Disco overdrive?

Hi guys.

Reading another post (Thread: Another series query...) brings to mind
something I've been thinking about for a while.

Basically, I love my Disco and it's off-road capabilities, but my off-
road use compared to on-road is tiny. I also do a fair amount of
motorway driving. Now while she's perfectly happy to go up to 80mph and
above, once I'm over about 60mph I can watch the fuel guage drop. I've
been wondering about some way to increase the fuel economy at high
speeds. Obviously an overdrive is one option, though there's scant info
on overdrives for Disco's on the net.

Anyone have any suggestions of overdrives that would fit, or other
options?

Cheers,
Aled.

Aled wrote:
> Hi guys.
>
> Reading another post (Thread: Another series query...) brings to mind
> something I've been thinking about for a while.
>
> Basically, I love my Disco and it's off-road capabilities, but my off-
> road use compared to on-road is tiny. I also do a fair amount of
> motorway driving. Now while she's perfectly happy to go up to 80mph
> and above, once I'm over about 60mph I can watch the fuel guage drop.
> I've been wondering about some way to increase the fuel economy at
> high speeds. Obviously an overdrive is one option, though there's
> scant info on overdrives for Disco's on the net.
>
> Anyone have any suggestions of overdrives that would fit, or other
> options?
>
> Cheers,
> Aled.

Bear in mind that above 60mph, most of the energy you are using goes to
overcome air resistance (which with a Disco is a lot). Whether your engine
is turning at 2500 or 3000 rpm to achieve this isn't very important. The
higher the gearing, the slower the engine turns, and the more fuel you need
per engine cycle to give the power you need to maintain your speed. I
accidentally did a large number of miles in D3 (4.6 RR) while towing a
caravan in France (I'm too embarrassed to say how many) and it made not a
scrap of difference to fuel consumption. Get an overdrive to reduce noise
and mechanical stress and wear, but common sense says it can't magically
give you more than a couple of extra mpg from the lower friction losses in
the engine & gearbox as they run more slowly. It's not like getting a more
slippery shape, or losing half the car's weight, or driving downhill, which
would give the engine less work to do and therefore use less fuel. You're
doing the same work, so you'll need more-or-less the same energy to do it.

My 2p worth. I could be wrong, and I usually am.

--

Rich

Series 2a
RR 4.6
V8 trialler
dog, wife, kids, whatever

"I've been wondering about some way to increase the fuel economy at high
speeds."
That is your problem, and your answer.
Basic physics I'm afraid. Fuel consumption is directly proportional to Power
used. Power used is directionally proportional to drag, and drag is
exonentially proportional to speed.
In short, quicker you go, more gas you guzzle. You want economy, slow down!
There is no 'magic' economy gizmo, and the best you can hope for is a few
mpg from efficiency gains - balence those few mpg against the cost to get
them, and you will probably find it will take quite a long time to see a
real saving
Any way,
"Obviously an overdrive is one option, though there's scant info on
overdrives for Disco's on the net."
GKN do one, try Ascrofts or Scorpion, I think Craddocks have advertised them
before now, try the 4x4 web for links to the specialists.

In news:[email protected],
Michael Williams <[email protected]> blithered:
> "I've been wondering about some way to increase the fuel economy at
> high speeds."
> That is your problem, and your answer.
> Basic physics I'm afraid. Fuel consumption is directly proportional
> to Power used. Power used is directionally proportional to drag, and
> drag is exonentially proportional to speed.
> In short, quicker you go, more gas you guzzle. You want economy, slow
> down! There is no 'magic' economy gizmo, and the best you can hope
> for is a few mpg from efficiency gains - balence those few mpg
> against the cost to get them, and you will probably find it will take
> quite a long time to see a real saving
> Any way,
> "Obviously an overdrive is one option, though there's scant info on
> overdrives for Disco's on the net."
> GKN do one, try Ascrofts or Scorpion, I think Craddocks have
> advertised them before now, try the 4x4 web for links to the
> specialists.

IIRC resistance to motion is proportional to frontal area. So solution saw off the
roof!

--
If Your specification is vague or imprecise, you'll likely get what you
asked for not what you want

In article <[email protected]>, [email protected]
says...
> Bear in mind that above 60mph, most of the energy you are using goes to
> overcome air resistance (which with a Disco is a lot). Whether your engine
> is turning at 2500 or 3000 rpm to achieve this isn't very important. The
> higher the gearing, the slower the engine turns, and the more fuel you need
[...]

Oh, of course. I should have realised that (ex-physics geek). I swear
nightsift melts your brain. Apologies for the muppetry.

Ah, well. I've got more than enough to be getting on with anyway, though
living in rented accomodation with no garage makes working on the Disco
a bit tough (had to use a Tesco carpark at 2am to change the oil one
night since I live in SE18 - nice steep hill).

Cheers,
Aled.

In article <[email protected]>, Michael Williams
<[email protected]> writes
>GKN do one, try Ascrofts or Scorpion, I think Craddocks have advertised them
>before now, try the 4x4 web for links to the specialists.



Although these overdrives will bolt to the gearbox the same as the
Defender. There is not enough room under the car to fit them to a Disco.
Unless you remove the rear floor and re route the exhaust.
--
Marc Draper

Forsale

Landrover Defender 90 300tdi county hardtop 1996 72K
Landrover Discovery comercial 300tdi S reg 70k
Landrover Discovery Comercial 300tdi R reg 62k
Toyota Hilux surf 2.4 AW/AC/EW/SR

Super winch X9 + genuine Landrover fitting kits for 200 Disco.