I just installed a digital Intellitronix air/fuel gauge I got from SUMMIT. What is the proper way to read this? Is it supposed to be read during everyday driving or at WOT?

Where should it be at? Dead smack in the middle...or a little lean..?

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'92 Formula
305 TPI
Mods: SLP catback,SLP air foil,ported plenum,Crane AFPR (49psi),MSD6AL,homemade cold air,K&Ns,3:73s,JET fan switch...SLP 1 5/8ths are coming...oh yes

 

When the engine is first started, it should read 0.450 volts (450 mv), since the ECM sources a 450 mv voltage reference on the O2 sensor circuit, before the O2 sensor heats up & produces its output. Once the O2 sensor heats up, but before the ECM goes closed loop, the meter should read on the rich side (> 450 mv). After the ECM goes closed loop, the voltage will oscillate between lean (< 450 mv) and rich (> 450 mv) at about a 0.5 to 2 second rate. At WOT, I have found that my setup runs best the mid 900 mv range (approx 11:1 A/F ratio). My setup is a '92 305 TPI, with 53 psig fuel pressure & a TPIS stage 5 PROM. Make sure you connect the "-" sense input of the meter to the O2 ground wire at the ECM (tan wire on E15 for '90 - '92 VIN F & 8) & not directly to chassis ground, or you will get a slightly incorrect voltage reading.

Here are some A:F mixture ratios that correspond to the O2 voltage outputs listed:

17:1 141 mv
16.5:1 202 mv
16:1 260 mv
15.5:1 320 mv
15:1 390 mv
14.7:1 422 mv
14.5:1 450 mv
14:1 515 mv
13.5:1 580 mv
13:1 645 mv
12.5:1 715 mv
12:1 790 mv

14.7:1 is the stoichiometric A:F ratio for gasoline.


Tim

 

At WOT, I have found that my setup runs best the mid 900 mv range (approx 11:1 A/F ratio). My setup is a '92 305 TPI, with 53 psig fuel pressure & a TPIS stage 5 PROM. Make sure you connect the "-" sense input of the meter to the O2 ground wire at the ECM (tan wire on E15 for '90 - '92 VIN F & 8) & not directly to chassis ground, or you will get a slightly incorrect voltage reading.

So should the car be a little rich or a little lean at WOT (I'm not sure I understand).

Where should I ground this meter at Tim? I have it grounded near the firewall.

Sorry, I get confused easily.



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'92 Formula
305 TPI
Mods: SLP catback,SLP air foil,ported plenum,Crane AFPR (49psi),MSD6AL,homemade cold air,K&Ns,3:73s,JET fan switch...SLP 1 5/8ths are coming...oh yes

 

The mixture should be on the rich side of stoichiometric @ WOT. The air fuel ratio (A/F) number is expressed as a ratio of weights. There is an optimum ratio for combustion, called the stoichiometric ratio. For gasoline, the stoichiometric ratio is 14.7 lbs of air to 1 lb of gasoline, or 14.7:1. A lower ratio (11:1) is on the rich side - more fuel to air.

If the meter has a separate power ground wire and a "negative sense" ground wire, connect the power ground to the chassis (or an ECM ground wire - blk/wht), and the negative sense ground to the O2 ground wire at the ECM. If the meter has only a single ground wire, connect it to an ECM ground wire - not the O2 ground wire, since you would not want to run any current through the O2 ground wire, as it would cause a voltage drop in that wire, giving the ECM a variable false O2 reading.

Tim