Questions about boost gauge reading - advice?
 

Today, I fired up my car for the first time since installing a supercharger.

http://986forum.com/forums/performance-technical-chat/49610-installing-imagine-automotive-super-charger-my-1998-2-5-boxster.html

Here is a sample images of the gauge.

http://986forum.com/forums/uploads01...1392000616.jpg

The Boost Gauge is reading Vacuum when at idle. I assume that's normal. When I increase the RPM, I do see the boost gauge increase the boost (REDUCE the vacuum), but its still in the vacuum range of the gauge. It's like there's less vacuum.

Does that seem normal for a supercharged engine?

I was thinking I should see the gauge in the boost range, not still in the vacuum range.

Am I correct to assume that without the supercharger, there would be MORE vacuum with increased RPM?

The boost sensor is installed with a "T" connection into the vacuum line the goes into the intake manifold after the throttle body (per the instructions).

Any ideas?

You have to be under load to actually see boost. If you're just idle, revving the engine, you won't see it.

Thanks! That makes sense. I guess I will have to wait and see. had to order some more coolant. When I arrives, I will be able to take her for a test drive.

I remember doing the same thing 12yrs ago when I built my own turbo system for my mx5. After all that work, I was so disappointed not to see any boost. It was a bummer to have to get the car totally roadworthy prior to seeing a reading on the positive side.
Good luck!

technically, you should see near zero vacuum on wide open throttle on a NA engine. The reason there is vacuum is because the throttle plate is not allowing all the air the cylinders want to be allowed in.

Same is true with a supercharged engine, if your throttle plate isn't open significantly, it should be under some sort of vacuum....this is all assuming your boost gauge is AFTER the throttle plate (which is where it should be).