Fuel economy question.

Lincoln Mark VIII

  1. capt fast

    capt fast Active LVC Member

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    I have a '98 base. 3.73 ratio with trutrac differential and 2.5" exhaust. srsly, the difference mechanically between the base &LSC is the gears and exhaust. 3.73s puts cruise rpm in the sweet spot for torque and I have not found any change in economy. the engine has two knock sensors and with knock sensed, the PCM will back off timing in a somewhat draconian manner and then advance it 2deg and listen for knock and keep doing that until it hears knock come back then back off 2deg. this tuning happens extremely fast. with very low torque at cruise, the timing is quite advanced. NGS mach2 tester has a nice readout on ignition advance. I am at 6800' altitude and run 87 octane on the city loop, but up into the rockies, I run with the premium. just finished running BG-44K and found the idle somewhat smoother, no change on power output. thinking about pulling the intake manifold and checking the IMRC system for function and cleaning.
     
    Last edited: Sep 16, 2019
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    • capt fast

      capt fast Active LVC Member

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    • capt fast

      capt fast Active LVC Member

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      lots of folks think that exhaust backpressure is good to have. WHY? exhaust back pressure slows the exhaust event in the cylinder and causes dilution of the fresh charge. it is almost as bad as having the ignition retarded all the time. you spend all the time and effort to get the crap out of the cylinder, why negate that by plugging up the exhaust? you already have EGR to drop cylinder pressure and heat.
      Kooks will help if you race, but on the street? I am having my doubts.
      I have kept the primary cats and removed the secondary cat and installed 2.5" true bendz dual exhaust and an x pipe after the cats to reduce the drone. I am in a I&M state so emissions is a must. have not flashed a new program. the stock PCM is doing ok with the new setup and the 3.73 gears reduced the required torque at cruise. same mileage as before the mods. the car is a lot quicker in town now, mostly a function of the gear change, I think. I renewed the speedo gear to correct the speed indicated to within 5% of GPS speed. used the NGS to get it dead nuts on.
      elder bro has a t-bird with a reman engine with a bit more compression and PI heads and cams and intake, he kept the secondary cat and I welded a feeder wye for his trubenz dual exhaust to take the 2.5" cat outlet to his exhaust. Removed the resonator can also. he still has the crappy iron headers which I hogged out to a fair thee well. now , that car would benefit from a set of Kooks and no, the BBK mustang pipes he had hit the steering shaft. maybe Christmas.
       
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      • Bullymong88

        Bullymong88 Active LVC Member

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        Considering that altitude I'd have thought it would run hella rich losing performance in the process but with the amount of computers in these cars I guess it compensates.
         
      • Bullymong88

        Bullymong88 Active LVC Member

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        Yea I plan on taking it to the strip some but as its a daily I don't want to break it, so I won't go as far as supercharging it but headers high flow primary cats and deleting the secondary cats is a must to let it breath better, but then again I like loud exhausts. My cousin has an 06 vette with a corsa exhaust and it sounds absolutely beautiful, I got back and forth on changing gearing, but like I said a lot of this is gonna have to wait till I get that lift.
         
      • capt fast

        capt fast Active LVC Member

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        Naturally aspirated engines lose 2% horsepower per 1000' rise in altitude because of less air mass per cubic foot. having fixed mixtures makes it worse. the computer gets barometric pressure altitude from the BARO sensor from the atmosphere side of the throttle all the time. Mass Air systems determine how much fuel according the mass of the air flowing into the engine and to the data it holds in memory and adds to that data by learning how the engine responds while you drive. Carburetors have a fuel air ratio fixed by jet sizing. EFI/SFI systems mixture ratios are only limited by how much fuel flow is available and environmental conditions. so, no it doesn't run rich like a carb would. In fact, at this altitude, it leans out to maintain the correct ratio for the emissions systems which is why there are different calibrations for engine control systems for vehicles sold at places like western colorado and wyoming. Hell, even mercedes runs test cars up here during the summer to see if they blow up going up and down the mountains.
         
      • Bullymong88

        Bullymong88 Active LVC Member

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        Huh I didn't realize that it makes sense though, in highschool auto shop all week had was carb efi was too expensive of a curriculum supposedly, so I really don't have alot of tinkering experience with efi I appreciate the explanation.
         
      • xtriggerman

        xtriggerman Active LVC Member

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        I just completed a 780 mile road trip in my 97 base. I started out with a reset Average reading and Plus fuel in the tank. The first 365 miles of the trip running 70-80mph included running up over the Smokies on I-40. The Average toped at 23.1 mpg. On the return trip, I filled it up with Exon Hi test and the average did not improve but stayed at 23.1 on the entire return leg. The trany acted up a bit twice. when slowing down by just letting off the throttle and then just easing back into it to pick up speed slightly, there was a very rough TC lock in making that transition. Is this not a normal quirk in these cars? 76K on the car and have not yet changed the fluid into Amsoil.
         
