Haltech E8 - Manual (Page 108)

Haltech E11/E8 Instruction Manual
The wastegate of a turbo is operated when the manifold pressure acting on the diaphragm within the
wastegate actuator overcomes the return spring allowing exhaust gas to bypass the turbine. With
electronic boost control, the object is to use a pulsating solenoid to bleed off the manifold pressure signal
seen by the waste gate unit so that it can see only a fraction of the manifold pressure. The solenoid
operates at constant frequency and the duty cycle is altered to control the drop in pressure signal through
the device.
The turbo wastegate map allows boost to be increased over the standard boost that the turbo and
wastegate combination provides. The turbo wastegate solenoid will only activate when it sees positive
manifold pressure.
To setup the wastegate map, it will be necessary to iterate through several trial and error runs to ensure
safe boost conditions. Use the following steps as a guide to setting up your Turbo Wastegate map:
Always start with small duty cycle settings and increase until the desired boost level is reached. Start with
a flat map (same duty at all loads and speeds) at low duty settings and drive the car noting any increase in
boost level. Watch you’re A/F ratios very carefully when increasing boost for the first time as this part of
the map will not have been tested if this engine has not been mapped at this boost level.
You can setup a flat map easily by selecting all bars then using ‘v’ to set a fixed value. Then use copy and
paste to copy this range to all other ranges to achieve the flat map shape. Make sure you run the engine
at the engine load and RPM at which maximum boost is typically reached.
Increase the duty of all the bars of the map and test-drive the engine once more. Again, make sure that
your fuel maps are adjusted to ensure safe A/F ratios at every step. Repeat until the desired maximum
boost is reached and not the duty cycle of the bars.
Now that you have set the maximum boost to the desired boost pressure, you can increase the duty cycle
at all engine speeds and loads at which the boost pressure is below the desired maximum boost. This will
help the engine reach its desired boost pressure quicker. This will alter the fuel requirements at these
engine loads and speeds so watch you A/F ratios carefully and adjust your fuel maps to compensate if
required.
Closed Loop Boost Control
Closed loop boost control is a method of controlling boost where the difference between the target boost
level and the current boost level is taken as an input to the controller and used to adjust the output, the
duty cycle of the solenoid, accordingly. An advantage of closed loop boost control is it is more resilient
to outside factors not part of the controller like air temperature making this form of control more
consistent than the wastegate map.
Page: 108 Copyright © Haltech 2008
WARNING
Adjusting the boost levels for a turbo engine can alter its fuel requirements
drastically. If the fuel requirements are not tuned simultaneously with changes in
boost characteristics, engine damage could result. To avoid engine damage, watch
your Air/Fuel ratios very carefully when increasing boost. Also check that your fuel
system will be capable of delivering the required fuel for the increase in boost.