Fuel economy 3.9 with O2 sensors

**PhilipA** · 12th November 2007, 07:48 PM

I just returned from 2 weeks in sunny? Victoria in my 92 rangie 3.9 auto with 140L long range tank
Towed my Campomatic which weighs about 600KG.

First tank from Sydney to Benalla 16.2 L per 100Km, at 110 Kmh and change down to (auto) third to maintain 100Kmh so the cruise control did not drop out on hills.
Second tank 110Kmh to Melboune from Benalla then running around without camper . Result 19.5 L per 100Km.
Third tank east of Melbourne to Cann River into 40-50Kmh headwind at 110Kmh.Wife drove most of the time and I asked her today whether she had her foot down? She said yes but not flat! Result 20L per 100Km.

Fourth tank Cann River to Dapto at max 100Kmh( or so) into variable winds. result 17.9 L per 100Km.This is hilly country and it was fun passing those TD Landcruisers towing vans up hills.

I do not know what it proves but my gut feel is that economy is about 10% better.
Just shows how hard it is to make any definite conclusions,as conditions change so much.

Over 4 tanks where I filled at about the same level, red light on on even mild LH bends, it averaged 18.4 Litres per 100 Km.Couldnt be shagged to get exact filling etc, and it well may be that the 16.2 was actually worse and the next one better due to filling errors.
But the overall average is pretty right.
Not as good as I had hoped but there you go.
Regards Philip A

streaky · 13th November 2007, 01:00 AM

Phill.
Do I take it that you've just installed O2 sensors to your car?
The reason I ask is that I have been experiancing dreadfull fuel economy on my Discovery 4.6Efi Hotwire and as a result I've just ordered a wideband O2 sensor from TechEdge in Australia.
Our Middle east spec Disco's don't have cats fitted so trying to monitor the fuel burn is impossible to do accuratly.

I'm getting around 250-280km to the 90lt tank. The tyres are 265/75-16's and the whole vehicle is approx 450kg over weight with winch, bumper, drawers, roofrack, under-sill tanks etc.
I think I'm getting around 3km per liter right now.... as opposed to 5-6km per liter for a healthy 4.6 V8.

What size tyres are you running? Are you carrying much more un-srung weight on the car or just the camper?

Thanks for the input... it all helps me diagnose my problems.

Regards.

S.

**edddo** · 13th November 2007, 07:31 AM

to me that looks like fantastic economy from a v8 towing. Id be v happy with that! NOt as if you were driving for economy either.

**PhilipA** · 13th November 2007, 07:47 AM

Do I take it that you've just installed O2 sensors to your car?

Yes, see the earlier thread.
If you PM or post your email address I will email you the procedure to fit them.
They are only narrow band, and it affectively provides closed loop (14.7:1) at smaller throttle openings to a 14CUX without cats.
I have 245.75x16 tyres and no bullbar. I also had an Engel fridge in the car and other stuff that probably added 100Kg, and of course the LR tank which adds 60KG of fuel at first.
Regards Philip A

streaky · 13th November 2007, 03:27 PM

Phill...thats great thanks.

Please send any related info to david@galfme.com
They haven't arrived from Tech Edge yet but I expect them next week sometime.

Thanks again.

Regards.

S.

**Utemad** · 25th March 2008, 07:07 PM

How's this going Philip?

**PhilipA** · 25th March 2008, 07:27 PM

How's this going Philip?

Its going fine.
Its hard for me to get accurate comparable economy measurements with my 140 litre tank. The last fill up was 17.5 Litres per 100Kms in strictly local NSW Central Coast suburban driving ( which I think is too good). It is easy to be out by up to 5 litres even at the same pump.
By seat of pants I am getting about 10% improvement in economy, even vs the previously optimised Unichip curve. Average seems to be 20 L per 100Kms local vs 22.5 before. Its really hilly here.
Have a look at the Megasquirt thread where there is a link to a good discussion on the advantages of closed loop.
Regards Philip A

**Utemad** · 25th March 2008, 07:57 PM

Thanks Philip.

**ytt105** · 22nd April 2008, 12:12 PM

PhillipA
I remember your thread some time ago about o2 sensor on 14cux.
Can't seem to find the thread anymore.
Do you have a link to it or any instructions on How to
I presume you still think its worth doing?

**Utemad** · 22nd April 2008, 12:30 PM

I'm currently doing this. Just waiting on the oxygen sensors before I start.

Some links
Closed loop 14CUX RRC 3.9
First fuel economy with 14CUX O2 sensors

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