In previous entries regarding this topic, I mentioned that after the engine upgrade, the subjective feeling says – in Sport/Sport+ modes, the turbo aggregate is managed more aggressively. Now it’s time for the first technical data.
Speed of the car: 90 km/h, 4th gear, 2700 RPM; required torque around 50 .. 60 Nm. Cruise control on.
On the 60th second, the Sport mode is turned on. On the 67th second, the Comfort mode is restored.
Purple curve – planned amount of air (Axys 3); brown curve – the measured amount of air (Axys 3), both in bold.
As we see, changes in the air amount are significant!
Here, zoomed air flow curves.
Purple curve – the planned amount of air (bold); brown curve- the measured amount of air.
An exciting nuance – the planned amount of air is with an overshoot. Why? BMW AG knows that the turbo aggregate has mechanical inertia. Creating such an overshoot, the impact of this inertia is reduced. As we see, the actual (measured) airflow is with rapid and exact increase “ladder”; no delay of the turbo aggregate is observed (it is compensated)! Of course, such compensation abilities are not limitless, but – this could be one of the trump cards of the manufacturer, as a result of which the engine is so aggressive.
Red curve – charging pressure (Axys 2). As we see, the turbo aggregate can develop a pressure of 0.1 bar in these conditions! Comparing to the Comfort mode. The boost pressure, created by the turbo aggregate, increased TWO times!
Redish-brown curve: planned pressure in the inlet (Axys 2); greenish curve – measured pressure in the inlet (Axys 2), both bold.
The most interesting is that when switching to the Sport mode, the relative pressure in the inlet (after throttle) increases; significant rarefaction is not observed (despite the low required torque)!
Here, the green curve: opening of the throttle (Axys 3), bold.
As we see, when the Sport mode is switched, the throttle is opened even slightly more. In addition, it has quite a large opening, around 15 .. 16o (required torque is tiny, only 50 .. 60 Nm). How so?
The answer is simple: DME continues active use of Valvetronic in this mode.
What are the bonuses “playing” with Valvetronic?
a. in the whole inlet manifold (before and after throttle), there is a lot of air, and the pressure is close to the charging pressure. This air is used in case of a quick increase of required torque and reduces the engine reaction to the accelerator pedal;
b. use of Valvetronic reduces pumping losses, allowing for saving fuel.
Instead, a slight pressure difference (1100 hPa vs 900 .. 950 hPa) between the charging tract and collector after the throttle is created to avoid turbulence and uncontrollable pressure fluctuations during swift transition processes.
Compared with tests before the upgrade (can be found here), conclusions are unequivocal:
a.the turbo aggregate is used much more aggressively (in initial tests, I did not manage to measure changes in the boost pressure when switching gears). As we see, even by torque 50 .. 60 Nm (as we know, this engine can work in atmospheric mode even till 260 .. 280 Nm) after the installation of the kit, the turbo aggregate is already spinning and “pumped” the pressure of 0.1 bar;
b. now, the engine behaves as a very potent atmospheric engine with a wide range of torque. For example, there is no need to “spin” the turbo aggregate to bypass another vehicle on the road in the 3rd gear.
