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Discussion Starter · #1 ·
Well, i wanted to install a custom boost gauge in my 87 Saab 9KT and I wasn't sure to where to mount it, till my friend asked me "do ya think it'll fit there?" I held it up to (there) the Analog Clock and it looked as if it should. Well short story shorter, he custom fitted it and we hooked it up the other day, fit perfect! Looks almost stock, and is in the ideal view to read while driving! It even illuminates with the backlights. And yes, the buttons still work for the controls in the gauge cluster. Take a look, what do ya think? Do ya think there would be a market for such an item? What would you pay for one? Just curious if we should produce them as after market bolt on part. ENJOY!
The Stock Look..aka the Before:

The NOW:

 

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Originally posted by sgould:
[qb]How did you get that 20 psi vacuum?   14.7 is max surely?    

[/qb][/b]
I've not seen anymore than about 0.85bar/13psi on mine... on overrun. Idle normally sits at about 0.7 bar/10psi- which suggests that the gauge pictured is reading incorrectly by a factor of x2 in vacuum, which would correlate with the difference noted by sgould...

Which 1c shop did you get it from?
 

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Surely it can't be less than one atmosphere (14.7psi) below atmospheric pressure, which is a perfect vacuum
The only way a reading of -20psi could be accurate, even assuming the engine could generate a perfect vacuum, is if the ambient atmospheric pressure were 5.3psi or more greater than it is at sea-level. To achieve this, you'd have to be driving at the bottom of a very deep hole. I mean very deep (about 2 miles below sea level)
 

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Actually, perhaps slightly less than 2 miles, as I neglected the fact that air density will increase as pressure increases. Still, it would be a deep hole and that's still assuming the impossible case of an engine that would create a perfect vacuum in the manifold.
 

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Originally posted by Mark E:
[qb]So, we're agreed then, the gauge is not telling the truth... [/qb][/b]
Unless I've got lost somewhere in my calculations or the car lives in a very low-lying area. Or unless it's not graduated in PSI.
 

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My car spikes at 1.4bar for an instant.. then reads max 1.2-1.3bar over 3500rpm.. then gradually spools down to 0.9bar at 5000rpm.

The car is fitted with several modifications to allow this to be managed safely. However gearboxes take a whack!
 

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Discussion Starter · #17 ·
ok, left side of the 0 is vaccume as the right is pressure, and i don't understand this "bar" [expletive deleted] use Standard terms please so it has a vac. of 20 at idle. max boost is holding at 10 in cooler weather, now it's a lil less. Anybody have a clue how to take out the stock 2.5 bar fuel sender, i wanna hook up the 3.0 bar. And the 3.0 i have is off a 900S . . . so it's a bit different mounting wise. Will it even work?
 

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I think the point everyone was trying to ask is?.. Vacuum of 20 WHAT??? PSI, BAR or WHAT?

It can't be PSI.. cos thats too low.. and it's not BAR.. so what is your gauge actually calibrated in ???

p.s. The S I unit of pressure is the pascal. And one BAR equals 100000 pascals.... sorry was using Standard Measurements ..
 

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Originally posted by Mark in Ireland:
[qb] QUOTE
Originally posted by Mark in Ireland:
[qb] It reads -30mm of water which = -1 bar [/qb][/b]
Is no one listening?????????? [/qb][/b][/quote]I'm listening, but -30mm of water is -0.003 bar, so that's not it. It could, however, be inches of mercury (in Hg): -30 in Hg = -1 bar. That also sounds more feasible to me, since I'd have thought a US gauge would be using the imperial units we taught them back when they were the best available and which we abandoned when something much better came along

However, if that is true there is a boost problem to diagnose, since 10 in Hg = 4.9psi, or approximately base boost on an '87 9KT.
 
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