700/900 Fuel Economy (Petrol Engines)

[popuptoaster]

Originally Posted by TurnipSpeed

Funny how the mpg can vary so much with the same engines.
I think my latest 940 revs lower than my previous, more thirsty 940 in top gear , or is it just how efficient an engine is running at a given time ( worn plugs , air filter etc) that makes the difference?

Maybe it has a different ratio diff in it, or different size tyres, or a different gearbox.

[TonyS9]

its 90% how you drive it, the route and so on. I'm beginning to sound like a broken record, but if you want MPG you need an MPG meter. The biggest variable is the driver. Driving gently isn't going to do it, but it slightly better than hammering it everywhere.

I'm still experimenting, but this is what I've got so far (95 HPT 940 estate);

Generally stay around 50, or accelerate reasonably (say 0 on turbo guage) then coast in neutral to slow down
accelerate reasonably downhill
decelarate slightly uphill
If you are at speed (limit or 50) downhill, coast in neutral (big benefit usually)
If you want to decelerate, coast in neutral for light decleration, using engine above 2000rpm for higher braking (fuel cut off starts above 2k, and stays until 1.2k, but if you start inbetween it uses more than coasting in neutral)
Try to avoid engine braking, but its better than foot brake.
Plan ahead and avoid braking
Look out for fuel management overfueling and back off if MPG<30,
Along flat aim to achieve 40mpg, back off if not (unless heavy headwind)
Avoid wot
When not accelerating keep rpm low say <1500 (around 30mph), change up early.

I can get 37mpg average on a long journey, NA should be better with higher compression compared to turbo.

[popuptoaster]

Vacuum gauge is cheap and easy to fit and will improve the way you drive, If you have a turbo buying a boost gauge that reads under 0 ( in inches of mercury usually) will do the same job.

The more vacuum you are making the less fuel you are using and it's surprising how often you're better off in 4th at higher revs than you are in 5th at low revs.

I fitted one in my old Ford cortina into which I had dropped a 2.9 litre 210bhp Cosworth V6, and I was averaging 30mpg which is better than a stock 2 litre used to be.

Can't get my Volvo up above 15mpg but i am using it around town for work, its all stop start from house to house over about 6 miles, perfect for an electric car but not a 2.3 turbo mile muncher. lol

[barkster1971]

I noticed when it's cold the ratio drops like a stone. I will be fitting an adjustable fpr soon to see if I can get 30 mpg again. Mine seems to be 27mpg if I thrash it or not.

[Apoplectic]

Originally Posted by Apoplectic

I isually get just over twenty, but I scratched 23.3 once.

Wait a bloomin second, you guys use a whole different gallon don't you?

I average 25 ukmpg, and hit just under 28 once.

[Will M]

A UK gallon is 1.2 US gallons.

[CTCNetwork]

Hi,

Well, a us gallon is still 8 pints. However, one assumes that commercial interests took over as the us pint is only 15 fluid ounces... Skinflints!

Des. . .

[Apoplectic]

Originally Posted by Will M

A UK gallon is 1.2 US gallons.

Hmm, just when I thought EVERYTHING was bigger in the US...

I wonder why we call it a gallon still even though it is smaller. Someone had to have realized it would cause rise to at least some confusion. It would be like us calling yards metres instead.

[Essexboydave]

In our old 740 fitted with the twin cam 16 valve 2.3 we often used to get 38-39 to the gallon cruising down to Cornwall, we did used to set off around 3am though so the roads would be empty as we drove along sticking to a steady 65-70. In our last 740 though a single cam redblock carb version the best I ever saw was 29 cruising at 60 and it was often under 20mpg!

[DWM]

Today I changed the oil, the spark plugs, and the air filter, and I swopped my (25-year-old) HT leads for a set that are only sweet sixteen.

Then I invented some errands to see to what extent it might have affected the fuel economy.

43.5 miles: a mixture of A-roads and town driving; 4.72 litres used.

41.9 mpg.