designing a car for pulse and glide...

[stillsearching]

I was curious about something... if you specifically design a car for pulse and glide conditions, rather than normal "low rpm steady state cruising" conditions, how might things change? Or what new options might it open up?

What I mean is that since the engine shuts off, it might be fully acceptable to use a larger and more powerful engine because no fuel penalty would be expected in P&G mode.

It might also be acceptable to use lower gearing (more leverage, numerically higher like 4.10 instead of 2.87) in the axle, and not caring about super steep over drives because you primarily accelerate up to the desired speed and then coast down - even a gearset showing say 3000rpm at 75mph on the highway may be fine, if that's your upper P&G target rpm for best SFC.


It is possible that certain vehicles could either be more cheaply modified for, or are more innately suited to P&G conditions, than they are for the normal strategy of real low cruise RPM's. They would return to "not so good" highway mileage in closer traffic where you are forced to stick to a steady state speed, but if that is not very commonly experienced, maybe that doesn't matter.

It's also possible that one may want a more careful selection of gears - 4th and 5th chosen for P&G but a 6th if you have it chosen for steady state cruise when it's unavoidable. Some transmissions are uniquely suited to swapping individual gears around with a wider choice of factory ratios. This could make certain cars "the hot ticket" for P&G driving, similar to how the geo metro is one of the holy grails of steady state cruise RPM driving. Ie - cars which beat the metro average MPG of say 55mpg highway, while keeping the same average trip speed.

*This was inspired by my first P&G experiment in my Saturn SL, where i noticed that my 4th was too short and my 5th too long to really do P&G the way I wanted, yet the ratios being perfectly suited to normal driving.