Best possible MPG from a 3.5L Rover V8?

Hey guys,

Im still toying with the idea of doing a V8 conversion using a 3.5L Rover V8 from British American Engines, with a K&N Air filter, uprated silcone hoses, new uprated stainless exhaust system. Possibly with an LPG conversion.

What kind of mpg do you guys expect I will get? On average on petrol

As well as on average on LPG.

Thanks.

My 3.9 V8i with lpg conversion I get 14 on petrol and 35lts gas I get 135 miles and a lot less if I drive like a TVR :rolly:

I did drive my TVR like a TVR and that did an average 20mpg sold it when I got a 3.5 RRC that did and average16mpg every where. The last time I checked my 3.9 it was around 18mpg average.

18 mpg on the motoray at 70 mph was thhe best I ever got from my 3.9 rrc

round town 12mpg or less. and it was running right, well tuned and plugs correct colour

I recently went on a journey in my car.

It has 33" tyres and lots of weight. We had 2 guys and lots of fuel on board. Weighed in at 2600kg probably all told.

Anyway, I worked out (probably incorrectly) that it did 23mpg on the motorway on the way up to yorkshire, and over the whole 250 mile trip including around 90miles green lanes, around 13mpg average.

They are definitely thirsty buggers but when it comes to off roading and laning, the diesels aren't far behind, it just road work that the v8s struggle with!

Thinking about it, it's difficult to work out. Probably uses about 20 quid to do 70-80 miles on the motorway. That works out about 21-24 mpg. It's difficult cos of the fuel gauge innacuracy but that's my best guess.

I don't know what a diesel does in figures, but recently did a long trip in my dads standard 300tdi, used 40 quid in fuel, mine would have used easy £60, probably £70, maybe even bloody 80!

And I was unclear about what I said about v8 and road driving, it's alright once it's up to pace, it's foot down acceleration that kills it, in any gear. Drive hard for a little while and you'll bust a tenner in as many minutes!!!

Stuff the MPG, wind the window down and drink in the noise.

Thanks for the replies guys!

Is there anything that can be done to increase MPG?

I fitted tubular headers and it is noticeably more torquey low end. It is also less likely now that I need to down gear, it will keep pulling/chugging up a hill in 3rd whereas previously would have needed high revs in second.

Other than that clean out your intake, decoke your heads and generally make it good as new.

Tuning the engine generally leads to better power and mpg, beciasr your are increasing efficiency.

Cheers.

I also meant to say my 3.5 manual on carbs is better on mpg than my 3.9 was.

thats despite my 3.5 being 40 years old

my 3.5L v8 with 2 K&N filters running the standard exhaust manifold but a Sports stainless exhaust from 'Longlife' gets about 15mpg on a run, down to about 5mpg if i bury my foot around town.
my truck is lighter than most though, no winches,spare wheel etc

Playsatan13 said:

my 3.5L v8 with 2 K&N filters running the standard exhaust manifold but a Sports stainless exhaust from 'Longlife' gets about 15mpg on a run, down to about 5mpg if i bury my foot around town.
my truck is lighter than most though, no winches,spare wheel etc

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My concern with open cone filters like them is the horrendous heat soak you must get.

Do you have bonnet vents to provide them with cold air?

Failing that, duct over them to the grille or wings perhaps?

You'll be amazed how crisp some dense air makes the engine feel!

i have 3.5 twin sus and get 16mpg overall includes green landing, going across fields on shoots and running about town
you have to keep them well tuned

Cheers guys. On average from what you have all said it will be somthing between 14 - 20mpg.

Probably a long shot but anyway of boosting it to about 22 - 25mpg on average?

Also whats perfomance like on LPG? in comparison to petrol?

bankz5152 said:

Cheers guys. On average from what you have all said it will be somthing between 14 - 20mpg.

Probably a long shot but anyway of boosting it to about 22 - 25mpg on average?

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no

It's a V8, you dont buy them cos their economical.
Thats what Diesels for.

im not running cones but more cylindrical filters, but when i have time i was planning a ducted, box filter system

bearing in mind its pushing a 2.5 ton brick it will be 7-12 round town and 16 to 20 on the motorway at a steady 65-70 if you have a 5 speed.

people quote silly figures for mpg and they are all bollix

Fett's right.

Even in an arguably more aerodynamic P6 I only get 23 on a long run, 17 round town.

Cheers guys. Just want to get all the facts before I go ahead!

I just love V8s. My dream cars are a Defender 90 & a 1969 Mustang