Consistent 23 mpg on the highway with tweaked APC box? - Saab 900 Bulletin Board - Saabnet.com
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Consistent 23 mpg on the highway with tweaked APC box?
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Posted by Joe98 (more from Joe98) on Fri, 5 Sep 2008 12:17:59 Share Post by Email
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I commute 120 miles every day, all on interstates and highways. 3/4 of the trip is fast-moving, never-having-to-brake cruising. The other 1/4 is stop-and-go traffic.

I tweaked the APC box according to the specs I've read here, installing the resistors into the box as well, to bring the output up to that of an SPG a long time ago. I also swapped in a 3.0 bar fpr.

The engine/tranny/car is running at tip-top shape, all maintenance being done on a regular basis. This includes things like the plugs, cap, rotor, wires, filters (gas/oil/air), fluids (coolant/tranny/oil), etc. I can't think of anything that has not been replaced or attended to. Base boost and timing is adjusted perfectly as well.

The exhaust system shows no signs of a rich mixture. There is no black soot coating the inside of the tailpipe, and the NGK plugs always come out clean.

From what I've been reading, this seems like a very low mpg rating for all-highway driving. I do tend to keep the speed around 75 when cruising, and will drive it hard once in awhile (for a thrill).

Is there something I'm missing that would give me the better gas mileage or is this due to the APC tweaking and 3.0 bar fpr? I assumed the bigger fpr would only cause a problem when driving it hard, not during normal cruising. The only thing I can think of that is still original is the O2 sensor. But I've never had any CEL codes related to a bad sensor, so I have just left it alone. I assume it to be the original, as I purchased the car with 124K miles on it about 5 years ago and I have never replaced it.

Any ideas, or is 23 mpg what I'm to expect with a tweaked 5-spd turbo?

Joe
'93 900TC 167K
'98 9000CSET 144K

posted by 167.211.6...

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