D40 Fuel Economy

[KraftyPg]

One thing I have noticed, and I won't be surprised if I'm totally wrong, the King cab's with onboard computers (scrambling for the correct lingo here), ones with buttons on the LHS side of the steering wheel seem to get better fuel economy.

As far as I know the actual ECU in the STX was not changed when they moved to the steering wheel controls in 2010. The LHS controls are only for sound and BT aren't they and therefore would be more reliant on the BCM not the ECU. There would be different instruction to newer ECU's but I'm fairly sure having looked at whats available after market they are essentially the same ECU.

If you take your foot off completely, it reports 0L/100km's. I took off from a dead stop up hill and it read 78.3L/100 km's.

When SG 0 represents a figure less than 1lph which when your cruising at any speed is quite feasible, not maintainable but feasible for the two second reading that gets taken. The high figure works on the same principal, feasible for a short time but to sustain such a level you be hammering the engine pretty damn hard.

 

[joe2006]

Achieved a personal best/worst. Towing the van yesterday @ 25.49 litres per 100 on one tank. Following tank was 24.08.

Admittedly it was a windy as buggery (buggery is windy?). Driving through dust storms and horrible head wind.

That is sitting around 80kph or less. Frustrating as hell. Any faster and the instantaneous consumption skyrockets.

Lucky the roads are quiet and the road trains can zoom past without hesitation.

Now where are the fcken matches.

 

[nathand22]

Now where are the fcken matches.

do you need them for the van or the Nav? or both?

 

[joe2006]

Maybe if I burn the arse off the van, it will be small and light enough for the car to cope.

 

[nathand22]

may be just burn your own arse, that way it will be so burnt, blistered and sore, that the last thing you will care about is the car??

 

[siringo]

Some interesting things I've noticed in the last 12 hours.

1 - Sitting at about 90km/h with a very gentle right foot, I've managed to get 99.6km's from the fule gauge needle above full to sitting in the middle of the full marker.

2 - Watching the Torque app, if I coast along in gear with no foot on the accelerator, or roll down a rise in gear, the app doesn't register any litres/kilometre reading. If I do the same in neutral it can register from 1 - 4 litres per kilometre.

I don't know why that is??

 

[KraftyPg]

If I'm on the highway for long enough and fill the tank until it's just short of dribbling over the top I can get 180ks at about 97kph before the needle hits the F mark. But no matter how full I fill the tank I only ever get between 200 and 250ks between 3/4 and 1/4 yet I'll easily get 800ks out of the whole tank. Fuel gauges are just glorified volt meters their accuracy should always be questioned atleast once.

Not registering instant fuel readings when coasting is reasonable, but I'm not sure whether my SG preforms the same in neutral.

 

[Black_Outlaw]

ok - coming from a Petrol tuning background - this would play out like:

1. in gear, no throttle..coasting along.. A function called DECEL FUEL CUT OFF (DFCO) comes into play.. basically no fuel is injected into the intake. This is a fuel saving fucntion.. The momentum of the truck is keeping the whole she-bang turning over.. once you get down to a certain RPM / speed, fuel will the be injected again...

2. Neutral - the engine needs something to keep it "running" as there is no momentum coming from the transmission / wheels driving it over.. The car goes into a "ready idle" state where enough fuel to keep the engine idling is injected...

Another thing is Clutch Fuel Cut Off, which basically kills the fuel when the clutch is engaged.. This is another "fuel saver" - but only small..

As stated, that's in a PETROL Engine tune.. I could only think the same principles apply to a diesel..

 

[KraftyPg]

^ I'll go along with that, I've never thought about it in that much detail but it sounds feasible and almost sounds like something someone else once told me which I wasn't really listening too.

 

[Black_Outlaw]

I love your out and out honesty, Krafty.. Never let anyone say otherwise

And as I am all new to the world of Diesel, I can only assume it works on similar principles.. After all they are all internal combustion engines controlled by a computer..

 

[KraftyPg]

I come from a fairly long line of mechanics, bush mechanics and diesel mechanics and have been around them myself since I was about 8 yrs old, but I also have a short attention span and if something doesn't interest me at the time I do have a tendency to let my mind wander but what you said did resemble things I have been told before so I don't care if others think you're wrong I'll go along with you!

 

[Black_Outlaw]

Where is the "Likes this Post / Bloke" button on this forum

I'd give you 100 points

 

[KraftyPg]

We can't be trusted to have a 'like' button, too many people (but not me ) abused such a feature and it lasted less than 24 hours!

