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nissan
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Discussion Starter · #1 ·
hello,
In a separate thread I mentioned that my freshly installed Dawes valve started playing up (leaking) so to get the car mobile again I decided to remove the dawes and needle valve and return the plumbing back to stock, i.e. reconnect the VNT and Vac control to the original solenoid.
I took it for a spin and low and behold I have stuff-all boost pressure and no power to boot. 5 to 7 psi at most. EGTs obviously going way too high.
I tried disconnecting the battery for an hour or so and double-checked the plumbing and its still the same. :headwall:
To triple check I have my vacuum plumbing correct, does anyone have a photo of the standard connections at the vacuum solenoid?
I'm at my wits end, I'm worried now that I may have buggered the turbo or something else.
Any ideas please guys?
 

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Discussion Starter · #3 ·
Thanks Geeyoutoo, That looks like how mine is. The hose with the green thingy on it, this should go to the VNT actuator, correct? And the one next to it on the outside goes to the vacuum supply? And the short loop goes straight into the resonator.
If thats correct then there's something else not right. I'm not getting enough boost for some reason.
Thanks again. Much appreciated.
 

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Discussion Starter · #4 ·
I owe Northern4x4 and Mr Dawes an apology. Although my valve was leaking a bit, the real problem was a burst hose. The hose going to my boost gauge ran beneath the IC, where (as I have found out), it gets very hot. All that heat softened it enough to make it bulge and burst.
While replacing and re-routing it, I decided add a second boost connection sensing point. One for the Dawes valve and one for the boost gauge. Advice came from Dieseltuner suggests tuning is better this way. Thanks.
I have found this set up to be completely different!
I now have the needle valve open a lot more (it was virtually shut when using just one sensing point for both). The setup still needs tweaking though. Here are a few observations:
Boost pressure fluctuates and bounces off its maximum setpoint (about 17psi) during acceleration or motoring uphill. I seem to have a hell of a lot of boost at low revs (its an auto). I am seeing 14 to 15psi @ 2000rpm.
When the Dawes relieves it can be heard and the pressure drops off sharply to around 10psi and then quickly rises again. This happens when under load and repeats several times. Is this what is referred to as boost bounce?
To help tame this, should I:
Open the needle valve more, how much is too much?
Fit a 'snubber' in the hose to the boost side of the Dawes valve (I'm thinking 1.0mm orifice)
Fit a lawn-mower-type fuel filter in the line to the VNT actuator?
Turn the VNT grub screw in a 1/3rd of a turn?
I'm pretty sure I'm on the right track with tuning it now. I just need some reassurance from people like yourselves who have been doing this for years.
One more query, since I now have two boost sensing points, one from the outlet side of the IC at the front and one on the IC inlet, does it matter which one I use for the Dawes? I currently have the Dawes piped up from IC inlet.
Once again, thanks for you help.
 
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