VR Conditioners

1
VR Conditioners

• Getting the best crank and cam signals for your
  installation

2
Why do VR sensors need conditioning?

• Output is not a clean square wave
• Signal intensity gets higher as RPM increases
• There is no one size fits all VR conditioner

3
Why isn't there a one size fits all?

• An aftermarket EMS has to work with a wide
  variety of VR sensors
• Different minimum and maximum peak voltages
• Different signal to noise ratios
• Different wheel patterns
• Virtually any aftermarket EMS may need some help
  when dealing with a sensor that is a bit away
  from average

4
Diagnostic / High Speed Loggers

• 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

5
Tooth logger

• Height of bars represents time between teeth
• Works best for wheel patterns where there are
  equally spaced base teeth with gaps 1-3 teeth
  long
• Suggested for generic wheel decoder with missing
  teeth, 36-2-2-2, 36-22, 420A, Rennix, Rover, and
  similar patterns

6
Sample tooth log

• 60-2 wheel while cranking

7
Composite logger

• 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

8
Composite logger rows

• Top (green) row cam sensor
• Middle (blue) row crank sensor
• Lower (red) row sync flag
• Pulses where the decoder lost sync are flagged by
  vertical lines on lower row

9
Sample composite log

• 36-1 wheel with cam shown

10
Trigger log

• 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)

11
Common problems Noise

• Random stray pulses

12
Common problems Phantom Tooth

• Consisten issue caused by small noise pulse in
  missing tooth range

13
Two main VR conditioner families in the
MegaSquirt line

• MAX9926
• Used on MS3-Pro, MicroSquirt V3.0

• Bowling Grippo design
• Used on V3.0, V3.57 main board, older MicroSquirt

14
Adjusting the BG conditioner

• 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

15
Common adjustments

• Loss of signal at high RPM
• Increase threshold voltage (R56)
• Install 10K resistor in line with VR sensor
  (usually done with 36-1 or 60-2 trigger wheels
  with phantom tooth issue)

16
MAX9926 conditioner

• Works on voltage, not current
• Double ended compares voltage on and
  terminals
• Ordinarily, negative terminal biased to 2.5 volts
• Signal clipped at 0 to 5 volts
• Adaptive based on peak voltages

17
Adjusting the MAX9926 circuit

• 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