Fuel millage

Discussion in 'Engine Performance + Maintenance' started by kennythewelder, Aug 14, 2019.

Car Parts
  1. L31MaxExpress

    L31MaxExpress I'm Awesome

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    Mexico had the 350 TBI until atleast 98. They also had a port fuel injected 250 I6 dubbed the 4100 down there. US market had a Vortec head TBI in 96 as well. Vortec boats were TBI into the 2000s as well. When Mexico switched to the GMT800s they also kept the 350 Vortec. I have driven a factory built GMT800 based 2002 Tahoe with a L31 5.7/5spd. I also have a Blue/Green 1 meg GM tune file for a 2006 350. The only emissions system enabled was canister purge and vent. No EGR, no Cats, and no rear 02s.

    I know Canada also had standard 4bbl Q-Jets all the way through our dreaded feedback carb years.
     
    Last edited: Aug 22, 2019
  2. sbnova

    sbnova OBS Enthusiast

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    1988 RCSB, 350/ 5-speed and 3.08's. Rear tires are 275-30-20's. I got 19mpg at the highest from central Florida to Houston Texas, the worst was like 17mpg, all highway. Stock engine, K&N in the stock filter housing, stock exhaust manifolds with a modified factory Y-pipe that exits to 3", no cat, and 3" mandrel bent full exhaust with a 2 chamber flowmaster.
     
  3. kennythewelder

    kennythewelder B31-3 (6-G) certified

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    Im glad to see all of the responces this thread is getting. Thanks guys, and keep them coming.
     
  4. DerekTheGreat

    DerekTheGreat I'm Awesome

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    That straight six sounds nifty. Where could find Vortec headed TBI stuff in the US, vans?
     
  5. 7thdarkangel

    7thdarkangel Just a guy with tools

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    1988 K1500 RCLB. 406ci engine, 700r4, 3.73 gearing 3 inch body lift, 35x12r15 Micky Thomson MTZ tires. Getting an impressive 7.9 MPG highway, and 6.5 MPG local driving.
     
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  6. fancyTBI

    fancyTBI half-ton fun

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    I believe the G vans had vortec heads with a TBI intake.
     
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  7. Jglew82

    Jglew82 I fix stuff

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    1990 ECSB C1500

    LQ9 .020 bore
    TSP 216/220 .550/.550 112 LSA
    Gen 4 intake and Flex Fuel injectors
    Long Tubes with high flow cats, custom Y-pipe into 3" Flowmaster 70 series
    Built 4L65e
    stock 3.08 10 bolt
    Stock ride height
    265/70/15

    Still working out kinks, with a lot of in town test/tune and commute mixed with driveway idling - 12.5mpg so far (slightly lower than actual due to uncorrected speedo). Hopefully I'll get some good highway data soon!
     
  8. Gibson

    Gibson OBS Enthusiast

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    '97 Sub K2500, 265x75x16s, 4.10, 350 Vortec.
    One time only; a 300 mile trip, flat/level/no wind, set the CC at 58, got 16.4,, increase speed to 65 and mileage drops to ~15 for a steady cruise.
    Normal mixed driving runs ~11>13 ,, it's the stop-an-go that kills mileage on a heavy vehicle.
     
  9. evilunclegrimace

    evilunclegrimace Does not always play well with others

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    1998 K1500 Suburban 3.73 gears 4l60E. 15.7 MPG all in town
     
  10. Trenton

    Trenton OBS Enthusiast

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    Where at in Colorado? I live here too.
     

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