mkee87 Posted July 27, 2014 Share Posted July 27, 2014 So on Thursday my radiator decided to commit suicide and blow its innards everywhere. Put in a new radiator went on a test drive, parked and coolant started puddling because my new radiator has a hole in it. With the new radiator installed I looked at my accessport when I turned the engine off and saw under boost that it had dropped to negative 39. Is this any reason for concern? Link to comment Share on other sites More sharing options...
MrTris Posted July 28, 2014 Share Posted July 28, 2014 So on Thursday my radiator decided to commit suicide and blow its innards everywhere. Put in a new radiator went on a test drive, parked and coolant started puddling because my new radiator has a hole in it. With the new radiator installed I looked at my accessport when I turned the engine off and saw under boost that it had dropped to negative 39. Is this any reason for concern? No, because your engine was off. You're looking under the "boost" heading under the live/realtime data, right? Your question doesn't appear to be worded correctly, unless you don't fully understand the concept of vacuum and boost. At rest (idle) or off-boost, your manifold pressure will read in hG, or inch grams; thusly known as negative pressure, or vacuum. When the turbo is making boost, it is read in Psi, or pounds per square inch; positive pressure aptly termed, "boost". When in hG, your boost guage should read in the negative (-15hG), and will get higher (-14, -13, -12. . ) until you reach zero, when it will read in positive pressure, or Psi (+1, 2, 3..) So when your engine is off and not doing anything, realistically, it's at zero, but, a different zero than when you're transitioning from hG to Psi. Make sense? Your coolant issue is something else entirely and has zero direct effect on manifold pressure. I assume you know what you have to do to fix it? Link to comment Share on other sites More sharing options...
mkee87 Posted July 29, 2014 Author Share Posted July 29, 2014 I had the radiator replaced today, when driving home I was at full throttle then took my foot off the gas and the boost gauge read -39.38psi. Link to comment Share on other sites More sharing options...
MrTris Posted July 29, 2014 Share Posted July 29, 2014 I had the radiator replaced today, when driving home I was at full throttle then took my foot off the gas and the boost gauge read -39.38psi. So what I said above applies. The base, or lowest value for vacuum, according to Cobb, is 39.38 hG. Link to comment Share on other sites More sharing options...
mkee87 Posted July 29, 2014 Author Share Posted July 29, 2014 The only reason it raises any concern with me is before my radiator difficulties the lowest it would read was around -10. Link to comment Share on other sites More sharing options...
mkee87 Posted July 31, 2014 Author Share Posted July 31, 2014 So now my ap is reading 39 pounds of boost too. I know it's not actually hitting that as it is mechanically impossible with the factory setup. What sensor sends the amount of boost to the ecu so I can check/replace it? Link to comment Share on other sites More sharing options...
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