Continued
IGNITION TIMING:
(Wikipedia Definition)
Ignition timing, in a spark ignition internal combustion engine, is the process of setting the time that a spark will occur in the combustion chamber (during the power stroke) relative to piston position and crankshaft angular velocity.
Setting the correct ignition timing is crucial in the performance of an engine. The ignition timing affects many variables including engine longevity, fuel economy, and engine power. Modern engines that are controlled by an engine control unit use a computer to control the timing throughout the engine's RPM range. Older engines that use mechanical spark distributors rely on inertia (by using rotating weights and springs) and manifold vacuum in order to set the ignition timing throughout the engine's RPM range. There are many factors that influence ignition timing. These include which type of ignition system is used, engine speed and load, which components are used in the ignition system, and the settings of the ignition system components. Usually, any major engine changes or upgrades will require a change to the ignition timing settings of the engine.
RULE OF THUMB:
A good rule of thumb to follow when taking a naturally aspirated vehicle into the realm of boost when it comes to timing is to retard the timing initially to safe yourself from experiencing knock/deto. Typically a globally accepted value of timing retard for boost is:
For every 1psi of boost added take away 1.5 degrees of timing. Keep in mind this amount of timing retard may vary (increase or decrease per PSI) depending on the motors starting compression. On the V6 motor of 10:2:1 compression I would recommend using 2 degrees retard per PSI of boost, 9 : 5 : 1 or 9:2:1 use 1.5 degrees of retard for each PSI of boost and 8’s and below use 1 degree.
This rule of thumb is in no way gonna make the most power initially but it will generally run you motor safely while you dial in your AFR. Once you target afr is met. Begin dialing up the Timing advance a degree or two until you are not making anymore noticeable power or u begin to hear or feel ping/knock/deto then retard it 2 degrees and you should be good.
WEATHER CONDITIONS: (WOT Air Fuel Tuning)
Anyone who assumes that the tunes can be left alone once they have been set is sadly mistaken. An overnight change in weather conditions may prevent an engine from running or may put it at risk of some damage if adjustments aren’t made to the fuel-mixture settings. While its highly uncommon, but has happened to not have a car start due to cold weather and etc. it can happen. Ignoring an engine’s tuning needs compromises its ability to make horsepower and at time can lead to detrimental engine damage. In response to certain changes in weather, equipment and other variables, engines must be regularly retuned, or at the minimum have a couple different tunes for different weather and driving conditions.
Temperature:
Hot weather requires a leaner mixture setting; cold weather requires a richer setting. Most people assume the opposite because they treat the mixture adjustments like a thermostat.
IE- the temperture goes up, you add more fuel, the temperture goes down, you take away fuel. It is wrong to assume that colder weather requires a leaner setting to keep heat in the engine and vice versa.
Cold air is denser than hot air. The denser, colder air packs more oxygen into the engine, so going from hot weather to cold needs a commensurate increase of fuel to balance ratio of fuel-burning oxygen and the fuel itself. The opposite is true in hotter weather. Going from cold to hot weather requires a leaner mixture setting.
Humidity:
Humidity is the amount of moisture (water vapor) in the air. Moisture in the air takes up volume that would otherwise be occupied by fuel-burning oxygen. Less oxygen means less fuel is required to maintain a proper ratio of air and fuel. High humidity requires a leaner mixture setting than dry conditions.
Barometric pressure:
A barometer measures the atmospheric pressure (generally listed in the local newspaper or on the local weather forecast on TV). Higher barometric pressure readings mean more air is getting into the engine, requiring a richer mixture setting to balance the air/fuel ratio.
Altitude:
Altitude is an important factor that most of us ignore, yet it affects the engine’s performance possibly more than any other element. The general formula for power loss with increases in altitude is 3 percent for every 1,000 feet above sea level. If you race in Colorado at 5,000 feet instead of in California at sea level, you can expect to lose about 15 percent of the engine’s potential power output, if the engine is tuned properly.
Air is thinner at higher altitudes, which means there’s less fuel-burning oxygen than at sea level. You might sense a common theme here: less air (oxygen) means less fuel to maintain the proper air/fuel ratio. So, running at higher altitudes requires a leaner mixture setting than running at sea level.
[center]This chart indicates the direction in which you should adjust the fuel mixture when faced with changing weather and other conditions. It assumes the engine is currently well tuned. You could face any combination of conditions listed in the chart; knowing which way to go with the mixture adjustments is half the battle.
Higher air temperature Lean
Lower air temperature Rich
Higher humidity Lean
Lower humidity Rich
Higher barometric pressure Rich
Lower barometric pressure Lean
Higher altitude Lean
Lower altitude Rich
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