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Re: Base boost for 8VT is not 1/2 yell n/m Posted by Justin VanAbrahams [Email]  (#32) [Profile/Gallery]
(more from Justin VanAbrahams) on Thu, 18 Jan 2001 19:22:37
In Reply to: Base boost for 8VT is not 1/2 yell n/m, Kevin K  [Profile/Gallery]
, Thu, 18 Jan 2001 15:18:12
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It could be, but it might not be... Saab changed the relative calibration of the gauge several times over the years, likely to adjust for the cars of any given year running the most boost. For example, in 1980 the Turbo was running a maximum of 8psi of boost - as such, the yellow/red border is about 8psi. On a 1990 900T, the SPG was running up to 13psi of boost - as such, the yellow/red border is about 13psi.
Base boost should always be between 4 and 6psi on ALL Saabs, but with the varying gauge calibrations "base boost" can wander all over the stock gauge. I learned this the hard way, when I swapped a gauge cluster from an '89 900T into my 1980 5-door (going for the better speedo). The Turbo needle *barely* moved either direction, since at its maximums the old b-motor neither produces as much vacuum nor as much boost as a 1989 SPG - with the original cluster I was perfectly pegging the needle at the yellow/red border at maximum boost. "Half yellow" on my '80s gauge is about 3psi, half yellow on an '89 900T's gauge is about 5psi.
Similarly, at maximum boost (with the stock APC box) my 1990 SPG hits the yellow/red border reliably, whereas my now-dead 1990 900T was always a needle width or so before that border, presumably representing the 1psi difference in the two cars' maximum settings. The same was true of my '88 SPG and 900T...
All that said, you NEED a calibrated gauge to measure base boost. Using the stock gauge is simply a bad idea. Fortunately, base boost is relatively low and you can use any standard vacuum/pressure tester - I bought mine at Pep Boys for $15. You don't need (and arguably don't want) a $60, 30psi Autometer gauge for this task. Just be sure the gauge you end up with hits at least 12psi, or you won't be able to check full boost...
-Justin
, Thu, 18 Jan 2001 15:10:24, Fri, 19 Jan 2001 09:02:44, Thu, 18 Jan 2001 15:18:12, Thu, 18 Jan 2001 19:22:37 <-- Viewing This Message, Thu, 18 Jan 2001 21:14:37, Thu, 18 Jan 2001 21:54:24, Fri, 19 Jan 2001 00:29:38, Thu, 18 Jan 2001 15:07:18
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