diesel fuel economy

PITOURET · 7th June 2012, 11:45

hi anyone any advice

does the diesel engine perform with greater economy if i have a road speed of 40mph and engine revs of 1600 and use 5th gear

OR

a road speed of 40mph and engine revs of 1800 and use 4th gear

this question applies when i am choosing the gearing for hill climbing

thanks for any advice

paul

MrDoodles · 7th June 2012, 11:50

As the diesel delivers it's peak torque at 2,000 rpm, whichever gear which get's you closest to that!

gefary · 7th June 2012, 11:53

Doesn't it depend on how steep the hill is ?

James.uk · 7th June 2012, 15:56

Logically the lower the revs per mile the more economic it is. But.... that may well be putting too much stress on your drive train...

...

spyder · 7th June 2012, 16:17

Quote:

Originally Posted by James.uk

Logically the lower the revs per mile the more economic it is. But.... that may well be putting too much stress on your drive train...

...

This would be true with an old direct injection diesel I think. If I play around resetting the computer, my auto seems to be better at 50MPH than at 40MPH in top gear. I think all the sensors, are changing the MPG at all the wrong times for us. The synergy on 9 and the decat won't help of course.

Craig

James.uk · 7th June 2012, 16:26

It's true of any engine. Old, new, petrol gas or diesel.

...

Jules · 7th June 2012, 17:23

That question is far too complex for me right now!

Just sat down for a biscuit before doing another handbrake Mod and pesky belts change on a CDT

PITOURET · 7th June 2012, 17:47

thanks to everyone

does this mean that the diesel engine is operating best at 2000 RPM at whichever gear is necessary to suit the road conditions inorder to achieve maximum torque from the engine ?

and that to obtain the maximum mpg it is best to drive at the maximum road speed for the minimum engine rpm?

MrDoodles · 7th June 2012, 19:49

Quote:

Originally Posted by PITOURET

thanks to everyone

does this mean that the diesel engine is operating best at 2000 RPM at whichever gear is necessary to suit the road conditions inorder to achieve maximum torque from the engine ?

and that to obtain the maximum mpg it is best to drive at the maximum road speed for the minimum engine rpm?

Correct!!!

7th June 2012, 11:45	#1
PITOURET Avid contributor rover 75 diesel tourer Join Date: Feb 2011 Location: Riscle Posts: 154 Thanks: 21 Thanked 1 Time in 1 Post	diesel fuel economy hi anyone any advice does the diesel engine perform with greater economy if i have a road speed of 40mph and engine revs of 1600 and use 5th gear OR a road speed of 40mph and engine revs of 1800 and use 4th gear this question applies when i am choosing the gearing for hill climbing thanks for any advice paul

7th June 2012, 17:23	#7
Jules This is my second home ZT 260 SE Twilight and 10 other 75 ZT's :O Join Date: Jan 2007 Location: Conwy NORTH WALES Posts: 11,094 Thanks: 512 Thanked 1,116 Times in 763 Posts	That question is far too complex for me right now! Just sat down for a biscuit before doing another handbrake Mod and pesky belts change on a CDT __________________ [SIGPIC][/SIGPIC] Newbies do now!! 1. Plenum drains..all 3 or 4 year dependent 2. Cooling fan..All speeds functioning 3. Bonnet cable divider block

7th June 2012, 11:50	#2
MrDoodles Banned MG ZT+ V6 190 Join Date: Nov 2011 Location: Spalding Posts: 13,245 Thanks: 369 Thanked 1,196 Times in 818 Posts	As the diesel delivers it's peak torque at 2,000 rpm, whichever gear which get's you closest to that!

7th June 2012, 11:53	#3
gefary Loves to post Rover 75 Saloon Join Date: Mar 2009 Location: Wimborne Posts: 328 Thanks: 0 Thanked 0 Times in 0 Posts	Doesn't it depend on how steep the hill is ?

7th June 2012, 15:56	#4
James.uk Passed Away 2002 Pale Blue. Rover 75 CDTi Connoisseur auto. 170K miles Join Date: Dec 2008 Location: Near the M67. Posts: 14,509 Thanks: 199 Thanked 585 Times in 397 Posts	Logically the lower the revs per mile the more economic it is. But.... that may well be putting too much stress on your drive train... ...

7th June 2012, 16:26	#6
James.uk Passed Away 2002 Pale Blue. Rover 75 CDTi Connoisseur auto. 170K miles Join Date: Dec 2008 Location: Near the M67. Posts: 14,509 Thanks: 199 Thanked 585 Times in 397 Posts	It's true of any engine. Old, new, petrol gas or diesel. ...

7th June 2012, 17:47	#8
PITOURET Avid contributor rover 75 diesel tourer Join Date: Feb 2011 Location: Riscle Posts: 154 Thanks: 21 Thanked 1 Time in 1 Post	thanks to everyone does this mean that the diesel engine is operating best at 2000 RPM at whichever gear is necessary to suit the road conditions inorder to achieve maximum torque from the engine ? and that to obtain the maximum mpg it is best to drive at the maximum road speed for the minimum engine rpm?