Have you ever converted your vehicle to run on CNG or LPG? If yes, then you may have already heard about the term timing advance processor. You do not need to be a mechanic to understand everything about TAP.
No matter if you are a mechanic handling fuel conversion or a fleet manager evaluating CNG vehicles, it is good to know how technology works.
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Here is everything that you must know about the timing advance processor, such as:
- What Is a Timing Advance Processor?
- Why Engine Timing Matters?
- How a Timing Advance Processor Works?
- Types of Ignition Systems and TAP Compatibility
- How to Choose the Right Timing Advance Processor?
- CNG vs. LPG: Timing Considerations
- Troubleshooting Common TAP Problems
- The Emergency Bypass Connector
- Benefits of a Properly Tuned Timing Advance Processor
Timing Advance Processor:
A timing advance processor (TAP) works as a small electronic control unit that modifies the engine’s ignition timing when the vehicle runs on alternative fuels like LPG or CNG.
In other words, every engine needs a spark at the right moment to ignite the air-fuel system inside the cylinder. It is called ignition timing.
Ignition timing is measured in degrees. Spot-on timing produces maximum power and efficiency.
When ignition timing is off, you face poor acceleration, wasted fuel, knocking, and rough idling.
Gasoline’s burn rate and factory ignition timing are calibrated precisely for that rate. But LPG and CNG burn differently. Alternative fuels have a slower flame propagation speed.
If you swap fuel without adjusting the ignition timing, then the spark plug will fire at the wrong time. It will cause loss of power, higher fuel consumption, and engine knocking.
This is where you require a timing advance processor.
It fixes the issue by intercepting the ignition signal. It shifts the spark to an earlier point in the combustion chamber. The earlier spark works best with alternative fuel.
It restores efficiency and protects knock damage.
Why Engine Ignition Timing Matters?
Ignition time is not just a performance variable. It represents the overall health of your car engine.
- Too early: Over-advanced or too early ignition time means that the fuel-air mixture ignites when the piston is still rising. It creates pressure against piston movement. This causes pining or knocking. It can cause damage to cylinder walls, pistons, and bearings.
- Too late: Retarded timing means the combustion happens when the piston is going downward. It causes a drop in power output, less fuel economy, and a rise in exhaust temperature.
- Just right: When combustion pressure peaks at the right time to push the piston down with maximum force. It helps the engine to run smoothly, cleanly, and efficiently.
When you switch between main fuel and alternative fuel or gasoline and CNG or LPG, the optimal timing window changes.
The job of the timing advance processor is to automatically shift the timing within ideal parameters.
How a Timing Advance Processor Works?
The timing advance processor works between the signal source and the ignition coil. It reads the timing signal, apply programmed offset, and output modified signal to trigger the spark at the best time.
Here are the core features of timing advanced processors:
- Select-able advance degrees: Technicians can fix how much advance to add. It can be between 0° and 30 °.
- Idle exclusion: Advanced is disabled at idle time to prevent rough idling. During low RPM, time sensitivity is higher. Most timing advanced processors bypass the advance correction during the idle phase.
- Petrol mode reset: When your car is running on gasoline, the timing advanced processor returns ignition timing to factory specs.
- Emergency bypass connector: If timing advanced processor fails or malfunctions, the emergency connector allows the ignition system to work in bypass mode.
Note: Advanced timing advanced processors also include vehicle-specific plug-and-play wiring harnesses. It allows easy installation without cutting or splicing into the original electrical system.
Types of Ignition Systems and Timing Advanced Processors Compatibility:
You must understand that different ignition systems work differently. The wrong timing advanced processor will not work for your ignition system.
Mechanical Breaker Point Systems:
Vehicles manufactured before the 1980s used a mechanical breaker point system. In that system, the ignition system uses contact points inside the distributor to trigger sparks. The advance mechanism controls the ignition timing.
The AEB531 is the go-to timing advanced processor for such vehicles. It connects the distributor’s negative terminal with the ignition coil’s negative terminal. This way, it intercepts the low-voltage signal from the breaker points. Its timing range is between 0–25°. It is compatible with LPG and CNG.
Electronic Ignition with Coil and Distributor:
Vehicles manufactured between the 1980s and 1990s used electronic ignitions. They also use the distributor to route the spark. It has eliminated the need for contact breaker points.
The AEB526N and AEB549N work best for those vehicles. They provide ignition timing advance between the range of 0–20°.
Electronic Systems with Ignition Modules:
After the 1990s, electronic systems started using ignition modules. They adjust the ignition timing based on load and engine speed.
The AEB515N is the best timing-advanced processor for such vehicles. Its adjustable timing parameter suits many engines and fuel types.
Crankshaft Position Sensor (CKP) Systems:
Modern engines eliminated the need for distributors. They use a crankshaft position sensor. It provides the engine control unit with precise timing data on the rotation of the crankshaft.
There are two types of Crankshaft Position Sensors:
- Inductive sensors: They generate an analog voltage signal. The most compatible timing advance processors are AEB510N and AEB516N.
- Hall effect sensors: They produce a clean digital square wave signal. The most compatible timing advance processors are AEB511N and AEB518N.
Crankshaft Position Sensor offers an ignition timing range between 0 and 30°.
