MSD87. Injector management. Idle

I had a free moment, and I decided to check – has the BMW engineers made conclusions since MSD80 (N43/N53) and is there any upgrades and corrections of flaws for MSD87 DME for F series. Of course, the comprehension regarding flaws can be different. So I will specify – flaws from my point of view.


When connecting to the injector, in idle, in Homogenous mode, we can observe the following picture:

It is clear: the architecture of the injector management hardware of MSD87 has not been changed. The high-side switch is common for the whole bank; low-side switch – individual for each injector. As I already mentioned in the description of the performance of MSD80, such solution allows economizing MCU resources (timers and ADC), hardware elements (OPamps), and also prevents the impact of the hardware element difference to each of the injectors (their opening times and measured voltage/energy).


Here, I marked in the image – to the injector of which cylinder each impulse is related (the oscilloscope is connected to the injector of the first cylinder, it is “active”):


Signal of the active injector:


Instead – if it is not necessary to open the injector, the signal on its outputs looks like this:

Another nuance is very interesting: in Homogeneous mode, only one injection pulse is used. Yes, in my opinion – it is more correct that in MSD80. The impulse is 1.5 .. 2 times longer (around 350 .. 400us) – the impact of the injector reaction parameters difference reduces. Accordingly – we can expect fewer problems with a persistent vibration in idle.

Second nuance: the algorithm of maintaining of idle of Homogeneous mode is reworked. Now it strongly resembles Stratified charge (MSD80) – the reaction to the changes in the mechanical efficiency of the cylinder is quick. Obviously – the BMW engineers have concluded. Now the idle of Homogeneous mode is almost as stable as previously Stratified charge. It can be seen in the Rough run menu very well. And yes, also feel – not the tiniest vibration, when touching the driving wheel.
INPA kindly offers to see the corrections (their reference values + idle/fuel mixture corection), applied to the injectors and individual momentous corrections at ../F5/F9


Have to admit – BMW has not vegetated, the progress in this area is obvious!