Member Since: 05 Jul 2007
Location: Cotswolds
Posts: 2515
I'll put that bottle of Rioja away Global Warming.... I'm luvvin it
29th Dec 2008 10:44 pm
simon
Member Since: 11 Jan 2005
Location: Shropshire
Posts: 18296
No keep it going.
I'm off to grab some port - well it is Christmas time
29th Dec 2008 10:59 pm
CY
Member Since: 16 Aug 2005
Location: Warwickshire
Posts: 4506
simonsi wrote:
max efficiency on any engine is at the max torque point, its where the output (torque) exceeds the friction and other losses in the engine.
So, does this mean that since my petrol car develops its peak torque of 127 Nm at 4 250 rpm this is the most efficient point to drive at? Further, given I drive usually at less than half that number of revs I should get significantly improved fuel efficiency if I double the revs, say on a motorway drive?
It just feels counterintuitive for me to throttle it thus doubling the 'effort' of the engine from what it seems to sit at comfortably - but then I don't really understand the mechanics of the engine as much as I'd like to 2007 Porsche Boxster (987) 2.7
2008 Discovery 3 TDV6 HSE G4 Challenge (1 of 68)
2023 Defender 90 D250 X-Dynamic HSE
29th Dec 2008 11:11 pm
simonsi
Member Since: 14 Oct 2007
Location: Auckland
Posts: 1264
Petrols introduce other sources of inefficiency such as runningg throttled (from an air intake viewpoint) almost all the time, and smaller petrols have max toque at engine speeds where noise etc beccomes more of an issue.
I suspect your gearing doesn't allow 70mph at 2000rpm though as LR petrols or diesels do, the gearing wil be tuned to the engine characteristics but the principle is the same that means others on here are gaining mpg by running in 5th instead of 6th, all other things being equal then running an engine close to max torque is where it wil be most efficient - but also take into account the shape of the torque curve on any engine, if flat then you can get most of the efficiency over a range of speeds, just one compromise is vehicle design....
Forgot to add, the D3 issue with 5th vs 6th is one of dropping off the bottom of the torque curve due to too high a gear meaning too few revs for the engine to work as eficiently as when running slightly faster.Cheers
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum
