I am not totally familiar with the JB options and maps but have learnt quite a bit over the years
Here is what I have gathered:
1. Aqaumist sends a real time 0-5V flow signal to the JB4s 25-pin connector, this is the yellow wire of the HFS4's userport
2. Upon receiving this signal, JB4 start to add boost. If this signal is interrupted, JB4 will do a few things such as shutting the throttle, revert to stock boost. There is a penalty to this strategy: Noticeable delay on throttle response.
3. Alternative to this, JB4 has an option to increase boost regardless of this signal (one of the map's sub-option), he calls this "SAP "spray and pray". This will not have any effect on throttle lag. This is a risk as the meth failsafe is now transferred to the meth systems
4. Aquamist has a reliable record on failsafe due to the use of a turbine flow sensor, monitoring the flow directly. JB4 still relies on monitoring pump current. It works well but only effective on a on/off operation. It is too crude for a progressive delivery system hence JB opted not to make their system progressive , having witness some CM's continuous issues with their "learning" FSB failsafe.
5. For this reason, JB's spray strategy makes the overall OE's short-term fuel trim table quite abrupt, having to constantly re-adapt itself every time the meth starts to spray. It doesn't do well on the LTFT either.
6. I believe the Aquamist/JB4 combination is excellent, BMS should start to support the Aquamist system properly, it is good for all concerned. As far as we are concerned, we have no ability to control/masking OE's sensors except delivering the meth accurately and reliably throughout the entire engine load.
I got this link from a JB4 user recently, sounds promising.:
http://www.bimmerboost.com/showthrea...-few-questions