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System Operation
Volume 1, 6/16/05
Section 6 - Page 23
The signal is infrared. The sensor saturates in direct or even indirect sunlight. Shadow tubes don't
help. You simply cannot use the device outdoors. The sensor doesn't work well in incandescent
lighting, either. The same frequency that saturates it in sunlight is also present with incandescent
lighting.
Any loss of signal results in erratic behavior. We have found that the system needs several
revolutions of the reflective surface before the signal will stabilize. On slow rotating assemblies,
multiple reflective points can help resolve this issue. When using multiple points, they must be
equally spaced. And the system must know about the multiple points in the channel definition to
properly calculate RPM.
• If possible, use a 1 inch by 1 inch square of the reflective tape to insure no loss of
signal. Observe vehicle movement during the test to see if that is what may be
causing loss of signal (the aiming point is changing).
• Aluminized tape won't work.
• Vibration affects the unit. Sometimes you cannot achieve a good signal when it is
sitting on the dyno chassis or eddy current unit. Move it off the dyno onto a stool, jack
stand, or whatever and you may achieve a stable signal. Bear in mind, that if the
vehicle wheel is severely out of balance, that may be causing you signal loss troubles.
The unit is affected by RFI and just plain noise. We've also had it go crazy when rev limiters are
hit. We suspect it acts as an antenna and couples noise interference into the sensor box
electronics. When this happens, try isolating the cable away from the dyno and moving the unit off
the dyno.
It will work up to about 4-6 feet away from the reflective surface.
6.9.3 Calculated Method
A final method SuperFlow offers to obtain engine speed relies on no pickups at all. Instead, we
derive the engine speed from the dyno roll speed. This is done using the following calculations:
WhRvPm = (Speed/60)*(5280/(TirDia*0.2618))
calculates the wheel revolutions per minute using the roll speed and tire
diameter. The constant 0.2618 equals Pi divided by 12 and is used to
simplify the equation for WinDyn.
EngSpd =WhRvPm*RpmRat
calculates engine speed in a specific transmission gear ratio as a function
of roll speed.
The only requirements for this method to work are to know the vehicle's overall ratio for the
transmission gear chosen to perform the test and to know the tire diameter. The tire diameter
value is entered into channel 84 (TirDia) and the overall ratio is entered into channel 94 (RpmRat).