Both the Street and Competition series of the IAG Air Oil Separator are designed to replace most all of the hoses and components of your PCV system, but there are a couple of key differences between the two. We wanted to go into a bit of detail about those differences so that you will have the information that you need to pick the right one for your application.


In the case of the IAG Street Series AOS, the kit removes all the stock hoses from your engine and replaces them with the AOS tank and the hoses that come in the kit. The important detail for this kit is that your stock PCV valve is retained, and the Air Oil Separator tank is connected back to the turbo inlet hose just as the factory PCV system is. In other words, the Street Series AOS just puts the IAG tank into a slightly modified version of the stock plumbing.

IAG Street Series AOS


Because the street kit is connecting the crank case to the inlet side of the engine, just as with the factory PCV system, any leaks or bad connections those will be creating a vacuum leak for the engine which can cause running issues, etc.


The advantage of the Street AOS is that because it retains the same connections and intent as the factory plumbing, you can install the Street AOS without needing to tune the car for it. Also, because the IAG Street AOS retains the PCV valve, and is connected to the turbo inlet, it can use the vacuum generated from each of those sources to actively scavenge any gasses or pressure from the crank case through the Air Oil Separator tank.


In the case of the IAG Competition Series AOS, it has nearly the exact same connections leading to the AOS tank, but the key difference is that once any gasses or pressure gets to the tank, it is then send through a large, 1” diameter hose that is routed under the car and to atmosphere.

IAG Competition Series AOS


Because the Competition Air Oil Separator tank is not connected back to the inlet side of the engine, all of those fittings must be plugged to prevent leaks, and the factory PCV valve must be removed.


The advantage of the Competition AOS kit is that it has a very large fitting to release any pressure that might build in the crank case. In addition, because the plumbing of the AOS/PCV system are completely separated from the air inlet of the engine, you now don’t have to worry about any leaks of the PCV system causing an air metering issue with the engine. But it is also worth noting that there is then no active scavenging of the crankcase to relieve pressure. For that reason, this type of AOS is ideally suited for high power and high boost builds.


Because any gasses that would normally be caught by the PCV system and sent back through the engine are released to the atmosphere, the Competition Series AOS is only for race cars, and for off road use only. For the same reason, you cannot install this type of Air Oil Separator without tuning for it because this does make a difference to the amount of useable air that is going into the air.


In short, if you have a car that is close to stock, or moderately modified, the IAG Street Series AOS is most likely ideal for your car. But if you have a highly modified race car, then the IAG Competition Series AOS would most likely be the best fit.

- Jon Cooley