Hi, just wondering which points you guys use for the MAP calibration

1 - M1/P1 @ under boost

2 - M0/P0 @ P0=0psig, car electrical on, engine not running OR

3 - M0/P0 @ car under vacuum - cruising at fairly high speed in gear with foot off the gas

Point 1&2 is really accurate from 0psig and up.

Point 1&3 is "not so accurate".

I thought that the wider the 2 points, the more accurate the calibration will be....but it does not seem to be in this case??

BTW its a ACDelco map sensor

 

Since its the GM map sensor (rectangle one with the three pin plug)

If you keep the wiring fairly short, and the vacuum line from your vacuum source fairly short, the stock calibration settings should be pretty damn close...

But the key is to log the data like it says, and hit your peak boost, then get your value at idle vacuum..

Also, if your measuring your vacuum from an open loop source (a place where the signal sometimes gets vented a good example is the bleed system for the boost control solenoid) your readings will be somewhat innacurate anyway..

Its also possible your gauge your using for reference is innacurrate or unstable makign it more difficult to tune.. But as long as you get your boost value, and your vacuum (or zero point) value, the wider apart the points are, the more accurate it will be.. You don't appear to be doing anything wrong, but the vacuum measurement should be standing still at idle..

 

Oh an the vacuum values are measured in negative PSI on the UTEC, and its in inches of mercury on mose SAE scaled gauges.. so the negative value at idle might be -10 pounds of boost at idle, where your engine vacuum would be roughly 16 in/hg on you gauge.. If your gauge is measured in BAR, its a little different and I'm not sure of the procedure..

Also be aware that on the UTEC you have two options, PSIg and PSIa, the difference is that absolute pressure will always read some positive value since its an absolute value from 0bar or a vacuum, where PSIg is gauge pressure, gauge pressure is basically offset from air pressure at approximately sea level which is around 14.7psi (where your gauge would read zero therefore idle would read 7-10 psi)

I think I have it straight.. someone chime in if I made an error here, my Bar/psi concepts can be a little confused..

 

The conversion from in/Hg to psi is right around 0.4912 so -20 in/hg on most gauges would be around -10 psiG

 

Oh.. and to bar it is tougher = in. Hg x 3.385 x 10-2 = BAR

 

Abner, thats where we screwed up. We used the in/hg reading for our value. We need to read our gauge and convert to psi then enter the value.......RRR