Manual

42
If the engin e misfires and blows black smoke then the mixture is rich and the bars n eed to be
lowered. If the en gine will not fire or fires but will not continue to run then the mixture cou ld
be lean and the bars need to be increased.
5.3.1 Tuning for Idle
The idle mixture is very sensitive to correct bar height. Idle injection times are usually around
1.5 to 2.5 ms. If the injection time at idle is much lower than this, it may become difficult to
set accurate idle and cruise air:fu el ratios.
If the engine is hunting at idle, then the map is probably too lean, particularly at the 500 rpm
point. Watch the movement of the map arrow carefully. The map arrow should remain stable
while the engine is idling. If the arrow is moving excessively in a M AP based system, then it
may be necessary to use the Zero Throttle M ap.
Remember that the F10 interpolates against both rpm and load. If the engine is idling at 800
rpm, then the injection time is computed as 60% of the value from the 1000 rpm range, and
40% of the value from the 500 rpm range, so both ranges would have to be adjusted to get the
correct mixture. Similarly, if the idle mixture is reacting poorly to changes of the bar indicated
by the map p ointer, then try adjusting the adjacent bars. Wait for the engine to heat to
operating temperature before performing further changes to maps.
5.3.2 Tuning with No Load
Using the throttle only, increase the engine speed to 1000 rpm. If the engine is at exactly 1000
rpm then only that range needs to be adjusted. Adjust for the crispest engine response.
Engines will usually idle rich, then head towards stoichiometric mixture at higher sp eeds.
Repeat for 1500, 2000, 2500, 3000 etc. The engine should now start and fast-idle evenly. You
should also have the engine running at operating temperature before going further. Go to the
Engine Data Page at this p oint and check all the sensor inp uts are reading corr ectly , and that
the temperatures have stabilised before continuin g.
While free-revvin g at higher en gin e speeds, check the Engine Rp m readin g on the computer.
If it becomes erratic, or fails to follow the actual engine sp eed correctly , check the section in
Chapter 1 on setting the trigger. Also make sure that the information in the Set-up pages is
correct.
5.3.3 Loading the Engine
Once the engine has been tuned properly for no load conditions it is possible to begin loading
the engine. The best method of applying load to the engine is using a dynamometer. However,
if access to a dyno is not possible the engine can be tuned on the road.