I did a little converting on my boost figures from my power fc. it said i was hitting 19.3psi when my boost gauge was showing 16psi, with a slight spike to 17. i've got a gm 3bar. i seriously don't think i could hit 19psi on pump gas without having issues so far. my boost gauge is a defi d series

 

The PFC Commander does not display boost correctly, however, that is a very large discrepancy and usually the PFC reads LESS than the boost gauge.

Where is your boost gauge T-ed into and what adjustments have you made to the PFC for the 3-bar sensor?

Also, if you don't have the data-logit, you can do a ghost trace and see what cells the PFC is actually in when it's reading 19 psi.

 

the boost gauge is running right off of my uim at the extra port like most people i know.

jason at the rx7store did the 3bar install and tune. he set it to option 3.

i just did the peak hold and was kinda glancin at it and at my boost gauge while doing a hard 3rd gear pull. it did it around 8k where my boost gauge had showed a slight spike

 

http://www.onlineconversion.com/pressure.htm

Do you use the kg/cm2 to psi conversion?

 

no, my friend told me that 760mmHg is equivalent to 1 atm, which would be 14.5psi. i just did the math with a calculator to figure it out

 

remember altitude also has something to do with it. here's my conversion calculations for my altitude;

absolute(psi) 8.0 9.0 10.0 10.5 11.0 11.5 12.0 13.0 14.0 15.0
pfc( kg/cm2) .54 .61 .68 .72 .75 .78 .82 .88 .95
gauge/manifold(psi) 10.3 11.3 12.3 12.8 13.3 13.8 14.3 15.3 16.3
so its kind of impossible to match them up, but imagine those are in columns. 8.0 absolute=.54 pfc=10.3psi on the gauge.
pretty crazy huh? my avc-r reads the same as my gauge, just in .bar.
imagine my suprise the first time i hooked up a boost gauge and saw over 12psi the first time i hit the gas!!!

 

I have said this before but I think the UIM extra nipple is the worst point to T from. Insert the T where the MAP sensor reads so you can know what your ECU is doing and so you can get a more stable boost reading. I remember seeing the change on Rich's car with his Profec reading there and then moving it. His boost would oscillate till we moved it-after the move rock steady.

 

Yep, the map sensor for my Defi boost gauge is T-ed off of the MAP sensor hose and not the UIM nipple (boost controller is connected there). The PFC Commander still reads a little less than the gauge though, but I think that's good advice.

 

i might have to try that and see how it works out

 

Thanks for repeating this....I guess you still learn something new everyday. CJ

BTW, my boost gauge is terriably inaccurate. When I thought I was running 13lbs on the non-seq twins, I was realy running 11! This was backed up by a dyno session with Ralph Friend. I just use it for a reference.