boost gauge vs MAP sensor

[toomanymodz]

I studied my powerlogger log file carefully and it appears that the boost reading on the powerlogger differs from the pillar-mounted boost gauge by about 2 psi. During my latest 1/4 mile blast, I watched the boost gauge during the last few hundred feet and it was a steady 20 psi, yet the log file read 22 psi.

Is this a common thing? I see that there are some voltage adjustment parameters that are changeable. But a 2 psi variance seems like an awful lot.

Comments?

 

[TurboBuRick]

I studied my powerlogger log file carefully and it appears that the boost reading on the powerlogger differs from the pillar-mounted boost gauge by about 2 psi. During my latest 1/4 mile blast, I watched the boost gauge during the last few hundred feet and it was a steady 20 psi, yet the log file read 22 psi.

Is this a common thing? I see that there are some voltage adjustment parameters that are changeable. But a 2 psi variance seems like an awful lot.

Comments?

IMO its not unusual. I see the same on mine. The map sensor is prolly more accurate. I would not be real concerned with it.

 

[russgoodman]

Same thing happened to me, I thought I was right on 25 psi according to my gauge. Powerlogger showed like 28-29 psi I've backed it down some since then but haven't driven it to check it out.

 

[toomanymodz]

I'm more inclined to believe the mechanical gauge rather than the MAP sensor. Voltages are a tricky thing on these cars. Just a few milivolts can change the reading.

If I had a 2nd gauge laying around i'd try it.

 

[Dabigguy]

There's no way to really figure out which is accurate unless you have access to a calibrated gauge. As long as you have a good tune and no knock, enjoy what you've got.

 

[Fast231]

This is the same conclusion i came up with--I was in the midst of changing locations of a boost gauge in a blown mustang and had two mounted...they both ready very close to the same--the map sensor was 2-3 pounds lower.....

Tune for no knock and be happy

James

There's no way to really figure out which is accurate unless you have access to a calibrated gauge. As long as you have a good tune and no knock, enjoy what you've got.

 

[gunslinger]

You need to pull your 5 volt reference from the ECM..not the dash.

Power Logger MAP

 

[Heg87t]

I studied my powerlogger log file carefully and it appears that the boost reading on the powerlogger differs from the pillar-mounted boost gauge by about 2 psi. During my latest 1/4 mile blast, I watched the boost gauge during the last few hundred feet and it was a steady 20 psi, yet the log file read 22 psi.

Is this a common thing? I see that there are some voltage adjustment parameters that are changeable. But a 2 psi variance seems like an awful lot.

Comments?

I saw the same thing on my car. The vacuum reading was quite different. Boost was close but I am only running about 10 pounds right now.

Does the MAP sensor get zero'd out at start-up or when when the Powerlogger connects?
I also noticed the last time I had my a-pillar pod off the nylon tube looked like it might be kinked. I am going to change the tube and see if they match then. You might want to check your tube. Do you guys have better luck with nylon or copper tubes?