Tuning over run/decel

Hi guys

Quick question on tuning fueling on overrun/decel (obviously this is with decel fuel cut disabled).

I've found that tuning this area of th VE table does not really follow the trend in the on throttle areas, hence end up using really small numbers causing a big step in the VE table, and still the lamda is not 100% on target.

Is this something normal? If so, how does one approach tuning this to get adequate control of the fueling such that you're not wasting excessive fuel.

This is an area that's certainly not as critical as the part throttle operating area since we're off throttle and hence not requesting torque from the engine. Unless there's good reason not to, I'd recommend running over run fuel cut which will give the best results for fuel economy. If you don't want to run fuel cut then the process is the same as tuning any other cell in the fuel table but a little more fiddly to stay in the centre of the cell (since you're off throttle and the engine rpm will be slowing down). The numbers in the over run areas are likely to be smaller and often they can start to drop away quite quickly compared to the part throttle values, however they do still follow a trend, or at least they should.