A turbocharged car without a boost gauge is no fun. It's not that you
really need it, but knowing what's really happening with your engine
helps a bit, and the pressure surges when you mash the pedal sure are
My car was among those unfortunate Saabs that came without a boost gauge
(not that the standard one is very useful though), and I long wanted to fix
that. Here's a detailed (maybe too detailed) description of the installation
process. (And I did wash the engine a couple of days after performing
this work ;)
The measurements I'm getting from a 1999 Saab 9-5 2.3t with a low pressure
turbo are: the vacuum is 18-20 Hg at idle, 15 Hg while driving, up to 24 Hg
when coasting. With the stock engine the boost during the moderate
acceleration settled around 5 psi, the highest I've seen at WOT is 9 psi.
An ECU upgrade from BSR raised these numbers to 12-13 psi in second gear
and 14-15 psi in third.