ScanGauge and boost pressure

[kennyv 0]

Hello All I have a Scangauge. I am wondering how accurate the boost reading is compared to a mechanical gauge. .....edit.... Ok, I just had another thought......So let me backtrack a bit.....I just bought a PowerPuck and an Quadzilla boost fooler (it plugs inline with the MAP sensor). I also just made a adjustable boost elbow and I do NOT have a mechanical boost gauge. At this point I have been watching my boost pressure via my ScanGauge. As my truck is unmodified the need to watch it at this point is for curiosity and MPG reasons only. I am planning on installing the newer goods today/this weekend, but I am now wondering if the Quadzilla boost fooler will alter my ScanGauge boost reading? Thoughts?? Thanks. Ken --- I am here: http://tapatalk.com/map.php?oqlhf0

[JLandry 0]

Unless something has changed recently, the ScanGauge doesn't display boost directly. It displays Manifold Absolute Pressure derived from the ECM, which is boost pressure PLUS atmospheric pressure. When I was running a ScanGauge II, I found the MAP reading being displayed simply stopped increasing at some arbitrary point (I can't remember exactly what) which was well below maximum boost (stock level) even though the boost pressure was still increasing. I contacted ScanGauge about this phenomenon and they said it was the fault of the ECM's external data stream (or something to that effect). I've since switched to using an UltraGauge and it exhibits the exact same behavior. The bottom line: In my limited experience, using either a ScanGauge or an UltraGauge to monitor boost pressure is a waste of time. A good mechanical gauge is the way to go. Best regards, John L. Sent from my iPad using Tapatalk HD

[Mopar1973Man 5,106 5 Vehicles 5 Vehicles]

Reason being is that the 98.5 to 02 Dodges tend to use a offset voltage for boost reading so it skews the SG or UG reading. JLandry is right you should consider a actual gauge for boost, fuel and pyrometer. Now on the CR engines the SG shows correct boost and rail pressure values...

[kennyv 0]

Yes. I know I should! (I need to kick my own ___ into gear) I do have a pyro and fuel pressure gauge so boost and trans temp are next. Thanks again for the input. I'll wait to install the elbow until I get a proper boost gauge. I did install the the PP this afternoon and it's nice. There seems to be just a bit of difference down low but in the higher rpms it goes like crazy now!! Thanks. --- I am here: http://tapatalk.com/map.php?wsypnt Sent from my iPhone using Tapatalk

[AH64ID 854 1 Vehicles 1 Vehicles]

Now on the CR engines the SG shows correct boost and rail pressure values...

It still shows absolute pressure, and still stops well short of peak boost (even stock). The OBDII limit is 255 kpa, which is 36.9 psi absolute, or (at sea level) 22.3 psi of boost is the most it will output. This is true for SG or UG, or any OBDII reader. The UG is supposed to take MAP minus IAT pressure for real boost, but it doesn't