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Thread: Increase MPG

  1. #11
    Join Date
    Dec 2009


    Quote Originally Posted by 81 TransAm View Post
    Danny, I don't use a key board a lot, where is that degree symbol?
    It's in the "Character Map", a Microsoft Windows Utility. Or you can hold the "ALT" key and type 248.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 MT tires.

  2. #12


    Quote Originally Posted by 81 TransAm View Post
    This is what I did. I created an Advanced Table that would lean the engine and another one that would advance the timing in my cruise area. I used an input to activate these table when I wanted to. I then found a nice flat piece of highway. I then created a Target AFR table and ignition table that would be considered normal for my engine (SBC). Then as I was cruising at a steady state I flipped the switch and leaned the engine from 14.7 AFR to 16 AFR and datalogged the difference. I could feel the loss of power and you could see the change in RPM, MPH, MAP, MPG, etc. So then I change the Target AFR table so the engine ran at 16 AFR. Then for the next test I added timing. At a steady state I flipped the switch and added 5° of timing, and I could feel the difference in the way the engine ran. It increased in power and again I could see the difference in the datalog. So I changed my timing table and gave it the extra 5° of timing. Then I went out again and repeated the same test. This time, when I added the 5° of timing, there was no difference in the way the engine ran, and no difference in the datalogs. I ended up at 16 AFR, 28° of timing at 2000 RPM. Nowhere near the 40° of timing everyone tells you to go to. At 65 MPH steady state cruise I can get upwards of 25 MPG. The reason I did it this way was because I also fell into that trap and followed everyone's advice and turned the timing up to 40° at cruise. All that did for me was to pound out the tops of the rod bearings and the bottom of the mains. Too much cylinder pressure at TDC. It was trying to push the crank out of the bottom of the engine. From everything I hear and read about LSx engines, you're going to need less timing than me. I will be putting a LSx in this winter, so I'll have to do this all over again.
    Thanks, that looks like a good scientific approach. I'll do some more research and see what I can come up with.

  3. #13


    Quote Originally Posted by SixPointOh View Post
    I'd like to get more MPG out of my stock LQ4. I'm getting about 14 MPG, Stock 6.0L LQ4, 4L60E, 3.55, 3200 +/- lbs.

    I'm reading the Holley help file and it says "If searching for maximum fuel economy at one point, you can monitor the Fuel Flow variable at a steady state point. Keep leaning the Target A/F value until either the Fuel Flow increases or the engine operation becomes unsatisfactory."

    Right now my idle is at the preset 13.8 and cruise is 14.7. Any recommendations on a good idle AFR? Manual says: “Cruise area” is tuned to maximize fuel economy and driveability. This area is typically 13.5 to 15.0:1 for gasoline engines. Should I touch timing or leave it be for now?
    Do you have a datalog of your vehicle cruising?
    I'd love to see a datalog of your setup to compare it to one of my old datalogs.

    On my old turbo LQ4/4L80E setup tuned with EFI Live, I was cruising at 2000 RPM/70 MPG
    and commanded mid 16 AFR and about 42-45° timing I think it was with 93 octane.
    As the load went up I found a decent slope for more fuel and less timing.
    Engine has 400,000+ miles on it now, so it must not have hurt it.

  4. #14
    Join Date
    Nov 2014
    Ont. Canada


    That sounds like a lot of timing for LSx engine at 2000 RPM.

  5. #15


    It doesn't knock and the plugs look good, so I ran it. It's still together and doing good. I can't run anything less than 93 octane though unless I pull some timing.

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