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Old 11-22-2013, 10:11 AM   #1
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Default Why Enrich at High RPM

I am trying to understand the logic of running richer AFR in the RPM ranges above 5500, when at 50-100kPA.

I ponder this because most posted maps show this, as well as most base maps.

However, Y8S and Westfield do not enrich this area, but leave it at 14.7, or whatever they were running for that kPA at about 5000 RPM.

So, again, I'm not talking about enrichment due to boost, or high kPA, but rather due to higher RPM.

Any thoughts?
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Old 11-22-2013, 12:54 PM   #2
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From what I understand this has more to do with the fact that you make more power when you run 13:1 AFRs and when you are at higher rpm's gas mileage is obviously not your priority. I do not believe there is any underlying reliability reason for it.
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Old 11-22-2013, 01:38 PM   #3
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Good jorb on doing some of the research, but fuel is only part of the story. Check spark maps for those same regions on those guys tunes. While you are looking at all these maps, try to figure out who is just using a map, and who is actually tuned on a load bearing dyno.
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Old 11-22-2013, 02:01 PM   #4
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E02K. Correct.

Those with 14.7 at 7000 RPM have aggressive timing maps to go along with the slower burn. To me that makes sense. I am presently trying maps close to Y8S and have seen no issues (Air temps are cool these days).

Just wanted to make sure I wasn't missing something that would eat a piston.

One could also look at the converse. Perez was looking into advancing his timing, but with that, he may want to keep the high RPM area stochiometric (again, 100 kPA and under).

Another thing about Y8S AFR's. Notice he does not go rich (13.0-13.5) at 100kPA with a turbo. Makes sense. On a NA, as I understand it, you go rich at WOT (100kPA) go gain power, not for protection. BUT if you have a turbo, then you have power above 100kPA.

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Old 11-22-2013, 04:23 PM   #5
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On turbo engine lot of cars run rich (13) to very rich (10) to cool down the turbine and/or cool down catalytic converters.

On NA as it was said, you don't really bother about fuel economy @ high rpm, but power, and thus your goal is to use all the oxygen in the cylinder, burn it fast and in the vincinity (centred) of the TDC. So you run with a AFR around 12.7

Last edited by Regis_92N; 11-22-2013 at 04:23 PM. Reason: orthographic flaws
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