Here's a brief report of the tests carried out lately.
There is no noticeable rise in charge temperature when the bypass valve is on its way between open and closed.
I feared that this would have been the case for the short time the system is operating on the slope part of the boost graphs posted earlier.
In real world all-day traffic situations this might be happening more than for a short time.
Also I just found out that on the twincharged VW TSI engine there is a "regulating flap" that is bypassing the charger and regulating the boost delivered. So it's probably not such a bad idea.
Air coming out of the charger does not exceed 90°C.
That is at WOT with the M45 spinning at 16200RPM and a boost of 10-11PSI.
I would have expected the air getting hotter when stepping into the lower-efficiency part of the charger performance map.
As for the timing related issue that's where I found it getting particularly interesting.
(average numbers, all counting from start=0)
Time needed to floor the throttle 130ms
Time needed for the bypass valve to close 215ms
Time needed for the boost pressure to rise till 95% of its nominal value in the plenum 510ms
That last one explains the lag that I noticed when testing on the track and I believe this can be improved only by decreasing the volume of the inlet path, in particular intercooler and tubes.
For reference, Kenne Bell states that supercharger reached maximum full boost in approximately the same "split second" (400ms) as the throttle being floored.
I could conclude that reaction time of my electric bypass setup is not bad at all and my right foot is almost supersonic because it reaches WOT 3 times faster than his

Under these circumstances I don't find it necessary to look for a way to increase the speed of the valve actuator, especially knowing that it's a straight DC motor and not a stepper (these are easier to speed up) and the drive consists of plastic gears.
An air-to-water intercooler might help in decreasing this lag because it has a lower volume.
So what's next? When I have some time I will try to fine tune the response curve of the valve (the graphs posted earlier).
Some fellow members have taken an effort in explaining that placing the throttle downstream of the charger is dangerous.
They are right.
If men didn't do dangerous things, we were probably all driving bicycles (which should certainly not be so bad after all).
I will think about building in some security systems but I'm wondering if this shouldn't be the object of a separate thread.
And last but not least, I'll look out for a larger supercharger because this one is far not dangerous enough
Jean
Train dogs,
Teach people.