Quote:
Originally Posted by Pupbelly
What level of boost should be displayed on the stock boost gauge under full boost?
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About 1/4 into the white zone corresponds to roughly 4 p.s.i. Full scale in the white zone is approximately 16 p.s.i. Here is a link to a useful page.
http://www.vpcuk.org/forums/showthre...o-they-compare
The standard settings for the T-5R are 11 p.s.i. on overboost (which supposedly lasts for up to
(but not always) 30 secs, and 9.5 p.s.i. under normal conditions. 11 p.s.i. corresponds to fractionally over 2/3 into the white, 9.5 p.s.i. is a bit under 2/3 into the white.
My own standard T-5R (automatic), when I kick down, shows initial surge for 3 or 4 seconds with the needle about 5/6 into the white zone (roughly 13 or so p.s.i.) dropping back to the 11 p.s.i. point and then slowly easing back to around the 10 p.s.i. point. These have all been confirmed using an accurate additional gauge temporarily plugged into the vac tree.
I've also attached the vac diagram for the T-5R.
Assuming all your vac pipes and turbo pipes are sound and clipped up tightly, the most common causes of poor boost seem to be firstly, a damaged diaphragm in the TRV (turbo recirculating valve) followed by a faulty TCV (Turbo Control Valve). Neither of these would be audible.
Wastegates are surprisingly reliable, even at huge mileages, but can fail due to weak springs and/or poor seals. If the wastegate is the issue, I would replace with one from Forge. They even tell you how to set it up easily without gauges, spring balances etc.
The turbo itself is unlikely to be a problem as at that level of poor boost, there would be other symptoms from the turbo (oil burn/noise) I'm sure.
Worst case scenario would be a split intercooler but you would almost certainly hear the escaping boost.
Hope this all helps to some degree.
John