cooljerk187

Hey guys im trying to pinpoint a problem in my cars vaccuum fueling issue (car wont run for **** under vacuum but under boost its fine) So is 45mmhg vaccuum OK under no running (key on but no start)?

DCrosby

No maybe under idle, but with no key on, it should read 0 or atmosphereic pressure.

c00lduke

under idle it should read ~300mmhg-400mmhg. At rest mine is also ~50mmhg

rotorbrain

this is normal. . . though very "out of whack". it can be easily changed by using datalogit.

first, turn the car on and connect using datalogit. select "read all". go to the "settings 3" tab. look at "PIM scale, offset". find the "option" that you have selected. look at the "scale" and "offset" to the right of that "option". while glancing at your commander (looking at the boost reading), change the offset +/-. play with those numbers until it reads "0". at that point your sensor is calibrated to basically our sea level range.

its a very easy fix if you have datalogit. . .

paul

btw, this is a good topic to be posted in the power fc forum. . . and i know its been discussed there a few times.

c00lduke

so would it be wrong through all readings if the resting state is off ?

Matt Hey

Yes, it's not accurate even if zeroing out the resting state unless a more accurate scale is used also. Do the conversion from kg/cm^2 to psi of your boost settings and you will see the PFC boosts some 1.5 psi more than what is set (PFC reads that low). Changing it now will mess up any tuning you have done as the fuel and timing maps will be read differently. However, if your just starting to tune then it's a good idea to make the PFC pressure readings more accurate. The correct readings vary with altitude though. Since you live in Mission, KS close to me in altitude you could use my scale=35500 offset=3370. It should zero your resting PFC pressure and make high boost more accurate. Don't try it without a wideband though. Here's a recent thread in the PFC forum which deals with it...

https://www.rx7club.com/power-fc-forum-47/barometric-stock-2-bar-sensor-does-work-466783/

45 mmHg = 1.77 inchesHg
Good conversion site...

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