The forum is quiet, so I have had time to do more research on what makes the engine tick, makes the ECU replacement project that I am undertaking easier to understand.
This thread is about the spark plug that has a tale as old as time, how it impacts on the ignition system and engine combustion.
There are many claims about performance improvements just by purchasing what appears to be a high end replacement spark plug. The basic three types of spark plugs are copper, platinum, and iridium. These can be further broken out. Platinum can be single or double platinum, iridium - single or double.
What spark plug do you need. The best source for this information is the owner's manual. The OEM has the engine tuned for a specific spark plug type. Older motorcycles such as the GW 1200/1100/1000 models use a standard copper spark plug and the ignition system is designed to use these specifically. This is not to say that premium platinum or iridium plugs will not work just as well; however, most of us will not notice an engine performance improvement with a well tuned engine.
What affects spark plug longevity? There are not a lot as follows:
Fouling with oil or fuel
Carbon deposits
Erosion and wear
Cracking due to vibration or physical damage
Spark plugs should be replaced according to the maintenance guide in your owner’s manual. Using the recommended OEM recommendation, a new set of plugs every year is a small price to pay for peace of mind riding.
What happens in the engine cylinder? The cylinder goes through the four stages of the four stroke cycle. The stages we are concerned with are the compression and power strokes.
When the intake valve closes and the cylinder stroke changes from the intake to compression stroke, and the piston starts to travel up the cylinder to TDC, the cylinder volume decrease and cylinder pressure increase. When the cylinder reaches the required ignition timing BTDC, the ECU triggers an ignition event and the coil charge is discharged through the spark plug. For example, using an ignition timing of 30 degrees BTDC, the combustion process is started. At an ignition timing of approximately 20 degrees BTDC, the air-fuel mixture starts to burn more rapidly causing the cylinder pressure to be greater than if there was ignition. It has taken 10 degrees of prank position to generate this pressure level, known as the ignition-delay period.
The air-fuel combustion progresses rapidly past this point such that the peak cylinder pressure (PCP) occurs between 10 and 20 degrees ATDC. The combustion process is 100% completed by about 20-25 degrees ATDC. Just like engine power, peaks than drops off. The 1200 GW engine reaches its peak HP at approximately 5500 RPM then levels off and decreases a bit up to max engine RPM.
The venerable spark plug can be expose to cylinder temperatures of up to 5000 degrees F, and pressures from 300 to 2500 PSI depending on the engine.
Engine knock and detonation is when the ignition event is started too early, and the PCP occurs before TDC and results in reduced engine power and performance.
If the ignition event is started too late, engine power and performance suffer as well.
This topic has a lot of information available to correlate and post, and as such will be doing several posts regarding this topic. This is the first.
I will end the first post with my usual disclaimer. I am not the author of this information, just reporting on it. It is also mostly for my edification, but I hope that others who may follow this thread will find it informative and a good read.
Cheers
This thread is about the spark plug that has a tale as old as time, how it impacts on the ignition system and engine combustion.
There are many claims about performance improvements just by purchasing what appears to be a high end replacement spark plug. The basic three types of spark plugs are copper, platinum, and iridium. These can be further broken out. Platinum can be single or double platinum, iridium - single or double.
What spark plug do you need. The best source for this information is the owner's manual. The OEM has the engine tuned for a specific spark plug type. Older motorcycles such as the GW 1200/1100/1000 models use a standard copper spark plug and the ignition system is designed to use these specifically. This is not to say that premium platinum or iridium plugs will not work just as well; however, most of us will not notice an engine performance improvement with a well tuned engine.
What affects spark plug longevity? There are not a lot as follows:
Fouling with oil or fuel
Carbon deposits
Erosion and wear
Cracking due to vibration or physical damage
Spark plugs should be replaced according to the maintenance guide in your owner’s manual. Using the recommended OEM recommendation, a new set of plugs every year is a small price to pay for peace of mind riding.
What happens in the engine cylinder? The cylinder goes through the four stages of the four stroke cycle. The stages we are concerned with are the compression and power strokes.
When the intake valve closes and the cylinder stroke changes from the intake to compression stroke, and the piston starts to travel up the cylinder to TDC, the cylinder volume decrease and cylinder pressure increase. When the cylinder reaches the required ignition timing BTDC, the ECU triggers an ignition event and the coil charge is discharged through the spark plug. For example, using an ignition timing of 30 degrees BTDC, the combustion process is started. At an ignition timing of approximately 20 degrees BTDC, the air-fuel mixture starts to burn more rapidly causing the cylinder pressure to be greater than if there was ignition. It has taken 10 degrees of prank position to generate this pressure level, known as the ignition-delay period.
The air-fuel combustion progresses rapidly past this point such that the peak cylinder pressure (PCP) occurs between 10 and 20 degrees ATDC. The combustion process is 100% completed by about 20-25 degrees ATDC. Just like engine power, peaks than drops off. The 1200 GW engine reaches its peak HP at approximately 5500 RPM then levels off and decreases a bit up to max engine RPM.
The venerable spark plug can be expose to cylinder temperatures of up to 5000 degrees F, and pressures from 300 to 2500 PSI depending on the engine.
Engine knock and detonation is when the ignition event is started too early, and the PCP occurs before TDC and results in reduced engine power and performance.
If the ignition event is started too late, engine power and performance suffer as well.
This topic has a lot of information available to correlate and post, and as such will be doing several posts regarding this topic. This is the first.
I will end the first post with my usual disclaimer. I am not the author of this information, just reporting on it. It is also mostly for my edification, but I hope that others who may follow this thread will find it informative and a good read.
Cheers
