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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,289
My car had the 934 style boost gauge with telltale in it when I bought it and it works perfectly...
I like having the origonal boost gauge in the tach working too even though I know it's not real accurate. The cool part of having both is that the origonal gauge takes it's pressure reading from above the throttle body butterfly in the intermediate manifold or the intercooler, and the aftermarket gauge in the clock space is taking it's reading from below the throttle body via the brake booster hose plumbed into the intake manifold.

At part throttle slightly boosted acceleration there is a big difference in pressure above and below the throttle body, and having both gauges displays that.
At full throttle the difference in boost readings displays the pressure loss in the intake manifold from the restriction of the factory single throttle body.

At part throttle acceleration with a K27 HFS turbo I've seen around .9 bar on the factory gauge with only .2 bar showing on the mechanical gauge because all that air pressure can't get by the throttle body when it's only open a little ways and the engine is swallowing up what does get by quickly.

I saw a youtube video of a mechanical gauge in the clock space that had 2 needles, one reading above the throttle and the other below the throttle. It was neat to watch the needles move and catch up with each other as the guy was driving on a track.
Old 01-10-2008, 09:57 AM
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