Typical A/F ratios:

• high 14's up to "0 PSI" AKA atmospheric pressure (1 BAR)
• mid 12's up to 6 PSI (1.4 - 1.5 BAR)
• mid 11's up to 14.5 PSI (2 BAR) and above.

Fuel related links:

http://www.rceng.com/technical.htm

http://www.maxcooper.com./rx7/how-to/fuel_system/index.html

Detailed information on both Gasoline/Ignition

Ignition related:

In terms of ignition, proper timing is needed to ignite the compressed air/fuel mixture at the most opportune time avoiding preigniting (detonation) or retarded ignition

What is DETONATION?

Typical timing advances:

• 30 to 35 deg advance to 90kpa (0.9 BAR)
• 20 odd up to 120kpa (1.2 BAR, 3 PSI)
• as low as 10 to 17 total advance up to 200kpa (2 BAR, 14.7 PSI)

If you stick to a total engine advance of no more than 15 deg, assuming your static timing (pick up) is set correctly, then you are much less likely to suffer engine failures due to timing

EGTs:

Exhaust gas temperatures is one way to measure timing.  If the timing is too retarded (combustion happens too late) then the fuel is still burning in the manifold causing higher EGTs

Effects of porting on timing:

*1 BAR boost assuming constant ambient temp of 15 C and charge temp of 30 C*

• STOCK PORT                  20-23 deg advance ...lowest effective "dynamic" compression at max power.
• STREET PORT                 15-17 deg advance...midrange effective "dynamic" compression at max power.
• PERIPHERAL PORT        10-12 deg advance...highest effective "dynamic" compression at max power.
   

Before you tune you must ask yourself:

1) What ECU are you using?
2) What amount of performance/reliability do you want from your car?.
3) How modified is your car?
4) How much boost do you plan on running?
5) What octane gas do you use? (better be more than 92 octane)
6) How easy is it to access a dyno, wideband O2 sensor and data logging kits for all vital engine information?
7) Where is your EGT sender located?

Wide Band O2 Sensors

1)  The output of a sensor with less than 5-wires is binary.  That means it'll only tell you if you are rich or lean.  It cannot tell you how rich or lean you are.   Once the mixture goes a little bit fat, the meter will pin to the rich side.  Likewise if the meter goes lean, the meter will pin to the lean side.  Very often, a meter maker using these cheap sensors will write on their faceplates that the meter goes from 10.0 to 20.0 AFR.  This is just paint on the panel.  It is simple dishonesty.  It is more likely 13.5 to 15.0 in reality.  They might as well use three LED's to tell you the AFR - LOW, MED and HIGH!

2)  There are only two wide band sensors widely available today.  One is made by Bosch and the other by NTK/NGK.  They have five wires.  These sensors require sophisticated closed loop controllers to determine the air fuel ratio rather than a simple switch type OEM sensor that requires only a voltmeter.  All sensors can only determine the air fuel ratio at the switch point where the mixture goes lean to rich.  This is any sensor's zone of accuracy.  The difference between the OEM sensors and the 5-wire widebands is that this zone can be moved around to different air fuel ratios in the widebands.  In other words, 5-wire sensors have an electronically controllable air fuel ratio in their reaction cavities.

What this means is that you can make the sensor operate in it's zone of sensitivity at air fuel ratios ranging from 8 to 24 or higher air fuel ratio.  The problem is that this requires some clever circuitry to keep the sensor in this delicate balance.  (lamdaboy)