Discovery 2 4.0 Thor V8 Fuel Consumption issues?

Now then lads, I bought myself a 2000 Disco 2 with the 4.0 thor in about a month and half ago and its about to get sold before I declare bankruptcy! 119k on the clock, runs sweet as a nut, bar the slight tappet tick when warm, its had a full engine service, new set of plugs, and in all honesty it runs like an absolute dream, now to the downside, I can physically watch the fuel gauge go down, and it mortifies me. Granted, I don't cover many miles, so I'm covering around 40-50miles a week if im lucky, but all the miles I cover, it seems to get up to temperature within a mile and they're 5-10mile runs, so it's not warmth and being on choke thats causing the issue (I don't think), but its starting to get ridiculous. I've worked out I'm using £50 fuel for every 90 miles, which is rather heartbreaking because I absolutely love the truck, it is the smoothest, most comfy Discovery 2 I have ever driven, and I've driven alot. So basically, what are the most common problems for fuel issues on these engines/trucks, and what are other people getting for fuel economy to soften the blow? I don't rag it, I simply touch the accelerator and sit at the speed limit and I was getting 35mpg out of a td5 a month before I bought the v8, so it's quite shocking to my bank balance at the minute! Cheers!

Mine still does 18mpg on local journeys and 20-22mpg on a long 200 mile run the last time I looked which was a while ago.... although I once had 13mpg doing a daily six mile run to the station for two weeks, much the same with all 3.9 D1&2s discos that are in good nick I would think.

Well thats not too bad then, it just concerned me that being a good running engine I may have some underlying issues, I think I'm going to have to strip it all down and have a good look, because it just doesn't ring right to me, a friend has a P38 with the 4.6 thor in, he's getting 22mpg and he pops in to town every now and then, which is what made me wonder about mine

I think the answer lays in the type of mileage you do, rather that the actual distance covered. Cold starts followed by short journeys are much more of a killer to fuel consumption that most people realise (ignorance is bliss perhaps) & that applies to any engine. I once had a high mileage 3.5efi auto that was down to 8 mpg on short runs in the depth of winter - welcome to V8 ownership

DanD90 said:

Well thats not too bad then, it just concerned me that being a good running engine I may have some underlying issues, I think I'm going to have to strip it all down and have a good look, because it just doesn't ring right to me, a friend has a P38 with the 4.6 thor in, he's getting 22mpg and he pops in to town every now and then, which is what made me wonder about mine

Click to expand...

Bollox is he getting 22mpg with ease or regularly. On a smooth motorway run 22mpg is possible, but that's the upper limit of "realistic" mpg from a stock Rover V8 in anything Land Rover!

People claiming high mpg with ease all the time are either lying or working it out wrong.

An auto RV8 in a Landy will typically see 16-18mpg average. When cold or on short journeys expect that to see lows of 12-14mpg. And 18-20mpg as typical high mpg expectations for longer journeys where you keep the speed down a bit.

This isn't to say higher mpg can't be attained, but it simply won't be through "normal" driving in mixed environments. Lower mpg will be a heavy right foot. Although if you are down as low as 10mpg or lower, chances are something isn't 100% or you are driving recklessly on very short journeys.

A megasquirted and fully sorted RV8 with a manual trans might see slightly higher, but only likely 1-2mpg higher across the board.


Land Rover only rate the 4.0 at 16mpg:
Land Rover Discovery (98-04) 4.0 V8i GS 5d Auto (5 Seat) - MPG, Dimensions & Performance | Parkers

And the Td5 at 30mpg:
Land Rover Discovery (98-04) 2.5 Td5 E 5d (5 Seat) - MPG, Dimensions & Performance | Parkers


So your 35mpg for your TD5 also seems a little high.


Can I ask how you are working this out exactly?


As for the 4.0 all you've said is 90 miles for £50, which is pretty vague at best, and hopelessly inaccurate most likely.

But for conversations sake, if I assumed £1.12/litre, £55 = 44.6 litres or 9.8 gallons.

Which = 9.2mpg

But your figures could be way out.


However excessive fuel usage could be cause by a binding brake. A knackered torque converter if it's an auto. Also check to see if the air con pump is jammed on (happens often on LR's!). It shouldn't run all the time and should disengage.

Fuelling is the next likely thing to look at.

If you sit there when its warm, out of gear does it hesitate when you rev it up?? If so then your MAF is dead, mine has a duff lambda sensor and does similar mileage to yours but at least I know the problem!

What were you thinking when you bought a 2.2 tonne 4-litre house brick?

On a long run, on LPG and not going too mad we get the equivalent of 28mpg in money terms, that's around 17-18mpg in LPG consumption.

LPG makes them viable, but not for short journeys only.

We'll be off to Holland & France later this month with the big 6-wheel trailer, that brings consumption down with a bang, but still manageable and so much easier than a TD5.



