Outer Limits 4x4 Board

Hi All,

About to move back into a Disco S1, and have been agonising over the choice of a 3.9 or 300tdi, either way it has to be a auto as the missus wont drive a manual

I have heard and read horror stories about the 3.9 auto combination and the way they drink fuel, but have also read where with some mods that they can be made reasonable, consumption wise, although no where near a tdi.

What I need is genuine day to day figures for around town, hiway and offroad, and I will make a judgement from there. It looks like there is about 4-8 gorrillas difference in the purchase price which offsets some extra fuel and mods cost, unless the consumption is horrendous.

Also if you've done mods did they perform to you're expectations.

Thanks in advance

BTW, have had Defenders before so know most of the tdi's issues.

Regards Glen.

You want economy go TDI.

iI get 22-25 mpg from my RR 110-120.
Can also get next tonothingfrom it to.

Michael.

3.9 V8 expect 20-24L/100K around town in heavy traffic and 17L/100K on the highway - that is what I have always got.

TDI probably about 13L/100K in traffic and 10L/100K on highway.

If you are buying secondhand I would never buy a TDI with over 200,000K on it - or if you do have about $5000 handy for when it has a catistrophic failure. The life of these is heavily dependent on the quality of the diesel, running conditions (highway or city - the city kills them ) and service history.

On the otherhand a V8 will keep on running and is simple and cheap to fix, they might round out the camshaft and have 50Hp at the wheels but they will still run.

My suggestion is to find a good V8 and put it on LPG and you are way ahead of the game - my v8 3.5L rangie was cheaper to run than a mates Isuzu 4BD1 3.9 Turbo diesel (but only just ) when you take into account the extra cost of purchase of a TDI and the cost of fitting LPG you will be $2K ahead straight away - that is a lot of tanks of gas

Tom

I had a 3.9 with the auto in my LS Disco.

The very best I ever got out of it was 530ks to 90 lts of fuel. This was after fitting a snorkel and a K & N filter and a straight through exhaust. The vast majority of that was highway cruising using cruise control. The worst I ever got was around 420ks to 90lts. That was driving it like I stole it and mostly around the city with short trips and a heavy right boot. I didn't find that much difference with 98 octane so I ran regular ulp.

Off road the usage was pretty good. I could go to LCMP from Brisbane, drive hard for about 4 hours, go to Bribie, cane it on the beach and get back to Brisbane on one tank. My mate who had a 5 speed 3.9, regularly came in under 400ks per 90lts.

It seems to me that the autos are more economical due to the controlled rev range with gear changing. Unless I really booted mine, I would average at 480 - 500 ks per 90lts.

I would go with the diesel if economy is an issue. If you, like me, think there is nothing better than a V8 yelling its guts out while your a climbing a hill, then get the V8 and drive sensibly around the city and give it some when you are sill deep in mud.

Micka

RaginRover wrote:On the otherhand a V8 will keep on running and is simple and cheap to fix, they might round out the camshaft and have 50Hp at the wheels but they will still run.

Tom

RaginRover

what do you mean by rounding out the cam? are the stock cams soft? whats the symptoms of this? and would it be fairly easy to replace with a better aftermarket unit?

Micka

If thats about the worst you got on average then I could easily live with those figures, (after all I have been running a V6 rodeo full of tools and gear and they can certainly suk some fuel) especially when your listening to that motor sounding out its sweet music

Regards Glen

My 3.9 is on LPG, and I average about 19/20lt/100kms, but at 35c/lt, I don't care! I don't do a lot of inner city driving, mainly urban and country.

Gotta love the sound of a V8!

seqfisho wrote:
RaginRover

what do you mean by rounding out the cam? are the stock cams soft? whats the symptoms of this? and would it be fairly easy to replace with a better aftermarket unit?


