Thread: How do I improve Fuel Consumption?

I've tuned my 3.9v8 rrc with great results. No fuel economy numbers yet but the tank is lasting a lot longer than previously. Stable idle and power restored too.

Tks Dougal, pls keep me informed as to the tech settings employed. No service personal have ever advised or implemented tuning settings of any worth over my 18 yrs of ownership.

It's all buried in the thread in the classic rangie section titled 93 hard dash, spark plugs and fuses. Skip to the end of the thread as the results are recent.

Service regularly
Advance timing to 10-12 degrees btdc
Fit a bosch ign module as per bee utey
Keep tyre pressures up
Free flowing exhaust
Drive with an egg under your right foot
If rebuilding engine,9 to 1 pistons,economy cam
ALL helps

Colin,
Unfortunately it's the old story, you get nothing for nothing, and the power, responsiveness and sound of a V8 is going to cost you at the bowser.
Was a time in years past that the cost of fuel was the most minor consideration in determining what car to drive, but even back in the early 90's when I owned an old '77 Range Rover classic, I had to decide whether 13 MPG on petrol was affordable for me to take the family on holidays and up into the State Forests or beaches on weekends to carve up a bit of terrain.
My answer and the saviour of that Rangie (and our family budget), was to have the old 3.5 V8 put on gas, which at the time was cheap, 14 cpl, as was the conversion cost, about $800 at the time, the fuel range was the killer. Now days even gas and conversion are lots more, but at that time that allowed us to afford to run and keep what I reckon was the best most fun and useful vehicle I will ever own.
Todays I drive a D1 300Tdi, goes nice on road and off and operates with an affordable/acceptable fuel consumption, 10 l/100klm. It is no powerhouse but it's sedate acceleration keeps me out of trouble with the revenue raisers.
A mate of mine had fitted a brand new Rover 4.6 litre V8 into his '86 RRC and spent a veritable fortune and lots of time on bolt on "do-dads" to try and improve the fuel consumption, in the end he gave up, that car now runs a 300Tdi diesel and manual tranny, all nicely engineered and it does all he asks of it for half the fuel consumption, the only thing he misses is the sound of that big V8.
Even Diesel power is getting costly but nothing like the costs associated with petrol V8 powered 4X4's. You love your car so much, (BTW, does your wife know?), Re-power it with a diesel, not a big'un, but a 2.5-3.0 litre turbo unit, it could just enable you to keep and afford to run your beloved D1 for another 18 years. Gaz

Tks gazby, you really have touched an emotional nerve with common sense logic. To be brutally honest, the V8i is now old tech although I love them dearly. Its 'used-by' date has truly expired. My conscious issue is that I will now look towards a newer Japanese or other brand hence ending my long association with land rover. I bought my first 2 door classic in 1980 2nd hand, owned 3 over time, and now that era will end. That's 34 years of attachment with membership of an associated club. Even if I were to buy an oldish 2nd hand diesel, I would not be happy with the transfer boxes, oil leaks and build quality that goes with lr. Yes, your comments are very sobering and will considered in my final decision.

Originally Posted by gazby

Colin,
Unfortunately it's the old story, you get nothing for nothing, and the power, responsiveness and sound of a V8 is going to cost you at the bowser.

While this is undoubtedly true, the fuel consumption the OP is reporting (3.5km/l) is about double what a healthy and in-tune rover V8 should be producing.

My 93 RRC had every sensor in spec but was running so rich it would paint the ground black under the exhaust when revved stationary. Fuel economy was similar to the OP.
I've retuned it, which involved pulling the original chip off the ECU board, getting a socket installed and then modifying the maps based on drive tests with a wide-band oxygen sensor and gauge.

I suspect the majority of V8's around this era are running this rich. I'm not sure of the exact cause, it can't be injectors worn oversize because I'm running my injectors at full open to get enough fuel at full throttle over 4000rpm.

All 14CUX have all the internal wiring for o2 sensors, which when fitted keep the AF ratio in the 14.2+ ratio.
I f you look way back in projects you can find my write up of that and also the Thor fitment.
My 92RRC which I sold last year got about 14Lper100km towing 700Kg at 100kmh, and about 17.5 around the burbs no trailer. On a beach they will all chew the juice .
Mine also had a Unichip, which was one of the greatest mods as it took control of the "vacuum" advance and introduced far more at cruise.
IMHO this and the o2 sensors were the greatest conributor.

In the end mine also had self modded heads and a Thor inlet. The Thor inlet changed the torque curve immensely and allowed climbing hills towing without kicking down. The heads added about 7% more power.
All this was dyno tested and proven.
If you want a copy of the o2 sensor how to email me, but to me the first thing to do is a Unichip or other interceptor which takes over vacuum advance..
Regards Philip A