Rimmer Supercharging Systems


Q.  Will the Rimmer Supercharging System fit my 1998 or 199X Impreza/Outback/Legacy, etc.?

A.   Each installation must be tested for hardware and software compatibility before it is released for sale. At this time only the 1999 models have been verified. 1998 vehicles are currently scheduled for installations in our shop and systems for these and other years/models will be released as they are completed, according to demand. California Air Resources Board (CARB) certification testing will be conducted in the near future.

Q.  Do the injectors or the ECU (computer) need to be changed to install the system?

A.  The Rimmer Supercharging System uses the maximum number of original equipment components, including the fuel injection system and engine controls. The factory fuel and ignition timing controls provide adequate adjustment characteristics to accommodate the supercharger installation as supplied in the package.

Q.  Why do you only show dynamometer results for the Forester?

A.  So far we have only been able to acquire chassis dynamometer results from a single pair of drive wheels, because the dynamometers are not set up for Active All-Wheel Drive configurations. We hope to be able to obtain these figures for Subaru AAWD-equipped vehicles in the near future.

Q.  How will installation of the Rimmer Supercharging System affect my Subaru warranty?

A.  An auto manufacturer cannot legally void your new car warranty merely because you have added other equipment to your car. For example, they cannot void an engine warranty unless they can prove that the supercharger was the cause of the problem or failure you are attempting to have repaired under warranty. However, a supercharger is considered "speed equipment" and therefore, you are putting it on your car at your own discretion and liability. (The supercharger unit is warrantied by the manufacturer for three years. The other components of the Rimmer Supercharging System are warrantied by Rimmer Engineering, Inc. for a period of 12 months or 12, 000 miles. Consequential damage, personal or property damage is not covered under this warranty.)

Q.  Does the Rimmer Supercharging System require upgrading of the engine or other parts of the powertrain?

A.  The supercharging system is designed to work with the existing factory powertrain as supplied by the vehicle manufacturer. Your personal driving style or vehicle use profile may make certain upgrades desirable (such as a stronger clutch, which we expect to be able to offer soon as an option) in order to take full advantage of the power and performance increases that become available when the Rimmer Supercharging System is installed.

Q.  How reliable is the supercharger?

A.  The Eaton supercharger has been designed to qualify as original equipment by manufacturers of new vehicles. Because of the very high standards necessary to meet these requirements, the Eaton supercharger has very high reliability. Eaton says, "... strict customer durability test criteria have been achieved. Successful completion of numerous 500 hour durability tests established a firm grasp on achieving a reliable product. In addition, numerous vehicles have successfully completed 100,000 mile, OEM (original equipment manufacturer), vehicle durability tests. Improvements in bearing and seal designs also aided in a product which meets all OEM durability criteria."

Q.  How difficult is it to install the Rimmer Supercharging System?

A.  The mechanical installation process is a true "bolt-on" and does not require any engine internal modifications, welding or fabricating. Typical installation times should be in the three to four hour range for a moderately experienced mechanic, plus see question below.

Q.  Are there any hood clearance problems?

A.  On the low profile vehicles a small opening in the metal hood (bonnet) is required to clear the drive pulley at the front of the blower. For this purpose we include a template to locate the opening, and a sleek, low rise, teardrop-shaped "bubble" fairing which covers the hole and the drive pulley. The finish is glossy carbon-fibre as shipped, but may be painted. Also, the blocking plate below the factory hood scoop on these vehicles must be removed for compressor clearance. Foresters have no hood clearance problems.

Q.  Does the addition of the supercharger require use of premium grade gasoline/petrol?

A.  It is possible to run the vehicle on a lower grade of fuel, but the engine control computer will dial back the ignition advance to eliminate knock (pre-detonation) in order to prevent engine damage. To obtain the designed power potential of the Rimmer Supercharging System, premium fuel should be used.

Q.  What is the effect on fuel economy?

A.  The biggest effect on fuel economy is caused by greatly increased driver enthusiasm. Because the supercharger is equipped with an automatically-actuated bypass valve, loads on the system are drastically reduced during low power demand conditions (such as at cruising speeds or while idling). Eaton Corporation, the supercharger manufacturer, states that "a typical domestic vehicle ... shows no fuel economy penalty for highway driving and only a one mile per gallon penalty for city driving." And that "during typical driving conditions, the engine is under boost around 5% of the time, which means the remaining 95% of the time the engine is under vacuum..." Our experience is that the "grin factor" will result in your engine being under boost more than 5% of the time, so there will probably be some fuel mileage penalty but this will occur mostly under city driving conditions, is usually nominal, and can be adjusted easily by decreasing the driver’s right foot pressure.

Q.  What about "throttle lag"?

A.  The Rimmer Supercharging System uses a mechanically-driven, positive displacement supercharger, which is coupled directly and proportionally to the engine’s crankshaft speed. The bypass valve system, which opens automatically when boost is not needed, also closes immediately when you press the accelerator pedal. Unlike a turbocharged engine, boost is right there when you want or need it...no lag.

Q.  Is an intercooler required?

A.  While desirable from a performance standpoint an "intercooler" (or, more properly, an aftercooler) is not a necessity. The Rimmer Supercharging System is designed and configured to work very well without one. We expect, however, to offer an optional charge air cooling system in the near future, for those who want even more power.

Q.  What comes in the package?

A.  The Rimmer Supercharging System is a complete installation package, except for tools, skill and labor time. It includes the supercharger assembly with bypass valve, belt-drive equipment and accessories, manifolding and plenum components, necessary sealers and gaskets, hoses and clamps, hardware, etc. required to connect the package components to the engine, to each other, and to the factory air filter and inlet system.

Q.  Where is the throttle control valve (throttle body) located?

A.  The original Subaru factory throttle control valve assembly is remounted on the "upstream" side of the compressor, providing air inlet control for the entire supercharging system. This design eliminates the driveability, reliability and safety concerns present in some competitors’ arrangements that place the throttle control on the "downstream", or outlet, side of the supercharger. Combined with the automatically-actuated bypass valve, this configuration results in precise control of power levels.


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