Will the Rimmer Supercharging System fit my 19XX Jeep, or the 258c.i. 4.2
liter Jeep engine?
Systems are applicable to port-fuel-injected (EFI) Jeep engines only; that is generally,
1992 and later four cylinder and 1987 and later six-cylinder engines, although some YJ
Wranglers were equipped with non-port-fuel-injected 4.2 liter six-cylinder engines through
the 1990 model year. Each vehicle model installation must be tested for hardware and
software compatibility before it is released for sale. Most Wrangler, Cherokee and Grand
Cherokee models have been verified. California Air Resources Board (CARB) certification
testing for the four-cylinder and six-cylinder applications is expected in early 1999.
Do the injectors or the ECU (computer) need to be changed to install the system?
The Rimmer Supercharging System uses the maximum number of original
equipment components, including the fuel injection system and electronic engine controls.
Supplementary fueling and spark control (knock sensor) equipment are included in the
system if needed for a particular engine. These modules are designed and programmed to
work with the factory fuel and ignition timing controls, providing adequate adjustment
characteristics to accommodate the supercharger installation as supplied in the package.
Why do you only show dynamometer results beginning at 2,100 RPM?
Our dynamometer tests are conducted on chassis dyno equipment in order to obtain the most
accurate readings of power output in an "as installed" condition. Because of
variables in driver technique between dyno runs, readings at low RPM as acceleration is
first applied are often inconsistent. We use the lowest RPM figure that we can confirm and
compare in both the stock and supercharged conditions, even though positive boost (and the
resulting power increase) is experienced at a lower RPM.
How will installation of the Rimmer Supercharging System affect my new
An auto manufacturer cannot legally void your new vehicle 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 vehicle 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.)
Does the Rimmer Supercharging System require upgrading of the engine or
other parts of the powertrain?
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
How reliable is the supercharger?
The Eaton supercharger has been designed to qualify as original equipment by manufacturers
of new vehicles. Because of the extremely 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."
How difficult is it to install the Rimmer Supercharging System?
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 four to six hour range for a moderately experienced installer.
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 automatically 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.
What is the effect on fuel economy?
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 or heavy off-road driving conditions, is usually nominal, and can be adjusted easily
by decreasing the drivers right foot pressure.
What about "throttle lag"?
The Rimmer Supercharging System uses a mechanically-driven, positive
displacement supercharger, which is coupled directly and proportionally to the
engines 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.
Is an intercooler required?
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.
What comes in the package?
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.
Complete, illustrated installation instructions are provided. Fuel controller and knock
sensor modules are included as required by the particular vehicle application.
Where is the throttle control valve (throttle body) located?
The original Jeep 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 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
What sort of performance improvements can I expect with a Rimmer Supercharging
Results will vary, depending on the driver, the condition of the vehicle, gearing and
other factors. Our test results show an average reduction in 0-60 MPH acceleration times
of approximately 3 seconds for four-cylinder vehicles, and 2 seconds for six-cylinder Jeep
vehicles. You can imagine what effect a 30% increase in torque will have in off-road