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  • Enrichment?

    With your cold enrichment map, do you want it to add just enough fuel that your afr's are the same when cold (just making up for the density of the air,) or do you want to actually run richer when cold?

    As for fast throttle enrichment, pretty much the same question applies... What afr are you looking to hit at the spike of the "tip in?" I noticed that it feels pretty doggy when the afr's are the same as when holding the throttle in the same cell. To clarify what I mean, say I'm running at 4500 rpm and full throttle (in boost) I would be around 11.5-12. If I was at that same rpm and light throttle (in vaccum) I would be around 13.5. If I mash the throttle the boost will spike to positive pressure and so I would want to hit 11.5-12 (just as if I steadily holding that same cell).... That feels a lot more doggy on tip-in than if I was more lean. If I spike lean here then go rich, it feels a lot more responsive, but is it safe? I don't have an egt gauge (or the required knowledge,) so I don't know how this should look as far as safe AFR's go...

  • #2
    You want it richer when colder. Running about 13.0-14.0 seems to work ok without wasting a ton of gas. It can start leaning out pretty quickly to where you get no cold enrich a fair bit below your thermostat opening.

    11.5:1 is too rich for right around zero boost, you want something more like 13.0-13.5. Taper that to ~11.5 at higher boost then hold it constant.
    '18 Chevrolet Volt - Electric fun hatch for DD duty!


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    • #3
      Good to know about the cold enrichment, thanks.

      As for the example I gave, that was just an off the top of my head drunken scenario, I was thinking I would go right into boost. I tested it out after reading your post and I do hesitate at 0 boost for a split second, so I guess my imaginary scenario was off... I do have that portion of my map around 13:1, good to know it's safe to go a little leaner to 13.5.

      But back to the original question (modifying the afr's to reflect accurately) on intital tip-in, would I want that enrichment to compensate just enough for the lean spot and bring it back to 13-13.5? Or should it spike a little leaner or richer for that split second?

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      • #4
        Carbureted cars used an "accelerator pump" to enrich on tip-in. EFI cars use vacuum controlled fuel pressure to enrich on tip-in. FI is another animal but in any case, when you "tip-in" the throttle opens and there is a rush of air into the plenum, in need of fuel, correct?
        Don Johnson (really!)
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        • #5
          Originally posted by ericb382 View Post
          Good to know about the cold enrichment, thanks.

          As for the example I gave, that was just an off the top of my head drunken scenario, I was thinking I would go right into boost. I tested it out after reading your post and I do hesitate at 0 boost for a split second, so I guess my imaginary scenario was off... I do have that portion of my map around 13:1, good to know it's safe to go a little leaner to 13.5.

          But back to the original question (modifying the afr's to reflect accurately) on intital tip-in, would I want that enrichment to compensate just enough for the lean spot and bring it back to 13-13.5? Or should it spike a little leaner or richer for that split second?
          I prefer to have throttle enrichment a bit richer. Not that it's a big difference, but it does keep things cooler, which is a good thing on track at the end of a straight going into a braking zone while heel and toeing through the gears.
          '18 Chevrolet Volt - Electric fun hatch for DD duty!


          DefSport Koni Sleeve and Spring Perch Buy!!!
          http://www.nissanroadracing.com/showthread.php?t=5902

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          • #6
            Originally posted by djsilver View Post
            Carbureted cars used an "accelerator pump" to enrich on tip-in. EFI cars use vacuum controlled fuel pressure to enrich on tip-in. FI is another animal but in any case, when you "tip-in" the throttle opens and there is a rush of air into the plenum, in need of fuel, correct?
            Our cars actually use the change in TPS voltage to determine throttle transient enrichment. The fuel pressure is a mechanical interface, so it will trail the actual increase in VE by quite a few engine cycles, especially at higher RPM. The TPS dot will immediately see a large throttle movement and add in some more injector pulsewidth that decays over time so the fuel pressure change and MAF voltage can "catch up."
            '18 Chevrolet Volt - Electric fun hatch for DD duty!


            DefSport Koni Sleeve and Spring Perch Buy!!!
            http://www.nissanroadracing.com/showthread.php?t=5902

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            • #7
              Cool, thanks Def...

              Originally posted by djsilver View Post
              Carbureted cars used an "accelerator pump" to enrich on tip-in. EFI cars use vacuum controlled fuel pressure to enrich on tip-in. FI is another animal but in any case, when you "tip-in" the throttle opens and there is a rush of air into the plenum, in need of fuel, correct?
              There is more to it than just the added rush of air, there's also the matter of fuel condensing and becoming less "burnable." Here is a good read that I found a while back. Specifically, read the third post down.

              http://emspowered.com/forums/showthr...-Pump-Settings

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