4000rpm @ 80MPH?

alastairq

I think the OP is lucky...I've known 4000 rpm in top to be 58 mph!

egyptiancotton

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80MPH is still breaking the limit. I don't what's clever about publicly owning up to speeding.

Shawn_Dark

The momentary increase of speed to 80 MPH was purely as part of the fault finding process (i.e. I was simply testing the car at that speed to see if there was a problem with the engine).

For example, if the car didnt increase above 3400rpm at 80 MPH then that would have suggested there was a problem/fault.

Ultrasonic

Forgotmyname - sorry I was so brief yesterday, I had to head out.

forgotmyname wrote: »

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.

In which case this is the data that it would be potentially useful for you to share in discussions like this. I really don't believe that your TPS data tells us anything useful at all. I suspect it most closely correlates with engine load, which you would expect to increase as you drop from 4th to low revs in 5th. This is precisely why the latter would be expected to give higher mpg.

If you have brim to brim data for different driving styles that supports your claims then I must concede there might be something in them for your car. But if so it must have a very unusual BSFC distribution, and widely recommending to others that driving with engine revs close to that of the torque peak will give maximum mpg is highly likely to mislead most drivers*.

If you are relying purely on trip computer data I'm inclined to doubt how accurate it is (consistent or not). There are lots of BSFC plots in the link I provided earlier, and scanning them quickly I struggle to see any which would lead to your suggested 40 mph effect.

*This doesn't appear to be what you are saying, but there is a oft-quoted misconception regarding maximum fuel economy at revs where maximum torque can be obtained. The confusion arrises because maximum engine efficiency (max. mechanical energy out per unit of fuel in) is achieved at high load a these revs (this is the minimum BSFC). This makes the max torque revs a good place to accelerate, but not it is not optimal for steady state driving where engine load is much lower. The latter is explained by my earlier link.

Ultrasonic

DUTR wrote: »

What car/engine is this?

Ultrasonic

lloydyyy wrote: »

80MPH is still breaking the limit. I don't what's clever about publicly owning up to speeding.

Nobody spoke about driving at (an indicated) 80 mph to be 'clever'. A huge proportion of drivers do this at least occasionally, and provided we're talking on motorways I think you'd be hard pushed to find many road traffic officers who care. Discussions on forums such as this about driving at 80 mph are simply honest and realistic, and nothing to get remotely excited about.

Richard53

lloydyyy wrote: »

Why are you driving at 80MPH? 70MPH is the speed limit on UK motorways and dual-carriageways.

Ah, there's always one.

For the record, he may have been driving on private land, or he may have been in a country where the speed limit is higher than 70 mph. French autoroute, 130 kph in good weather, some German autobahns, unrestricted. People do go abroad, you know.

forgotmyname

Ultrasonic wrote: »

Forgotmyname - sorry I was so brief yesterday, I had to head out.

No worries, Just don't let it happen again

In which case this is the data that it would be potentially useful for you to share in discussions like this.
Except it would only apply to my car on that stretch of road, So putting a graph to show the fuelling would be boring and quite meaningless to others.

I really don't believe that your TPS data tells us anything useful at all. I suspect it most closely correlates with engine load, which you would expect to increase as you drop from 4th to low revs in 5th. This is precisely why the latter would be expected to give higher mpg.
BINGO... Its the extra load required in a higher gear.. Thats why it uses more fuel.
I previously linked it to cycling up a hill on a bicycle (sitting). in 1st gear you pedal like crazy but little effort, Change up and a bit more effort is needed. As you move up the gears it gets to a point where you dont have enough power to pedal up the hill whilst sitting so you stand up, The car can only do this by adding more fuel to increase the power/torque not the revs. Using more fuel.

A modern car has silly high gearing that makes the unfit cyclist wheezing and panting at the slightest incline.


If you are relying purely on trip computer data I'm inclined to doubt how accurate it is (consistent or not).
OBD reader mostly.. Trip backs up the extra MPG in each gear. But i admit on its own i would not believe it. Which is why i tried it with the OBD reader. My 1st reason for testing it was the trip showing better fuel consumption in 5th at just under 60mph than 6th gear.




*This doesn't appear to be what you are saying, but there is a oft-quoted misconception regarding maximum fuel economy at revs where maximum torque can be obtained. The confusion arrises because maximum engine efficiency (max. mechanical energy out per unit of fuel in) is achieved at high load a these revs (this is the minimum BSFC). This makes the max torque revs a good place to accelerate, but not it is not optimal for steady state driving where engine load is much lower. The latter is explained by my earlier link.

The max economy at max torque sort of works.. But it varies on the amount of torque the car has and its weight and several other factors.
A lighter car with a high torque low revving engine will be able to pull higher gearing and/or use lower revs. So yes its flawed.
But its too much effort typing..

Maximum economy is at peak torque unless the gear your in has sufficient torque at lower revs.. etc etc.... blah blah....

I dont have the figures saved for the fuel flow. If i get really bored one day i may repeat the test and give the fuel flow. Which maybe easier actually as i can use cruise control to keep the speed exact.

Looks a bit dodgy driving up and down the same stretch of dual carriageway though. :A

A few guys with the 1L ecoboost engines are finding the same, Using a few more revs than you think is economical actual improves the MPG.

Im an old fart so popping it into 4th gear at 25mph is something we could do with old lumps of cast iron and long stroke engines.


Happy cyling

andygb

lloydyyy wrote: »

Why are you driving at 80MPH? 70MPH is the speed limit on UK motorways and dual-carriageways.

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If the OP had been driving in France then their limit is just over 80MPH, so it would have been legal.
For legal purposes I expect this is what they were doing;)
Anyway, back to the high RPM and (lack of) fuel economy.
We got rid of our 1.6 petrol Mazda 3 ages ago, because it was doing 3500RPM at 70MPH and 4000 RPM at 80MPH, resulting in us nearly running out of fuel in France having done only 250 miles since brimming it at Calais.
The engineers who designed these cars should be shot.;)

Shawn_Dark

The diesel Skoda I have been using temporarily was far better, giving about 2600 rpm @ 70 MPH.