Vauxhall corsa 1ltr- shocking MPG!

tomstickland

See page 37 of this: http://me.queensu.ca/courses/MECH435/2.%20Engine%20Performance.pdf

That's a graph with the x axis as engine speed, the y axis as engine load and the z axis (countours) representing fuel consumption per unit of output.

When driving you can select the road speed and the gear.
Load is a function of the road speed (and any inclines).

For one road speed then each gear will give a single point somewhere on the contour plot. Higher gears will reduce the engine rpm but increase the engine load.
So there will be 5 points, say, on that graph, falling from upper left to bottom right, but not in a straight line.
Lowering the road speed will cause each point to move downwards and to the left.

The best gear is one that puts a point at the most efficient zone on the map; at the lowest contour.

For that example map, at WOT (wide open throttle) then it's over 3000pm, falling to between 2000 and 3000rpm for mid range loads. At minimum loads it falls to 1500rpm.

To obtain good efficiency from that engine then working in the 2000-3000rpm range would be best, aiming low at low loads and high at high loads.

Hammyman

tomstickland wrote: »

To obtain good efficiency from that engine then working in the 2000-3000rpm range would be best, aiming low at low loads and high at high loads.

That pretty much describes how I drive my Mondeo.

nikki2804

I have a 2006 1litre corsa and I seem to get >50mpg out of it. I do drive very economically though (can't say the same for OH)

bexyboo1312

Well just to report back, we did the brim it and calculate....i got 32 mpg, however about 170 of those miles were dual carriageway / out of town roads, so not really a true reflection what I normally do in a month. Better than previous but still not a touch on the 50 advertised.
Driving in 3rd is a lot better for the car but its still slow....looking at trading it in for something else now...thanks

bexyboo1312

Well just to report back, we did the brim it and calculate....i got 32 mpg, however about 170 of those miles were dual carriageway / out of town roads, so not really a true reflection what I normally do in a month. Better than previous but still not a touch on the 50 advertised.
Driving in 3rd is a lot better for the car but its still slow....looking at trading it in for something else now...thanks

cyclonebri1

Falls in line with what was said earlier then, a combination of innacurate mpg measurement and constant town driving. Again as you have know realised it's probably not the car for your usage.

And for Hammy who had great difficulty in understanding the bit I wrote; ie;

"Methinks the biggest issue the op has is that she is driving around in 3rd gear all the time, that is nor even going to come close to the lowest fuel consumption guideline, ie, "under urban"? if youn see what i mean. "

It does not mean she should be in 5th gear under urban driving but simply that she will be in 3rd.

In simplistic terms the car will use roughly the same fuel at 30mph in 3rd as it would at 50 in 5th but will only cover approx 3/5 of the mpg, unless of course it's Coner's Mondeo:eek:

Hammy I love you.
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Not

keith1950

Hi, as part of my job I have to drive a 1.0 ltr Corsa most of the time doing about 900 miles a week. Yes it is an underpowered car and you need to rev it to get any performance out of it , but I get at least 38mpg on mainly urban but with some slightly longer runs no matter how hard I thrash it- do the usual 'fill the tank/run it down/fill again', a couple of times, along with mileage logs and then take your figures to the dealer. If you just say ' I put in £20 and only got 100miles' they wont give you the time of day.

cyclonebri1

The problem is that unless a fault code come up when plugged into the diagnostics there is nothing that can be done. There are no adjustables on todays cars. Faulty parts that usually trigger the engine management light get logged and replaced in the absence of that changing the air filter and plugs as per recomendations, plus keeping the tyres pumped up is about all that can be done

Of course there's the dreaded right foot :eek:

jeferey

newfoundglory wrote: »

So general rule to improve efficiency.... stay in 3rd when doing 30mph?

...only in a small car with a lawnmower engine . No, seriously if you have a petrol engine, driving in top gear at 30mph will probably labour the engine, however in my 2.2 Honda diesel, 30mph in 6th on a flat road doesn't labour the engine. It all depends on the car, the gearing, the weight, etc.

funkycoldribena

keith1950 wrote: »

Hi, as part of my job I have to drive a 1.0 ltr Corsa most of the time doing about 900 miles a week.

Your boss must hate you.