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Thread: Base Fuel Table changes for bigger engine.

  1. #1

    Default Base Fuel Table changes for bigger engine.

    I have Dominator V4 setup on my '55 Chevy and I'm going to a bigger engine. Current 6.0L LS is coming out and new 408 is going in. This is a turbocharged combo and I'm curious what you guys think about changes needed to the Base Fuel Table. It's a 12% increase in size, should I just increase the entire table 12% or 15% to be safe and begin tuning from there? I wouldn't think it would need that amount at idle or cruise, but will it need more under boost? Current engine hurt the mains and I decided to get an new short block from Thompson.

  2. #2

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    Base Fuel Table is all about BSFC rather than engine size. If you're using the same heads and cam, but adding displacement then maybe you can bump the table a set amount. But when you change engine design all bets are off. 12% is a small enough difference that if it was me I'd probably just let Learn take care of it.

  3. #3

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    Same heads but different cam. I think I'll bump the upper end a bit for safety and let Closed Loop/Learn make up for anything needed and tune from there. I didn't think about it in BSFC terms, but that makes sense.

  4. #4

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    Take some good before and after datalogs so you can see the difference. Since you're changing cams you have a big variable being thrown into the mix. If the new cam is the same exact lobe family as the old cam, but just a few degrees bigger, then you might not see much difference. If the new cam has different lobes or a different LCA then your fuel map might change a bunch at part throttle. Adding a little bit of fuel at the top of the chart is a smart idea if you're expecting the new engine to consume more fuel.

  5. #5
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    Andy, post #2 is very good.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 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, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, 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 M/T Street Comp tires.

  6. #6

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    If your fueling strategy is based on VE%, then all you do is enter the new displacement in the System ICF. From there, I'd go through the normal tuning process and change the areas of the VE% table, since your new cam will have different idle and torque curve characteristics. Andrew
    Contact me for Holley EFI remote tuning.
    IG @projectgattago

  7. #7

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    Just to update: I added fuel up top before starting it up. It started right up and idled, it did require more fuel down low than I thought it would, but that was likely the cam change. Been driving it a few weeks now getting the engine broke-in and the Base Fuel Table tuned. Haven't really pushed it much yet, waiting to get to 500 miles and change the oil the first time. Boost is set really low, but it's pulling fuel in the upper end where I added it, so the BSFC comment was dead on.

  8. #8

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    Thanks for the follow up. With a larger engine and a different cam, I'm not surprised that it's using more fuel down low. I'm also not surprised that the fuel use is similar up top since you kept the same top end on the engine. Sounds like your tune is in good shape if you can watch the difference between two engines like that.

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