4000rpm @ 80MPH?

Ultrasonic

Abu_Yoosha wrote: »

No, but I am hoping that I can get through the week with £20. Its not like I'm putting my foot down (i.e. sticking to the limits).

You should be OK. You'll need to average about 30 mpg to do 100 miles on £20 worth of petrol.

If you have any interest in fuel economy you ought to start calculating mpg not seeing how far you can go on fuel bought for a certain amount of money though.

forgotmyname

A petrol engine produces its power and torque ar higher revs than a diesel. With no turbo to help it along you need to rev it more to get the same performance.

If you think pootling around town at low revs = economical then your going to learn something new. Peak economy will be close to peak torque.

You should be using more revs.

Shawn_Dark

forgotmyname wrote: »

A petrol engine produces its power and torque ar higher revs than a diesel. With no turbo to help it along you need to rev it more to get the same performance.

If you think pootling around town at low revs = economical then your going to learn something new. Peak economy will be close to peak torque.

You should be using more revs.

So what are you saying? I need to accelerate hard/quickly with this car to get better economy?

Ultrasonic

forgotmyname wrote: »

Peak economy will be close to peak torque.

You should be using more revs.

No. Low revs for steady state driving does mean best fuel economy. More revs for more power, yes, but not more mpg.

(I haven't got time to argue now, but read this:

http://ecomodder.com/wiki/index.php/Brake_Specific_Fuel_Consumption_%28BSFC%29_Maps#Volkswagen_Jetta_TDI_1.9L_ALH_1999.5-2003)

Ultrasonic

Abu_Yoosha wrote: »

So what are you saying? I need to accelerate hard/quickly with this car to get better economy?

That on the other hand is true. High load acceleration close to the torque peak will generally mean best engine efficiency, but once you've reached the speed you want to drive along at you want to be in as high a gear as your car is happy at (i.e. minimum revs).

Gotta dash so can't debate more now.

forgotmyname

No. You need to know where the peak torque is.

example in my car. tested with an OBD reader..

4th gear at 40 mph uses LESS fuel than the same speed on the same stretch of road in 5th gear.
Although 5th gear cruises happily and lowers the revs, I am actually pushing the throttle down further to increase the torque required to maintain that speed.

9% throttle usage in 4th but 18% in 5th.

The torque available in 5th gear isnt quite enough in 5th gear.

If the road is downhill then the lower revs in 5th will work to your advantage. Less torque will be needed to go down the hill.

Ultrasonic

forgotmyname wrote: »

No. You need to know where the peak torque is.

example in my car. tested with an OBD reader..

4th gear at 40 mph uses LESS fuel than the same speed on the same stretch of road in 5th gear.
Although 5th gear cruises happily and lowers the revs, I am actually pushing the throttle down further to increase the torque required to maintain that speed.

9% throttle usage in 4th but 18% in 5th.

The torque available in 5th gear isnt quite enough in 5th gear.

If the road is downhill then the lower revs in 5th will work to your advantage. Less torque will be needed to go down the hill.

We've had this debate before. You are still wrong. You can't judge this by throttle position reported by OBD. You need to look at fuel flow rate (gallons per hour) or mpg.

goonarmy

Yeah






Minimum characters are pants.

forgotmyname

As i have stated before the fuelling figures also state more fuel is being injected. And the trip computer which i must admit is not 100% accurate but consistant.

Shawn_Dark

Okay as my question was answered I'll say good night.