Poor MPG / High(er) than normal fuel consumption
 

All - I wonder if my memory of my old C4 is a bit rosier than perhaps it should be. This new-to-me C2 Targa seems to be hoovering fuel more than it should. Combine that sensation with an occasional 'she's rich' smell stopped at a traffic light makes me think my fuel is out of whack. Overall with non-agressive driving I'm getting somewhere between 16 and 18mpg per tank. 60% highway speeds & duty-cycle. Low-end power seems not quite what it should be, but once the revs are up she really sings. Which is another symptom I think of being overly rich and until the revs and engine-load are up she's just bogging a bit.

I've got a new 02 ready to toss in there, but I seem to recall that there are other inputs that have more authority over the fueling than the 02 sensor. Does anyone have the authoritative list, and the check-out procedures to exonnerate each one so I'm not just blindly throwing parts at her? As I recall from long ago the order of precidence is:
1. Air Meter - flap-door-contraption
2. CHTs - cyl head temp
3. OT - oil temp
4. 02 sensor

BTW: I am learning to love the Targa experience. 4 days of top-off driving down here in TX already...:bigbye:

When I did my 02 I did get noticably better mileage but lost some of that upper end grunt. Porsche ran them lean for fuel economy and for emmisions. One of the main things a perfomance chip will do is remap the fuel ratio.

When the O2 goes bad it open loops.

Althought it will never get great mileage. It was originaly rated 18 city 20 highway.

I got about 28 mpg on the way to Liverpool recently, i thought that was pretty good. So the 18mpg does seem off

I'm lucky to get 20 consistently

I am lucky to get 20 also.

28?

There's 4.55 litres in an imperial gallon vs. 3.78 litres in an US gallon, which may explain why our fellow Rennlister from across the pond achieves 28 mpg or around 23 miles per US gallon.

Hmm - so maybe my consumption is more in line with the other aged USA cars. I suppose the question becomes, are they all suffering from older and perhaps nearly out of spec fuel-trim related components or not?

I guess I will be the lab-rat and make a change to see how it manifest in power or MPG. First up will be the 02 sensor replace. But even before that I have to dive into the front-suspension and see what mistakes the PO did in there. New Bilstein and some stock-looking-but-new Weltmeister coil springs installed. Alignment rack has LF @ -1.7deg, and RF @ -0.7deg on camber, and the shop couldn't find any adjustment... I got worried when they started calling me asking for concentric control-arm bolts. So I came and brought it back home. Spec says 0.00deg on front camber so clearly something ain't right. I can't see any evidence of any non-factory sheetmetal in the front-end so I doubt she's been bent.

Yeah sorry just checked it was about 26-27mpg not 28mpg. 430miles on a tank approx

Or is my maths that bad...

Unkle, what gallons do you refer to ? Imperial or US ?
I live in the netherlands and we have litres, I have a calculated 20mpg consistently,
26-27 looks to me impossible, Porsche gives 20-22 mpg !

Euro/uk gallons.

I did mention it was a run to Liverpool, so all motorway and back but compared to you guys it seems high. I get 20-22mpg driving normal and locally around town, but then i am in the country within 1mile from my house so i don't do a great deal of urban driving its mainly B roads or motorway.

On the inside back page of my handbook is a page giving the figures, your book must be different to mine.

Here's a pic, i do thinks its optimistic with the quoted 56mph figures though :roflmao: but then i have never tried driving at 56mph on a motorway.

http://i58.photobucket.com/albums/g2...er2429/MPG.jpg

yeah on my c4 on combo I get around 24mpg and driving on long trip highway I got just over 27mpg

its not just me then :)

I think it depends how you drive, leave a big gap to the car in front and never brake unless you life depends on it really helps. My other car did 63mpg on a European trip in 2010 but its no where near the same fun :D

I will be interested to see if you get any improvments RallyDogRacing :thumbup:

I have a rather heavy foot, but that's the fun with a Porsche !
But with the gasoline price of 1,65 per litre. (thats around 6,5 usd per gallon)
it is hurting now.

I get between 18 to 20 around town depending how much I put my foot in it. 17MPG if I am really doing heavy traffic in Portland, but usually on the freeway going to Salem or up to Seattle I get around 24MPG.
Basically the MPG I expect from this era of high performance automobile.
I have noticed that I get better mileage if I let her shift the gears instead of me :p (yes I have a Tip) -D²

@ Rarebear- I thought $3.62/gl was getting a bit much but I can see your way over what us yanks are dealing with here.

Dirty air filters, dragging brakes, too much toe in or out, high ambient air temperatures, etc. etc, and a heavy foot in the city, all contribute to less fuel mileage. Growing up under the Dominion, I think in Imperial and on a regulary travelled 150km highway jont with the cruise set on 100 kmh, I've recorded 28 mpg many times, but once I start getting a bit heavy on the foot in the city I see my mileage easily go below 20 mpg.

£1.33 a litre here in the UK, so €1.57 if it was in Europe

£6.03 a gallon = $9.78 gallon, car takes approx 16.5 gallons. Yeah its very expensive in Europe and especially the UK

See sig.

The European governments earn more on oil than the OPEC does !!!!!
and now they are promoting Electric cars... OMG !!!! they must have concocted a new trick to
rip us off !!! tax on batteries ???
2/3 of the gas price in Holland is tax !!!

The diagnostic system has been bullet proof for detecting bad components on problems I have encountered on my car and on others I have helped out. Have you read the codes?

Well, I'm old enough to remember a $0.13/gallon gas war in the 60's in West Texas, heart of US oil production before our government stopped us from drilling and made us totally reliant on places like Iraq, Egypt and Libya. I'm guessing $5.00/gallon by the end of the summer. It will make for a polarizing campaign season.

Mine routinely gets 26 mpg (U.S.) with highway usage (70-80 mph) and that's with 10% ethanol in all U.S. gasoline in my part of the world these days. Prior to the introduction of ethanol, I would routinely get 28 mpg. Around town, somewhere in the low 20s.

Just a bit of trivia: more than half the gas comsumed in the US, comes from Canada, and if you need more, we have lots, something the average American have no knowledge of.

:cheers: