C H A P T E R 5
Connecting the RPM Pickup
Above Ground Model 250i Motorcycle Dynamometer Installation Guide
5-4
CONNECTING THE RPM PICKUP
Your Dynojet dynamometer includes two primary wire inductive pickups and a
secondary wire inductive pickup. These small “clothespin like” inductive pickups are
used to sense RPM. An RPM pickup is required if you want to view torque graphs.
Generally, you will use one secondary wire inductive pickup on a spark plug wire.
Vehicles with wasted spark ignition systems may require two secondary inductive
pickups. On a wasted spark ignition, typically one coil will be connected to two spark
plug wires. Attach one secondary pickup to each of these wires. If the pickups are
connected to two plug wires that do not fire at the same time, an erratic RPM readout
may occur. The primary wire inductive pickup senses RPM pulses from the coil.
Although this pickup location generally works better, it is harder to find the correct
location to connect the RPM pickup.
Note:
If a pickup is not being used, disconnect it from the dyno electronics to
prevent any stray pick up of signals.
Inductive pickups are very fragile. The ferrite core can easily be damaged
and is not covered under warranty. Dropping, snapping, vibration, and
heat can all damage the ferrite core.
The DynoWare RT contains the electronics that sense the RPM pulses. An auto-gain
circuit looks at only the peak voltage of the vehicle’s spark, ignoring the lower voltages
to help reduce electronic noise problems. Wasted spark ignition systems will produce
a lower voltage level on the exhaust stroke than the compression stroke. By definition
of the auto-gain circuit, lower voltage spark levels will be ignored, missing every other
spark the vehicle would produce.
You will need the following parts:
RPM P
ICKUP
D
ESCRIPTIONS
part
description
part
description
inductive primary
pickup (2)
P/N 76950201
inductive secondary
pickup (2)
P/N 76950203
RPM pickup
description
Secondaries (Non-wasted spark system)
Use one secondary pickup. Unplug the other pickup from the RPM
module and set the degrees between plug fires to 720° in Power
Core.
Secondaries (Wasted spark ignition
system)
Use two secondary pickups. Attach one pickup on each spark plug
wire on the same coil and set the degrees between plug fires to 360°
in Power Core.
Primary pickup
Attach the primary wire pickup to the primary side of the coil. Set
the degrees between plug fires by taking 720/number of cylinders.
For example, the number of degrees between plug fires on a V-8
engine with a single coil is 720/8=90 degrees.
