Piggybacking BMW N62 valvetronic engine

Hello guys,

I've an interresting question. I've boosted my BMW N62 engine with a centrifugal supercharger. The interresting with the engine that it uses Valvetronic system. Which means the delivered air is set by valve lift not by the throttle body which means there are no "real" vacuum in the manifold therefore I can't use speed density tune. I wanted to find a self-tune cost effective way tuning the engine. Local companies were not offering factory ecu reflash and also did not want to go fully standalone because of the high cost. (I've also tried running parallelly a Megasquirt with the OEM ecu but went into limp home mode because of valvetronic and automatic transmission issues...). As there's no manifold vacuum I can't use also a blow off valve (and also because of the MAF sensor). So I decided to piggyback the engine.

I used 2 additional auxiliary injector for fueling and an additional pre supercharger throttle body which controlls boost. The piggyback works quite good with the ecu I just need to find the correct load setting for tuning. Maf sensor maxes out at 1000 kg/h but my air consumption is about 1800 kg/h. (4.4 V8 with 0,6bar boost) I've also installed a map sensor into the tubing before the throttle body (so not into the manifold as the main TB never closes fully).

For boost controlling I've chosen TPS as the load. For ignition and injection load I think MAP sensor is the correct value, used only the boost side. I'm struggling with these settings as I can't find the correct boost setting and the A/F setting is also still not good. Until now I tried mapping it on the street but I was not successful.

Any advice is highly appreciated! And valvetronic system could not be disabled else it goes into limp home mode.

Thanks!

Actually the problem is part throttle overboosting. If I close the pre sc TB it's good for decelerating but I won't be able to accelerate. I'm using an Ecumaster DET3 piggyback. 97% fully open, 3% fully closed. any other value results fully opening the TB boost regulator.

inj table. not finished.

ign table. not finished

Hello,

It might be instructive to examine Alpina's strategy for supercharging the same engine for the B7 of 2007. It sounds like you have somewhat accomplished this by adding an additional pre-supercharger throttle body, but the trick is achieving true control over both throttle bodies and coordinating their response with the Valvetronic system. Which is likely not possible without a full standalone ECU . . . . see link below.

https://myautoworld.com/BMW/cars/bmwcars/bmw-07-ALPINA/bmw-07-alpina.html

Thanks Chris,

I’m aware of this. I’m using Alpina parts for the project. If I’d go standalone, than I’d delete the valvetronic system. It’s planned, but only later. First I’d like to find the solution for this matter.