In this entry – a compact outline regarding power-increasing options for B58. This time, I will not prove anything with the data, graphs, or scientific articles – “chip-tuning” fans will still continue their “business”; smarter people will find additional info by themselves.
My personal experience with B58 in the F32 LCI body has a mileage of around 200.000 km. Initially, this car was 440i with 450Nm torque. Later, the BMW AG Performance and Sound kit was installed. The engine’s torque was increased to 500Nm, power – from 320hp to 360hp.
If you want a very short conspectus:
a. 500Nm is the ultimate limit with the existing hardware;
b. to increase the power from stock 320hp, another exhaust is necessary. With the exhaust with better flow-through, you can reach the 360hp offered by BMW AG, which is the maximum limit without performing more radical changes.
Yes, at this moment, many will oppose it – but the “chip tuning” specialist is promising a much larger gain! Yes, he promised, but he “forgets” to mention some side effects.
I will mention only some facts:
a. in the first gear, the car accelerates so swiftly that (not particularly “torturing” it) the turbo aggregate is not able to “catch up” till the required boost (wastegate is completely closed) and the actual torque is slightly above 400Nm;
b. when accelerating with the second gear (engine with 500Nm torque), the wastegate is completely closed even in perfect conditions (air temperature around 20oC; a good oxygen saturation; 0m above the sea level);
c. in the 3 .. 6 gears, the wastegate opening is only 10 .. 15%, which means – it’s a critical reserve to “pull” the required boost pressure in harder driving conditions (mountain area; temperature around/above 30oC; bad oxygen saturation).
If the required boost pressure is increased above this level – with a guarantee, DME will switch to the limp mode when driving in adverse driving conditions. Yes, the “chip tuners” will mask the error messages regarding the plausibility of the air amount, rich fuel mixture, and not reached boost pressure, but – the car will not drive better due to this.
There are “specialists” who oppose – “yes, but by lower RPM (below 4000 RPM), there are larger reserves. The torque can be increased here!”
a. if the vehicle is equipped with the automatic gearbox, the engine (driving aggressively – with max required torques) does not use RPM range below 4000;
b. even if the car is equipped with a manual gearbox, the time, which is necessary for the turbo aggregate to reach the required boost, will increase significantly. Accordingly – what’s the point of such a boost? In the second and third gears – the engine will reach a larger RPM before this larger boost will be reached. Instead, in higher speeds – much faster will be to switch to lower gear!
And finally – there are several “magic” methods to reach larger power. What are they?
a. VANOS – I don’t know a single source that would claim that there are some magical VANOS settings with which the engine would have the largest torque/power possible. Instead, those who are publishing their experience all as one are admitting that the existing VANOS maps already provide the maximum performance of the engine;
b. modifying the ignition maps. Yes, in theory, it is possible to create an earlier ignition for these engines. But you must understand that gaining several % of the torque will lead to a much harder fuel-burning process. As a result – there is a much higher (30 .. 50+%) short-term (over)load on the piston group and crankshaft. Much higher load on bearing shells. Is the oil pressure proportionally increased, too (is it possible to increase it)? The answer is – no. Are the knock sensor maps modified to allow the stronger knocking of the engine? Typically – no. As a result – after some time, DME will restore (re-adapt) the modified ignition in the previous status (according to the allowed knocking level); only/additionally the error messages regarding poor quality fuel will be recorded (yes, these error messages will be masked too). And for some time, the engine will run incorrectly, on the verge of mechanical damage.
Even if the engine had some more considerable hidden resources, I would not use the modification of the “chip tuners”. Why? The DMEs of this generation are complicated. Modifying several management maps means only one thing – DME will work in a harsh limp mode. Consequences? Vibration, shivering, incorrect fuel mixture. Melted pistons, damaged turbo aggregate, CO catalytic converter. Loss of power, which can occur at any moment. I don’t need anything of that!
My recommendation: if you really want to “squeeze” the maximums from your B58, ask the “chip tuners” to install the software version intended for the Performance and Sound kit. Install the appropriate exhaust. And enjoy this engine for all 100%.