      • Bullymong88

        Bullymong88 Active LVC Member

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        Like a hard shift? Because if that's what you're describing I'd check the dipstick you could be a little low on trans fluid, ours has 139k and it sat for 3 years before we bought it, and when we started driving it we knew it was a tad low but had no choice but to run it a little low, and at that time it shifted hella hard but we knew the reason. When we could finally afford to put mercon v in it the hard shifts went away immediately.
         
      • germansheperd

        germansheperd Active LVC Member

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        Most of the transmission ‘act ups’ on these cars are due to the fluid. Drain all the fluid: pan, Trans, torque converter and refill with Motorcraft MerconV and throw in a new filter. You will be surprised what just MerconV does for these transmissions.
         
      • capt fast

        capt fast Active LVC Member

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      • capt fast

        capt fast Active LVC Member

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        my '98 has mercon V fluid. my experience has been that the TC clutch engagement is always noticeable on the 4R70W. not the throw you into the headrest noticeable. but there. My trans hasn't been out of the car since built 22 years ago. fluids and filters, yes, but not rebuild. Pretty sure it is due. shifting is slow, but that is the luxury car calibration for you. smooth before speed. the TC clutch holds very well which you can see by the tach display while going up and down the 11K ft passes here in Colorado mountains.
        Trans control software is very flexible depending driving style. the EEC-V will learn your style of driving if you reset the memory with a STAR NGS. it will self tune the trans shift points to what your do and lay that over the factory default programming, within limits. the PCM mixes emissions, engine and transmission management together and while you won't get a race car like experience, you do end up with a drivable car that probably won't blow up the first time you hammer on it.
        fuel economy is not why I bought this car. I had a VW Passat TDI that got 48mpg highway and 32city. there were other reasons for selling that car than economy.
         
      • xtriggerman

        xtriggerman Active LVC Member

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        I find the most annoying thing about the way this trany is, is when partly getting into it in 2nd, then backing off once you reach 45 or 50, the TC is still waiting and waiting to grab 3rd. So the revs just sort of hang there until it realizes I'm not going WOT then eventualy locks up in third. I find that extremely lame. The trany in my 05 Honda Odyssey is way, way more in lock step with throttle position and snappy TC lock up. That's a sad commentary on the Ford. I was thinking about trying the Aftermarket trans tune chip just to see if it eliminated that retarded quirk.
        I had a 05 Passat wagon Pump Duce and sold it once VW would not repair the bicycle chained balancing shaft on their dime. The car still didn't have the rattle can noise coming out of the self destructing chain guides at 89K. If they warranty repaired the problem with the new idler gear set in lew of the no longer available chain, I may have kept that car. I'll not support VW again, ever. Any thoughts on the trany chip?
         
      • Bullymong88

        Bullymong88 Active LVC Member

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        Start with a simple filter and fluid then call around to see if there's any shops near you that do dyno tunes they'll more than likely be able to tune your trans how you want it if that doesn't work go for a chip but be warned these aren't camaros mustangs or corvettes there might not be a good chip but a generic shift fast "race" chip off eBay a dyno tune is the safe way to go.
         
      • Bullymong88

        Bullymong88 Active LVC Member

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        And since I've had a second to think about it I've been driving it all day and i haven't had a single problem with third like at all except when this kid in his little scion thing tried to race me I guess at a green light either way I had to let off briefly to like 80% for it to shift I was pushing 5k rpms though a full second later it shifts and I went right back to wot but that's a specific scenario though
         
      • xtriggerman

        xtriggerman Active LVC Member

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        Just one more note on the millage thing...... I had to do part of the same trip over the Smokies on I-40 and back home as I mentioned earlier where I got 23.1 mpg on hi test 93 oct. This time I put 87 oct. in the car for the same road and the 23.1 jumped up to 23.4 on the 87. And I wasn't wasting time on that trip running 80-90 on the good parts with Uniden R-1 on the look out. Still 23.4 mpg. Unless there's some long term issue with the PCM timing control, Premium fuel is more or less a waste of money as a full time fueling.
         
      • 97 Octane

        97 Octane Dedicated LVC Member

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        I have a '94 and a '97 Mark. When I do drive my Marks, they're mostly driven within the city and average about 16-18mpg but I don't drive them as much as before.

        The best mpg between my two Marks was with my '94 on a long round trip, with only me and my wife in the car, driving from Chattanooga TN to Pittsburgh PA and back doing about 70-80mph on I-70, 71 & 75.

        We averaged 27mpg going to Pittsburgh but on the way back, we averaged 29mpg, all on 89 octane pump gas. The discrepancy may be due to driving up to a higher elevation (1365ft) at PA, then coming back down home to a lower elevation (676ft) at TN.

        Other than doing the 'Octane suspension lowering mod', the '94 was completely stock. Comparatively, my '97 does about 2-3mpg less on average.
         

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