air intake it often feels just as powerful in that low end power (throttle response) is more drastically affected. A short ram intake also offers a more drastic sound improvement than a cold air intake due to its shortened length. All of these benefits are not without drawbacks, the short ram intake is susceptible to heat soak. Heat soak is caused by hot components of the engine bay rising temperatures to dangerous levels. A short ram intake can contribute to this by feeding hot air into the engine causing tis temperature to rise above reliable temperature levels. Note this is not a normal problem to see in naturally aspirated engines and many short ram intake kits offer a heat shield to help eliminate this problem. Here is a picture of a kit for the Honda K24 that comes with a heat shield.

Honda K24 Short Ram Intake

As an overview here are the general benefits and drawbacks of a short ram intake:

Benefits

  • Lower priced option
  • Easier installation and maintain
  • Better throttle response
  • Lower fuel consumption
  • Louder (if this is what you want)

Drawbacks

  • Lower power gains
  • Lower torque gains
  • Possible heat soak problems

Over all the decision is not necessary an easy one but your main deciding factors should be; budget, performance goals, application and personal technical skill. To make the best decision review the manufacturers dyno graphs and CFM improvement information. Also if you plan on later adding a supercharger or turbocharger to your setup I would recommend to not replace the factory intake as this well likely be replaced again with your turbo or supercharger kit. Always remember do the research first to spend less and get more.