Injector Cutoff - Do D40 injectors turn off on deceleration?

[joe2006]

After 2 years I have finally got around to properly calibrating the Ultragauge. One of the things it will factor into the consumption calculations is injector cutoff. Some manufacturers will turn off injectors on deceleration and I was wondering if anybody is aware of whether the D40 does this?

Thanks in advance.

 

[tweak'e]

yes.
i would say every electronic diesel from ~2000 would have that feature.
really noticeable on the egt gauge.

 

[Old.Tony]

I'd say yes. ECU is reporting 0.0 litres per hour fuel flow rate when decelerating, despite a fuel rail pressure that's in the 4-5K range. The only thing that could cause that - apart from a miscalculation (because things like load% are negative) is that the injectors are not being asked to open at all.

 

[joe2006]

Thanks guys.

The default setting on the gauge is for there being no cutoff. To date, when I decelerate and change down, the instantaneous consumption figures increase, corresponding with the increase in RPM. I will set it for injector cutoff now.

As a matter of interest, or perhaps of no interest I have also calibrated distance and the calibration factor is 1.07 so for every 20ks that I do, the odometer reads 18.7ks. After taking into increased diameter of the 265/75/16 tyres, I suspect that the odometer may have always been a little inaccurate, even when running the stock tyres. Mind you there can be a few mm difference between tyre brands and then there is always the issue of tread wear

 

[oldmate45]

On my 2013 ST - tyres are stockers - for now.
I calibrated my ScanGauge II speed from GPS and the indicated speed on the speedo is about 8% out. i.e. speedo shows around 108 when I'm actually doing 100 by the GPS.
But the utes odometer/tripmeter is nearly bang on the money.
I suspect the OBD port is reporting the odometer reading/time (V=D/T) to my scangauge because I only have to have it calibrated to 1% for it to show "true" GPS speeds.
I've also confirmed that the odometer/tripmeter and Scangauge trip meters are correct against the 5km speedo check thingemeys on the highways.

and yes my fuel consumption drops to zero on my SG when I'm off the go pedal

Hope this all makes sense...
Jas

 

[joe2006]

Thanks Jas.

You are right about the odo being far more accurate than the speedo. Now I have changed tyres, my speedo is accurate but the odo is out

On the weekend I will see what difference the setting changes to the Ultraguage made.

 

[Old.Tony]

The odometer/speedometer issue is actually very easy to explain.

With standard tyres on, the odometer is quite accurate (as you've observed). The ECU's calculation for speed is also quite accurate - ask your Scanguage for the ECU's speed, or ask Torque for its reading on it (it's in the list as "Speed (OBD)" which is just after the "Speed (GPS)" entry). You will find it remarkably close to the mark.

What's NOT accurate is the needle on the speedo that you look at. The figures in the ECU are right, the voltage sent to the needle is right, but the needle doesn't deflect properly for the voltage sent to it (that's the technical reason). Put simply, everything except that stinking needle is right!

That's why I keep advocating a GPS unit. If your tyres are out you'll need to cater for that difference in your fuel economy formula - a 5% variation (eg 255/70R16 to 265/75R16 tyres) makes a difference on a trip to Uluru and back.

 

[JPMC]

Old Tony is right.

On my 2012 140kw model if I put the stereo into diagnostic mode even that shows the correct speed to match GPS and Torque App but not the speedo.

 

[joe2006]

Well that was a waste of time. The Ultragauge obviously doesn't support injector cuff off on the Nav.

Luckily it says that setting only makes a marginal improvement in accuracy because when I back off, the instantaneous lph figures still show it using fuel.

It seems that the Scangauge might have a few more usable functions.

 

[Old.Tony]

The ECU's LPH figures fall to zero on mine. Torque (the app I'm using) is just pulling the PID (01 5E) and displaying that. What does your Scangauge show for that PID?

 

[joe2006]

I am sorry Tony but most of what you said was chinese to me. I am laughing at me, not you!

PID?

 

[Old.Tony]

It's the code you'd ask Scangauge to look at in the ECU.

 

[joe2006]

I don't ask it to look for anything. When the gauge is plugged into the OBD11 port it does whatever it needs to do automatically. It just needs calibrating for engines size etc etc.

Tony you are talking to a technical nuff nuff.

Edit: The instructions say, "Once connected UltraGauge will begin scanning the interface to determine the vehicles protocol." It then says, "UltraGauge will then begin discovering the gauges supported by the vehicle."