Higher or lower revs?

Dogbreath · 24 Mar 2006 at 15:02

As a sweeping generalisation, engine efficiency is increased at lower RPM (less frictional losses), and wider throttle openings, (better cylinder filling = higher dynamic compression ratio = higher thermal efficiency).

Simon · 24 Mar 2006 at 16:21

Dogbreath said:
As a sweeping generalisation, engine efficiency is increased at lower RPM (less frictional losses), and wider throttle openings, (better cylinder filling = higher dynamic compression ratio = higher thermal efficiency).

Agreed. This is why small engines get good consumption, you have to full throttle everywhere

The_Dark_Side · 24 Mar 2006 at 18:25

Morba said:
that will be why it was on ebay and will be on autotrader from tomorrow!! haha

you're selling?
no way!
i thought you loved the thing.

PMKeates · 24 Mar 2006 at 18:37

Is this why my particular driving style of using maximum/heavy throttle up to a set cruising speed and sticking there tends to return very good fuel economy?

The_Dark_Side · 24 Mar 2006 at 18:58

PMKeates said:
Is this why my particular driving style of using maximum/heavy throttle up to a set cruising speed and sticking there tends to return very good fuel economy?

roughly speaking, your fuel consumption drops while accelerating so if you briskly step up to your cruising speed rather than gradually reach it you will return better mpg figures.
in a nutshell, the less time you spend accelerating the better.

PMKeates · 24 Mar 2006 at 19:07

Ah, that explains it then. My dad always says I don't drive economically when he's with me, and always assumes I'm lying when we work out that I keep getting better economy out of a 1.8 Xsara than he can out of something like a 1.3 Fiesta, despite having similar journeys!

GlasgowTitan · 24 Mar 2006 at 20:56

PMKeates said:
Ah, that explains it then. My dad always says I don't drive economically when he's with me, and always assumes I'm lying when we work out that I keep getting better economy out of a 1.8 Xsara than he can out of something like a 1.3 Fiesta, despite having similar journeys!

Anything is better than a 1.3 Fiesta. Seriously, I put £34 quid in it today, I have since done 49 miles and the needle has gone from OVER the full line to nudging the 3/4 tank line. WTF :confused:

PMKeates · 24 Mar 2006 at 21:09

I wouldn't trust the fuel guage, tbh. My first car seemed horrendously inaccurate. I regularly drove that in to the red, then the white line, then in to the black and it was still going fine. I'd then fill it up and struggle to get 50l in a 55l tank - 40 miles left to go!

needmorespeed · 24 Mar 2006 at 22:41

GlasgowTitan said:
Anything is better than a 1.3 Fiesta. Seriously, I put £34 quid in it today, I have since done 49 miles and the needle has gone from OVER the full line to nudging the 3/4 tank line. WTF

i've done 80 miles in my v6 and its still above 3/4 tank LOL