7 fine tuning the engine – Haltech E6X Manual DOS Version User Manual
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E6X Manual
69
Full load tuning should be approached with caution. An engine at full load that is too lean
may begin to detonate and destroy pistons and crankshafts. Before loading the engine,
increase the heights of the right-most bars so that they are higher than the line projected by
drawing a straight line from the idle and free-rev settings and through the part-load settings.
WARNING:
RUN THE MAP RICH, AND LEAN IT TO THE CORRECT
MIXTURES. DO NOT RUN THE MAP LEAN AND ATTEMPT TO
ENRICH TO THE CORRECT MIXTURES.
6.5.6.2 On the Road
Tuning on the road is similar to tuning on the dynamometer, but with hills, acceleration, gear
ratios and brakes providing the necessary retarding force. Although it is harder to maintain
constant load and speed, it is still possible to use a similar procedure used on the dyno. It will
be necessary to have one person drive while another does the tuning.
Load the engine by selecting an appropriate gear and either driving up a constant grade hill,
applying the brake or handbrake.
WARNING:
BE VERY CAREFUL USING THE BRAKE TO LOAD THE ENGINE.
THE BRAKES CAN GET VERY HOT AND SUFFER FROM BRAKE
FADE (REDUCED BRAKING CAPABILITY) AND THE CARS
HANDLING MAY BECOME UNSTABLE. ALL ROAD TESTING
SHOULD BE DONE AT LOW SPEED.
6.5.7 Fine Tuning the Engine
When fine-tuning the engine for the road, the same principles apply to all engines. Under full
load at all rpm the fuel mixture should be rich. Naturally aspirated engines an air to fuel ratio
of around 12.5:1 to 13.5:1 is usually best (high performance turbo vehicles may go as low as
10.5). When cruising (light to medium load) the mixture should be as close to stoichiometric
(14.7:1 AFR) as possible and decelerating conditions may allow the engine to be run lean to
save fuel. This will result in a particular shape for the map.
Note: All maps for all engines should be smooth. A map with a "lumpy" curve
is most likely wrong. If, when you have finished tuning, the map does have
lumps in it; try to make it visually smooth.