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LS tuning glossary
Plain-English definitions for the terms you'll run into.
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- 24x / 58x
- 24x (Gen III: LS1, LS6, LQ4, LQ9, Vortec trucks through 2006) uses a 1x cam sensor; 58x (Gen IV: LS3, LS7, L76, L92, 2007+ Vortec trucks, and the 58x LS2s: 2006–07 Corvette and CTS-V, 2007–09 TrailBlazer SS, 2008–09 Saab 9-7x Aero) uses a 4x cam sensor. Exception: the 2005 Corvette, 2005–06 GTO and SSR and 2006 TrailBlazer SS LS2s are 24x, so they need a 24x harness and computer. PCM, harness and sensors must match; a Gen III PCM on a 58x engine needs a conversion box. More →
- AFM / DOD
- AFM (introduced 2005 in Tahoe-class SUVs) deactivates both valves on four cylinders using oil-pressure-controlled lifters fed by the LOMA/VLOM valley-cover manifold. More →
- Drive-by-wire (DBW)
- Drive-by-cable: throttle opened mechanically (early Gen III trucks, Camaro LS1). Drive-by-wire: PCM opens the throttle from a pedal-position sensor (all Gen IV). A DBW swap needs the pedal wired and calibrated. (Check your exact application: the C5 Corvette LS1 was drive-by-wire while the F-body LS1 was cable.) More →
- PCM / ECM
- The PCM reads crank, cam, MAF, coolant, IAT and O2 sensors to control fuel, spark and idle (and shifts on automatics); on drive-by-wire engines it also controls the throttle. More →
- Standalone harness
- A standalone harness keeps only the circuits the engine needs to run, removing body-specific donor wiring. More →
- VATS
- GM's anti-theft system. In a swap, it has to be deleted in the tune or the engine won't start. More →
- Stall speed
- How far the engine can rev with the brakes locked and the transmission in gear before the wheels turn; it rates a torque converter. More →
- Line pressure
- The transmission's hydraulic pressure. On a 4L60E the computer controls it, along with shift timing. More →
- TV cable vs kickdown cable
- A kickdown cable just forces a downshift at wide-open throttle. A TV (throttle valve) cable, used on transmissions like the 700R4, controls shifting and must be adjusted precisely. More →
- Torque model
- Part of the factory calibration that an aftermarket cam requires changing, along with idle, fuel and spark. More →
- Self-learning EFI
- Standalone systems that adjust fuel and timing from real-world driving, like Holley's Terminator X. More →