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need help finding a fault

1K views 16 replies 9 participants last post by  KevinC 
#1 ·
i have and 89 2.0 carlsson, and cant seem to find where all my fuel goes...!!! i get around 200-230miles (max) on a full tank, i had it fully serviced, changed the air mass meter, throttle position sensor and still cant find out where all the fuel is going.........im very strict with my car and only use v-power so it is running clean.

any help please..
 
#4 ·
Carlsson GT said:
yeap ur rite
i havent had a look at the fuel pressure or injectors, i noticed that if i take the car for a quick thrash, when i pull up and let her idle she idles at around 1300rpm, would be this be linked with the fuel pressure or injectors?
Also if you give it much of a thrash, your mileage goes way down. On a big track a 9k Aero can get thru a gallon every three or four miles if you are really thrashing it...

All gets back to the baic laws of physics; big heavy object, accelerate fast all the time, does not matter big engine or small 2.3L w/ turbo, needs lots of energy (fuel) to make it happen.
 
#7 ·
Running very rich can only be caused by a few things:
Air Mass Meter
Massive vacuum leak
ECU
NTC resistor

(In very rare cases, a fuel pressure regulator can have a leaky diaphragm; disconnect and plug the vacuum line to eliminate this possibility)

Sure, all the other stuff has an effect, but if you're emptying a gas tank in half the normal time, look carefully at the above; don't worry about ancillary issues like timing, fuel pressure, filters, type of plug etc.
 
#8 ·
Don't mean to hijack this thread, but using either WOT or full brakes the fuel can go real fast. Saabs driven all out on 12.5 mile track can get through more than 3 gallons a lap, and need more fuel after 4 or 5 laps (driven hard on an empty track, not a crowded Sunday afternoon).


Jim, what is a NTC resister?
 
#9 ·
djtaylor said:
I can't quite see it that low. Isn't an Evo 8 supposed to be something like 8 MPG flat out and that's nearly twice the power of the Aero.

David.
On a track with lots of curves is much different than going flat out but at a steady speed. On the curvy track, you are always slowing and then accelerating hard. On the other hand, driven flat out at even 130 MPH, you will use much less fuel by maintaining that speed. I used to have a brochure about the 1986 'Long Run' at Talladega Superspeedway. I can't seem to find it, but distinctly remember it saying the cars averaged about 8 MPG going flat out (by that I mean full throttle all the time). The average speed was just over 130 MPH.
 
#11 ·
around town i noticed im only getting around 15mpg, that not when im giving it, ive done a whole tank on careful driving and still it drinks like a horse. I thought i mite have a leak in the tank or piping but petrol evaporates so cant notice any puddles, i was thinkin of taking its to SAVAGE SAAB, see if they can find the problem,


KEVINC,
you said a while back that you had your wheels refurbished for £32 a piece, that is a good price, where from?
 
#13 ·
KevinC said:
Don't mean to hijack this thread, but using either WOT or full brakes the fuel can go real fast. Saabs driven all out on 12.5 mile track can get through more than 3 gallons a lap, and need more fuel after 4 or 5 laps (driven hard on an empty track, not a crowded Sunday afternoon).
Fascinating side topic; Kevin, for you car to consume fuel at that rate it must have the ability to produce 400bhp, fuel consumed and power output are tied, I'm no where near clever enough to expalin, but this website helps me clarify what I am thinking pumaracing under track conditions with mostly WOT and no over run fuel cut my 200bhp V6 gave around 12mpg which is correct. My thoughts are that you have a very high rich mixture under high load which is good for engine protection, but not optimised by any measure.
 
#14 ·
Have not done any real science on this, but do know that driving is a much better test of a car than dyno tests. Have been out on empty autobahns with perhaps a total of 15 other Saab turbos, and following some of them, they really let you know when the go to full boost as the black cloud of smoke always appears (you should see the chipped VW and BMW diesels, they use a smoke-screen to hide their escape). My car, as viewd from lots of other Saabs, gives out no smoke of any kind at warp speed acceleration, so combined with plug examinations I don't think it is too rich. Have noticed five hard laps is about all I can take in a morning, and about all the fuel tank is good for.

Most other BMW, Porsche, Audi ect. guys with approx 300hp cars at the Ring report similar consumption if pushed hard on an open/empty track with as stated, constant full on accel or brakes. There is also way more than 1,000 feet of climbing, I think almost 65% of the circuit is steer up or down, so that changes things.

Driving home from Italy late at night at WOT the fuel consumption is much better, seem to remember I can go about an hour and a half on a tank of fuel which is over 200 miles. Will try some more scientific measures this year, driving to Cologne, Stuttgart and Berlin on the weeks before my thre Ring visits. Saab Aeros are at there best on an empty autobahn, effectively no 1993 era stock sedans can keep up. Things have moved on, but a modified Aero can still keep up with most hi-performance cars in the real world on autobahn, but not track, conditions.
 
#15 ·
ragtopcav said:
Fascinating side topic; Kevin, for you car to consume fuel at that rate it must have the ability to produce 400bhp, fuel consumed and power output are tied, I'm no where near clever enough to expalin, but this website helps me clarify what I am thinking pumaracing under track conditions with mostly WOT and no over run fuel cut my 200bhp V6 gave around 12mpg which is correct. My thoughts are that you have a very high rich mixture under high load which is good for engine protection, but not optimised by any measure.
Pumaracing site is great source of info. However measuring consumption with constant acceleration is completely different from steady WOT. I will try something more accurate this year, but I'm certain it will be below 10mpg if high speed laps are possible based on German Saabers I have visited with.
 
#16 ·
KevinC said:
Pumaracing site is great source of info. However measuring consumption with constant acceleration is completely different from steady WOT. I will try something more accurate this year, but I'm certain it will be below 10mpg if high speed laps are possible based on German Saabers I have visited with.
The most scientific you'll need involves filling up before and after as well as using your trip gauge. If you've emptied the tank and done 60 miles, then you can work out your fuel economy easily. And no amount of scientific horse**** will be able to change the results. It's all to easy to get caught up in theory and ignore real world results.

Kenneth
 
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