Timing Advance Processor Selection
| Model | Ignition System | CKP Sensor Type | Fuel Types | Timing Range | Emergency Connector |
|---|---|---|---|---|---|
| AEB531 | Mechanical breaker points | N/A | CNG, LPG | 0–25° | Yes |
| AEB526N | Electronic with distributor | N/A | CNG, LPG | 0–20° | Yes |
| AEB549N | Electronic with distributor | N/A | CNG, LPG | 0–20° | Yes |
| AEB515N | Electronic with module | N/A | CNG, LPG | Programmable | Yes |
| AEB510N | CKP sensor | Inductive | CNG, LPG | 0–30° | Yes |
| AEB516N | CKP sensor | Inductive | CNG, LPG | 0–30° | Yes |
| AEB511N | CKP sensor | Hall effect | CNG, LPG | 0–30° | Yes |
| AEB518N | CKP sensor | Hall effect | CNG, LPG | 0–30° | Yes |
How to Choose the Right Timing Advance Processor?
Here are the steps to choose the best timing advance processor:
Identify Your Ignition System Type:
It is best to find out your vehicle’s ignition system type. Take the help of the service manual or check online for the vehicle’s year, make, and model.
Find out:
- Does your vehicle use breaker points or electronic ignitions?
- Does your vehicle have a distributor, or does it use a CKP sensor?
- If CKP: is the sensor inductive or Hall effect?
Confirm Your Fuel Type:
Most timing advance processors support both LPG and CNG. Yet, it is best to find out if your system is optimized to use one or the other.
Confirm fuel source before purchasing the TAP.
Determine Required Timing Range:
Different models and fuel combinations need different advanced amounts. CNG requires more advances than LPG.
Ask your conversion technician or the alternative fuel system manufacturer.
Check for Harness Compatibility:
Does your timing advance processor come with plug-and-play harnesses for specific vehicle models or make? Is it available for your vehicle? What is the extra cost?
Verify Emergency Bypass Availability:
Check if the timing advance processor has an emergency bypass connector or not. Make sure that your advanced TAP has a bypass connector.
How to Install Timing advance processor?
Only hire an expert technician to perform the installation.
Here is the overview of the process:
- Disconnect the battery
- Identify connection points
- Wire the TAP inline according to the manufacturer's wiring diagram
- Set the initial advance using the adjustment controls
- Test at idle and across the RPM range
- Fine-tune based on performance
CNG vs. LPG: Timing Considerations
Both CNG and LPG behave differently from gasoline.
CNG (Compressed Natural Gas)
- Higher octane rating
- Slower flame propagation speed
- Very clean combustion
- 10–15° more advance
LPG (Liquefied Petroleum Gas / Propane)
- Octane rating similar to premium gasoline
- Slightly faster burn than CNG
- Different vaporization properties
- 5–10° more advance
These details help your installer dial the best advance settings.
Troubleshooting Common TAP Problems
| Symptom | Likely Cause | Fix |
|---|---|---|
| Engine knock on CNG/LPG | Insufficient timing advance | Increase advance setting |
| Poor acceleration | Excessive timing advance | Reduce advance setting |
| Engine won't start | Wiring error or bad connection | Check all connections per wiring diagram |
| Rough idle on gas | Advance not excluded at idle | Check/adjust idle exclusion setting |
| No advance effect | Power or ground issue | Verify 12V supply and ground |
| Check engine light after install | CKP signal interference | Use oscilloscope to check signal integrity |
The Emergency Bypass Connector:
The emergency bypass connector is a must to keep the system secure.
If the timing advance processor malfunctions, then the emergency bypass connector allows the ignition system to function without TAP.
- The vehicle returns to factory ignition timing
- The engine can still run on CNG or LPG
- You can drive to a shop rather
Commercial and fleet vehicles often have an emergency bypass connector.
Benefits of a Properly Tuned Timing Advance Processor:
Here are the notable benefits of a timing advance processor:
- Better fuel economy: Optimized timing advance processor improves energy extracted from each unit of fuel. Users report 5–10% improvements in fuel economy.
- Restored power output: CNG and LPG conversions suffer a 10–15% power loss without timing adjustment.
- Reduced engine knock: Proper advance eliminates the knocking.
- Lower emissions: It produces fewer unburned hydrocarbons and less carbon monoxide.
- Longer engine life: It eliminates the knock and incomplete combustion and reduces accelerated wear.
Conclusion:
The timing advance processor is the most important part of vehicles with alternative fuel. It improves CNG or LPG conversion. Without TAP, you are burning alternative fuel with gasoline timing, which causes lower power and unnecessary stress on the engine.
Choose the right timing advance processor after understanding the vehicle’s ignition system. It is a must to use timing advance processors when planning a CNG or LPG conversion.
FAQs:
What is the timing to advance the processor?
It is a device that sets the ignition timing and reduces the stress on the engine.
Do I need a timing advance processor if my car has a modern ECU?
A dedicated timing advance processor is always the best choice, even if your vehicle comes with a self-adjustment for alternative fuels.
Can I install a timing advance processor myself?
No. It is best to hire an expert for LPG or CNG conversions.
How often should a timing advance processor be recalibrated?
There is no fixed interval. It is best to verify timing after significant work.
Will a timing advance processor void my warranty?
In the US, manufacturers cannot void the warranty just because aftermarket parts are installed.
Is a timing advance processor the same for CNG and LPG?
Yes, but with different settings. CNG requires more advances than LPG.
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