[boostjustkickedin]

Originally Posted by Freon

The accelerator pedal in this car is not so much controlling the throttle plate as it is defining a target load. Then the ECU decides how to get the load through changing the throttle plate angle and wastegate control, and at least to some extent even timing.

The idea that your foot controls the throttle plate has been broken for years as just about every modern car has an electronic throttle. Even in naturally aspirated cars there is a fair amount of decoupling.

Correct, I never said the accelerator pedal was directly linked to throttle body valve angle...I fully understand how LOAD based management works on turbo cars...

Originally Posted by savir04

the ECU is obviously trying to control BOV operation via intake manifold vacuum using throttle body angle...

Originally Posted by Freon

You are unnecessarily fixated on the BOV. The BOV's primary purpose is not to be manipulated to make cool sounds. It's there to avoid damage to the turbo from compressor surge.

Look, I've been working on load based, DI, turbo engines for a while, I know exactly what the function of a pressure relief valve is...this thread has nothing to do with sounds of a BOV, I am using reference to the sound as "double blow off" as a measure of diagnostics, and so ya'll can grasp a feel for the issue I have because I need help on this one.

I am here because the DME is internationally creating a 5PSI spike letting off at HI LOAD/HI RPM...and I am concerned that the turbo's are surging during this event, it also introduces a bunch of drivability problems that i'm not even gonna get to.... huge drivability issue for me.

Originally Posted by Freon

Your statement is like saying VANOS's purpose is to manipulate oil flow rate through the oil filter. While they are attached functionally, your line-drawing between the two is nonsensical.

I think you've misunderstood what I wrote...let me explain....Now a days a lot of turbo cars use a solenoid to control the pressure relief valve, for example Volkswagen, ford. This set up gives the ECU full control over the pressure relief valve via the solenoid, this means the ecu can open the pressure relief valve regardless of intake manifold pressure..in the n54 engine, bmw interestingly chose to use a 100% mechanical/analog set up for the PRESSURE RELIEF VALVE, on top of that 2 valves! from factory, which is an odd setup imo for such a recent car...no solenoid inline or nothing, just pure mechanical vacuum operated set up...The DME has no DIRECT CONTROL over the pressure relief valve.

With that said, The DME has very smart logic, I am sure that the DME knows there are mechanical pressure relief valves in place, and knows that it does not have DIRECT control over them...and I'm sure that it is written in its logic that if it needed to control the pressure relief valve for whatever reason, it would by manipulating intake manifold pressure using throttle body angle...its literally the only tie the DME has to the mechanical pressure relief valve...right or wrong?...according to you, that's actually exactly what the DME is doing right? spiking the throttle body open after letting off the accelerator so that the pressure relief valve seals and holds 5 PSI between gear changes?...I understand, I just need to get rid of this for the sake of drivability

Originally Posted by savir04

I just don't know for what reason...

Originally Posted by Freon

Already answered this for you. It reduces lag. If the throttle remained closed, the turbos would spin down further and faster, increasing lag when you press the accelerator again.

Particularly for turbocharged cars, keeping the throttle closed when you are coasting in gear is just wasting energy, both from a performance and fuel economy perspective.

I understand the concept, But I haven't found any genuine technical explanation of why the car does this, there's a lot of GUESSING going on IMO in reference to this hiload/hiRPM throttle body spike...but if I had to come up with an explanation myself, I'd agree with you that the DME is intentionally doing this to hold 5psi between gear changes...does your car do it? like in my video? are the turbo's not surging?

Originally Posted by savir04

iirc, cobb gives you access to absolutely all ECU reference tables

Originally Posted by Freon

Not remotely true. It's not practical. But do they expose enough? In my opinion, yes.

This was more of a question, not a statement...which is not shown here because only half of the sentence was quoted, completely isolating it from its original context...the quoted text should have been quoted entirely.