Fuel consumption

Stephen

New Member
Hello there I have some follow up questions regarding fuel consumption on my 1975 3500 auto, how much is held in reserve litres wise. My car smells very rich when running so I am going to get carbs set up, can they be set a little on the lean side or will this create other running problems . Is electronnic ignition a good move and is it simple to fit. Any tips on how to save on fuel will be helpful as I went onto reserve after 170 miles. I knew these cars used a lot of fuel but mine seams very greedy. Thank you Stephen.
 
170 is a bit low unless its all urban short journeys....

I'd suggest Getting the timing right, and sort the carbs out first.

Then if you want to help the economy Electronic ignition might give you 1 or 2 mpg. Swapping the engine driven fan for an electric one can help too.

On the idea of running lean needles in the carbs, experience seems to suggest that running richer needles actually has a better effect for mpg, as modern fuel is different enough to mean that the needles as supplied by rover are on the lean side.

On the fuel front using super unleaded, or tesco momentum makes the engine run much better, and if you're using standard unleaded it'll probably cost you more than the super unleaded in terms of lost mpg.

Rich
 
It just won't run well lean and you risk burning valves. Using colortune I add one flat in summer rich and two in winter.
 
Don't go lean you will regret it as your car will be bad on cold running and all the joy will be lost as your car will feel very under powered with little get up and go.
If your car is a 9.25:1 standard fuel will be fine.

You should be able to get 25 mpg on the motorway ( I used to get 27.5 ) round town 22 to 23 should be OK

Graeme
 
Not being funny it is a v8 my 5 litre drinks like a fish--economy and v8 dont seem to go in the same sentence
However if timing and carbs not set right your economy on a 3500 will be worse than my 300ci v8
so check your settings first mate--then you should get good results
 
20mpg upwards is what you should be aiming for as an average... on a run 26mpg is doable, round town 15-18mpg is about as good as it gets.

Rich.
 
Stephen said:
Hello there I have some follow up questions regarding fuel consumption on my 1975 3500 auto, how much is held in reserve litres wise. My car smells very rich when running so I am going to get carbs set up, can they be set a little on the lean side or will this create other running problems . Is electronnic ignition a good move and is it simple to fit. Any tips on how to save on fuel will be helpful as I went onto reserve after 170 miles. I knew these cars used a lot of fuel but mine seams very greedy. Thank you Stephen.

Hello Stephen..

Just thought I would throw in my two cents worth - seeing as I've been using a 1974 3500 Auto as a daily driver for over a year now (my one and only car :mrgreen: )

When I first bought my car it had been sitting for many years in a garage up in Birmingham - so if your car has been sitting for a while, its likely the carbs will need a rebuild rather than just a tune.

My car used to run rich enough that motorcyclists who were behind me would pull up and complain that the fumes were making them cry (lol).. Fuel consumption was not something you could measure - and after putting in a gunson colourtune plug, it was clear that it was running very VERY rich (like black smoke that would hang in the air for an hour if you rev it rich.)

The No.1 carb (drivers side) was easily taught the value of petrol using a screw driver, but the other carb refused to listen.. Try as I might (even unwinding the screw fully) it was still rich..

It was only until I pulled them both off and began rebuilding them that I found out why. HIF6 carbs have an interesting choke mechanism, a cam with holes drilled in it that meters the fuel, at the far end is a rubber seal (which had perished) - this mean that this carb was essentially running at full choke all of the time.

I rebuild the carbs, put them back on, and then I could cruise around for ages without watching the fuel gauge following closely behind the tachometer..

Further improvements were made after I had new points fitted, I even bought a vintage snap-on dwell meter to make sure everything was perfect, then had a garage time it and balance the carbs..

I fitted an electronic ignition conversion kit from MGBD, fitted new springs and V8 BBV needles in place of the worn out BBG ones that were in there (jets were replaced when I rebuilt both carbs.) And somewhere along the line a cherrybomb ended up bolted to the back of it for MOT purposes :roll:

My engine is not original to my car (its a later goldseal engine) - you can tell this because its gold colour :wink: - and I use NGK BP5HS plugs opened up to 0.9mm (check your heads if they take short or long reach plugs) a scribe with a 90 degree tip will easily let you check this..

My current fuel economy (in London morning rush hour traffic) is 12.41MPG if you are careful, and 9.87MPG if you like to cane it along the A406 in 1st gear doing 60Mph :shock: (so not much in it really.)

I should mention that these figures were taken after my mechanic hooked the car up to a gas analyser and concluded that it was running lean - he then proceeded to ask me to richen the carbs by half a turn several times, until the HC's were at about 200 and CO was 4.87 or so.. It gave it more Oomph, and it still doesn't smell like petrol.. BUT I'm sure it was more economical before - even though an economical V8 is an oxymoron..

I will report back when I have done some more motorway cruising..

However, I drove all the way to York from London and used no more than half a tank or so a few months back.. Didn't calculate the MPG, though it was quite late in the evening, and I never dropped below 60~70Mph..

Hope this helps..

