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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/2800 RPM converter, M4602G aluminum driveshaft, FRPP 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 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.

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