Hi guys,
i have a 1988 defender 110 3.5 V8 and does anyone know what is the normal mpg for one. Mine does 14mpg and is changing it to LPG help a lot and run well with the 3.5.
Yours Sincerely Nicholas

14mpg sounds about right. Depends how you drive it etc but, being a Land-Rover and a V8 you're not going to be getting perfect economy! I think you are running on twin SUs? You could possibly get slightly better by fitting a hotwire injection system, improved torque, power, throttle response etc. Thats petrol side though.

Rover V8s run well on LPG, there are a lot of LPG conversions out there & it depends how you do it. Good thing about LPG is that its cheaper than petrol! Yay! So if you do some basic maths you can work out what the equivalent mpg is for petrol. So getting 12mpg on LPG might be like getting (depending on prices) say 23mpg on petrol. Which is a lot nicer for your wallet!

There are loads of different conversions, be careful though your insurer may want to see a certificate for it or something. You could get a second hand one, be careful & fit it yourself. This will probably have a tank that goes in the back, you can get sill tanks that go under the body each side of the chassis rails... Loads of options.

If you are going to get LPG then the basic system is: Tank -> Vapouriser -> mixer ring(s). Which what happens is the air rushing past sucks a reasonably correct amount of gas into the air stream and then all the normal things happen. Suck, squeeze, bang, blow.

An improvement on the mixer rings is a BLOS carburettor. I don't own one (yet! its on the list and I will be getting one!), but from what has been said about them, you're not going to get much better unless you go for full sequential injection. Which is another option! Its basically LPG but has injections etc, its far better than mixer rings!

One thing you will have to think about a little is timing. LPG runs better on far more advance than petrol, you can get modules that advance the timing when running on LPG.

What normally happens is you start on petrol, then flick over to LPG when the engine is warm. Some people can start on LPG apparently but its not the norm?

If you want to keep your carburettors but want to run well on both LPG & Petrol, then you can get something called megajolt. Which uses some coil packs and is an Electronic Distributorless Ignition System! Its neat so you can run two different spark maps (like a fuel map on electronic fuel injection!). One for petrol and one for LPG.

Now thats about as far as my knowledge goes... I don't have a BLOS carburettor and nor do I have megajolt. But megasquirt+EDIS and LPG is something I have been looking into for a while as it will make running my 3.5L RRC a lot nicer. There are people on here with far far more knowledge than I and will add and correct anything I've said.

Anyone want to rip any of that apart, drag me down the street for heresy and misinformation? Correct me please where needed!

My ex-RAF 110 3.5 V8 averages about 18mpg with a variety of traffic conditions, in fact it hardly varies in day-to-day use. I have got about 22 on a long run, but I usually drive at about 55 so that helps. Being ex-MoD it had restrictors in the inlet manifold, but whether that would make it better or worse i'm not too sure. As someone said "when you drive something with all the aerodynamics of a garden shed you can hardly expect economy".

hctbn said:

My ex-RAF 110 3.5 V8 averages about 18mpg with a variety of traffic conditions, in fact it hardly varies in day-to-day use. I have got about 22 on a long run, but I usually drive at about 55 so that helps. Being ex-MoD it had restrictors in the inlet manifold, but whether that would make it better or worse i'm not too sure. As someone said "when you drive something with all the aerodynamics of a garden shed you can hardly expect economy".

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feckin ell...22! you sure???on a 110??best i got was 11-12 (12 downhill)


re original post..14 is really good...3.5 in a 110 and the word efficency do not go..

re lpg..previous post is correct..go lpg standard timing and expect 10-20% less mpg..BUT advance timing.say using aeb timing advance unit will get the mpg to about the same AND inprove power...so thus getting about double mpg per £(at current lpg versa petrol prices)

your main problem re lpg and petrol mpg/power is your ****tttty su's and worn out dizzy..

I used to get about 12, if I was lucky on a steady run then 15.

Lpg was a little less but cheaper

I'd have thought that mpg was about right. I run a P5b,pretty much the same engine and weight but maybe a bit more aerodynamic and without the drag of the four wheel drive set up. it does around 17mpg with 20 on a gentle run.

Shame on you for soiling the v8 section with talk of mpg and economy! V8 equals low mpg and its very hard to compare with different driving styles.
Low mpg is great imho as it makes v8s cheap to buy and rarer than diesels and 4 pots etc. Makes its exclusive ; )
In all seriousness 14mpg is normal.

I agree with ronseal but want to add: please do sums and work out how long it will take to recover the cost of lpg conversion and all this mega squirt/ jolt stuff from the saving in fuel.

Never worth it better an efi conversion

Or cough (other v8 not out ark)

timc1967 said:

I agree with ronseal but want to add: please do sums and work out how long it will take to recover the cost of lpg conversion and all this mega squirt/ jolt stuff from the saving in fuel.

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TWO things..

one..go buy a micra if worried about mpg..

two..do the lpg oneself..then not long...

megasquirt has nowght to to with mpg..its gpg (grins per gallon)

I don't like LPG on carburetted cars. The modern LPG direct injected systems are OK though. If you want better MPG buy a diesel powered defender. Less maintenance as well.

If you want GPG keep filling it with petrol

well....me meagasquirted v8 goes better on gas than petrol.(99ron)..so i get best of both worlds..
20mpg on a run..(equiv 40ish mpg petrol prices) and more power than petrol,,,but i do run much more advance on lpg..and it isnt a rv8 and its boosted,,,which helps the gpg

lpg instal done by me...easy paid for itself now..

I think once we worked out it was 6- for a pay and play day with 12 on road with it not running right. But its a V8, with these prices i just count in overdraft digits :/

zen said:

well....me meagasquirted v8 goes better on gas than petrol.(99ron)..so i get best of both worlds..
20mpg on a run..(equiv 40ish mpg petrol prices) and more power than petrol,,,but i do run much more advance on lpg..and it isnt a rv8 and its boosted,,,which helps the gpg

lpg instal done by me...easy paid for itself now..

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Can't argue with that amount of gpg or diy lpg install.

When I had a skyline I decided cheapest modification for saving fuel was to buy a fiesta.

i get about 6-8 on the fields and about 15-16 on long runs - use shell vower - always keep the carbs well tuned as well

timc1967 said:

Can't argue with that amount of gpg or diy lpg install.

When I had a skyline I decided cheapest modification for saving fuel was to buy a fiesta.

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+1 I did the sums and it was cheaper for me to run my diesel mondeo plus a 3.9 rrc on classic insurance, than buy and run a td5 110 as a daily driver. People took the **** for me having two cars but they were naive to the fact that their 52 plate honda jazz cost them more to pay in finance and sundries!