Hi, recently I bought OBD Bluetooth and connected to my Journey with Android Phone and Torque application.
I wanted to check my fuel consumption on Idle, Neutral and Drive.
I was surprised when I get foot from gas pedal car was slowing and I still saw 5litres/hour consumption. When I put Neutral during slowing consumtion fell to 3litres/hour and my car was coasting, slowing less.
This is very strange. Engines should block supply of fuel during slowing with no gas....
I had always suspition that this car is doing that, progress bar for actual fuel consumption is blacked for values lower than 5litres/100km(45mpg)
Can somebody explain that?

 

I have never used the app but possibly the software
is the problem.
The DJ drops to idle mix when slowing or braking and
injectors are actually timed out until system reaches
idle mix values at which time the injectors are enabled again.

 

But remember that when slowing or braking RPM are around 1000 - 1700, This is creating much more friction in engine than at idle 600 RPM. I have doubt that there is SW issue, this is "dumb" system, just measuring length of injection and showing as litres(galons)/hour.
Yesterday I tried to drive 2 my everyday trips where I know my consumption with extreme coasting. Just get speed and then Neutral. I got consumptions 31MPG instead of usual 15MPG and 21MPG instead of usual 15MPG.
I'm telling you this car is consuming fuel even during slowing when fule flow should be turned off completely.
I see also during slowing that my immediate fuel consumption meter is showing 4 - 5 litres/100km.
I have feeling this is because of high friction in big 3.6 engine and if ECU would cut fuel completely car would slow down very quickly. It is more pleasant when you get feet from gas and car is slowing only decently. But it is burning fuel...
I think this is reason for extremely high consumption of fuel with this engine in city driving.

 

I dont know anything about using phone apps to check fuel consumption, but i do know that the fuel cannont be shut off completely because the engine will shut off and these engines do not have a start stop system.

 

These Fuel consumption apps are just a math equation where you plug in the number with Engine RPM, displacement, vehicle speed, and Manifold pressure. they are NOT 100% accurate, especially on newer cars.

 

Yes I know they are not 100% accurate, but when you are comparing relative values that in this mode car is taking 2x more then in another, this should be exact. But my problem is that when decelerating fuel should be cut off completely this is standard behavior, but in Journey 3.6 it isn't. I think this has something with automatic transmission or simply too high friction in big engine. If you would cut fuel completely car would decelerate too sharp and it is not good for smooth feel from ride.
My feeling is that this feature is main source of real high consumption of fuel in city cycle.

 

Only Hybrid vehicle shuts off fuel to the engine on deceleration... Because it has an electric motor assist.


I've heard some newer cars that does that, but I haven't seen one yet.


The reason it consumes a lot of fuel for city driving is simply because it's a SUV.

 

No as I know from Europe all cars with electronic injections control are shutting down fuel supply when decelerate on gear. There was big debate there if it is more fuel efficient to decelerate with gear and 0 consumption, or neutral with idle consumption. I'm sure, that cars are switching off fuel supply on decelerate. Engine is rotating only by inertia of car. You can simply see that by onboard computer with actual consumption 0.0l/100km during deceleration. It is little problem to see in US units, because it would be unlimited MPG.
But as I see on my Journey it is consuming fuel always, I'm going downhill, braking with engine, braking with brakes, no gas, I have around 3000 RPM and OBD is still showing some fuel consumption. This is definitely not good.
Imagine situation in city, you are 200 yards from red signal, going 40mph, you take your foot from gas and you will come to crossing with 0 fuel consumption just by engine braking, this is normal behavior.
But Journey is behaving way that it is still consuming gas and not slowing enough, so you need to push brake to slow down till signal. You effectively turning your fuel to brake rotor heat! You can simply check it with your actual consumption bar which is still showing fuel consumption around 5l/100km or 45MPG during your slowing down.

 

Can you find any links or documentation on this subject? Only vehicle I've heard that have such features are few post-2011 Ford. And according to Ford, it improve fuel economy by approximately 1%. That means you save a dollar for every 100 dollar you spend on gas.

 

The 5.7L hemi "with fuel saver technology" has "Interactive Decel Fuel Shutoff", which shuts off the fuel during deceleration. The 3.6L Pentastar does not have this feature. That is why you are seeing fuel consumption during deceleration. It's supposed to.

http://www.mideast.dodge.com/12charg...ain/index.html