Quote:
Originally Posted by SPL
gpsman1 — In that case, I accept the results of your careful test, and congratulate you on producing data that convinces me that the 2005 FEH's fuel efficiency can indeed benefit from driver intervention, to maximize the amount of pure-EV-mode operation that occurs. This tells me that there's a lot of scope for improvement in Ford's control software. I wonder whether the 2008 FEH is significantly better in this regard? It would be interesting to have an owner of the new FEH repeat your experiment in his/her vehicle.
In the TCH, gliding in 'N' removes the small amount of regenerative braking that normally occurs when coasting with your foot off the accelerator in 'D'. Neither MG1 nor MG2 operates while in 'N'. What you have done sounds to me a bit more like "pulse-and-glide" driving, which we know can significantly improve FE compared with normal "in-gear" driving — use the ICE to get up to speed; shut off the ICE, put the vehicle in 'N', and glide down to a lower speed; then repeat. This eliminates all the ICE losses during the glide phase. In your case, the ICE was already "off" while gliding in EV-mode, and I guess I could have achieved the same effect as putting the vehicle in 'N' by carefully feathering the accelerator while leaving it in 'D'. This being the case, what you did is equivalent to optimizing EV-mode while driving in 'D'.
Now, if only some TCH owners would rise to the occasion and either repeat my test or do a good one of their own!
Stan
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OK Stan, I'm going to make one last try to convince you that your initial hypothesis was indeed fallacy and not fact.
Look at your post #29, part 1.) You assume (correctly) that the BSFC @6.47kW is 250g/kWh.
Unfortunately, you also assume in part 3.) that the BSFC @9.84kW is also 250g/kWh.
IT IS NOT! The BSFC @ 9.84 kW drops to 245, per the published BSFC contours for the Prius. A trivial error? NO! The additional 3.37kW is thus obtained at an incremental effciency of 34.5%! The break-even energy storage-retrieval point is thus 32.4/34.5=93.8%. Yes, you can't get there with the Prius HV pack, but start dropping your calculation speeds and you will see this change dramatically. In fact, just dropping your speed to 35MPH for the Prius results in about break-even FE by going EV. Perhaps it was just a coincidence, but the 6.47kW power level is almost exactly at the knee of the efficiency curve for the Prius. Once below this, the efficiency decreases with decreasing power become substantial (can't run the ICE less than 1000 RPM). Consider going from 5.00kW @ BSFC=266 to 8.37kW @ BSFC=246. Your incremental efficiency is then 37.5%, so the break even point is 30.5/37.5=81.3%. Doable with EV? P&G? Hills? All three are methods of energy storage-retrieval, and at lower speeds they will probably all give you better results than pure ICE cruising. What about forcing the ICE to produce more power through MG1/MG2 loading without storing? ALWAYS worse for MPG. More power from the ICE always means more gas, even if the incremental effciency approaches 100%.
For the FEH, with its less flat efficiency curves and larger HV battery and motor/generators pushing EV gives fantastic results. I would assume that for the Camry it would be less than the FEH, but perhaps better than the Prius.