Hello, many reaction here, that's cool!
Liam22 said:
Take a look at how many sensors the N52 engine has
https://www.e90post.com/forums/attachment.php?attachmentid=1584168&d=1488747614
Modern engines are hugely adaptive, although mostly optimised for degraded conditions, not enhanced conditions. Mass air flow sensors directly control fuelling - how many reports of engines running better on cold days?
So the question is, can an optimised air intake help the engine suck more air? Standing still on a dyno - no chance. At >100mph - perhaps. So a dyno test will prove nothing. Whether it works or not will be down to high speed acceleration tests, or by comparing top speeds achieved on a track.
Many thank for this documentation, I really agree with you. A dyno run isn't dynamic. So you are not going to benefit from the "ram effect".
As I said before, the "ram" effect is present well before 100mph. I had my wife drive (our renault clio with 90cv of pure power

), during this time (I was in the passenger seat) I passed the part through the window. An incredible volume of air engulfs from 50km/h (30mph).
OK, it's not the most scientific experiment in the world, but it's real life.
ph001 said:
Quite right. Also, in terms of the sensors - the one that concerns me most is the MAP sensor (manifold absolute pressure, or Differential Pressure Sensor as BMW call it). The E86/E86 ECU oem mapping has zero ability to manage any positive pressure in the inlet manifold that is above atmospheric. If there is genuine 'boost' in the inlet manifold due to air ram effect then I would expect you would get an engine management light on due to MAP sensor values being out of range.
First, thank you for your argumentation. It's always a good thing to discuss technique.
We have two different situation:
- The first: Z4 using HFM (and MS45.1):
You can read that in the documentation:
"Due to the elimination of the grill, it is more compact
than its predecessor and therefore decreases pressure loss in the intake tract."
Therefore the engineers at bmw also want to limit pressure loss.
"It supplies the ECM with an analog signal proportional to air mass"
The signal will increase in proportion to the amount of air, not to mention the temperatures (also detected by the HFM) which will also be more favorable.
- The seconde situation is for Z4 using HFM only for temperature, and with MSV70
If my memory is ok (I did these studies a long time ago), this concerns models "SI".
The calculation of the AFR (ari fuel ratio) is made like that:
This calculation makes use of the following signals:
• Valve lift of intake valve from VVT (load acquisition)
• VANOS setting (load acquisition)
• Throttle setting (throttling)
• Intake air temperature (air density correction)
• Engine temperature (air density correction)
• Engine speed (cylinder charge)
• Intake manifold pressure (throttling correction)
• Ambient pressure (air density, altitude correction)
If I understand correctly what worries you, it is this line (sorry I'm french, it's sometimes difficult for me to understand you perfectly):
"Intake manifold pressure (throttling correction)"
That's it?
While waiting for your answer and to reassure you here is the 3.0si from a friend, he "will never go back".
one defect however, he noted a slight increase in consumption. He has only been using it for 1 month, let's wait and see if it's not the noise that makes him want to drive faster ...
thank you all, this subject is of a very good level and fascinating
