Thanks for all the help Bidja. Unfortunately I don't have any compressed air.
The Dawes is one of @mudski
Thanks for all the help Bidja. Unfortunately I don't have any compressed air.
The Dawes is one of @mudski
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Bidja (3rd March 2023)
All good, will be good to sort it mate.
Per @mudski advice: With your Dawes, should have a seat insert_not sure if machined into body (brass) or a fitted type seat. Check and let us know?
With the needle valve adjustment, 12 psi would be a good cruise target boost. IMO_For now, until we get Dawes/Boost sorted I would close needle completely and run max spool to remove a variable.Yeah the Dawes has like a tapered seat for the ball.
With needle closed go for a drive, check cruise and max boost with the Dawes set as now and then unwind Dawes one turn at a time and see how max boost changes.
Can check Dawes target boost with a bike pump with gauge but no big deal.
Last edited by Bidja; 3rd March 2023 at 09:57 AM.
2008 GU WAG ST Manual CRD - To do the job
Well. I wound the needle almost all the way in, left a 1/4 turn out, boost was great, I was getting 23 PSI at 90 kmh in 4th without trying.
Pulled over, undid the Dawes 2 turns. That made it terrible. Screwed it back in 1 turn, still terrible, wouldn't boost over 10PSI. Stopped again, turned off motor, unplugged battery in case the thing had gone into limp.
Wound the needle right the way in and noticed that the actuator rod bounced up & down off the screw.
Set the needle valve so the rod is just touching the screw and fiddled with the Dawes a bit more and I think I've got it to as good as it will get.
Now getting 11psi at 100kmh with EGTs on the 200s in todays weather.
I'm happy with that, the vehicle drives nicely enough.
The only thing I'm unsure about is that the Dawes is pretty much screwed completely in. There's still some room left for adjustment, but not alot.
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Somethings amiss.
What intercooler are you running too?
Yeah this performance would not cut the mustard with me. If cooler is in good condition I would change out the boost controller (Dawes) to start with.
2008 GU WAG ST Manual CRD - To do the job
What I think is happening is:
Dawes spring has become worn and has a reduced spring rate which allows the ball to bounce on/off its seat even at very low boost pressure (ie at idle). Maybe this why you see the actuator arm rise/drop rapidly at idle with the needle closed because the Dawes ball is bouncing on/off its seat causing sudden fluctuations of +ve air (boost) pressure from cooler side into vacuum hose (downstream of Dawes). This rapidly changes vacuum to actuator causing the rod up/down movement especially at max turbo vane closure (needle closed).
Also with Dawes screwed nearly right in the spring maybe compressed to a solid height forcing the ball very hard up against seat not allowing any boost / +ve air to pass thru Dawes to vary the vacuum to actuator. Hence allowing full vacuum to actuator (nom 24”Hg) causing max vane closure and this produces the max boost from turbo (say 24psi), but as you open the needle this reduces vacuum to actuator and opens the turbo vanes slightly causing boost to reduce.
This is what you are currently doing along with opening Dawes slightly.
Could try stretching the spring but any improvement may not last long.
Yes I can send you my spare Tillix boost controller and see how goes. PM me you address.
Will also send a Tillix needle valve as this can be installed down stream of the boost controller (Dawes or Tillix)_use two needle valves. In your case, would set the Tillix to 10psi and adjust the downstream needle to a target max boost of say 16psi and you retain your current needle valve for spool adjustment. Called Boost controller plus two needle valves. This is for later.
Last edited by Bidja; 4th March 2023 at 01:33 PM.
2008 GU WAG ST Manual CRD - To do the job
Pulled the dawes apart again today. Measured the spring, 18.75mm. Stretched it to about 24mm.
Put it back together. Wound in the needle valve right in, the actuator no longer bounces off the stop screw. Set the rod to just sit on the stop screw and wound out the dawes, about the thickness of the lock nut. Test drive gave me nice linear boost up to 16psi while accelerating up to 100kmh. Took up the same stretch of road and am now getting 14-15 psi at 100kmh with cruise on, up from 11psi.
Boost is peaking at around 16-17 psi which is where it should be if I understand correctly.
EGTs are under control, high 200s low 300s.
Going to keep an eye on it and chase up some springs to keep in the spare parts bag.
Thanks everyone for the help.
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Bidja (5th March 2023)
Just read your last post. You must have one of the first revisions of the Dawes if you had to stretch the spring.
But, still check the IC for oil deposits in my opinion. Stock IC’s are known to spring a leak.
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