Volvo RWD 120-130 Forum

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My Mileage... Is WAY up 120-130

This is just a tad bit premature, because I've not fueled up this week, but I've just crossed 218 miles on my current tank as my fuel tank has just reached the top of the white "Reserve" section. I'm probably down to one to two gallons now... and have used around nine gallons of fuel.

My odometer has at least a 1.05 error ratio putting my true mileage about 229 miles. If I put only about 9 gallons into my car tomorrow morning, that kicks my fuel economy up to 25 MPG!

Considering I could not break over 16 mpg for the last year - that is a huge jump into "normal" territory.

What has changed?
I replaced my throttle shafts, jets, and "riveted" my butterfly plates closed (hot brass rivets nicely). I do not think this made any real difference as I had tried this approach before. Plus the jets are at right about 12 flats and the throttle will not adjust down under 1600 rpms... This should be a recipe for bad economy, but the opposite has happened.

What I think changed is this...

I replaced the old 1968, self-adjusting rear brake drums with manually-adjusted 1967 drums. The shoes in the old drums were worn to almost nothing and a lot of dust came out of the drums when I removed them. I think the self adjusting setup was ratcheting up the shoes causing the rear of the car to drag. I could not "feel" the drag, but I think that shoes worn away within 1 year is the proof that this may have been the *real* problem.

I'll post after I fuel up and provide a real calculation.








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    My Mileage... Is WAY up 120-130

    Glad you got the mileage up finally!

    I think though that if your brakes were dragging enough to make that much of a difference in mileage you would've noticed something before- like a smell or heat emanating from the rear wheels!








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      Maybe a bad rear hose? 120-130

      Yeah, that bugs me too.

      I'd like to think that I would have noticed if the rear of the car was dragging when I was coasting or that my drums were heating up and the brake pads were being burned away, but I never felt, heard or smelled the issue. The wheels always spun free when I checked them.

      I can say that over the last year, I gradually lost my parking brake. Before I pulled both whole drum assemblies off the axle, I could roll the car with "full e-brake"

      My only other thought there is that I just replaced the rear flex line with an SS flex hose and I replaced one of the rear hardlines that twisted off when I was replacing the drums.

      I could see this making sense if that had collapsed and was binding the rear brakes. I had replaced the front flex hoses with new and I had replaced the rear brake limiter, but I don't think I ever replaced that rear hose. I was always checking the front.

      It might also have something to do with the brand new brake master cylinder I just put on.

      I dunno, really. I can't argue with the improvement I've seen this week.

      I'm fairly glad that I did not just drop $400.00 on a carb rebuild. I would have been livid when the bad fuel economy continued. I could still use a good re-bushing though...








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        Actual Mileage 22.9 mpg 120-130

        Upon a 10-gallon fill-up this AM, I calculated my most recent mileage as 22.9 mpg.

        Not as nice as 25 mph, but I think if I can get the carb tune and idle speed sorted out, I can get it higher.








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          RE: Fast idle 120-130

          Repairman,

          Fast idle speed can have only one cause: air. If the throttle plates are completely closed and the idle screws are backed out you should be able to get the idle down to where the engine is barely running. I haven't measured that low idle but I suppose it might be just below 600 RPM. If you cannot get the idle down, either the throttle plates are being held open (fast idle adjustment?) or unmetered air is entering the intake tract somewhere.
          --
          Mr. Shannon DeWolfe -- I've taken to using mister because my name misleads folks on the WWW. I am a 52 year old fat man. ;-)








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            RE: Fast idle 120-130

            Shannon, thanks. I do realize that. I posted previously about the plate leaving an open crescent on the pivot sides. No matter how I adjust the plate, I can't seem to get this adjusted out.

            I don't know if that plate is worn or I'm just not getting the thing in right.

            I will say that I've stripped and reassembled several SUs now and I know the workings very well. There is a certain finesse to this that I've not fully developed yet...








