Rather than messing with a fixed piece of hardware (N75)
Which give hit and miss results (dodging limp mode / surging).
Is it not better to control the boost with a "Dawes Device"or (manual boost controller).
You could use both together?
Info Below:-
Below you see 3 boost curves. First we start with just a hypothetical chip. The next two show two different ways of adding an MBC to the system and how they affect this chip's boost curve.
The
N75 Only shows a hypothetical boost curve with a chip and your standard N75 valve in place.
The
N75 & MBC in Parallel shows the MBC set at ~17psi, such that any boost above that will get bled off by the MBC, but the N75 will still control the boost curve below the MBC's set limit.
- Here the MBC functions to remove spikes.
- In this configuration, the MBC is only capable of reducing boost lower than what would occur without it.
The
MBC Only shows the MBC set at ~17psi, such that the MBC has complete control over the boost.
- Here the MBC functions to control the boost.
- In this configuration, the MBC has full control, and can either raise or lower boost, and thus caution is suggested when doing this. One should have knowledge of fueling limitations, turbo capabilities, etc.
Here's Matt's drawing of the
N75 & MBC in Parallel:
PS - It should be noted that with the MBC in place (Only. Parallel too?), the initial ramp of boost may occur quicker as well.
PPS - Having a MBC Only set-up, if you set the boost to a value greater than the turbo can physically achieve, the resulting curve will merely be the max boost (for the given RPM range) that the turbo can sustain. An example of this is that the S4's K03's can not sustain the 17psi at high RPMs as illustrated above. In this case, once the turbos can no longer sustain the 17psi, the boost curve would begin to taper and follow the maximum achievable boost.
