Optimizing fuel economy with EGR

I found some interesting charts/graphs in SAE 2009-01-1061 paper and I thought it would be beneficial to squeeze out the most efficiency of our GenIII Prius (including PiP) and perhaps Prius v and CT200h (basically the same engine). If you think they are helpful and would like to read the rest, support it and purchase it like I did.

I made it a background pic in Torque app so I can glance at it by switching to an empty gauge page. EGR and Timing Advanced are available in Torque as a gauge so I can monitor it.

For more info about BSFC based on the rpm and engine torque, see this thread.

Sample text from the SAE paper:

Figure 12 shows fuel consumption rates and pumping-loss during low load conditions plotted against the EGR rate and VVT-i angles. As VVT-i was advanced to an early closing timing for the intake valve, the pumping loss supressed by the effect of Atkinson cycle increased at whole EGR rates. Because pumping loss mainly affects low load conditions, in this situation, increasing the EGR rate is better to improve the fuel efficiency rather than increasing effective compression ratio by advancing VVT-i.​

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Figure 13 shows fuel consumption rates and spark timing during high load conditions plotted against the EGR rate and VVT-i angles. In high load conditions, the throttle is almost fully open, so the ratio of pumping loss is reducing. In this situation, advancing the VVT-i angles increases the effective compression ratio. This makes it advantageous to increase indicated work, however, spark timing could not be advanced due to the knocking on the Atkinson cycle with 13.0 compression ratio. Then by introducing cooled EGR gas, the reduction of the combustion temperature and advanced spark timing could be improved fuel efficiency.​

 

I think SGII has IGN and EGR.

I am guessing Ignition timing advance is the same as VVT-i angle. So, using those two, you'll have x and y axis to plot it on the low or high load graphs. The goal is to stay in the blue region (good fuel consumption area).