We bought ours solely for its towing capabilities and performance with a load, fuel consumption was not a consideration.

Peter

DanD90 said:

Now then lads, I bought myself a 2000 Disco 2 with the 4.0 thor in about a month and half ago and its about to get sold before I declare bankruptcy! 119k on the clock, runs sweet as a nut, bar the slight tappet tick when warm, its had a full engine service, new set of plugs, and in all honesty it runs like an absolute dream, now to the downside, I can physically watch the fuel gauge go down, and it mortifies me. Granted, I don't cover many miles, so I'm covering around 40-50miles a week if im lucky, but all the miles I cover, it seems to get up to temperature within a mile and they're 5-10mile runs, so it's not warmth and being on choke thats causing the issue (I don't think), but its starting to get ridiculous. I've worked out I'm using £50 fuel for every 90 miles, which is rather heartbreaking because I absolutely love the truck, it is the smoothest, most comfy Discovery 2 I have ever driven, and I've driven alot. So basically, what are the most common problems for fuel issues on these engines/trucks, and what are other people getting for fuel economy to soften the blow? I don't rag it, I simply touch the accelerator and sit at the speed limit and I was getting 35mpg out of a td5 a month before I bought the v8, so it's quite shocking to my bank balance at the minute! Cheers!

Click to expand...

then you cant afford it

my p38 did
9mpg london
14mpg driving normally
mate got 17mpg out of it

Stripping down can't be of much help really. If there is a problem it is likely something ancillary or injection related. Your mate may get 22 downhill with a tail wind. Not up on Thor but other problems I have encountered are locked up viscous fan , holed fuel tank and holed filler neck.

Welcome to v8 ownership... They are thirsty beasts.

Before you start tearing down the motor, work out your fuel economy accurately, and make sure you don't have a different problem.

Top off the tank, do a decent mileage, then top it off again.
Record distance and fuel.

Use the same petrol pump if you can, to be sure of an accurate reading.

Also, record the type of mileage - or do an economy run on a specific journey, so you know the conditions it was driven under...

22mpg is the absolute best you could expect in an auto d2 or p38.
This plummets horribly if you do stop start motoring.

I've got a 4.6 "Hotwire" RRC auto, high comp (10:1), stage 3 tune running lpg.

When I was bedding the engine in after rebuild, ( light throttle, no full throttle, no high revs) I was getting about 16mpg on petrol, but it's set to run a bit rich on petrol, due to the 10;1 comp ratio.

After bedding in, and tuning to optimise for lpg, the best I saw was 18mpg on lpg, while towing an unbraked trailer at 53 mph for 100 miles. This was the speed that the torque converter locked at, and is the most efficient. I was very happy with that.
A d2 or p38 might manage a little better ( longer gearing, better transmission control, better fuel injection) - but not much.

Regular 20 mile trips to work ( 18 miles on motorway, 2 miles mixed urban roads, and a medium heavy foot) would return in the region of 15 to 16 mpg.
But this would drop to 12 mpg if snarled in traffic, and single figures while towing and manoeuvring heavy 3 ton trailers etc,.

Before I rebuilt the engine, I was getting 16mpg at very best on petrol.

These are thirst beasts, and at times, it really feels like a " gallons per hour" consumption, rather than a " miles per gallon". A more athletic drive wouldn't seem to impact fuel economy much when compares to a lethargic drive...

Only other thought - at 119k, the cam would be pretty worn, and might be worth checking / changing?

I knocked out a bottom end bearing, and had a slipped liner, which is why I had to rebuild mine.
I decided to go to a top hatted 4.6 block, and increase the CR to 10:1 to improve economy on LPG because it didn't cost any more to spec this at rebuild.
But the rebuild cost £2500 ten years ago...
Now, this would be closer to £3500... How much is this compared to the purchase price of the truck...

Doing a full rebuild "to improve economy" is perhaps not the most cost effective thing to do.

Check out what you have got as a first step - do a basic check of engine health.
Is the ignition system in good order? Check the condition / colour of the plugs - this will tell you how well the engine is running, and show any anomalies.
Are the cylinder compressions good? ( since you have the plugs out, this is easy to check)
Is the fuel injection in good order ( are all the sensors working properly)?


Once you have checked all this - and made sure it's all working right, then ( and only then) should you start looking inside the engine.

If the compressions are good, then a bottom end rebuild wouldn't be indicated.

The next port of call for me would be the condition of the cam and chain and valve gear.

At 119k miles this is likely to be pretty worn. The cam lobes wear, as well as the rockers, so you might not be getting the right lift ( and will effect power and efficiency Also, the camchain wears, which will pull the cam timing out, which will effect economy.

But the very first step is to check everything else - start at the simple stuff first.

