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Dawes Setup Dual or Single

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For anyone wishing to fit and tune a Dawes valve system. The following shows an in cab needle setup and single or dual Dawes valves.

Single Dawes setup with early model vacuum surge canister, the tank is not really needed and often one of the barbs will break off so bypassing is OK, if you don't have one (around 2002/2003 it was deleted anyway) just go straight to the vacuum take off point under the IC


This is the dual dawes setup, the same info as above applies to the surge canister, the solenoid that controls which dawes is selected is setup to default to the high boost side if the solenoid fails, this could be handy when doing a lot of towing


This is the standard setup for ecu control of vacuum to the VNT through the ECU


This is the bypassed vacuum switch giving more linear control of the VNT vac hence better boost control


My personally prefered position for the boost take off point, easy access and easily protected


Internal view of the fitting in the IC inlet pipe showing a smooth transfer


External finished view of boost take off point


Boost line from take off point is 4mm ID, the gauge usually has 3mm OD (1mm ID) tube, so a 3mm quick fit coupling was adapted to a 1/8th BSP barb fitting to make the transfer of size before the 3mm tube went through the firewall, The 3mm tube was pushed inside 6mm airline which made a protective shield before passing into the firewall


Vacuum damper relocated as schematic


Dual or single Dawes secured inside a rubber shield and cabled to the loom on the passenger side


Location of needle valve in the cab, this hole exists and only needs opening a little, the needle valve has been fitted with 90 degree 1/8th BSP fittings for ease of tube attachment


Fabricated a steel bracket to hold the dual Dawes solenoid to an existing threaded hole in the firewall


Location of dual Dawes solenoid control switch beside driving light switch, picked up power from the cigarette lighter


Dual Dawes solenoid and Dawes overview


Dual Dawes Solenoid and Tube overview


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  • 7 years later...

Could you please indicates suitable values for the two boost pressures settings on the individual Dawes valves?

My 2002 GU Y61 has already “hand grenaded” and been rebuilt with EGR blanked off, catch can fitted, needle valve and single Dawes (giving 14 psi boost) in place, and an electric Boost Controller Switch and second Dawes valve supplied.  The mod.s are working well and I would now like to fit and use the second Dawes valve, hence the question regarding recommended pressure settings.

The vehicle is running 33” x 16” tyres, a 50mm suspension raise and spring/shock absorber upgrade with a 3” exhaust and front winch/bar replacement.  It is used mostly for off-roads and also a bit of camper trailer towing (about 1500 kg).

I have read quite a bit of yours and others output about this “interesting” engine with great attention, but have not come across much in the way of definitive guide lines on these pressure values involved.

Many thanks for your continuing interest and output and I look forward to your reply.  




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The above is now pretty much just as historical info. Most of us have moved on onto next level which is basically re-mapped engine ECU making Dawes valve and similar as such redundant. The reason for Dawes valve or Timid valve are still valid though in case the factory ECU map is used.

I run combo Dawes with Tilix  valve because I have retained the dual boost control setup I had before going full re-map. GU2 has reinstalled factory boost control since the re-map fixes the short comings of the factory setup (limp mode due to overboost etc.)

I have retained manual overide so I can force low boost ( set to 14 psi)on  Dawes valve for economy or high boost setting ( 24 psi) on Tilix valve for mx power output and auto switching based on TPS percentage via voltage switch.  Before re-map high boost was set to 18 psi due to factory induced limits.


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  • 4 years later...

Sorry to comment on an old post, but I’ve been searching for 3 days for a wiring diagram how I can wire up the solenoid for a dual setup! The very few out there dont have much detail! I don’t want to go chopping into tps and lock up wiring without being sure! Any help appreciated! 

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If you need to run dual Dawes setup you'll need to check old Chaz's posts where he uses excellent examples of all the possible setups.

I will need to dig in to my old .... actually its still on his site ==>  http://chaz.yellowfoot.org/Manual Boost Controller.htm


There are various ways you could set it up, use voltage controller/switch to set tps voltage at which it will trigger however good luck finding one out.  jaycar don't seem to sell those anymore.  if you are after which wire to hack in to from TPS for signal you will need to tell us which model is your Patrol....first.

Edited by Rumcajs
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