Like the title states how accurate are your boost gauges? R u running electronic or mechanical? I have a autometer eletronic boost gauge that come with the 3 bar map sensor.. Between the gauge and my hp tuner log i have a 7psi difference, expecially when i first step into it then it will keep climbing up to 15 psi then work its way back down on the gauge to 10 or so, i check the hp log and it says my highest boost level was 8psi.... anyone else ever had this problem?

 

maybe ill just get another map sensor

 

What computer/pcm are you using? I have used both mechanical and electric gauges and have never seen more than 1psi difference, as long as the MAP is scalec correctly

 

1psi or 2" vacuum are all the sway you should allow for. 7psi error is huge

Get a different gauge

 

its a brand new autometer cobalt... but check this out, i am using a 3bar map sensor on my boost gauge and for reference on my computer..... I swapped the map sensors to verify both were operating right and hp tuners told me that the sensor on the boost gauge was no good!

 

I have a mech. autometer phantom gauge. After reading your first post and watching my hpt, I noticed that mine are quite a bit off. My mech gauge will say at least 2-3psi more than my 2bar map on my hpt log. Never really paid attention. I wonder which one is more accurate?

 

The MAP sensor you are using for the gauge might not be a 3 bar. Did it come with the gauge? sounds like it's only a 2 bar.

Also, unless your showing right around 100kpa with engine off, key on with your scanner, your boost gauge and scanner aren't gonna match. The boost gauge will show boost for your atmospheric pressure of your elevation, which will be lower with more elevation. The Scanner will show boost as anything over 100 kpa. For instance, I live at 4800' elevation. My boost gauge says I'm making 13psi of boost, but since normal atmospheric pressure up here is only 85kpa, the scanner so it showing about 2 psi less boost then if I was at sea level, so it say I'm only making about 11psi.

 

I bought a mechanical one solely for this purpose. One logs the mechanical read about .5psi higher but only because it's not as precise as hp tuners.

 

These figures may be off, but ya get the point. I thought 1 bar is for N/A. 2 bar is for a particular boost level, say 15-30#. Then 3 bar is whatever's over that. I know I saw these figures somewhere, but my CRS prevents me from remembering where. So, like I said, I'd need to verify & adjustfor accuracy. I just meant given ranges according to if it 1, 2, or 3 bar MAP.

 

1 bar=100kpa, or 14.7 psi which is Atmospheric pressure at sea level (NA).
2 bar=200kpa, or 29.4 psi which is 14.7 psi ABOVE atmospheric pressure at sea level (14.7 psi of boost)
3 bar=300kpa of 44.1 which is 29.4 psi ABOVE atmospheric pressure at sea level (29.4 psi of boost)

Now to see how much you need to adjust for YOUR normal atmospheric pressure, you need to turn your key on engine off and see how much kpa you have. Anything under a 100 kpa, you can multiply by 6.9 (6.9kpa per lbs of boost) and subtract from 14.7 and that will show you how many psi of boost your actually making.