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Car Forum / Driving, Maintenance, Tuning / General Car Topics / February 2008

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fuel use the effect of gears and throttle position

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Obakesan - 08 Feb 2008 08:19 GMT
Folks

just wanted to see if others here have the same findings as me. I don't
have an accurate fuel consumption meter to confirm it.

5 speed manual:

flat road driving with a constant speed best fuel economy is the highest gear
you have

however, as soon as you start to climb a hill, then reduce the gear to keep
the revs closer to the maximum torque range of the engine.

On my mitsubishi (V6 3L) at 100Km/H in 5th I find that I change back to 4th or
perhaps 3rd depending on the hill / load of passengers n stuff.

My mate on the other hand just keeps his foot on the pedal untill the revs
start to slow (meaning he's loosing speed), then changes down to get to the
same gear as I got to earlier.

On an automatic gearbox:

I flick it out of OD as soon as I start up the hill, and flick it back on
nearing the crest (as speed starts to rise anyway). This often requires no
change in pedal indicating to me that I'm not needing to open up the
'throttle' more meaning using less fuel.

no?

See Ya
(when bandwidth gets better ;-)

Chris Eastwood
Photographer, Programmer              
Motorcyclist and dingbat

please remove undies for reply
Mike Walsh - 08 Feb 2008 15:19 GMT
Many years ago it was better to keep the revs down and open the throttle to get good engine efficiency. These days engines will not run efficiently at wide open throttle because of the high compression ratio; which requires that the spark be retarded and the fuel mixture enriched to prevent pinging. This is worse in hot weather with low octane gas; not so bad in cool weather with higher octane gas. You are probably doing the right thing by keeping the revs up and avoiding wide throttle opening. An automatic transmission should do it - automatically.

> Folks
>
[quoted text clipped - 33 lines]
>
> please remove undies for reply

Signature

                  Mike Walsh

user@domain.invalid - 08 Feb 2008 21:15 GMT
Mike Walsh,

How about changing the email address in your news reader. Yes spamsucks
really is a valid address, I've had the address for about five years. I
don't want to get your usenet post. So change it. Send me a private
email if you don't believe me, so I can forward your The National MS
Society email to you.

Change it!!!!!

> Many years ago it was better to keep the revs down and open the throttle to get good engine efficiency. These days engines will not run efficiently at wide open throttle because of the high compression ratio; which requires that the spark be retarded and the fuel mixture enriched to prevent pinging. This is worse in hot weather with low octane gas; not so bad in cool weather with higher octane gas. You are probably doing the right thing by keeping the revs up and avoiding wide throttle opening. An automatic transmission should do it - automatically.
>
[quoted text clipped - 35 lines]
>>
>> please remove undies for reply

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