02-21-2018, 10:54 PM | #15 |
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I would love to see your car dynoed closer to sea level. Seems like they start wheezing when oxygen content is off even a little. Lol
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02-21-2018, 11:58 PM | #16 |
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I posted this in another thread, but Mazda talks about how high compression motors typically require a torque dip at low rpms to avoid engine knock. High temperatures at low rpms when flow is poorer results in increased knock risk, so they adopted a long 4-2-1 manifold, which increased exhaust flow, lowering temperatures in the cylinder, reducing knock. That allowed for more power at lower rpms through having better flow or through the ability to tune more aggressively or both. The problem is emissions at startup because the catalytic converter takes longer to heat up. They resolved this issue with a piston cavity and a stratified flame front, which allowed for them to safely retard timing.
http://www.mazda.com/en/innovation/t...iv/skyactiv-g/ Obviously this isn’t a concern for anyone removing the precat anyways, but it kinda gives reason behind the torque dip and the “crappy tune” Subaru and Toyota use. And it shouldn’t be a surprise a long 4-2-1 header will make a difference. |
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02-22-2018, 12:55 AM | #17 | |
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02-22-2018, 12:57 AM | #18 | |
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02-22-2018, 03:36 AM | #19 |
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02-22-2018, 03:51 AM | #20 |
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Mike: & .. + overpipe to other header.
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02-22-2018, 07:46 AM | #22 | |
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02-22-2018, 10:31 AM | #23 | |
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02-22-2018, 11:38 AM | #24 |
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Imo that revworks tune was well done. Probably some still to be had with the ace.
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02-22-2018, 12:06 PM | #25 |
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02-22-2018, 01:05 PM | #26 | ||||
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In summary... Quote:
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02-22-2018, 02:50 PM | #27 |
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Right, but the assertion that high compression has a strong correlation to the FA20's dip is still off base. You're relying on Mazda's very simple comment about a "drop" to mean a "dip" when they could mean that the torque drops off altogether in lower rpms, which is the more plausible scenario with extremely high compression, 87 octane, and low rpm knock problems. Look at something like the BMW S65. It has high compression, port-only injection, and 4-1 headers and it's one of the flattest NA torque curves out there. This is probably not the thread for continuing this tangent, but if you'd like to discuss more I'd be glad to in your engine thread.
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02-22-2018, 03:09 PM | #28 |
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That chart looks way better then the ones that I have seen for the nameless header, and what my butt feels.
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