[LINK] Fuel consumption

[Bernard Robertson-Dunn]

On 26/05/2011 8:48 PM, stephen at melbpc.org.au wrote:
> This is off-topic for Link, but, am wondering if the physics/engineering
> (whatever) people here can suggest how to resolve something I've been
> wondering, besides doing road tests.
>
> If a vehicle has an overdrive gear that kicks in at 80 klm/hour, would it
> be better for fuel consumption to drive at 75 klm/h and higher revs, or
> faster at 85 klm/h but with lower revs?

You don't say at what speed the overdrive gear drops out at. You could 
try getting up to 80 k/hr, let it kick into overdrive and then slow down 
until just before the car changes up again.

BTW, there is another strategy that is quite useful. When coming up to 
lights or a roundabout, change down and let the car drive the engine. 
Fuel consumption drops to zero. That's because an idling engine requires 
fuel.  If you let the inertial of the car provide the energy, you don't 
use fuel for idling.

My car can show instantaneous fuel consumption. I've noticed that 
changing from 5th to 4th makes no difference to the consumption, but the 
changing down strategy makes a significant difference. It also reduces 
wear on the brakes.

-- 

Regards
brd

Bernard Robertson-Dunn
Canberra Australia
email:	brd at iimetro.com.au
website:	www.drbrd.com



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