Poor fuel consumption ?

[Beebop]

My 1991 964 turbo II has recently been upgraded by replacing the wastegate with a Tial unit, with the boost set currently to a fairly modest .85 bar (or say about 360 bhp). The bypass valve was also replaced; the ignition was renewed; the fueling system was completely refurbished 3 months ago.

The fuel consumption I am getting seems to me to be completely outside what I would have expected. 100 miles of say 15 fairly spirited country road miles (but not silly) + 35 miles of "normal" country road driving (i.e. light on the accelarator) + 30 miles of steady 30 MPH town + 20 miles of motorway cruising (top end of legal) returns 10 or 11 MPG.

Does anyone know what I ought to expect? I was expecting something in the region of 17 to 20 MPG. (I know "spirited", "silly" and "normal" are subjective but I think I am using them as a "reasonable" person would.

I know that the lambda sensor was U/S and was removed. Does anyone know what improvement I should see if I get a new one fitted?

Many thanks,
Iain.

 

[911addict]

Don't know the answer.
What I do know is these cars (I have one too) guzzle gas and I don't bother trying to measure how much. I drive, enjoy and refill.
Wouldn't think you'd ever get 20 mpg....

 

[DuncanF]

Similar story here. I did the sums when I first bought mine and it was down around the 15 - 16 mark. Since I was driving a bit like a granny for the first couple of weeks I'd be surprised if anyone could get much more than that out of a standard car. As for a tuned car ... who knows? Hopefully someone will step forwards.

Duncan

 

[John_Ward]

That actually strikes me as thirsty.
I had a 3.3 turbo nominally rated at 381bhp ( with adjustable boost and fuelling available if required for 450bhp ), and in normal use I regularly had fuel consumption figures in the high teens / low 20's....to achieve the sort of figures that you are talking about, I would have had to be pushing it pretty hard.
It's probably worth you getting in touch with one of the modified 911 turbo experts ( Colin Belton or Bob Watson for example ) and have them check your cars fuelling and ignition characteristics.
Cheers
John