Quote:
Originally Posted by freebeard
Since you can't be bothered to look at the link before posting:
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I said that I looked at the link but
then couldn't be bothered trying to work out the obscure message.
Thanks for the explanation but I don't think it's germane to what is being discussed here.
I don't think any ratio of drag reduction: mileage improvement is particularly helpful, because, as I have already written:
Before you can even start to describe such a relationship accurately, you need to know:
1. The starting Cd (a car with a Cd of 0.35 will have a higher aerodynamic contribution to overall resistance than a car with a Cd of 0.25).
2. If at a constant speed, what that speed is (aero drag goes up at the square of the speed; rolling resistance does not), so if the term 'highway' is used, we need to know what highway speed is.
3. If it's in a drive cycle test, what is that drive cycle?
...and there are other points as well, eg environment in which the car is being driven, absence/presence of regen braking, etc.
As soon as anyone introduces a rule of thumb, especially without heavily emphasising caveats, people will in ignorance subsequently blindly adopt it. Just as Aerohead did in another thread with:
Maximum torque occurs @ approx. A/F = 13:1 ( 'best power mixture' )
A perfect example of an incorrect rule of thumb in engine management!
Rules of thumb are bad news in any car modification area - suspension, engine management - and aerodynamics.