So I've installed a boost gauge and now I get to see my SC working. But I've got questions. My number are 10.5-11lbs boost, 16hg normal cruise with an occasional 14. But the number I'm really worried about is when I get off the gas. Well call it coasting. That number dips to 24-26 hg. Is that normal or for that matter are my other numbers normal. I knoow boost is probably about right. I forgot, no pulley reduction.

 

Yes, this is normal. It drops in the 20s when coasting. Your numbers are on par.

 

Yes, increase in vacuum is normal when you let off the accelerator. My boost gauge is metric, so I typically see vacuum draws in excess of 500mm Hg.

If you have an air/fuel gauge, you will also notice the engine go into a lean condition when decelerating. This is also normal because the increase in vacuum causes more air than fuel to enter the engine. This lean condition is OK because your timing is reduced and the engine is not under a load. Heat buildup will be minimal and no detonation occurs.

 

Perfectly normal. Stock boost on your car in a perfect world is 11.6

 

How about with a 15% pulley?

 

Well, with a 15% s/c pulley AND a 2% oversized crank pulley, I see around 17 psi at wide open throttle. Normal get up and go I see Round 14 or 15.

 

Sweeeeet. Can't wait to get my pulley. Probably gonna be a little under that, I don't think I'm gonna change the crank pulley.

 

I've seen about 1.125 BAR with my boost gauge, which comes out to 16.3 PSI.