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VR Conditioners

Getting the best crank and cam signals for your installation. VR Conditioners. 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. Why isn't there a one size fits all?.

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VR Conditioners

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  1. Getting the best crank and cam signals for your installation VR Conditioners

  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, 36-2+2, 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 B&G 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

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