Thread: 1990 3.9i, appalling fuel consumption

Originally Posted by UncleHo

If you suspect the Vacc Advance unit, it may be worth getting an exchange one to suit it,www.advancediaphramoptions.com in Qld

can you check that link

Advance Diaphragm Options

This worked. Note the "g" in diaphragggm

at speed limit only!- and managed 5.77km/l = 16.3mpg = 17.36 l/100km
- Feeling a bit happier !

This is still pretty bad.

The official fuel economy on the UK test AFAIR was about 20MPG at 75MPH or 14.12L per 100Km. That would be on a very flat road.

Do you have 205.16 tyres? Remember you have to add a % to the travelled distance if you have bigger tyres.

Regards Philip A

these have been useful for me :

get a high performance coil fitted
get a pod filter fitted
drive at 90km on the freeways because you will save 1/3 more fuel according to the handbook
ok, 4 , dont drive like a typical lead foot australian !

any ideas on what are good coils?

Originally Posted by 85 county

any ideas on what are good coils?

There's always this conversion I do, it's good enough for gas so should be excellent for petrol:

http://www.aulro.com/afvb/technical-...sch-024-a.html

Reliable and cheap.

Philip,
should have mentioned it, the EH (Event Horizon) came with COOPER "Discoverer ATR"s, 235/70R16 and the fronts are 85% or so, and the rears much older (time-wise) and around 40 ~ 50% tread.
- Thats just guessing from a 'visual', not measured... but the back two are showing signs of a tread sep in the near future.
Dunno what the spare is, I suspect its "original" and on a steel rim.

According to the Bridgestone site mentioned here, they would give a diameter of 736mm, whilst the 750R16 is 8kg better load rating, and 809mm.
- Thats over 60mm differance... Which could account for a couple of mpg. Perhaps.

I should have mentioned that 80 to 90% of driving is going to be on sealed and gravel roads, with only a little bit crossing sand dunes or up beaches to reach fishing spots. I've got enough natural hairs on my chest, so I don't need to drive to 'prove' myself !!!

I used to work for a sweeper, (y'know, those little green ride-on noisy park & pavement sweepers..) and used an '89 'Classic' as the tractor, towing 1.6 tonnes of sweeper / trailer.
Said workhorse was shod with Pirelli Scorpions and we had a very nice ride and reasonable life from them.
On virtually 100% LPG and gave us a between 3 and 3.5 km/litre, depending on who did most of the driving for those 2 or 3 days.....

- This was the vehicle by which I was infected with Range Rover - itis.....

Incidently, at 144k and 16 years (nice low mileage !) I reckon the shocks are showing their age, so a set of Rover "normal" shocks is next to vanish down the Credit Card slot !

Have'nt priced the appropriate Michelins or Pirellis yet. - Should I be sit down first ?

Cheers,

James in Perth

Originally Posted by cockie55

Justin chime in here as you have probably seen more Lucas Vac Advance units than I have had hot dinners.

Doing a test on vacuum advance that only entails checking if they hold pressure is NOT ENOUGH. These units are shot long before the diaphragm either splits or loses it seal around the edge revealed by the leak test.

The rubber diaphragm in the advance unit starts to become stiff and shrink after only a few years service. That translates to the vac advance kicking in later and coming to an end too late (useless when richer fuel map has already started to be seen) or not even reaching the maximum advance it is supposed to deliver as the amount of vacuum at throttle plate starts to decrease.

I have seen rubber diaphragm shrink so much that initial advance is 10° out when fitting a new unit. Yes ….a must do is check timing when fitting a new vac unit.

If you don’t have a vacuum pump to check health of the diaphragm one quick test is to plot the amount of mechanical advance at say 250 RPM steps both with and without vacuum connected. Vac advance should kick in by 1,100 RPM and majority of vacuum advance component of say 15° be all in by 2,250 RPM and certainly all in by no later than 2,500 RPM (at no load). If not and say vac advance is still working beyond 3,000 RPM and doing most of its work between 2,000 and 3,000 RPM then its is either well past its use by date or the wrong unit for a EFI RV8. Note this is test only as vac/RPM are different under load. Don't have a timing light/tacho....here is one...LOL Message - AULRO Classifieds

I have seen Lucas EFI vac units with different style nose cans (with a shoulder and with no shoulder) and stamped (where 1st and 2nd # are the start and finish vac pressures in inches mercury and last # is advance in dizzy degrees so double for crank advance) and some unstamped. Seems to me what advance unit a dizzy got was lottery at the lucas factory???

Someone else might know what the specific design operating pressures and the amount of vacuum advance for each RV8 EFI engine setup are to enable proper checking of dizzy with a vacuum pump.

Yes, the vac advance is a pretty crude set up, and not very reliable. I have done heaps of VW full mech advance dist conversions over the years too, they are way more reliable and easy to set/ tune than a dual advance unit.

The most succes I have been able to get with these Lucas distributors is firstly check that the mech advance is even working. I have seen many that are sticky or even siezed solid thereby very little advance and non at all with the vac disconnected If that is OK, then check you are getting up to 30 deg MAX at about 3500rpm, any more and the performance will start to drop off and economy with it. The other better alternative is to fit a Bosch aftermarket distributor, Very reliable and simple. Not cheap, but worthwhile if you plan on lots of KM.

Unfortunately there are lots and lots of limitations with any petrol engine, especially the 8.13:1 compression V8's we get, so you can spend lots of $$$ to try and get 1 or 2 MPG better. Sometimes if you are only doing low KM a year, it just isn't worth it. Just suck it up and enjoy the ride

JC