When I check the boost level with the predator on my 03 cummings i get a reading of 13 psi @idle & wot@35 psi. My Idle readings are the same no matter what tune I use, even stock. Is this normal? I would think there shouldnt be any boost at idle. I'm getting the quad recon monitor next week for my gauges so I dont have anything to compare the readings with. By the way I have a bone stock truck, but not for long.The predator has unleashed the beast inside!

 

Subtract 14.7 from your readings. The Predator is reading PSIA which is boost pressure without atmospheric pressure removed from the calculation.

 

OH I see said the blind man... But, if i subtract 14.7 from 13 I would end up with -1.7 boost?? (I think Im smarter than a 5th grader.)

 

I never said that the OBD2 stuff or Predators interpretations of it were perfectpr even that accurate. Also the 14.7 can vary some, not a lot, based on several different factors.

Keep in mind that we also have a tuner (GM) and it has the same functions of the Predator. In our minds these are meant to be used as tools and not as absolute gauges. They are not set up like gauges and OBD data is not inteded to be as quick or accurate as gauges. All this info available to us in an open source was intended for troubleshooting and repair type help. So if you MAP sensor was malfunctioning you would see that you have a problem.

I cannot speak for Diablo but, I have to imagine they would have similar thoughts.

 

That would be called vacuum. I don't know much about diesels, but gassers - our turbo charged race car for example - have vacuum at idle.