Dual Dawes report

[Dr Gary]

About two years ago I installed a dual dawes setup-first with a TPS switch and electronic control, then with a simple "high/low" manual switch. I ran 10 psi low and 17 psi high. Logic was to save on fuel with low boost when puttering around.
Watching fuel consumption over two years I have discovered there is virtually no fuel saving, EGTs are similar, and the GU certainly runs better on the higher boost.
Final outcome--I removed the low boost dawes and now run a single system.
BTW, anyone needing a dawes valve should PM me.

[threedogs]

When I first heard of this dual dawes set up I always had my
doubts on how by lowering boost you could acheive better economy.
I can now sleep soundly without tossing and turning.
Im sure you'll be able to sell your "low boost Dawes valve" to a member lol

Placebo until you do the math lol

[BigRAWesty]

Thats very interesting.. So do you think is a lot more to do with style of driving more than amount of boost??
also pm on its way

[mudski]

About two years ago I installed a dual dawes setup-first with a TPS switch and electronic control, then with a simple "high/low" manual switch. I ran 10 psi low and 17 psi high. Logic was to save on fuel with low boost when puttering around.
Watching fuel consumption over two years I have discovered there is virtually no fuel saving, EGTs are similar, and the GU certainly runs better on the higher boost.
Final outcome--I removed the low boost dawes and now run a single system.
BTW, anyone needing a dawes valve should PM me.

Thats been my exact thoughts for a long time about the dual setup. WOFTAM.
Lower max boost just equates to higher egtscand thats a big no no especially for the di motors. So whats the point hey.

[Dr Gary]

Thats very interesting.. So do you think is a lot more to do with style of driving more than amount of boost??
also pm on its way

Nope! I drove the same with either setting.
Just does not seem to make a (good) difference.

[Sprock]

Unless I'm missing something here , isn't low boost at cruising speeds the basis for the 'grenade' problems ? So in theory wouldn't this setup amplify the problem Dawes & needle valves are put on for - increase boost at cruising speeds to avoid the computer over fueling the engine & melting Pistons ?


2002 GU wagon 3.0lt , auto , piranha dual batteries , 3" lift , chip , needle & Dawes valves - just gettin started

[mudski]

Unless I'm missing something here , isn't low boost at cruising speeds the basis for the 'grenade' problems ? So in theory wouldn't this setup amplify the problem Dawes & needle valves are put on for - increase boost at cruising speeds to avoid the computer over fueling the engine & melting Pistons ?


2002 GU wagon 3.0lt , auto , piranha dual batteries , 3" lift , chip , needle & Dawes valves - just gettin started

There's many theories Adam. Thats my theory as now three motors i have seen, all suffered the same fate, all went the same way. Cruising. The third one did notice his boost was under 10psi when it went too. No egt though....

[Dr Gary]

The Dawes valve is to limit boost the whatever maximum you set. It has zero effect until it hits that maximum. The needle valve replaces the computer control for VNT (turbo) and helps with spool up rates.
My EGT was pretty much the same with either setting, just less "puff" when needed.
I did once hit 500 c, but that was with high boost, pulling a heavy camper and a long, steep climb. My Auber setup has a warning light at 500 c so I know this is the only occasion.
I removed the low boost part because it gave virtually zero benefit and slowed things down,

[Rumcajs]

I run/force lower (sub 12 psi) boost when engine is cold or when I want to avoid limps cause I have max spool up (needle valve nearly closed) as high boost is at 18 psi max. I did observe better fuel eco with lower boost mode especially during cruise on the highway as long as I tolerated higher EGTS (+50°C-80°C) on average.

Running "high boost" only causes me a lot of grief especially under "spirited" acceleration (switching over from low to high slows the airflow a little)I get limps at pre-determined RPMs as designed by the a holes from Bosch/Zexel brigade. Nothing to do with safety but everything to do with emissions and look what the bastards did it on VW/GM and possibly others.....

Regards

[Dr Gary]

I run/force lower (sub 12 psi) boost when engine is cold or when I want to avoid limps cause I have max spool up (needle valve nearly closed) as high boost is at 18 psi max. I did observe better fuel eco with lower boost mode especially during cruise on the highway as long as I tolerated higher EGTS (+50°C-80°C) on average.

Running "high boost" only causes me a lot of grief especially under "spirited" acceleration (switching over from low to high slows the airflow a little)I get limps at pre-determined RPMs as designed by the a holes from Bosch/Zexel brigade. Nothing to do with safety but everything to do with emissions and look what the bastards did it on VW/GM and possibly others.....

Regards

I avoided the limp mode by fitting an aftermarket oversize AFM (air flow meter) housing. Aluminium and just fits in place of original. It came from HPDiesel in SA. Not cheap at $250 but it just works !!
EGT seemed to be pretty safe in both modes.

Just in case anyone cares :-(