AFR Targets

The AFR table is a 3×3 matrix – the AFR is interpolated between these breakpoint values. This means that if you’re breakpoints are 45kPa at 14:1 and 95kPa at 12:1, operating at 70kPa will result in 13:1 target.

Idle AFR Target = Target AFR of fuel control when the engine is at Idle. Most engines will tolerate as rich as 12.7:1, and some will “like” 14:1.
1100 45kPa = AFR at 1100 RPM and 45kPa – this is typically just “off-idle” with very low throttle opening. Different cams will require different AFRs at this point. A stock cam will work fine at 14.5:1. A lumpy cam might like 13.3:1 or 14.5:1.
3000 45kPa Cruise = AFR at 3000 RPM and 45kPa – typical of a light cruise, but not, for example, overdrive cruising at lower RPMs and higher loads. Suggested range 13.4 – 14.7:1.
6000 45kPa = AFR at 6000 RPM and 45kPa – this is only used in free-rev, or something like autocrossing in a low gear and throttle is just barely open. Suggested range 12.5 – 13.8:1 (richer to keep parts a little cooler, and so that the tip in to full throttle is starting from rich.
WOT 1100 95kPa = AFR at approximately 25-100% throttle at low RPM. Intake manifolds are not very good at cylinder to cylinder distribution, so, there might not be a “perfect” AFR for here, but, 12.6 is a typical good enough AFR.
WOT 3000 95kPa = AFR at approximately 45-100% throttle at 3000 RPM. Intake manifolds are not very good at cylinder to cylinder distribution, so, there might not be a “perfect” AFR for here, but, 12.6 is a typical good enough AFR.
WOT 6000 95kPa = AFR at approximately 75-100% throttle at 6000 RPM. Intake manifolds are not very good at cylinder to cylinder distribution, so, there might not be a “perfect” AFR for here, but, 12.6 is a typical good enough AFR. But, sustained time at this RPM can put a lot of heat into the exhaust valves, and richer might be needed to keep temperatures in check (at the expense of some horsepower).
Boost 1100 180kPa = This is full throttle but with a supercharger or turbocharger boosting to about 11.6 psi. If no intercooler is used, the engine may require as rich as 11.0:1. If an intercooler, other charge cooling device or a fuel with plenty of octane is used, leaner can be tolerated. Richer than 12.5:1 is recommended.
Boost 3000 180kPa = This is full throttle but with a supercharger or turbocharger boosting to about 11.6 psi. If no intercooler is used, the engine may require as rich as 11.0:1. If an intercooler, other charge cooling device or a fuel with plenty of octane is used, leaner can be tolerated. Richer than 12.5:1 is recommended.
Boost 6000 180kPa = This is full throttle but with a supercharger or turbocharger boosting to about 11.6 psi. If no intercooler is used, the engine may require as rich as 11.0:1. If an intercooler, other charge cooling device or a fuel with plenty of octane is used, leaner can be tolerated. Richer than 12.5:1 is recommended.

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