Quick story - from experience.
I friend who has a 1963 bentley s3. Several "specialists" had told him that the engine needed a rebuild. It was rough, smokey and drank like a fish!

I offered him to see if I could fix it - no fix no fee, and he agreed ( especially as it was mates rates!) the engine wasn't knocking, and made no untoward noises, so I was sure the bottom end was ok.

I spent a weekend tuning it - absolutely everything was set wrong or out of kilter.
New plugs and leads, electronic ignition and high power coil sorted out the tired ignition. ( the ignition timing marks are on the bottom of the bell housing!

I flushed and changed the oil and filter ( I don't use flushing oil, I just used standard 20w50 oil, But ran it fully up to temp first) - this cleared the old oil out and reinvigorated the hydraulic tappetts.
I set up all the carb linkages, and re- synchronised the carbs ( a fiddly job on this car), then reset the transmssion throttle linkage, and freed up and re set the auto choke.

I then treated the bores to some Redex overnight, as it looked a bit coked up.
Today, I would consider this terraclean treatment perhaps.
The compression pressures were a little down, but didn't improve with a teaspoon of oil down the bores, but the plugs were coked up, so I suspected top end coking around the valves, so did the redex treatment.

All in I used a tank of fuel in setting it up and testing, but at the end of the weekend, the car started at a flick of the starter, and settled down to an idle so slow and smooth that you could read the writing on the fan belts...
Engine response was instant, and no smoke.
Fuel economy improved to 13mpg, ( was about 6!)...
Compression pressures returned to spot on.

All I did was return it to standard ( the electronic ignition was the only upgrade, and is worth it, as the points are expensive and a pain to set).

The object lesson for me was to check all the simple stuff first...

My P38 does 21mpg on average
A long run at 70 will see 25mpg - at 60 it does 27mpg
It has a V8D 5.3 with GEMS using 36lb/he Bosch injectors
and Tornado Systems ignition and fuelling maps
It was mapped live by Mr Adams himself
Prodigious torque makes it very relaxing to drive

The only downside is that the check engine light comes on from time to time - the car often thinks there is either too little or too much fuel being injected.

That is impressive mileage.
Sounds like it's set up nicely.
I guess the CR is a bit higher than std, and a better cam too - giving an improved efficiency?
Also - electric fan or viscous coupling?

captainbeaky said:

That is impressive mileage.
Sounds like it's set up nicely.
I guess the CR is a bit higher than std, and a better cam too - giving an improved efficiency?
Also - electric fan or viscous coupling?

Click to expand...

Yes it is well set up - cam is a Kent 218 and engine has slightly bigger valves

The lack of skirts on the Pistons makes the gudgeons clack a bit on tick over but otherwise for a what is in effect a slightly de-tuned race engine it is quite a refined unit.

Funnily enough I have a viscous fan - hadn't thought about that - and I have the air con activated all the time - would be even better.

Yesterday I tootled over to Chichester and back cross country - about 70 miles - and averaged 24mpg.

It is a joy to drive - full stainless pipes - but not too loud.

Got 26 couple of months ago
Return leg on the back of an AA truck

My 4.6 is coming out of my RRC and going into my 50th anniversary 90, so I will have to strip it down to change the front cover, so I will be putting new bearings etc in it while it's on the bench, and expect that I will need a new cam too.

What's the spread of power like on the 218?

I've got a "lund le2" in mine with enlarged valves, and it doesn't come on song until above 2500 rpm - seemed fun at first, but grates after a while - doesn't really pull in top gear till 80! Which is a bit tiring in an auto!

Yup, it's a lund engine - I seem to have been lucky, and actually got my engine, and not had any problems ( apart from a leaking rear oil seal), but then I havent stripped it down yet, so I don't know what I will find...

Watch this space....

Probably well matched to your big valve heads. Even better if everything else can flow well enough. Exhaust inlet manifold trumpets and 72mm throttle. Steve did a lot of porting on heads and inlets till the ali dust nearly killed him.

Yup, has larger trumpets, tubular manifold.

Didn't do the throttle mod, but will on the Gems throttle body in the 50th.

Now, if I can only find the time to do it all, in between work, and the other million projects I have to repair/ restore / service.

You will need to change the cam for a short nose and the flex plate as well as the front cover etc - if you have a fully zero-balanced engine you will have to zero the gems flex plate too

Also remember there is no adjustment on the GEMS cam timing gear - and you cannot fit a double chain.

The 218 is a great all-rounder - but is as high as you can go with an auto gearbox of any description really - as your 50th has a hydraulic box with fixed
Change up points you may want to stick to 180

We dos a nice 50th Cabrio recently with an Eales 4.6, stage 1 heads , Kent H180, Hedman manifolds, stainless exhaust and Tornado ECU

It was lovely - fast, torquey and over 20mpg

Good luck