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les_garten les_garten is offline
Macht Schnell
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Join Date: Jun 2003
Location: PSL, FL
Posts: 861
Originally Posted by lucittm View Post
Thanks to all that responded. My 964 turbo does indeed have the electric boosted brakes that do not run off engine vacuum. I know I have to run the line back to the engine now. But I still don't know where I am going to get my signal for the PLX Boost Indicator. If the instructions tell me then I'm home free and I will report back to the forum where I tapped into the induction path.

Why didn't I think of modifying my 993 tachometer with the PLX Boost Indicator? That would solve both of my problems at once and I wouldn't have to hack into a 964 tachometer!

Now, how do I get one of these beauties?

I think the factory tapped into the Intercooler. I have a gauge tapped into the intercooler and one tapped into the brake line.

The IC tap is in "Front" of the Throttle Body, and the Brake line tap is behind the throttle body.

If you tap into the Intake manifold or at the base of the Throttle Body you will have a reading closer to what your intake valves are actually seeing in reference to Boost.

So here is what I "see" when my car is starting to boost.

First the IC tap shows boost coming on, and depending on what gear I am in, I may "see" .5 Bar before the Tap in the brake line starts to move. Now when the IC tap is indicating boost, and the Brake line tap shows no Boost, I can tell by the seat of the pants dyno, that boost is "starting to Happen.

When the Brake line tap shows boost, there is no doubt how the car feels, it is definitely positive pressure in the manifold.

I don't think you can go wrong in either location. Most likely, the tap below the throttle body is more accurate.

The only other thing to consider is that the control line for your Wastegate is coming off the Intercooler. So that's basically the "POP Off" pressure for boost, and it is being referenced off the IC body. So maybe that's where you should read boost.

There's a great Video on the Forum by JIM2 that shows his aircraft dual manifold gauge while he's hauling Azz on a racetrack. It shows what is going on if you have a gauge that shows two taps, one below and one above the throttle body. It is very interesting to watch, especially if you are trying to figure out where to plumb you Boost Gauge.

Check out his video here. Watch the two needled gauge in the Clock position. I just bought one of these and will put in place during my next go round.
---Les Garten---85 930, Andial IC, GHL Headers, Fabspeed Dual, K-27 HF2, 3.4 JE Full Finned 7.5:1 CR, 964 CAM'd, Carerra 3.2 Manifold Cut/Flipped, Tec3r, Siemans 55#, GSF Fuel Rails, Clewett Crank Trigger, Clewett Cam Trigger,Dual Plugged, ARP Head Studs/Rod Bolts, Clewett Wires.Tial 46mm WG, Tial 50mm BOV, WEVO Shifter,934 Boost Gauge, Wideband EGO Sensor/Gauge, C2T Head Gaskets, '88 MB 300TE,BMW R100RT
Old 03-03-2008, 08:40 PM
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