It's tough to know exactly how much boost the ecu is seeing, because my analog boost guage always seems to give me a different reading than the pressure level on the SAFC. The SAFC is only in my car because i'm too lazy to take it out; I am using Uberdata. The SAFC settings are all on 0%. My question is, if the boost guage is displaying 10 psi, and the SAFC is only at about 0.5 bar (7.4 psi I guess), is the ecu only seeing 7.4 psi of boost, or is the SAFC just interpreting the MAP sensor voltage incorrectly?

 

when your at ambient, is your analog gauge right on 0?

I have one of those Autometer Ultra Lites, and it sits at about 2lbs at ambient.

Maybe your gauge is off? ..I wouldn't lean towards the SAFC being too off unless you set it correctly(?).

 

Unfortunately I don't know; I am using a Banks Boost Guage, and it only shows positive pressure (can't go south of 0). I guess Banks stuff is mainly for turbo diesel stuff, I dunno.

 

Honda MAP sensors are absolute aren't they not?
most boost gauges are relative so the boost gauge may be seeing 10psi of preasure difference from the manifold to ambient while the ecu is only seeing 7.4psi above sea level?

correct me if i'm wrong

 

Would this make the reading on the SAFC more accurate than the boost guage?

 

are you using check valve or anything to hind the boost from the ecu?

 

IMHO obd0 maps read about 1-1.5psi lower than my autometer gauge.
This was referenced to my Hdata loggings.

 

if the map sensor is absolute then yes. it will see the absolute pressure inside the manifold as it would be at sea level. makes sense to me but i really have no idea if the map sensor is relative or absolute.
but yeah; the general rule of thumb is that cheap boost gauges aren't verry accurate.