No worries, so here's my view on it (I'm sure other people may have other views/inputs to add):
The stock air intake system comprises of four main components; airbox, intake hose, intake elbow and a turbo muffler. (This is the order the air passes through the system)
- Airbox - channels the air through the front of the car, and via the air filter. There's a few mods that can be done to the stock air box to improve and increase air flow, such as removing the snow grate and opening up both sides of the air duct (only the left hand side is open normally). The stock system also allows air to flow through to the engine bay, reducing the amount of air going to the filter.
- Intake Hose - This channels the filtered air from the airbox through to the turbo via the elbow and turbo muffler. The stock hose is grooved/bumpy to disrupt the air flow to minimise the noise.
- Intake Elbow - This is essentially a 90 degree hose that connects from the intake hose to the turbo muffler. The stock elbow reduces in size as it joins to the elbow, again to disrupt the air flow to minimise the noise.
- Turbo Muffler - this is a part that 'muffles' more of the noise of the air flow, whilst allowing some of the air to escape through some cut aways before it gets to the turbo. This also reduces in size before getting to the turbo.
Essentially the stock air flow is designed to keep the noises down for 'driver comfort' - Not quite what you want when buying a performance car in my opinion.
The good news is, there are a few products available to maximise air flow, but this does increase the air flow and turbo noise. Which I'm sure everyone wants and loves! I can only speak for the Racingline products, but I'm sure someone will jump in with other product
reviews.
The Racingline R600 is a direct replacement for the stock airbox. It draws air in from both the left and right side of the front grill, and blocks off air going through to the engine bay. This way, all air into the air duct is filtered to the turbo. The air filter for the R600 is a huge dome filter, rather than the traditional flat panel filter. The air box that the filter sits in is smooth and larger in size, allowing for greater and smoother air flow.
The intake hose upgrades are made from silicone traditionally, and are smoother inside the hose to prevent disruption to the air flow, and they dont compress during hard suction which would reduce the air flow like the stock hose.
The elbow upgrades are the same as the hose really - these are usually made from metal rather than silicone, and provide a smoother air flow, and don't reduce in size to keep the air flow at it's maximum. Some intake hoses actually include the elbow, I'm not too sure on the implications/benefits of a seperate elbow and hose over a single hose with the elbow.
The muffler delete essentially 'deletes' the muffler (as the name suggests). It replaces to the stock turbo muffler with a part that doesn't reduce in size, and doesn't allow any air to escape before hitting the turbo.
Hopefully that all makes sense - the aim of the upgrades is to ensure that the maximum air flow is delivered to the turbo, but in doing this you do generate more air suction noise, and turbo spooling noise. Boost is generated quicker,
lower down the rev range.
Now, to add something else into the mix, we have the stock diverter valve which sits at the top of the turbo, above the air inake. The stock diverter valve is designed to recirculate air back into the turbo, helping the boost and trying to be more econmical with the air. Something like the GFB DV+ is an upgrade to the to this which just provides more noise during hard accelleration, and then a 'woosh' type noise when letting off the accellerator. It's deisnged to
help hold boost for longer, whilst provding boost a bit sooner. It is a recirculation valve, rather than a blow off valve (BOV). A blow off valve dumps the air into the atmosphere, and this is what provides a loud release of air which some people like. Forge sell BOV for these engines.
GBF have gone one step further with their product DVX, which can be changed between a diverter valve or a blow off valve. It has a slider which controls the airflow and essentially the noise. So you can have it set to 50% and it'll be 50/50 of a diverter valve and blow off valve.