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          Factory Rating? 120-130



          Hey Guys,

          Interesting thread. Considering today's gas prices I'm surprised that more readers here aren't concerned with lowering per-mile consumption. I may be too young to remember when the brand-new-from-factory gas-milage system came into effect and was posted on new cars for sale. Does anybody know if 122's ever came with a factory tuned rating? (in-town/hwy?) What should we be expecting or hoping for in our relatively unmodified B18s and B20s?










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            Factory Rating? 120-130

            Actually, the 122 predates "official" fuel mileage ratings (at least the ones we're now used to seeing) by several years. The EPA numbersfor fuel mileage began appearing on window stickers in the mid-70's, if memory serves.

            I do have, however, some fuel mileage calculations taken from a logbook that I kept on my then-new 1968 122S (115 hp B18), and I can even pin down the driving environment for this particular set of numbers. This was on my honeymoon trip (!) from Kansas to San Antonio, wandering back up through Texas and Oklahoma to southwest Missouri, then back home. About half of this would have been done at 65-70 on two lane highways, about half would have been interstate cruising at 75+, with some urban driving (prolly 3-5% of the total) thrown in for good measure.

            The trip totalled 2441 miles over 9 days, using 105.3 gallons of regular leaded gas, for an average of 23.8 mpg. Highest single tank mileage was 25.3 mpg, lowest was 22.4 mpg. (Oh yeah - the total cost for fuel was $36.80, or 34.9 cents per gallon!)

            At the extreme end, I also have records that reflect 33.2 mpg for a 145 mile economy run (SCCA event) in an identical '68 122S, done in and around Wichita, Kansas in late 1970. This was a mix of urban and (mostly) open rural driving, 45 mph average for the entire course. But it was accomplished using every trick in the book... 60 psi in the tires, SU's dangerously lean, short shifting, engine-off coasting, etc. I remember finishing 2nd in class (1500-2000 cc sedans, I believe) to a 1600cc Ford Cortina, losing by something like a 10th of a gallon!
            --

            Gary L - 1971 142E ITB racer, 73 1800ES, 02 S60 T5
            BlueBrick Racing








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            Factory Rating? 120-130

            I saw "25 mpg" in a vintage ad once. I think it's one over at Swedish Embassy, but I could be mistaken...

            That's nothing stellar, unless you consider that was 40+ years ago and many modern cars don't even get that now. I chuckle when I see those "gas saving" 25mph highway" cars...








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              Factory Rating? 120-130



              Yah, it seems like 20-25/mpg is a reasonable estimate, and not too bad at all considering the technology of the time and all that "flying-iron" sheet metal mass!








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                Factory Rating? 120-130

                From the "Volvo Owners Handbook" published by Floyd Clymer; pre- 65' 122s 4dr.

                Los Angeles to Lake Arrowhead- half heavy traffic, half winding mountain roads
                23.9 mpg

                Lake Arrowhead to Mojave Desert- winding mountain roads
                26.8 mpg

                Testing 200 miles over Mojave Desert roads
                32.4 mpg

                Lancaster, via Angeles Crest, snowy and slippery highway, to Mt. Wilson, and then
                to Los Angeles
                23.3 mpg

                At steady 30 miles per hour
                36.1 mpg

                Premium gas of various brands was used.








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                Factory Rating? 120-130

                well some do report up around 30 mph, and the D-jet conversion is supposed to put it up that.

                MegaSquirt and some judicious engine work might up it further.








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                  Mileage 120-130

                  Guys;

                  I got around 30MPG on a trip from Hartford to Chicago...obvously all highway and fairly constant speed, where the motor is strictly making up for air and rolling resistance...tire pressure is certainly a big factor, but mileage is mostly a function of your right foot...don´t forget also, that todays fuel is not what it used to be...that percentage of alcohol just doesn´t have the BTUs that gasoline has...so there´s just not the amount of energy in the todays fuel to begin with...and that will translate to a decrease in milage...

                  Cheers







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