UPDATED overview:
OLD and now out-dated introduction:
Is this a stock Z4?
Well, almost... (click to enlarge)
TL;DR - Summary of highlights (added October, 2018, after almost finalizing the build)
[TBODY] [/TBODY]
Frequently asked questions
If you wanted a track-ready car, why didn't you get an M-car?
- I like 2 seat roadsters.
If you wanted a track-ready roadster, why didn't you get a Boxter
- I don't like the Boxter. Also it is not a roadster.
Where's the M-stripes, carbon bits, stubby antenna, wings, fenders, LCI parts, lowered suspension etc that other track builds feature?
- With this build, I went the sleeper-route. I want to surprise people at tracks.
Why don't you get a dedicated track car, get a racing license, and leave the Z4 stock
- At the moment, I cannot think of anything that interests me more than beating M and P cars at time attack events in a stock looking Z4.
Why is your car only slightly faster than an M4 100-200kph.
- Because it is all I should need to beat those cars on track, and I already love how fast it is. I am not interested in drag racing, and reliability was already a concern at stock power level with this car.
Intro (original text from early 2018 - now outdated)
This build thread is about a Z4 35i DCT I bought back in 2012 working as a foreigner in China. Over the years I have become more and more interested in cars, drifting and doing track days. Now it is time for the car to become similarly interested in these activities.
The main purpose of this thread is to describe the changes done from the beginning of this year as listed in the picture above. The build is expected to be finished in June, and I will try to share my experiences here as I progress.
The car has been running stock during most of its life, featuring only de-catted miltek midpipes, ESS tune and non-RFTs. Given that the roaster market is very small in China, and since I still love its design, the Z4 is still the most desirable/cost effective fun car for me to own here. I have therefore decided to see how far I can take it.
Goal for acceleration/braking: Street, drift and track-readiness. Responsiveness, predictability and reliability trumps power. Power goal is somewhere just above a stock M4. I don't drag, and track-reliability is important to this build.
Suspension goal: Street, drift and track-readiness. Lowering not an option because the car needs to work on Chinese roads. I also think M sport suspension is too harsh for street use here. (I later decided against this and installed Eibach pro-kit in order to improve stability above 150km/h)
Interior/exterior design goal: Sleeper / OEM. I do not want the car to look modded at all.
Complete list of mods, and timeline
Here is the complete list of mods as well as some stuff I am not changing that may surprise
Engine N54
Stock silencer - because it is silent. Have yet to see proof that it significantly limits power below 500hp.
VTT inlets - installed in May
VTT GC lites 2.0 - installed in May (rear WG stuck open on OEM turbos).
VTT Alu hot-side charge pipe - installed in May (these were later found to be leaking due to over-heated hoses, and additional alu shielding was added)
Custom-made race-catted downpipes and new O2 sensors - installed in May (These were later replaced with OEM catted downpipes in order to be able to pass annual inspection)
Miltek de-catted midpipes - installed
VRSF race FMIC - installed in May (This was later replaced with 7in nonHD FMIC)
ER charge pipe (DV, Z4 type) installed in May
Turbosmart Kompact DVs w/ Z4 kit - installed in May
CSF coolant radiator - installed in May
High speed oil cooler fans - installed in April, then removed again in July.
NGK 95770 spark plugs - installed in June
S63 injectors - installed in May
Precision Raceworks ignition - installed in July
VTT PCV valve and BMS oil catch can - installed in July.
"Semi-dry oil sump" with additional oil cooler and oil pump connected directly to baffled oil pan - installed in May
n20 tmap sensor - installed in October to avoid occasional 2ABC codes
Transmission DCT
M4 flywheel - installed in April. Adds a form of chatter in certain driving situations, and is not recommended for daily driven Z4s.
SSP DCT oil cooler and oil pump connected directly to the SSP DCT oil pan (turned on at track only) - installed in June
Differential/sub frame
New OEM rubber giubo - installed in May (I wanted the OEM alu version, but wrong part was shipped by ECStuning. Currently waiting for better options to hit the market)
Powerflex subframe rear inserts - installed in May, then later replaced with bimmerworld solid mounts in October
Powerflex diff front and rear poly bushings - installed in May.
Quaife ATB differential - installed in May.
Suspension front
Koni FSD - installed
Eibach pro kit - installed
M front tension struts - installed, later added bearing kit in october
M front wishbones - installed
Ground control camber plates - installed in August
H&R 28mm sway bar - installed in April
Suspension rear
Koni FSD - installed
Eibach pro kit - installed
M RTAB + RTAB limiters - installed in May
Powerflex lower wishbone outer bushing - installed
Powerflex sway bar bushings - installed
H&R 21mm adjustable sway bar - installed in April
Chassis strengthening
CIDEP front strut tower bar
CIDEP lower bar kit (see picture below)
Brakes (changed brake bias from 67/33 OEM to 69/31)
Front PB big 6 pot, 356mm floating, no PB logo, OEM colors - to be installed in March
Rear PB small 6 pot, 330mm floating, no PB logo, OEM colors, E-brake - to be installed in March
EBC yellowstuff - installed in March. Switched to PB race pads for better track readiness.
Redline RL 600 brake fluid - installed
Wheels OEM (car was delivered with cast 293 wheels from factory)
Rear 18inch custom made 293 replicas, forged aluminum, 18x9.5 ET40 (stronger, wider, yet lighter than OEM)
Front 18inch custom made 293 replicas, forged aluminum, 18x8.5 ET35 (ET changed compared to OEM in order to reduce kingpin offset)
Rear tires 265/35
Front tires 235/40
Exterior
None
Interior
Custom made sport seats in OEM color prepared for 4 point racing harness. (These were later removed again, please jump to page 4 to read why)
OLD and now out-dated introduction:
Is this a stock Z4?
