[SrKun]

Hi everyone,

This thread documents the evolution of my 2009 BMW 335i E90 LCI (N54) as I develop it into a reliable, balanced and consistent Nürburgring-focused track car, while still keeping it usable for spirited mountain driving. The build is ongoing, so I’m sharing everything I’ve learned along the way for the benefit of others working on N54/E9X track platforms.



After initial spirited driving and the first trip to the Nürburgring, the car revealed the typical E9X weaknesses when subjected to long, high-load sessions:

• Oil temps shooting up to 140°C in only a few minutes.
  
• Noticeable chassis roll and mild understeer at high speed.
  
• Front brakes overheating, inconsistent pedal feel, vibration.
  
• Rear end feeling soft on compressions and weight transfer.
  
• Cooling clearly insufficient for repeated laps.

The N54 heat management weaknesses appear instantly at the Ring, so cooling became priority #1.

Installed

• 95°C thermostat – lowers oil temperature baseline.
  
• 7.5” intercooler – stabilizes IATs on long pulls.
  
• VRSF aluminum chargepipe

These helped, but Nürburgring still overwhelmed the stock single oil cooler.

Final solution (2025)

Dual 25-row oil coolers, mounted behind fog light openings
Fog lights removed for airflow
Custom ducting to force direct cooling air
Designed for long, repeated laps

This setup is the first time the car could run multiple laps without excessive oil temperature buildup.


Suspension, Chassis & Geometry Development

I started with KW Clubsport 2-way coilovers

Test sessions (2024–2025) revealed:

• Excessive roll in long corners
  
• Understeer on turn-in
  
• Rear instability during compressions
  
• Car much more precise at the front than the rear → imbalance

Braking System Evolution

Brakes were the main limitation during the 2025 season.

• Stock-sized brakes failed at the Ring
  
• Warped rotors in only 3 laps
  
• Cracks developed
  
• Heavy vibration
  
• Pedal became inconsistent

Final braking setup (2025)

• BMW M3 F80 front calipers and discs
  
• Ferodo DS1.11 pads
  
• HEL braided lines

Aerodynamic

Rear stability at high speed is essential for the Nordschleife.

Aero installed

• GTS wing
  
• Set at 10° angle of attack

Engine & Reliability Work

Current performance mods

• MHD Stage 2 tune(394hp)
  
• Catless downpipe
  
• 7.5” FMIC
  
• VRSF aluminum chargepipe

Reliability

• All ignition & fueling maintenance up to date
  
• Oil cooling significantly improved

Wheels & Tires

Current wheels:

18x9 square setup

Tires: 255/35/18 (Nankang NS-2R)

The 255-square setup keeps the car road-friendly for mountain driving (I also drive narrow mountain roads frequently).

A future upgrade to a higher-tier semi-slick is under consideration, I want to be quick and prepare the car based on these tires until I notice that the limiting factor are the tires.

Upcoming Parts (Already Purchased)

Adjustable Rear Control Arms (Uniball)
Upgrading to fully adjustable, spherical-joint rear arms

Solid Aluminum Subframe & Differential Bushings
A major upgrade for rear-end stability

H&R Front and Rear Stabilizer Bars
These will reduce body roll significantly, especially with the current spring rates

Plate LSD
M3 Front Control Arms (Uniball)



Next Steps & Looking for Input

My next goal is straightforward:
go sub-8 at the Nürburgring on NS-2R.
The car is getting closer every season, and with the upcoming upgrades (rear adjustable arms with uniballs, solid aluminum subframe & diff bushings, H&R sway bars, front M3 arms with uniballs, and new LSD plates, brakes), I expect a noticeable improvement in stability, mid-corner precision and traction.

I’m currently evaluating a few final upgrades and would appreciate feedback from those with more experience on track-focused E9X setups.

leave some photos of the car currently and the last trip to nurburgring

[momentx]

Nice build!

Currently also working on my ring build, but only a 330i

[StradaRedlands]

Amazing SrKun and momentx!!!
Thanks for sharing the images and build out... please continue to document your experiences with the car and at The 'Ring!

[SrKun]

Originally Posted by momentx

Nice build!

Currently also working on my ring build, but only a 330i

Nice build too!

What mods do you have on your E90?

Are you looking for times on BTG or just enjoying the ring?

[san40k]

my 335i is also an evolving track toy, heat was my worst enemy - ie https://www.e90post.com/forums/showp...postcount=1013

Now replacing shot turbos with rb's and a bunch of related maintenance while the subframe is dropped

[SrKun]

Originally Posted by san40k

my 335i is also an evolving track toy, heat was my worst enemy - ie https://www.e90post.com/forums/showp...postcount=1013

Now replacing shot turbos with rb's and a bunch of related maintenance while the subframe is dropped

The best advice I can give you about temperatures is to install 2 oil radiators, it’s the only thing that has worked for me.
With that I stopped having temperature problems of both oil and water.
After 25 minutes continuously on the circuit without cooling, the temperature did not exceed 120°C/248°F.

[san40k]

SrKun which thermostat are you using (and is it temp based or just a spring like MMR's https://www.turnermotorsport.com/p-4...mostat-n54n55/)

I plan on giving it another season (or 2) with just upgraded csf oil cooler, will see how it goes.

[SrKun]

Originally Posted by san40k

SrKun which thermostat are you using (and is it temp based or just a spring like MMR's https://www.turnermotorsport.com/p-4...mostat-n54n55/)

I plan on giving it another season (or 2) with just upgraded csf oil cooler, will see how it goes.

Spring that start opening at 90 and full 110. Just like the one you post.
I did 1 season with only one big oil cooler but was impossible to stay more than 5-6 min without getting the oil really hot.
Here in Spain we have hot weather, especially in summer, when we can hit more than 40ºc/104F.