| The flat spot is due to several factors: 1) wastegages are starting to open. However, due to the fact that boost controller was turn off (14psi run), the boost was regulated by springs only hence they don't response quick enough. 2)fuel pump voltage jumps from 8v to 12+v at around 4.5krpm, hence sudden rich in A/F. The dual walbro pump out much more fuel at that time and AFR has not yet able to regulate the increase fuel pressure until ~6krpm. The few dips on the 20psi and 26psi run are due to the combination of sudden rich A/F and weak wastegates springs trying to hold the pressure. 3)All dyno runs are not tuned. AFC was set to 0 (no point of tuning when I know the spring can't hold). Aquamist was not used on the dyno runs or at the drag. (I want to resolve the weak spring issue first before water injection).
1990 Nissan 300ZXTT Twin Greddy TD06L2-20G
745rwhp 593rwtq (26psi no nitrous)
10.9 @ 139mph 1.75 60ft
Waiting for stronger wastegates spring
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