Note: The reserve tap seal might be leaking by now (this gave my car a slight petrol smell) - my reserve tap is in the engine bay at the firewall, and I saw it dripping fuel every now and then - so I changed it.. Changing it is no easy feat - best to make sure the tank is almost empty before attempting it! Otherwise it will gush out like a fountain.. Fortunately for me I have small hands :D - so I got it apart easily and fitted the new viton seal from MGBD..
 
rockdemon said:
London to york is 215 miles - that's extremely good on half a tank, about 30 mpg.

:shock: - wow.. In your face Prius owners 8)

I'm not normally one to break out the calculator, mainly because I find the prospect of calculating my MPG terrifying.. BUT....

Last time I filled up, I reset the trip back to 000[0] (with the car on reserve) - then put in £30.00 worth of fuel. My commute has been strictly through London rush hour traffic - averaging maybe 15MPH ~ 20MPH I think. In drive my car idles at 650RPM, and I covered 90 miles on those £30.00..

So...

26.87 / 4.54 = 5.91
90 / 5.91 = 15.228 (almost 15.23!!!) 8)

I should mention that I backed off the carbs by 1 turn each (but it had been enriched to make it "run better" a good few days earlier..) I can justify this since my mechanic friend admitted that his gas analyzer wasn't calibrated :roll:

So - in conclusion.. :mrgreen:
 
Mines a 300 cubic inch(5 liter) and now got twin pipes and my economy has gone up :shock: three quarter tank=185 miles and 50 of those cruising at 80 mph on M40
 
Hi, careful Richard, Jeremy Clarkson got rebuked by Toyota for comparing their cars to
washing machines. Which I'm guessing you already know. :wink:

Colin
 
colnerov said:
Hi, careful Richard, Jeremy Clarkson got rebuked by Toyota for comparing their cars to
washing machines. Which I'm guessing you already know. :wink:

Colin

Somewhat unfair, never seen a Toymota washing machine but they do make sewing machines :LOL:


Graeme
 
I really wouldn't know about Priuses making good washing machines, but I have seen a LOT of broken down Priuses - which is kind of weird, because I thought that modern cars were supposed to be more reliable than these 40yo motorway chewers :roll:

Anyhow - seeing as my boss has been kind enough to send me on-site to carry out repairs (to Cambridgeshire and Oxfordshire) - I can now report on my "combined cycle" (hope I'm using that term correctly) fuel economy (or lack there of.)

So.............

In order to cover 412[8] miles, I filled up three times..

£30.00 (25.44L), £40.01 (35.13L), £40.00 (35.12L) - total of 95.69L (or 21.07Gal in these weird imperial measures.) 412.8 / 21.07 = 19.59MPG :mrgreen: (is that good? I've never had any other car :oops: )

Wimbledon to Cambridge (100Miles, M25, M11) Noteworthy points: Heavy rain, visibility down to end of bonnet, saw a lorry go on two wheels and a hatchback on its side with broken glass everywhere.
Journey back was on A Roads (71Miles), still raining.
Wimbledon to Oxfordshire (62Miles, A Roads) Nothing worth mentioning..
Oxfordshire to West Hampstead (58Miles, A Roads) 100Mph down the A418 8) - Amazing how stable the car is even at that speed..
Rest of the distance was done in the city.

So - that's it, from now on, I will not measure my MPG, in case someone tells me that its bad.. I used to think that it was about 8, so I'm very pleased with the results :mrgreen:
 
I'd say that's probably not bad at all considering.

With my 3500s I get 24mpg (or used to, when the car worked, but was made mostly of fibreglass) and that was doing daily total of 60 miles motorway, and 10 miles stop-start rubbish into and out of Kingston town center.

I track my fuel consumption with fuelly - I find it useful as it can help highlight any issues as they start (often before you see/hear something), as anything running sub-optimally usually manifests as a drop in economy.
 
24MPG!! Now that's pretty awesome.. Does/did your 3500S have the original 4 speed, or a 5 speed LT77 or equivalent? The auto does definitely feel like it needs another gear - especially since 100Mph is taken care of at nearly 4500RPM..

With a webasto and a cherry bomb, the sound is quite ummm.. Noticeable :shock: - but the ride is superb! That ultra weird suspension works wonders.. :mrgreen:

I guess having fiberglass panels might help fuel economy, did you put the panels on to make the car lighter and more nimble? Or were they as a result of discoveries made whilst prodding with a screw driver? :?

I've noticed fuelly on a few other posts before, but didn't know what it was.. Is it an app? Because I couldn't find it in the android app store..
 
Or were they as a result of discoveries made whilst prodding with a screw driver? :?
I like that way of putting it... :D
I made a few "discoveries" on my Disco the other day.... :shock: Definitely not a pleasant feeling....
 
hi I have been following this thread with interest as I was going to take the rover on a road trip to Bratislava for charity (now cancelled) if u click on quagmires "fuley"
badge/pic it takes u to the website the u can click on home and sign up I guess.... when I clicked on home i went to my profile so i guess i have already signed up

hope this helps
coop
 
Back
Top