ca993twin

Pong,

That is excellent fuel mleage, although I have NEVER driven that slowly for any length of time to compare.

What sort of compression ratio is in your BTR?

CP

Steve,

8.4 to 1. I did the run deliberately as a test. I wanted to see if I can cruise for 400 miles in one tank (that's my personal target for my road cars).

Most tanks I only average betwwen 15 to 17 MPG. Any amount of first to third gear driving just kills the mileage.

CP

ca993twin

Pong,

The compression ratio in the stock 993TT is 8.0:1, and I don't think Ruf modifies that in any way. That difference (along with your aero and narrower tires) probably accounts for your better mileage.

Rassel,

My doofus brain just can't think of how you can acheive a variable compression ratio and still get good combustion sealing. Rubber pistons? Can you describe the method that Saab was using? Was the cylinder head hinged? Hard to imagine how you could seal it. I remember reading about this a year ago or so.

doogle

Excuse me if all our European readers had already thought of this but don't forget when comparing gas mileages between UK and US cars to factor in the difference in US and Imperial gallons. I can get 27 mpg (Imp.) on a run which is about 22.5 mpg US.

CP

Steve,

The stock 993tt has lower compression, but mine started as a 993 C2 which spotted 11.1 to 1 compression ratio. RUF tore into the engine, substituted a bunch of titanium parts, ported the valves etc. and lowered the compression ration. The goal obviousely is long-term engine reliability.

In addition, my BTR weighs 2,996 lbs. A little bit lighter than a 993tt.

CP

pstoppani

Ditto. And 6 MPG at the track.

ca993twin

Pong,

Yes a "mere" 300 pounds lighter. However, that plays a very small part in "cruising" gas mileage (only as it affects the rolling resistance, which is slight). The weight makes a huge difference in acceleration and around-town mileage, where the aero stuff is of little consequence.

What parts are titanium? Rods? I mean "rod$"?

CP

Steve,

I believe that the connecting rods are Ti, may be the sleeves as well.

CP

EEE

I'm really jealous; you guys can truely enjoy your machines in a free and efficient manner. In the hot summer in HK, if you drive in the crowded city (1st to 3rd gear) with air-con on, you'll read (dashboard compputer) as much as 33 or even 34 litres of fuel per 100 km. You can't get lower than 20 with long drives in winter.No kidding! Fuel is expensive here too. Almost HK$14( US$1.8) per litre.

EEE

Sorry, HK is Hong Kong.

Stummel

That is really bad

I also get 33 litres per 100km but the difference is that I am then going above 300 kph for longer distances.

Fuel price seems high. We now have ~ US$1.6 per litre. But we 993tt owners are lucky with that because our fuel tank is so small

Rassel

Me neither! I have no idea how they managed it (but it's typically SAAB to invent stuff like this), so I had to look it up. I suggest you look at the attached link, it was quite interesting read actually.

SAAB Variable Compression and SAAB Combustion Control

ca993twin

Thanks for the link. It really sounds like a great idea that needs a chance to succeed.

In the US, our gas is too cheap (91 octane is ~$2.80/gal), so I've searched out a station that sells 100 octane for $5.00/gal, just to make my overseas brothers feel better.

ACEparts_com

My MPG only reads as low as 11.5mpg - I guess it doesn't want to scare me as I've calculated it at 7mpg on the track.

robroy72

I used to get about 9MPG out of my Impreza Turbo when I drove it over the dava moor in Scotland. Never got out of 3rd gear. Boost in any car isn't good for fuel consumption ... and it hurts like hell when its over $7/gallon!