Quote:
Originally Posted by RedDevil
If I fluctuate my speed downwards, topping that hill, wind resistance might even be lower rather than higher. Wind picks up at height.
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I will agree that the correct speed to use for wind resistance is the air to vehicle speed and not the vehicle to ground speed ... so sure.
I will agree to that exception ... if you are able to accurately predict the wind speed changes correctly in real time before they happen ... then sure ... it would be possible to combine vehicle speed fluctuations with that precognitive ability in order to not have a net of more aerodynamic loss joules.
Quote:
Originally Posted by RedDevil
But even if it gets higher, that's probably preferable to the 50% or so you lose in the charge-to-discharge conversion.
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The round trip can loose 50% ... or in other conditions it looses only 25% ... or maybe in yet other conditions as little as ~13%... it depends.
It is not the HEV that is % wasteful with joules of braking , compared to the non-HEV.
The ICE can also change that much or more in it's operating efficiency.
And there is also the other potential losses from other sources ... including the air to vehicle speed fluctuations... route choices ... etc.
It is not HEV% loss vs 0% loss ... the non-HEV option can have losses too.
If the choice in a specific condition is 43% loss or 42% loss ... the 42% loss is better ... it is better if it is the HEV round trip ... or it is also equally better if it is the avoid using the HEV option.
Quote:
Originally Posted by RedDevil
When the speed variation is low, the amount you lose on the bit you go faster is hardly any bigger than the amount you gain while goiing slower. The relation between wind resistance and speed is quadratic; so it rises sharply by raising the speed but also drops almost as sharply by lowering it. It pretty much equals out.
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(Bold added)
No ... it does not.
The smaller the fluctuation the less of a penalty ... but there is always a aerodynamic joule penalty for the air to vehicle speed fluctuation.
We can crunch the equations if you like ... but ... it does not balance out.
Quote:
Originally Posted by RedDevil
It is impossible to attain perfection on such a complex matter as this in just a few sentences. But that does not mean that you cannot draw general conclusions.
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Agreed.
Quote:
Originally Posted by RedDevil
Cobb's statement was more to the point than many like.
The "Hybrid is good, must use it always" rule simply does not work. The system is great to have when you need it, but you get better mileage and longer battery life by minimising its use when you don't.
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I disagree with the "must always use it" people ... just as much as I disagree with the "can do better without ever using it" people.
Just telling people to avoid it ... avoid it... and avoid it some more ... is ultimately less useful and helpful than explaining the + and - ... of when using it is + to MPG ... and when using it is a - to MPG.