Every car enthusiast loves the whirl of a turbocharger. That tornado-like sound screaming from under the hood is a drug that most of us cannot get enough of. A rather delicious side dish to turbo spool is the “pfffftttt” sound from a blow off valve. This aural treat is just as addictive as turbo spool. So much so that, I have heard of N/A vehicle owners fitting one onto the piping of their “cold air intake system,” hoping that they could hear that hiss when letting off the throttle. (This usually generates a laugh or two among people I know) But a blow off valve isn’t designed for sheer driving entertainment. Rather, it serves a rather important function that increases turbo performance and life span.

Imagine a turbocharged engine under 20psi (1.5 bar) of boost. Then you let off the throttle to shift or whatever reason. Where does all that compressed air in the intake piping, intercooler and so on go? That compressed air has nowhere to go except back toward the compressor wheel, creating a negative intake charge. You get on the throttle again. Exhaust gases are now spinning the turbine side, thus spinning the compressor side. But you have negative airflow driving the compressor wheel in the WRONG direction. As a result, you have a battle between the positive charge created by the turbine wheel and the negative charge created by the backwards flow of air from the throttle body on. Under certain conditions, this will create damage to the turbo and / or inefficient turbo performance.

A blow off valve is designed to eliminate this problem by “relieving” the trapped intake charge once the throttle is closed. With that excess intake charge gone, the compressor has a “clear path” through which to send in the compressed goodness that the turbo creates. No lag, no compressor surge, no damage to the turbo.

In the case of the HKS Super SQV II blow off valve kit, a couple of issues arose before installation was executed. MAF (mass air flow) sensor-equipped vehicles are particularly sensitive to vent-to-atmosphere blow off valve systems, often creating stalling at idle and stumbling problems under operation. MAP (mass air pressure) sensor-equipped vehicles don’t have this problem, as fuel calculations by the ECU are done based on the intake charge temperature and air pressure levels at the manifold. MAF, however, takes a literal reading of the level of air flow coming in through the intake system so everything after the sensor itself isn’t accounted for.

In stock form, the Evo is equipped with a by-pass valve that connects the upper intake pipe before the throttle body and the intake pipe before the compressor side of the turbo. Any built up intake charge pressure is fed back into the compressor side for quick throttle response and turbo performance. The HKS system eliminates the bypass valve altogether and rather than feeding the excess intake charge back into the system, it dispels it into the atmosphere, creating that awesome sound.

The 4G63 powerplant is indeed a MAF-based system and many Evo owners experienced VTA-related problems. Suspecting that the same type of problem would exist with the HKS Super SQV II kit, I contacted HKS USA to get the scoop on what could be done. Apparently, the VTA-related problem was pervasive in the Evo VIII, but not for the Evo IX. Garrett Wong @ HKS USA assured me that such stumbling problems would not happen with our Project Evo (IX).

Installation was relatively straightforward, but it did necessitate the temporary removal of the battery to make things just a bit easier. Sure, the Pioneer AVIC-N4 multimedia navigation unit did have to be reset and reprogrammed, but it was a small price to pay for ease of installation. Open ended wrenches and socket wrenches of the 8mm, 10mm and 12mm variety are all you need, in addition to some elbow grease obviously. But do make sure to have a snap ring plier handy to fit the Super SQV itself onto the piping fitting.

With that infamous “pfffffft” and swish of the blow off valve letting the world know what’s under the hood, the HKS Super SQV II & piping kit is an attractive and effective solution for any turbocharged vehicle owner.

Sourcebox

HKS USA
13401 S. Main Street
Los Angeles, CA 90061
(310) 491 3300
www.hksusa.com