Thread: 3.9 v8 fuel economy

I have a 96 V8I and get under 13 LPH on the highway using cruise at 110 klm that's on 91 RON fuel, heaps better than my mates Land cruiser. I don't think that's to bad for 2 tonnes of metal with the aerodynamic properties of a brick wall.

bee utey

"6. read weather forecast, plan trips down wind" Still have tears (of laughter) running down cheeks.

Some great suggestions from all involved.

We all know these 3.9s are exceptionally thirsty buggers. Mines no different. I have recently had a win after diagnosing a dodgy vacuum advance on dizzy. This common fault will kill economy and most people will not even know just how bad until its discovered.

All the best and thanks everyone for the laughs!

[QUOTE=Neesaan1via;1753286]Ok so as the title says I want to no about people fuel economy on these engines and also what you can do to improve it ?

Mine was getting about 20 LPH when I first bought.
in the last 2 years I have:

Replaced dead vacuum advance unit.
Replaced Lucas ignition module and coil as per Bee Utey Bosch conversion as the Lucas module was missing when hot, definatly had more torque uphills after this.
Replaced tyres with slightly larger 245/70/16 Pirelli Scorpions ATRs
Cleaned MAF
Retarded timing to 9 deg BTDC this also stopped a stalling on startup issue.

Now goes like a stabbed rat and gets under 13 LPH on the highway at 110 using cruise on 91 RON
Very little difference with higher octane fuel so I stick to cheap 91 unleaded (dont use e10)

Sparky

I get 20l/100km if i'm lucky, lpg 27l/100.
How do i check if the vacuum advance is working as it should?
Don't worry, found some great older threads for the answer!

Originally Posted by vogue

I get 20l/100km if i'm lucky, lpg 27l/100.
How do i check if the vacuum advance is working as it should?

Take the vacuum advance hose off the top of the manifold, remove the dissy cap, suck on the hose and watch for movement of the pickup behind the plastic shield. A working vac advance will hold vacuum as you suck on it, hold the vacuum for a few seconds and let it go, the advance should snap back into position.

Alternatively use a timing light to check as you connect/disconnect the vac hose at say 2000rpm engine rpm. You should have a timing light to check the idle timing (around 10 deg BTDC) and mechanical advance anyway. Cheep on fleebay, a tool every D1 V8 owner should have. Also put your finger on the vac nipple on the manifold while holding 2000rpm. there should be suction on your fingertip. Sometimes the port in the manifold carbons up. A thin piece of stiff wire can poke it out.

Don't mean to revive an old post but is 450 to 470km off a tank about average? I run 235 85 16 tires and my speedo reads slower 100km/h is around 110 on a multinova base reference, would the odometer read lower?

Sound pretty excellent to me!... Disco 1? V8??? if it is, that's awesome! and yes... larger tyres show lower (on the speedo) than actual road speed. Therefore: odometer will read lower distance travelled than actual distance travelled. I have 33's on my Disco 1 and it reads 87-89 (depending on psi neglection haha) at an actual road speed of 100kph. To satisfy your curiosity, if you have a GPS, reset the odometer function on the GPS and the dashboard and compare the two over a tank full.

Hope this helps.

Originally Posted by Spydz

Don't mean to revive an old post but is 450 to 470km off a tank about average? I run 235 85 16 tires and my speedo reads slower 100km/h is around 110 on a multinova base reference, would the odometer read lower?

Depends how close you get to the bottom of the tank.
Litres are a better measurement than tanks.