Haltech E6A - Manual (Page 54)

54
5.5.4 On the Dyno
Whether the vehicle is on a chassis dyno, or the engine on an engine dyno, the principles of
programming the Haltech E6A are the same. Take the engine rpm up to 1000 and apply partial
load and adjust the 1000 rpm range. Return the engine to idle and on the 1000 rpm range
adjust the bars to draw a straight line from the idle point through the part load setting tested.
Continue, adding more load, up to the full load settings. This should be a fairly good
approximation to the required curve. Repeat this for the 1500 range, 2000, 2500 etc. The
engine should be fairly drivable at this point.
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. 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.
5.5.5 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 the same 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. 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.
5.5.6 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. On non turbo cars 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 (best mixture)
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. A typical map is shown below. The absolute values
will vary greatly, but the shape should be similar.
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.