Haltech E6X Manual DOS Version - Manual (Page 72)

E6X Manual
72
CHAPTER 8 COLD STARTING AND RUNNING
The ECU has four features to correct fuel delivery and ignition timing to aid in starting and
running a cold engine. The cold start prime map gives a cold engine an initial burst of fuel
just as the engine begins cranking, the coolant correction map modifies the normal fuel
injection until the engine reaches normal operating temperatures. The ignition-cranking map
sets the crank advance for different coolant temperatures and the ignition coolant map corrects
the ignition advance from the Ignition Map for different coolant temperatures.
8.1 Cold Cranking
At cranking speeds the air speed at the inlet manifold is very low. This combined with the
low temperature results in much of fuel that would normally travel in the air sticking to the
manifold walls and consequently it doesn't enter the engine. The cylinder chamber
temperatures are also low which leads to poor combustion. To overcome these inefficiencies,
it is necessary to prime the engine with a long pulse of the injectors at the start of cranking to
ensure that the engine has enough fuel in the cylinder to fire.
The ECU provides a cold start fuel prime that is adjustable across coolant temperature. This
allows the duration of the prime pulse to be optimised for cold cranking under a wide variety
of conditions. Over priming the engine will cause it to flood and not start. To clear a flooded
engine, open the throttle fully and continuously crank the engine. Do not pump the throttle, as
this will only worsen the problem.
The ignition timing can also be set for cold cranking. As with the Cold Prime Map, the Crank
Ignition Map sets the ignition timing to be used while cranking according to the coolant
temperature. This Map is set flat to 15° at factory, but it can be adjusted to give better starting
at all temperatures.
8.2 Fuel Correction Versus Coolant Temperature
Once started, an engine requires more fuel when it is cold than when it is hot. This is a result
of low manifold and in-cylinder temperatures where fuel sticks to the walls and doesn't burn
properly. The ECU corrects for this by using the fuel coolant map to determine extra fuel
required based on the coolant temperature. The ECU will automatically reduce the amount of
coolant correction applied to the engine as the throttle is opened and air speed increases. The
fuel coolant map should not be adjusted until the base fuel maps are correctly tuned at
operating temperature.
The fuel coolant map should be tuned during the engine warm-up. Start the cold engine and
adjust the fuel coolant map by following the map pointer and adjusting the bars of the map
that the ECU is using to obtain a smooth idle. Do not touch the throttle while adjusting this
map. The coolant correction map should be at zero for normal engine operating temperatures.