 

[Old.Tony]

Some interesting things I've noticed in the last 12 hours.

1 - Sitting at about 90km/h with a very gentle right foot, I've managed to get 99.6km's from the fule gauge needle above full to sitting in the middle of the full marker.

2 - Watching the Torque app, if I coast along in gear with no foot on the accelerator, or roll down a rise in gear, the app doesn't register any litres/kilometre reading. If I do the same in neutral it can register from 1 - 4 litres per kilometre.

I don't know why that is??

Krafty's spot on with the fuel gauge - it's like the speedo, it's nothing more than a vaguely accurate voltmeter.

Black Outlaw has also outlined things as I recall too - with enough vehicle speed when decelerating, the fuel flow to the engine is cut off. Even at idle (typically 2 litres per hour in our engines, idle @ 750rpm) the calculation ought to yield an instantaneous fuel rate of 2LPHK if you were coasting at 100km/h. Even with rounding errors, the ECU should show some flow so the answer is the fuel cut-off.

Try coasting and dropping the car in neutral and noting the flow rate.

 

[siringo]

ok - coming from a Petrol tuning background - this would play out like:

1. in gear, no throttle..coasting along.. A function called DECEL FUEL CUT OFF (DFCO) comes into play.. basically no fuel is injected into the intake. This is a fuel saving fucntion.. The momentum of the truck is keeping the whole she-bang turning over.. once you get down to a certain RPM / speed, fuel will the be injected again...

2. Neutral - the engine needs something to keep it "running" as there is no momentum coming from the transmission / wheels driving it over.. The car goes into a "ready idle" state where enough fuel to keep the engine idling is injected...

Another thing is Clutch Fuel Cut Off, which basically kills the fuel when the clutch is engaged.. This is another "fuel saver" - but only small..

As stated, that's in a PETROL Engine tune.. I could only think the same principles apply to a diesel..

This is exactly what I suspected was happening, but not having enough background in it all I couldn't explain it, all I could come up with was "while in gear, the momentum of the vehicle is 'powering' the motor via the transmission, so no fuel is needed"

So, if you were down to your last drop, you actually save more fuel by coasting in gear with your foot off the pedal, than you would rolling along in neutral. That's really good to know.

And yes, I looked at Torque again and rolling along in neutral, the 'Litres / KM' setting bobs around 2, but rolling along in gear (no foot of the peddle) it's always 0.

One more thing, I found a setting within Torque that uses additional counters. It's meant to improve the apps accuracy regarding fuel consumption. It's now what I get working it out from the fuel pump method.

 

[River Rat]

G'day all
On a recent trip to Sydney & back to pick up a caravan the Nav returned 9.2 to 9.6 l/100 @ 115+ on the way over
On the way back with 1800 kg poptop van it returned 15.7 l/100 @ 105 on cruise flat terrain with light cross wind
When I got into undulating terrain with strengthening cross wind it returned 18.4 l/100 at 105 with cruise on
As the cruise was feeding it a bit going uphill I decided to try the last leg by good old foot control, also undulating terrain with a couple of steeper hills and with even stronger gusty wind, speed between about 98 and 110, returned 16.8............reckon the foot wins
Considering I experienced a few issues on the trip due to EGR valve issue (subject to recall) am reasonably happy with the fuel consumption. I will cover the EGR issue on the appropriate thread
Cheers
John
2013 Navara D40 (Spain)

 

[Tappet]

Your brain connected to your foot will always win. Cruise controls are dumb things that only try and keep the revs the same no matter what the surrounding conditions are. They don't anticipate anything.

Your higher Consumption on return could quite possibly be EGR related. Although your 9odd liters per 100K @115K's towing a van seems too good to be true.

 

[River Rat]

not towing on the way over, definitely too good to be true......

 

[River Rat]

btw I suggest all those with new vehicles read my post on the EGR issue

 

[Dpwmlc]

Hi Dazza welcome to the forum! Im getting around 10 litres per 100ks combined around town and highway. About 650 to 680 km before the fuel light comes on.

Hi I have just picked up my new nissan navara d40 when I am in 5th auto and put it across to manual mode it drops to 4 th gear everytime . I was doing 110 km an hour on highway and it dropped straight to 4 th when I moved the geat lever across is this normal.?