KJ Fuel economy thread

[JEEPaul]

Thanks Glen. On a related topic, because my V6 is a limited, I have the instanteneous fuel figure readout as well as the average figure.

As you can imagine one spends quite a bit of time watching the readout to see how it responds to different speeds, road gradients, gears etc. What I've noticed (with all else being equal) is that at 80kmh in overdrive (the TC is unlocked), my fuel milage is the same as it is at 100 - 110kmh. At 90kmh it's actually slightly worse.

I'm well aware of the relationship between drag and speed so it's quite frustrating my TC doesn't lock up a little earlier should I wish to achieve some 'long range' cruise/fuel flow figures. I'm sure that if I was locked up at 90 then on a long distance crosscountry run I could get under the magic 10lt/100km mark. Best I've done to date is 10.5lt/100km over a 300km loop (Melb to Ballarat and return). Pretty bloody good still for a petrol I guess. That was driving 'with an egg between my foot and the pedal', with no wind out and a strong tailwind home. (I've noticed a good 20kt headwind vs a 20kt tailwind accounts for around 3-4lt/100kms in the V6!!)

There was a heap of info available for the AW4 in my XJ on DIY manipulating of the TCM; haven't been able to find much on the 45RFE as yet.

[BeagleCamper]

Originally Posted by glend

Well that is not that simple a question, because it depends. In my case I am running one of the few GDE TCMs in original configuration, which means that my transmission (545RFE) upshifts at a much lower rpm than the stock settings (that means around 1500RPM). Obviously if you really have your foot in it then it holds on for longer but for just normal driving it will upshift at 1500 in order to lug the engine and get better fuel economy. The OD button is also programmed to have 'other' uses on the GDE TCM tune, it can be used to lock the transmission in third. It also will shift with the torque converter locked, from 3rd, to 4th and 5th (up and down) without going back on the pump (ie dropping down into third then going back up).

Now at 90 I have choices with my TCM, I can run in 4th and hold it there, or I can run in 5th. I prefer 4th because it is a thermally more efficient gear for towing and 5th is really an overdrive gear.

Perhaps someone else can answer because I can't remember when the stock TCM does lock up.

I have 06 CRD auto.
With overdrive switch off ( 4th & 5th locked out), torque converter locks up at 60 km/h
With overdrive switch on, torque converter only locks for 4 th & 5 th gear. Locks at 80km/h when changes into 4th, then 100 km/h when changes into 5th. (Note, doesn't lock at 60km/h in third gear as does with overdrive off)
When speed drops to 90 km/h it drops back to 4th with torque converter remaining locked.

How do I drive it?
Towing I leave the overdrive switch off (= no overdrive) so torque converter locks at 60km/h, then turn on at 80 km/h so it changes to 4th with torque converter locked. When speed drops below 80 km/h, I turn overdrive switch off again so torque converter locks in third.
General driving I generally leave the overdrive switch on, which means up to 80 km/h the torque converter doesn't lock up.
If driving in hilly/twisty conditions where speed is mostly below 80 km/h I will turn overdrive off, so driving in third with torque covnerter locked.
By experimenting over time I find this gives me the best fuel economy and makes the car feel the most drivable.

[JEEPaul]

Thanks guys.

[alice springs]

I have an 02 3.7 v6, using about 18l per 100km any suggestions

[anthonygubbin]

Originally Posted by alice springs

I have an 02 3.7 v6, using about 18l per 100km any suggestions

Is that at 130kph or 95-100kph?

Regards A

[alice springs]

Hi Anthony, at 130,has just been fully serviced

[anthonygubbin]

Originally Posted by alice springs

Hi Anthony, at 130,has just been fully serviced

130kph that is your economy problem. If you test it at 95-100 you will improve your economy by about 15% maybe more.

Regards A