Learn About your LTG - Ignition
If fuel is the heart of the LTG and the turbo is its lungs, then the ignition system is its brain firing the neurons — delivering the spark that turns compressed air and fuel into controlled explosions. Without precise spark timing, you don’t get power; you get misfires, knock, or worse, a damaged engine.
The LTG’s ignition system is fully electronic and designed to fire high-energy sparks at exactly the right moment in each cylinder’s cycle, under all conditions — from cold starts in winter to high-boost pulls on E85.
1. The Main Components of the LTG Ignition System
1. Crankshaft Position Sensor (CKP)
Works with a reluctor wheel on the crankshaft to tell the ECM exactly where the crank is in its rotation.
Provides critical RPM and position data so the ECM knows when each piston is at top dead center (TDC).
2. Camshaft Position Sensors (CMP)
One sensor per camshaft (intake and exhaust).
Lets the ECM know camshaft positions relative to the crankshaft — essential for accurate cylinder identification and timing fuel injection events.
3. Knock Sensor (KS)
Bolted to the engine block to detect abnormal vibrations from knock (detonation).
Sends signals to the ECM so it can instantly pull timing when knock is detected, protecting the engine under high load or poor fuel quality.
4. Ignition Coils (Coil-On-Plug Design)
Each cylinder has its own dedicated coil.
Controlled individually by the ECM, they generate the high voltage (often 20kV+) needed to fire across the spark plug gap.
5. Engine Control Module (ECM)
The command center — takes all sensor data (MAF, throttle, temps, CKP, CMP, KS, etc.) and calculates the exact timing to fire each spark.
Continuously adjusts spark advance for max power, efficiency, and emissions compliance.
2. How the LTG Ignition System Works
Position Sensing – CKP tells the ECM the crankshaft’s position and speed, while CMP sensors confirm cam positions.
Timing Calculation – ECM uses airflow, load, throttle position, and temperature data to determine when the spark should occur (spark advance).
Spark Delivery – ECM sends signals to the correct ignition coil, charging and firing it at the exact moment needed for peak cylinder pressure.
Knock Feedback – If the knock sensor detects detonation, the ECM retards timing until knock disappears, then gradually advances it again for performance.
3. Why Spark Timing is Everything
In a turbocharged direct-injection engine like the LTG, spark timing determines:
Power output – More advance (to a point) means more torque and horsepower.
Fuel efficiency – Correct timing burns more of the air/fuel mixture, reducing waste.
Engine life – Too much advance under boost causes knock; too little and you lose power and run hotter exhaust temps.
4. Modding and Maintenance Tips for DIYers
Spark Plug Selection: For stock or mild tunes, factory iridium plugs work well. For high boost or E85, drop 1–2 heat ranges colder to prevent pre-ignition.
Gap Adjustment: LTG coils are strong, but higher boost can blow out the spark. Close the gap slightly (e.g., 0.026–0.028") if misfires occur under load.
Sensor Health: CKP and CMP sensors rarely fail, but if they do, expect misfires, no-start, or erratic idle. Keep connections clean and free of oil.
Knock Sensor Sensitivity: Overly stiff engine mounts or excessive engine noise from mods can trigger false knock — address before pulling power in the tune.
Coil Maintenance: Swap coils between cylinders during diagnostics to quickly confirm a bad coil.
5. Diagnostics and Fail-Safes
The ECM runs constant checks on ignition components:
CKP/CMP Errors: ECM can enter “limp mode” if a sensor fails.
Knock Control: Aggressively pulls timing during abnormal combustion to prevent piston damage.
Misfire Detection: Logs which cylinder misfired and when — essential for troubleshooting.
