Dawes Valve

The Dawes Valve allows Manual Boost Control (rather than ECU solenoid control) of boost levels. It eliminates the boost spikes (often observed over 25psi) in all ZD30 engines.

Exhaust Gas Temperatures (EGT) are reduced due to a predictable, controlled boost. It is the excessively high boost that leads the ECU to over-fuel the combustion mixture – which ultimately manifests itself in engine failures – due to the excessively high combustion temperatures that are common in the ZD30. Once the Dawes Valve is fitted, it is impossible for the ECU over boost/Over fuel to occur.

As per Fitting Diagram, the extra tee piece is for Boost Gauge fitting (optional).
Weld a spigot (8mm) into the intercooler pipe, fit hose provided from this spigot to the Dawes Valve (largest pipe fitting)
Remove vacuum supply to the OE solenoids, fit to the Dawes Valve – either of the small ends. Cut OE hose to suit. Retain the green plastic damper in the line.
Connect the last of the small hose fittings to the turbo actuator, using OE hosing.
Set the boost by adjusting the spring tension (turn the body of the valve), then use lock nut to secure at the desired setting.
Upper limit suggested be no more than 18psi, 14 to 16psi preferential.
Now it’s impossible for the engine to boost over the manual setting.

Other useful modifications for the ZD30
3″ larger exhaust (more torque lower in RPM as turbo spools up earlier, improves fuel economy)
Unifilter air cleaner element – more airflow with less contaminates (washable)
Snorkel air intake – more power and economy with less contaminates
Power or Performance Chip – 20%+ increase in Power and Torque
Catch Can and EGR Block off plate