BMW F-Chassis B58 140i/240i/330i/340i Tuning and stock HPFP limitations

Updated: Oct 14, 2021


So, you want to tune your B58 engine, and what an engine it is! 3.0l Twin-Scroll Turbocharged, direct injection using the latest MG1 ECU from Bosch (GmbH) with a whole heap of features and hidden gems that just aren't utilised.

b58 bmw engine
B58: From the gods?!



Let's get started!

So, first thing's first, the best £ to performance gain is simple, a tune on a stock hardware vehicle, this doesn't require any changes with hardware, risking bloody knuckles trying to fit that aftermarket intake into a tight space. A simple tune on a stock hardware vehicle is commonly referred to as "STG1/Stage 1" - This is very cost effective and typically yields the best £ to Performance. From us, its £400+VAT, (£480) and we would expect to achieve 430-440BHP and 600-620Nm of torque.


Stock Figures

There's many different variants of the B58 engine, with that come different quoted stock power figures: 326PS, 340PS and 360PS are all claimed figures, with it will come different tuned results, or shal we say different absolute results (Before and After), rather than claimed paper figures vs actual dyno results. For example, most 140i/240i B58's will typically achieve 360PS when stock, 20PS or so over the claimed stock figures. Below is a Dyno graph of a completely Stock 140i B58, and you'll find many other stock runs of B58 engines making much more than the quoted figures.

Making 20PS and 30Nm~ over book figures, but it's quite a common occurrence on the B58.


Let's extract some power!

So you decided you wanted to tune your B58 powered vehicle, no problems at all, but as a tuning company, we have a responsibility to ensure what you're getting is safe and useable in all conditions, sure there are plenty of off the shelf (OTS) tunes available which work, but all vehicles are different, and each one needs to be looked at to ensure reliability, whether that be with logs on the road or on the Dyno.


For example, the vehicle below, although on moderate boost pressure (1.4bar or so), had a 50bar deficit on the high pressure fuel side. As stock, the 140i/240i/330i/440i F Chassis B58 cars run 200bar on the HPFP, but because of the increase boost/charge pressure, fuel pressure on the high pressure side was dropping to 150bar! 25% pressure loss, even when running a fairly lean Lambda of 0.93 (13.6 AFR)


So what are our options?

2 options really, but only 1 works for STG1, we have to drop the torque, typically by running less boost pressure, although it can be done in other ways too, boost pressure is the best option. The other option is to upgrade the HPFP with the "tu" pump found in the Toyota Supra and G-Chassis BMW's (Z4 etc), this is an OEM upgrade that fits, and there's even a OEM wiring harness extender available direct from BMW. By using this OEM HPFP upgrade, we get to keep OEM reliability.


So, it all depends on what you want to do, run less torque or upgrade the vehicle further, typically this comes down to cost, and the £ to performance balance.


We did it! Responsibly and safely.

And here we have it, the final results of a 140i, tuned with no drop in high pressure, maintaining 200bar through the RPM range and in the higher gears, so torque had to be limited on this particular example, although some cars do seem to have more headroom than others, this is very much vehicle dependant, mileage and service history. A worn camshaft for example will cause a loss in high pressure, although unlikely and rare, can and does happen. We have seen it on other vehicles with similar setups, Ford Fiesta ST MK7 for example and older MK5/MK6 Golf GTI with camshaft driven HPFP setups

Below is the log of the HPPF system, with no pressure drop, ensuring it's as safe as possible, with 0.9 lambda (13.06AFR) - It's all a bit of a balancing act to ensure torque is low enough to not cause a pressure drop, but also high enough to make the torque that most people want ~600Nm, we can of course create less torque, enrichen the AFR further to ensure even more reliability and heat management, especially if the vehicle is driven a lot on track or similar. This is where customised tuning will always trump an off the shelf (OTS) tune, it's specific to what you, as the owner want and need from their vehicle.



Maintaining 200bar of high pressure throughout the RPM range.


And now you want more Power?

So after pushing the limitation of the stock fuel system safely, the only way we can increase torque and power now, is with some additional hardware, mainly the upgraded High Pressure Fuel Pump (HPFP) so that we can run more boost pressure, without leaning out the fueling, and then by adding a sports-cat/de-cat, we can aid airflow/reduce back-pressure, especially at high RPM, this is clear from the Dyno graph below, as the power doesn't drop off after reaching peak power quite as quickly as it does with stock hardware and tuning only (STG1). With the upgraded HPFP and downpipe, this hugely aids in maintaining peak power, creating a flatter power curve (as below). This is where the 100-200KM/H times start to drop drastically.

and there we have it, finalised tuning for the B58 F-Chassis, until we start throwing a larger turbocharger on and starting to push that fuel system again.

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