http://members.lycos.co.uk/threelandrovers/petrol_v_diesel.htm
This doesnt quite do it either-still interesting....
DID YOU KNOW?- The Land Rover 2.25 diesel engine had many lives outside
the Land Rover. It was used in the Leyland Sherpa van and the Austin
FX4- the classic London 'Black Cab'. Under the global BMC brand, it was
specially adapted for use in boats and small trucks. Boats sold in
America with the engine used adverts showing a motorboat towing a
water-skier with the slogan 'ski all day for a dollar'.
Land Rover was one of the first companies to offer a small capacity
high-speed (don't laugh!) diesel engine in its vehicles. At a time when
petrol was cheap and petrol engines were tough and reliable, a diesel
that was noisy, difficult to start and would top 45-50 mph on a good
day didn't make much sense. The diesel option only really went to two
sorts of buyers- farmers and specialist buyers who used their vehicles
off-road all the time or in wet conditions where a petrol would
flounder. Because of the diesel's agricultural image, the combination
of short wheelbase, truck cab and Ifor Williams load bay cover with a
diesel under the bonnet is a very common one for the Series III. The
MOD on the other hand only took its Series IIIs with petrol engines
because they were more powerful and easier to service.
Land Rover did much work in the early 1960s into producing a 'dual
fuel' engine that could work on both petrol and diesel. Presumably it
would have some form of adjustable cylinder head for compression, a
switchable ignition system and fuel injection. It didn't come to much,
but it did mean that Land Rover produced two engines, the 2286cc petrol
engine and and the '10J' diesel of the same capacity. The two engines
shared the same block, timing gear, cooling system and many other small
parts. Abo
ut 75% of all the 2.25-litre engines sold from 1962 to 1985 were
petrol. It offered power, reliability, simplicity and not unreasonable
fuel consumption (15-20mpg for an engine in good condition). The diesel
was reliable and a good workhorse, but was lower in power, slower and
its injection system required specialist knowledge to service.
However, as fuel prices began to rise, fuel consumption became
important. By 1985 about 60% of the Series IIIs sold that year were
diesels, and owners reveled in their 28-30 mpg.
So here we go, a comparison in theory and practice of the Series IIIs
most popular powerplants.
Petrol
A classic powerplant that will run for ever and ever and ever with only
the most basic servicing. A totally standard 4-cylinder, OHV, Zenith
carburetor- fed engine that presents no difficulty for the mechanic to
service.
The engine develops 74 horsepower at 4000 rpm (with a maximum speed of
4500 rpm), and 113 lb-ft torque at 2000 rpm. This means that a SWB
Series III can be wound up to 70 mph if needed, although 60-65 would be
more realistic. The engine's big cylinders produce healthy amounts of
torque that allow heavy loads and trailers to be moved around in
safety. The engine has no problems with reliability, and usually the
only problems are caused by the piston rings and oil seals being
out-lived by the engine they're fitted to. Because the block is
designed to cope with the much higher stresses of a diesel engine, the
petrol powerplant is under-stressed and will last for ever. This also
means it will take plenty of tuning. 100 horsepower has been tweaked
out by gas-flowing the manifolds, raising the compression ratio and
fitting sporty valves.
The big problem with this engine is modern use is its thirst. 2.25
litres is a large engine, and it is fitted to a heavy vehicle with no
aerodynamics. In 109s (especially Station Wagons) the engine has to
work hard. Fuel consumption normally averages around 18 mpg, but this
can fall to 10 mpg if towing a heavy trailer. This means a range on a
tank of fuel of under 200 miles for an 88, maybe 210-20 for a 109 (they
have bigger fuel tanks, but also higher fuel usage). Off-road, the
engine does have problems. The torque peak of 2000 rpm is a bit on the
high side, meaning that to keep momentum through mud or on rocky ground
you have to travel a bit faster than is comfortable. The low
compression ratio (8:1) means that braking on steep hills leaves much
to be desired, often needed careful use of the brakes. The ignition
system is adapted for off-road use, but still conks out in the wet.
Diesel
Land Rover's 10J diesel engine was released in 1962 and was kept in
service until 1985, and as the Did You Know? spot at the top of this
page says, made it's home in several other applications. By the time
its life ended, it was out of date. It is a typical, old-fashioned
diesel, with in-direct injection, mechanical injector system and dismal
power figures for its size. It produces 62 horsepower at 4000 rpm, with
a maximum speed of 4200 rpm. Total torque is 103 lb-ft, which comes at
1800 rpm.
This means that a diesel Series III has a top speed of 60 mph, but
you'd go deaf if you held this for long (its a noisy engine), so 50-55
is a better plan. Of course, this stunted performance is compensated by
good fuel consumption. Land Rover quoted 28-30 mpg for an engine in
good condition, and this is achievable. If worked hard towing, 20 mpg
can be the worst to expect. In moderate off-road the engine will gently
sip fuel all day, if full use of the engine's torque is made. The
engine is very reliable, needing less day-to-day tinkering than the
petrol.
As the graph shows, torque is this engine's strong point. Whilst the
total is lower than the petrol, at low speeds the diesel has much more
(at 1,000 rpm the diesel produces 92 lb-ft, the petrol 72 lb-ft). This
means that trundling through mud, water and rocks is easy. Engine
braking is impressive (23:1 compression ratio) and the engine will keep
going in water as long as it has air to breath.
The disadvantages are clear. Lower power means that acceleration is
glacial and the engine lacks top-end torque, meaning that hills have to
be taken at a crawl. The diesel has a reputation for being a bit on the
weak side, but this is because many engines have been thrashed into the
ground. Like all old diesels, if they are serviced well with regular
(and frequent) oil changes they will chug on forever. If neglected they
will quickly fall apart. Off-road, the low power means that steep hills
are a challenge (but they can be done), and sand is an almost no-hoper
(sand requires light, powerful vehicles, a diesel Series III is
underpowered and heavy). If something goes wrong, adjustment and repair
of the injector system requires expensive professional work.
Conclusion
The petrol is powerful, faster, bomb-proof and provides good towing
torque at road speeds. Off-road it will go almost anywhere, but its
lack of low-speed torque and waterphobic electrics limit it when the
going gets extreme. It will guzzle fuel.
The diesel is a reliable workhorse that will work hard all day on a
cupful of fuel. It is good off-road, being torquey and waterproof.
However it is underpowered on the road, noisy and requires faithful
servicing.
As much as it pains me to say it, the better option for day-to-day use
is the petrol. Considering that most Series IIIs spend 90% of their
time on-road, the petrol engine is ideal. It provides adequate road
performance, yet off-road will match the diesel in 9/10 situations. A
good LPG kit will effectively halve the fuel consumption, making it
cheaper to run than the diesel.
If you work your Series III, spend a lot of time off-road or are on a
very tight budget, the diesel makes sense, but hopefully you aren't the
sort of driver who likes to get everywhere fast......