Regards Glen

Becuase they are a dunga push rod engine that rounds the lobes off the shaft and the cams are soft IMO.
They are easily replaced - due for one at around 200,000 i reckon, that will give it a bit of pep back. I would stick with stock cam - keeping them stock is quite beneficial - easier to troubleshoot and fix and it will last you another 200,000k before it needs replacing again.


Tom

My 3.9 in Aquarangie drank fuel like buggary. Average fuel consumption was 25L/100kms Stock is the way to go if you want something a bit more economical, plus if you drive it like a lead-foot (which I did and loved every minute of it ) you won't get much more than what figures I had stated before.

My 3.9 had a slightly bigger cam plus ported and polished heads and a 2 1/2 inch exhaust system, but apart from that it was stock bottom endd wise (never was touched.

My 3.5 carby V8 in the 83 is a bit more economical (not much) but gutless, especially with 1.1 high range and 32 inch MT/R's

Regards,

Trav

My 3.9 auto Disco gets 22-24 l/100km on LPG

Hard off road use can see fuel consumption double!!!!

My worst was 29ltrs LPG for 68km, 90% low range

Not a problem while lpg is cheap & we play close to home

Cheers Dragonwagon

My current consumtption is 15.73l per 100 for the past week. This is a 36 km trip done twice a day most of which is done at 80 or 90 on cruise control (would be 80 and 100 but P plates killed that option). Around town we are lucky to get 18l per 100 driving like a granny stole it.

I'm hoping exhaust and some airbox mods will help it slightly aswell as some electric thermo fans for these hot summer days.

Stuee

yer, I get 25L/100 average country city/highway driving on LPG, up to 27/100 if you push it.

You will notice this, they really are gutless, esp. at hills!

The old man's Td5 110 would beat me up the Maleny range, and my mates GU 3.0 would whip us both

On highway I would estimate 18-20L/100k on LPG. Remember that it's hard to find one on LPG, and those that do have these damn scuba tanks that only hold 55L, ie. 250Km range max.

I have scuba tanks which hold 70 (?) litres and get me 320+ on highway

Had a JD high output 4.6 in my RR, used 130l for 500km, this is the reason I've shoehorned an Isuzu 3.9 Turbo intercooled diesel into it! I'm expecting 26mpg and the same torque output at 2000rpm.

...and I can run it on free used vegetable oil....

JC

There seems to be a bit of variation in results, maybe some of you have heavier right feet than others or is it possible that there is a huge difference in the quality or accuracy of the Rover ECU.

Regards Glen.

Tyres, lift, weight and other bits (bull bars, bash plates, rear bars, sliders)
all add up. Number of Ks, different transfer cases, all have a bearing.

I have never seen a disco get better than 20L/100K around town in a major city - I couldn't ever get better no matter how much effort I put in, some are better than others, stuee's must be a cracker - hold on to that one mate !

If you are looking at what you should get out of your 3.9, if you get 20L/100K around town IMO is running about right. If you are getting higher consumption then look into the basics on how to make it better.
16L/100K or less can be had on the highway depending on trip, fuel, cruise control

If you are buying a v8 bank on the 20L/100K figure around town.

RaginRover wrote:stuee's must be a cracker - hold on to that one mate !

Its mainly because the trip to work is around 35 k's one way, most of which is free flowing freeway (6.20am) and being speedlimited to 90 (P plates and engine sits just above 2000rpm) with no loads carried. But yes I have been quite pleased with it , last week it went down to 15.16l per 100 with one day of around town driving thrown in . Actually I've just taken ownership of it (was parents car) and will hopefully be using it more appropriately (ie off road) .

From the excel sheet we've been keeping our around town consumption over the past 6 months has been around 19-20l per 100. If your trying to cut down on fuel an excel sheet is a great idea as you can see how different driving, weather, fuel, services etc make a difference. Thats my tip for everyone.

edit* adjusted long term fuel economy.

My 3.9 returned 22l / 100km running 235/75/16 at 110kph
Car has F+R bars, winch and kid
4.6 in same car now returns 20l / 100k using 3.9 injection and reworked chip. Kids getting bigger.