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      12-13-2019, 04:55 PM   #262
OzBMR's Avatar

Drives: BMW M140i
Join Date: Aug 2019
Location: Brisbane, Australia

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Originally Posted by kern417 View Post
Yep, the only thing I see are the fuel pressure drops. Likely because you are spiking 18+psi. It seems like 16-17 is the safe zone for us on stock fuel system, I'm just not sure why downpipes seem to prevent B58s from controlling boost efficiently. Everyone with a catless downpipe since the JB4-only days get the boost spikes and throttle closures.
In the ones I've looked at with the boost spike the WGDC remains too high, at 100%, for too long. The high flow and catless systems build boost earlier, so to prevent shooting past target the WGDC should drop down (to about 89%) about 200 - 300 RPM earlier than a car with stock downpipe.
M140i LCI Mineral Grey
Dorch Stage 2 HPFP, CG Precision DS-1, XHP, MHD Stage 2 HPFP E30 @ E42 100 - 200 6.96s 10.93@127mph
Stock DP, XHP, MHD 95/102 OTS E30 fuel, Hoosier DR2 11.5@121mph about 8.0s 100-200