randy Posted December 21, 2003 Share Posted December 21, 2003 I have a Greddy 60mm boost gauge reading off the vacuum line and I have my Apex- S-AFC reading the turbo pressure off the computer. There is a difference in the reading when the gauge shows 1.2bar boost. The S-AFC shows only 1bar? Can someone explain why there is a difference in the readings? Link to comment Share on other sites More sharing options...
THOR Racing Posted December 21, 2003 Share Posted December 21, 2003 First of all tell us where the two gauges are physically plumbed in. If not at the same point they will be different. Regards Pete Link to comment Share on other sites More sharing options...
randy Posted December 21, 2003 Author Share Posted December 21, 2003 I boost gauge vacuum is to the Fuel pressure regulator/Intake manifold 3way... and the S-AFC pressure is read off the ECU turbo pressure sensor wiring. Link to comment Share on other sites More sharing options...
randy Posted December 23, 2003 Author Share Posted December 23, 2003 bump _______ Link to comment Share on other sites More sharing options...
suprarob Posted December 23, 2003 Share Posted December 23, 2003 O.k. IF there both going to be different then which one do you take as the correct reading Only just really starting to try and make sense of all this can anyone enlighten me Link to comment Share on other sites More sharing options...
THOR Racing Posted December 24, 2003 Share Posted December 24, 2003 You need to be measuring manifold inlet pressure, not say pre-intercooler or at the turbos for instance. At the end of the day the Toyota or Apexi or whatever MAP sensor should read the same as your mechanical boost gauge if it's any good. As 1 bar is 1 bar no matter where you are. It's all based upon sea level anyway. The answer you are looking for is here........ I would however note that electronic gauges are only accurate within there specified range of operation. (much like a mechanical needle gauge is only good for the range as show on the dial face) SO as the Stock Toyota MAP sensor ONLY goes up to a max of around 18.5psi it starts to get a little flakey and inaccurate, out of range. So while the mechanical dial gauge is good for 1.2 bar the AFC which uses the MAP sensor reading from the stock MAP sensor then it's at it's limit of operation and thus cannot be trusted to be accurate. This is why you can never fool the ECU into injecting more fuel at WOT with just an AFC (or similar) as it's limited partly by the inaccurate (or out of range) MAP sensor. So I bet at 1.0 bar they both probably read the same. However ...they "should" both read O.K. up to the limit of the stock MAP sensor which is about 1.2 bar but I guess in your case the MAP sensor is poor ********OR********* the setting on your AFC or set up incorrectly. Ahhh! Could be the AFC is plumbed in after the Fuel Cut controller or something and it's this that is clamping the max output of the MAP sensor to 1.0 bar ?? The AFC should be loom side and FCD (VFCC) ECU side. regards Pete Link to comment Share on other sites More sharing options...
suprarob Posted December 24, 2003 Share Posted December 24, 2003 Thanks Pete things are becoming more clear Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now