N54Tech.com - International Turbo Racing Discussion
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macrorain macrorain is offline
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Default JB+ and dropping boost. Trottle closure? - 02-21-2019, 02:00 AM

I have the JB+ on a 320i spec B48 (330e). It's on it's default setting.

What I experience is the following: boost initially rises to around 13-14 psi and stays there, but then at around 4500rpm it starts dropping off again, all the way down to around stock boost when I reach 5500.

Is this the famed "throttle closure" issue, or what can typically be the cause of this?

Thank you in advance for any advice.
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808ron 808ron is offline
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Default 02-24-2019, 11:21 AM

I’m still learning but I think in your situation your fueling might not be enough so the JB4 is cutting back boost. Maybe too much boost on not high enough octane fuel. Throttle closure happens at the shift points while pedal is 100%
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Terry @ BMS's Avatar
Terry @ BMS Terry @ BMS is offline
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Default 02-24-2019, 02:10 PM

Might be completely normal, turbo is undersized, so most of the potential to pickup power is at lower engine speeds.


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