Stewart Warner Performance Catalog - Auto Electric Service, Inc.

Electric vs. Mechanical RFI
Electrical Movement
We often hear, “Should I buy electrical or mechanical
gauges.” There are in fact NO significant performance-related
differences between electrical and mechanical
gauges. Both types of gauges provide features and benefits
which may be useful depending on your application.
The chart below will help determine which type of gauge
would be more appropriate.
ELECTRIC GAUGES
Clean design—No tubing or
bulky connectors and no
danger of fluids entering the
passenger compartment.
Easy installation in cramped or
unusual areas, or if located
farther away from the point of
sensing.
90° sweep.
Mechanical Movement
Safe remote mounting of
sender.
Small temperature sender (e.g.
1/8” NPT).
MECHANICAL GAUGES
Can operate without any
voltage source; not just limited
to 12V (Lighting is the only
part that requires 12V).
Convenient tubing allows for
installation directly to the point
of sensing.
Full 270° sweep for better
resolution (“readability”).
Pressure tubing routed from
cockpit to sensing port.
Large Temperature sensing
bulb (e.g. 1/2" NPT).
114254 114512
Electrical Pressure Gauge
Mechanical Pressure Gauge
www.SW-Performance.com
A tachometer counts how many times your ignition fires
for each revolution of the crankshaft and. Sounds fairly
simple and bullet-proof, right? NOT REALLY! Radio Frequency
Interference (RFI), also referred to as “electrical
noise”, can force your tachometer to give you false readings.
False readings will skew the accuracy of memory tachometer
functions. Stewart Warner Performance Tachometers
are protected from RFI related to racing, although
electrical noise could reach such an excessive level that
the tachometer may see it as legitimate ignition signal and
react accordingly, thus causing an inaccurate readout. So
the question is, “How can I prevent RFI?” Here are some
“rules of thumb”:
1) Be sure there are good electrical grounds throughout
your car, and check to see that: a) your tachometer AND
ignition system both have a good grounds, preferably
at the battery ground post. (The battery acts as a huge
capacitor, sucking up excessive amounts or noise.);
b) the engine block is appropriately grounded to the
battery.
2) Route all tachometer wires as far from ignition system
wires as possible.
3) Use high-quality plug wires, as poor plug wires are a
large source for RFI.
4) Make certain that the spark plug gap is properly set.
5) Check to make sure there is no mismatch of ignition
system and coil—this can also cause excessive RFI.
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