VR Conditioners
Getting the best crank and cam signals for
your installation
Why do VR sensors need
conditioning?
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Output is not a clean square wave
Signal intensity gets higher as RPM
increases
There is no one size fits all VR conditioner
Why isn't there a one size fits all?
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An aftermarket EMS has to work with a
wide variety of VR sensors
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Different minimum and maximum peak
voltages
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Different signal to noise ratios
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Different wheel patterns
Virtually any aftermarket EMS may need
some help when dealing with a sensor that
is a bit away from “average”
Diagnostic / High Speed Loggers
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Available in MS3, MS2/Extra, MS1/Extra
(no composite logger in MS1/Extra)
Tooth logger displays time between
crankshaft teeth
Composite logger displays oscilloscope-like
graph of crank and cam signals
Trigger logger is post wheel decoder
Tooth logger
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Height of bars represents time between
teeth
Works best for wheel patterns where there
are equally spaced base teeth with gaps 13 teeth long
Suggested for generic wheel decoder with
missing teeth, 36-2-2-2, 36-2+2, 420A,
Rennix, Rover, and similar patterns
Sample tooth log
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60-2 wheel while cranking
Composite logger
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Displays crank and cam signals
Best for spark modes that rely on cam
sensor, or wheels with large gaps between
teeth
Preferred for dual wheel without missing
teeth, Subaru 6/7, 4G63, '99-'05 Miata, GM
7X, and others
Composite logger rows
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Top (green) row – cam sensor
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Middle (blue) row – crank sensor
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Lower (red) row – sync flag
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Pulses where the decoder lost sync are
flagged by vertical lines on lower row
Sample composite log
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36-1 wheel with cam shown
Trigger log
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Shows ignition event triggers after wheel
decoding, in same style as tooth logger
Only shows raw input pulses on modes
with no decoding (fuel only, EDIS, etc)
For modes with wheel decoding, only
useful to diagnose wheel decoder
configuration mistakes (usually in
MS1/Extra)
Common problems: Noise
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Random stray pulses
Common problems: Phantom Tooth
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Consisten issue caused by small noise
pulse in missing tooth range
Two main VR conditioner families in
the MegaSquirt line
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Bowling & Grippo
design
Used on V3.0,
V3.57 main board,
older MicroSquirt
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MAX9926
Used on MS3-Pro,
MicroSquirt V3.0
Adjusting the B&G conditioner
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Conditioner works on current, not voltage
R56 adjusts threshold level that triggers the
conditioner
R52 adjusts hysteresis level
Can also be adjusted by placing a resistor
inline with VR sensor
Common adjustments
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Loss of signal at high RPM:
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Increase threshold voltage (R56)
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Install 10K resistor in line with VR sensor
(usually done with 36-1 or 60-2 trigger
wheels with phantom tooth issue)
MAX9926 conditioner
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Works on voltage, not current
Double ended: compares voltage on + and
– terminals
Ordinarily, negative terminal biased to 2.5
volts
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Signal clipped at 0 to 5 volts
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Adaptive based on peak voltages
Adjusting the MAX9926 circuit
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To deal with noise at high RPM, put a 5K to
10K resistor across the terminals of the
sensor
Triggering threshold can be increased by
running a resistor from negative terminal to
signal ground
Smaller resistor values increase offset, so a
larger resistor is a less drastic change