Journal of My BMW 128i Project: Performance Updates After a Summer of Track Events

After conducting essential maintenance tasks, the reliable N52 inline-six engine has not leaked any oil and has maintained optimal temperature during intense track sessions in scorching weather conditions. It’s surprising to describe any BMW component as “sturdy.”.

Despite various travels and moments away from car-related activities, I had the chance to hit the track thrice this summer. It allowed me to contemplate my progress in understanding the chassis and evaluate the modifications I’ve made. In short, no regrets!

During the replacement of the oil filter housing gasket and lower coolant hose, common maintenance tasks for the N52 engine, I utilized a ratio of 70% distilled water and OEM BMW coolant. In warmer American regions, a higher ratio of distilled water aids in dissipating more heat from the engine. However, using such a mix in colder climates may risk freezing in the cooling system, leading to severe engine complications.

Effective heat management is paramount for consistent track performance, particularly in summer when trackside temperatures often surpass 100 degrees.

I’m satisfied with my choice of the 128i over its turbocharged counterpart, the 135i; the potential overheating due to turbocharging could have limited my driving experience. Thus far, critical water temperatures have not been reached, even during a sweltering day at Buttonwillow Raceway Park. I empathize with my colleague Chris Rosales, who battled these extreme conditions in his warm FK8 Civic Type R. The peak temperature witnessed during the hottest session was a momentary 221 degrees, averaging 215 elsewhere on the circuit. Feedback from fellow N52-powered BMW owners suggests this range falls within safe operating limits.

However, I intend to monitor oil temperatures closely. Unfortunately, the OBD II port of the 128i does not transmit.transmit this information to my Apex Pro II application, which I utilize not only to monitor lap times but also to provide me with real-time readings of coolant temperatures during sessions.

From the outset, my aim with the 128’s configuration was simplicity. I aimed to avoid concerns about cornering balance or finely adjusting the ride height as I would with a set of coilovers. I simply desired mildly firmer spring rates, the capacity to alter the dampers’ rebound, and, ideally, maintain the factory 50:50 weight distribution of the chassis along the way. Opting for Eibach Pro-Kit springs and Koni Sports has proven to be a wise decision: The ride strikes a balance between enthusiast appeal and comfort in any setting, and body roll is effectively minimized after experimenting with the shocks’ rebound. Particularly with each corner configured to level three, equivalent to three half-turns… reasonably certain.

Thanks to BMW’s interchangeable parts from the parts bin, the upgrade of the front sway bar with that of an E93 M3 (the convertible version) has become necessary, being the firmest choice the Bavarian manufacturer had on offer at that time and seamlessly attaches to my vehicle. According to fellow enthusiasts, a larger rear bar isn’t really required. Lastly, one of the most cost-effective mods that should not be overlooked: the installation of rear subframe mount reinforcements was an extremely wise move as well.

The same applies to its braking system. The front-drilled Zimmermann 335i rotors, OEM 335i calipers, and Ferodo DS2500 pads have performed exceptionally well. They have not overheated on the track yet, and the rotors display no indications of cracking. These pads may be costly, but they have served as a superb dual-purpose compound and still possess a decent amount of remaining life. However, after six events and numerous miles of street driving, a brake bleed using Castrol SRF is certainly overdue.

My self-applause doesn’t end there: The 245/40/17 Kumho Ecsta V730 tires on each corner have also delivered excellent performance. They still have at least two events worth of tread life left in them, following a total of five events and approximately 2,000 street miles.

Although not the most adhesive compound, they exhibit a progressive breakaway, offer great feedback, and show minimal signs of overheating on the somewhat sleek 128i throughout a session.

Thanks to these enhancements and acquiring a significant amount of track experience over the past eighteen months, I recently secured the second position in the B5 class at Speed Ventures’ CSF Bimmer Challenge. It wasn’t based on my fastest lap of the day or anywhere close to my personal record, but I’ll gladly accept it!

Once again, I am thrilled with the progress of my beloved BMW 128i as it continues to prove itself as an exceptional track car suitable for dual-purpose use and, hopefully, will remain sufficiently reliable, as long as I maintain vigilance.

Before my upcoming track visit, a number of things require fixing: Replacing both inner and outer tie rods, ensuring proper alignment, and addressing an issue with one of the swaybar mounts. While investigating a subtle clunking sound, I accidentally broke one of the bolts securing the front sway bar to the subframe. Though slightly frustrating, I have purchased a suitable replacement and just need to extract the old one. I must do this carefully to avoid damaging the nearby radiator. Your thoughts are appreciated.

Combining all these improvements, I am eagerly anticipating my track sessions in the final months of 2023. Besides actively participating in the CSF Bimmer Challenge, I am also engaging in the GridLife Time Attack event at Laguna Seca from October 20-22. More details about this exciting event will be shared in a future blog post, but I am thrilled to compete in such a renowned series and enjoy driving on this exhilarating track.