14.7:1 is not a "Pinging" range...from what i've seen on a Dyno with the A/F
Meter hooked up (on three Dakota's) we are hitting 15.5-15.7:1 in some
cases...that in conjunction with the 40+ degrees of timing in before 3000rpm is
a major factor in the pinging problem.
Ideal for performance is 12.3-12.6:1 (12.5:1 being the norm for "Best
Performance".)
- Bernd
> In open loop, the 14.7:1 does not apply. This afr is used in closed loop
> because this ratio ensures that current OE cats operate at their most
> efficient. Unfortunately, it also the ratio at which pinging problems
> could most likely occur.
>
> In open loop, the built-in tables (which are based on R&D historical data
> for a specific engine) are used. The afr part of these tables are
> deliberately
> on the more-than-needed rich side for 'warranty' reasons. How rich, I have
> no idea. While there is much argument as to what the ideal afr for max.
> performance
> is, I really got the impression from Zimmer that the afr in these built-in
> tables are richer than the ideal performance afr range.
>
> Bob. Burlington, Ont., Canada.
> '97 Dakota CC, 5.2L, 4x2, 3.92 SG, auto., 4265 lb.
> Dyno: 231.2 rwhp 340.0 lb-ft rw torque
> PB: 14.737 @ 91.75 9.364 @ 72.95
>
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