AMS Reviews the HKS Rotrex Supercharger Kit
Installed on an Automatic Nissan 350Z
About HKS Rotrex Nissan 350Z Supercharger Kit
The 350Z Rotrex supercharger by HKS adds approximately 70-80 additional horsepower at the wheels over stock. The kit utilizes a self-contained, closed oil circulation system to lubricate the centrifugal-type supercharger. The traction drive uses fixed ratio planetary rollers that are more efficient than traditional gears used by other kit manufacturers. Because the planetary rollers do not have teeth like traditional gears, noise is decreased and reliability increased. The closed oil circulation system cycles a specially-formulated Traction Oil that lubricates and cools the supercharger, dramatically increasing longevity and reliability. The Traction Oil is cooled through an air to fluid oil cooler hidden behind the front bumper. Amazingly, the oil has to be changed very infrequently, up to 600,000 miles, and comes with an easy to check reservoir which also tucks away behind the front bumper with a dipstick neatly hidden by the radiator shroud.
A small front-mounted intercooler allows the air charge to cool down before being forced into the engine. The fitment is good and the appearance is very unobtrusive, barely noticeable. The HKS Rotrex kit arrives with everything you need to bolt the kit on and drive, including 2 auxiliary fuel injectors and a full piggy-back fuel controller.
We’ve installed a variety of supercharger kits at Atlantic Motorsports, however the HKS Rotrex is by far one of the best looking, most complete , and best performing kits to date. It comes with every piece of hardware you need to install the supercharger and the fuel management controller. It is a well-built, well-designed, complete forced induction solution.
Difference between HKS Rotrex Kit & ATI Procharger, Vortech Type Kits
Rotrex kits are not readily upgradeable to produce more boost than the preset 7 psi. You can’t cost-efficiently upgrade the Rotrex kit to make more power. Unlike the Vortech-type kits, you cannot upgrade the pulleys to run more boost, the Rotrex is only good for producing the power that it was designed to run. Vortech / ATI Procharger type kits can be upgraded easily to run higher boost levels and produce more power, AS LONG AS THE ENGINE CAN HANDLE THE ADDED BOOST. Another drawback to the Rotrex is its price – it is significantly more expensive than the Vortech kit. So why would anyone choose an HKS Rotrex?
The answer is simple – great quality parts, outstanding fuel management solution, great drivability and performance. The Rotrex is a perfect kit for anyone who wants a well-designed complete bolt-on supercharger kit that adds safe power to the 350Z.
The Rotrex kit utilizes dual 525cc fuel injectors installed in the intake plenum. The additional fuel injectors are controlled by a piggy-back ECU unit which plugs into the stock wiring harness. HKS completes the fuel system upgrade with a standard high-volume fuel pump which replaces the stock unit. The Rotrex fuel system upgrade is unique and very efficient. Unlike the HKS Rotrex the ATI / Vortech kits arrive with the standard fuel pressure riser, a bunch of additional fuel lines and the EFMU (Electronic Fuel Management Unit) and an auxiliary inline fuel pump. In the case of the ATI Procharger the way it works is simple – the EFMU picks up a vacuum signal, as soon as boost is detected it activates the in-line fuel pump and forces immense amounts of fuel to the stock injectors. The EFMU has slider-knobs that can be used to “tune” the fuel mixture. Such a fuel system works and it works well – however the Rotrex offers a much more sophisticated and technically advanced fuel / tuning solution.
Moving onto parts quality – the Rotrex pulley panel matches the stock color and material, the quality is slightly higher than Vortech / ATI’s; this piece is actually cast rather than machined. The HKS Rotrex air filter and intercooler piping fit perfectly without modifications needing to be made. In the case of ATI Procharger, the piping was cumbersome, fit rather poorly and took a lot of work to fit nicely. The ATI uses an air filter tucked away behind the front bumper and inside one of the intercooler pipes – the design is a bit awkward. The ATI blow off valve is another poorly designed piece - it leaks boost, does not seal the piping properly. The HKS Rotrex comes with a very simple, yet efficient blow-off valve.
Overall, the HKS Rotrex is a better engineered, well put-together complete supercharger kit; where as the Vortech / ATI type kits are a bit cruder in their design and component functionality. However, the Vortech / ATI type kits have the potential to make a lot more power than the Rotrex.
Driving Impressions
First things first - how does the Rotrex sound? The HKS Rotrex, because of its unique traction drive and the centrifugal design, is extremely quiet. Unlike other supercharger systems, the idle is very steady and silent, the pulleys / rollers make little to no additional noise or squeaks, nor does the supercharger produce a typical whine. You would not be able to tell that the vehicle is supercharged sitting next to a Rotrex’d 350Z at an intersection. Once the throttle is applied, the only noise you hear is the whooshing of air, there is still very little supercharger whine. The system is very stealthy – perfect for a daily driven Nissan Z. The ATI Procharger and Vortech produce a loud, very apparent supercharger whine which is noticeable at both idle and acceleration.
The HKS Rotrex driving performance is unsurpassed! The power is extremely linear and readily available. The system complements the Z motor greatly – acceleration is very smooth and torque is available all throughout the RPM range. The bottom line is that the Rotrex kit performs very well – it does what is advertised, while be very smooth and quiet.
The HKS Rotrex is designed to be the complete forced-induction solution for someone who wants to run moderate boost, maintain full drivability, and use the highest quality parts available.
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