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Fuel Economy

T

theogeor

Albert Park
Joined
22 Sep 2008
Messages
1,504
Today we visited some friends at Bristol with a total round trip of 245miles. Basically it was a bit of M25 then M4 and last a bit of M5 plus 5 miles each end in local roads so most of it motorway driving.
I am pleased to say that I got 28.8 MPG with an average speed of 64MPH (cruising most of the time with the CC on) and that was with two adults and two kids in the car
So who said that the 911 is not an economical car to drive :thumbs:
 
I thought the 997 was meant to use less fuel than the 996...


20081006_160622_DSC_1614a.jpg


Fair play though - mine just had me in it :thumb:

I struggle to average 15 mpg in its replacement - currently showing 12.7 I believe :eek:
 
theogeor said:
Today we visited some friends at Bristol with a total round trip of 245miles. Basically it was a bit of M25 then M4 and last a bit of M5 plus 5 miles each end in local roads so most of it motorway driving.
I am pleased to say that I got 28.8 MPG with an average speed of 64MPH (cruising most of the time with the CC on) and that was with two adults and two kids in the car
So who said that the 911 is not an economical car to drive :thumbs:
Click to expand...

I told you they were economical Theo! The day I reported 29.4mpg just had me in the car, not 4-up like you........

~ Maxie
 
I got 31.something mpg on 300 mile trip to Nottingham cruise set 70 ish, very boring. Only got 25 on the way back, interesting, can't recall speed! :cop: must have been a strong head wind with top box on top and towing a caravan! :floor:
 
mpg

Lol on the roof box and caravan.

I get 25-26 on the 8 mile side road and main road country commute to work, and 29.5 on 110 mile regular drive up A30/M5 to Somerset at 80mph ish with a few bursts a little above :wink: .

So far not had worse than just under 25 on a tank. Seems amazing. Glad I didn't buy a Mazzer !
 
Over 1200 miles my 997 GT3 has averaged 25.5 mpg. This includes a lot of slower town driving. So I'm not too unhappy :lol: .
Regards Big Bob :bye:
 
Drove from Hertfordshire to Devon for Mother's Day (yes I know, but please keep you applause until I am finished) covering 250 miles each way.

I averaged 30.4 mpg with the CC set at the national speed limit (or at least within the legal error allowed under the law where a caution may be given etc etc). Sorry, I realize that without an actual speed this economy figure is slightly pointless.

Having read the thread about the parsimonious TT, on my return I tried the 18 mile trip to OPC Cambridge and acheived 38.4 mpg at 56 mph.

If you know the area, that also frustratingly included a wait at the level crossing at Foxton!

Unfortunately, on return of a nice valeted car, sun out and no charge from OPC my left foot celebrated and 22 mpg normal service resumed.
 
On a similar note about legal speed does anybody knows the speedo accuracy (electronic part in the centre and not the dial )??
 
theogeor said:
On a similar note about legal speed does anybody knows the speedo accuracy (electronic part in the centre and not the dial )??
Click to expand...

If you have a TomTom or something use that to check it (GPS is pretty much 100% accurate on a straight road). It is illegal for it to read slow, or more than 10% fast, so most manufacturers aim for around 4% fast - this also allows scope for tyre wear and small changes of circumference with different size tyres (e.g. 265/35 vs 285/30)

So don't rely on it, but probably about 4-5% fast on the digital readout.
 
As mentioned, for the most precise reading use a good GPS.

However, for the car's idea of its true speed, interrogate the ECU outputs.

The speed may still be wrong as the car does not know what tyres, wear or pressure for instance you are running (which are the most likely errors), but it does give the measurement prior to adding a safety error for both digital and analogue outputs (needle). Compare to dash digi readout (sorry, 996 ECU only reports KPH, so you will need to swap to KPH for comparison, again not sure on 997, newest VAG products display both KPH and MPH, so perhaps 997 do now also)

I am not sure how 997 works, but 996.1 works like this:

Press and hold the UP button then at the same time press and hold the RECIRC button in.

After 5 seconds or so of holding the buttons in the display changes to 1C.

To see the reading corresponding to 1C press the centre button on the climate control below the UP button (this is the button for directing air through the centre dash vents).

To move back to the 1C press that button again. To go to 2C, 3C, 4C etc etc press the + button on the temperature control (not the fan speed +).

To exit this mode press the AUTO button
---------------------------------------------

20C - Vehicle Speed in kph, updates once per second. This is True Speed, not the Speed+Safety Margin displayed by the Speedometer
Click to expand...
 
Wattie said:
theogeor said:
On a similar note about legal speed does anybody knows the speedo accuracy (electronic part in the centre and not the dial )??
Click to expand...

If you have a TomTom or something use that to check it (GPS is pretty much 100% accurate on a straight road). It is illegal for it to read slow, or more than 10% fast, so most manufacturers aim for around 4% fast - this also allows scope for tyre wear and small changes of circumference with different size tyres (e.g. 265/35 vs 285/30)

So don't rely on it, but probably about 4-5% fast on the digital readout.
Click to expand...

Thanks Wattie but I am aware of the issues around accuracy. I was wondering if someone else did the check and knows the answer. If not thn tonight when I go home I will get my old NavMan and go for a quick spin.
 
Theo, at low speeds (ie below 50 leptons :wink: ), my speedo reads 3 leptons lower than my Pogo Alert. At around 100 leptons, it is reading 4 leptons lower. So I guess more or less in line with what Wattie states.

~ Maxie
 
Maxie said:
Theo, at low speeds (ie below 50 leptons :wink: ), my speedo reads 3 leptons lower than my Pogo Alert. At around 100 leptons, it is reading 4 leptons lower. So I guess more or less in line with what Wattie states.

~ Maxie
Click to expand...

Woaaahhh... If your speedo is reading LOWER than your Pogo alert, that is highly illegal my friend! :eek:

It should read about 4 leptons HIGHER! :thumb:
 
theogeor said:
On a similar note about legal speed does anybody knows the speedo accuracy (electronic part in the centre and not the dial )??
Click to expand...

speedo must show true speed or up to 10% + 4kph over.
 
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