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  1. #26
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    Click here to enlarge Originally Posted by V8Bait Click here to enlarge
    Gas max power lambda is .84 to .9

    E85 max power lambda is .71 to .87

    There are catches, however. Richer OR leaner lambda will slow flame speed, which is fastest around the max power lambda's. So, if you are targeting max power lambda's and have high advance, you will have a faster flame speed and higher cylinder pressures. This could induce knock.

    Also, since richer lambda's increase cooling, leaner lambda's to the point of max power lamdba's may not cool the charge enough to prevent knock at such high cylinder pressures encountered with the higher flame speed as well, inducing knock.

    With gasoline, this is a problem, because the octane is 93 (in DI vs PFI it's effective octane is much higher, but still meh)

    With E85 or race gase, due to higher Octane (and with E85, octane and fuel volume), you are not limited by detonation, thus you can increase timing and lean to a max power lambda. Due to our fuel system, with E85 we just happen to be forced to run at max power lean lambda for the fuel because we cannot run at max power rich for the fuel. It's fine because of the nature of the fuel. If we could support a .71 lambda with E85, you wouldn't need an intercooler.

    Target lambda should not be the same regardless. We target rich lambda/AFR (in relation to max power) for gasoline because of it's characteristics. We target a comparatively LEAN afr/lambda for E85 due to its characteristics and our fuel system limitations. Just because it works great to target .8-.82 lambda for both fuels, don't misconstrue the reasons why.
    Yes. I agree. I also should have clarified that my success at .8 has primarily been with e85 and e98. I agree there are many factors to making peak power in relation to lambda and what fuel is used. However, I disagree that .71 lambda can replace an intercooler running e85 (at least via the injectors). There are too many factors to make that statement definitively true. I have personally tried and failed with e98. Maybe if a portion of your overall fuel was injected in the charger pipe.

    Good info though.

  2. #27
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    Click here to enlarge Originally Posted by lulz_m3 Click here to enlarge
    Thats a hell of a break down, but you are likely wasting your energy typing it. Me and the diver went back and forth one evening on the N54 enthusiast fb page, he's pretty dead set on only acknowledging his own opinions.
    With me? I dont remember the discussion... remind me.

  3. #28
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    Click here to enlarge Originally Posted by V8Bait Click here to enlarge
    Gas max power lambda is .84 to .9

    E85 max power lambda is .71 to .87

    There are catches, however. Richer OR leaner lambda will slow flame speed, which is fastest around the max power lambda's. So, if you are targeting max power lambda's and have high advance, you will have a faster flame speed and higher cylinder pressures. This could induce knock.

    Also, since richer lambda's increase cooling, leaner lambda's to the point of max power lamdba's may not cool the charge enough to prevent knock at such high cylinder pressures encountered with the higher flame speed as well, inducing knock.

    With gasoline, this is a problem, because the octane is 93 (in DI vs PFI it's effective octane is much higher, but still meh)

    With E85 or race gase, due to higher Octane (and with E85, octane and fuel volume), you are not limited by detonation, thus you can increase timing and lean to a max power lambda. Due to our fuel system, with E85 we just happen to be forced to run at max power lean lambda for the fuel because we cannot run at max power rich for the fuel. It's fine because of the nature of the fuel. If we could support a .71 lambda with E85, you wouldn't need an intercooler.

    Target lambda should not be the same regardless. We target rich lambda/AFR (in relation to max power) for gasoline because of it's characteristics. We target a comparatively LEAN afr/lambda for E85 due to its characteristics and our fuel system limitations. Just because it works great to target .8-.82 lambda for both fuels, don't misconstrue the reasons why.
    Good info but I wanted to add that the effective octane is higher due to the cooling effect of the direct injection process. With ethanol, this seems to be exemplified further leading to even better detonation resistance.

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

  4. #29
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    Click here to enlarge Originally Posted by andy_divers Click here to enlarge
    Yes. I agree. I also should have clarified that my success at .8 has primarily been with e85 and e98. I agree there are many factors to making peak power in relation to lambda and what fuel is used. However, I disagree that .71 lambda can replace an intercooler running e85 (at least via the injectors). There are too many factors to make that statement definitively true. I have personally tried and failed with e98. Maybe if a portion of your overall fuel was injected in the charger pipe.

    Good info though.
    Yeah that's kinda a blanket statement on the intercooler, it's not necessarily the right answer, but it can be. Just illustrating the point. I've done it on a few builds, usually with meth/water injection, lower compression and efficient setups to begin with (high flow boost max of 20ish psi, before gtx era wheels in LSX land), but that was knowing less about things than I know now, and before direct injection. Some day I will have another go at it, without meth, hopefully on one of those glorious new LT1's if I can talk my family member out of a stupid supercharger.

    Just wanted to elucidate some lambda there. Numbers aren't really dogma, just general guides and targets to be aware of. On a hot day and with turbos max power rich lamba can go a little lower anyway, since it has to do with many variables. Terry's suggestion of 11.8 is DI conservative buy very reasonable for E10 pump on a hot turbo car, negligable losses and no gains, but safer is nice I'm sure. Back to books

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