Well, almost... (click to enlarge)
TL;DR - Summary of highlights (added October, 2018, after almost finalizing the build)
Feature | Products used | Reasons | Result | Link |
Semi-dry oil sump | Custom oil pan modifications (baffle, oil inlet, oil outlet), oil pump, on/off switch hidden in cabin | Avoid oil starvation on track | Seems to be working well. No problems so far (edit 9/2019: turned out I was loosing oil pressure on left hand turns with slicks, still working on this) | Installation Thread on topic |
Increased power and upgraded turbo etc | VTT GC lites 2.0, @BQTuning, 7in FMIC, PR ignition, S65 injectors | Wider and increased power band, better turbo reliability (running only 18-20psi on +25psi capable turbos) | 100-200km/h in 9.4s | Link |
Upgraded cooling | CSF Coolant radiator, additional radiator, larger stock location oil cooler, additional oil cooler installed on drivers side. SSP DCT oil cooler. | Avoid limp mode on track. Local climate is hot and humid, with summer highs exceeding 100F | Coolant cooling still being optimized. Currently hitting 106C on track. Iats also sometimes exceed 130F. DCT and engine oil temps are OK. (Edit 9/2019: still working on this) | Oil cooler install Optimizations Testing results Update |
Stiffer bushings, chassis, dampers and coilsprings | Bearing RTAB, BW solid subframe mounts, PowerFlex diff and rear lower control arm bushings, front M camber arm, front M tension strut with bearing kit, Eibach prokit (rear only), Koni FSD dampers, Ground control camber plates, H&R sway bars (front one modified to be adjustable) CIDEP chassis bars | Better steering feel, easier to place car on track, easier to control acceleration and braking | Car is more fun to drive on good roads and more predictable on track. Car is less fun to drive on bad roads as the front end bottoms out more easily. | Eibach install Track tour of China CIDEP bars |
Limited slip differential | Quaife ATB | Better control-ability in dry. Ability to drift in rain. | Car is more fun to drive, and easier to control on and off limit. Differential locks faster in the dry and is now also able to lock in the wet. | Install Diff bearings went out |
Lightweight DCT flywheel | M4 DCT flywheel | Faster rev changes on up and down shifts. Less strain on drive-train. Engine sounds more race-car-ish. | Car is more fun to drive fast and sounds better. D-mode is rendered unusable due to flywheel chatter in high gear, low-rpm, high load situations. | Installation |
Upgraded brakes | PB brakes, custom cooling ducts, Redline brake fluid (recently swapped to endless which seems to perform better) | Reliable braking on track, slightly more front biased brake balance, OEM look. | 100% satisfied, race pads are needed for track use. | PB Installation Custom brake cooling ducts |
Sleeper look | Custom forged wheels in OEM design, brakes colored to match color of car. | To fool the enemy (in particular M and P cars attending track events) | Only very few people can tell this car is not a standard Z4. Most people even think the brakes are OEM. Absolutely love it. |
Frequently asked questions
If you wanted a track-ready car, why didn't you get an M-car?
- I like 2 seat roadsters.
If you wanted a track-ready roadster, why didn't you get a Boxter
- I don't like the Boxter. Also it is not a roadster.
Where's the M-stripes, carbon bits, stubby antenna, wings, fenders, LCI parts, lowered suspension etc that other track builds feature?
- With this build, I went the sleeper-route. I want to surprise people at tracks.
Why don't you get a dedicated track car, get a racing license, and leave the Z4 stock
- At the moment, I cannot think of anything that interests me more than beating M and P cars at time attack events in a stock looking Z4.
Why is your car only slightly faster than an M4 100-200kph.
- Because it is all I should need to beat those cars on track, and I already love how fast it is. I am not interested in drag racing, and reliability was already a concern at stock power level with this car.
Intro (original text from early 2018 - now outdated)
This build thread is about a Z4 35i DCT I bought back in 2012 working as a foreigner in China. Over the years I have become more and more interested in cars, drifting and doing track days. Now it is time for the car to become similarly interested in these activities.
The main purpose of this thread is to describe the changes done from the beginning of this year as listed in the picture above. The build is expected to be finished in June, and I will try to share my experiences here as I progress.
The car has been running stock during most of its life, featuring only de-catted miltek midpipes, ESS tune and non-RFTs. Given that the roaster market is very small in China, and since I still love its design, the Z4 is still the most desirable/cost effective fun car for me to own here. I have therefore decided to see how far I can take it.
Goal for acceleration/braking: Street, drift and track-readiness. Responsiveness, predictability and reliability trumps power. Power goal is somewhere just above a stock M4. I don't drag, and track-reliability is important to this build.
Suspension goal: Street, drift and track-readiness. Lowering not an option because the car needs to work on Chinese roads. I also think M sport suspension is too harsh for street use here. (I later decided against this and installed Eibach pro-kit in order to improve stability above 150km/h)
Interior/exterior design goal: Sleeper / OEM. I do not want the car to look modded at all.
Complete list of mods, and timeline
Here is the complete list of mods as well as some stuff I am not changing that may surprise
Engine N54
Stock silencer - because it is silent. Have yet to see proof that it significantly limits power below 500hp.
VTT inlets - installed in May
VTT GC lites 2.0 - installed in May (rear WG stuck open on OEM turbos).
VTT Alu hot-side charge pipe - installed in May (these were later found to be leaking due to over-heated hoses, and additional alu shielding was added)
Custom-made race-catted downpipes and new O2 sensors - installed in May (These were later replaced with OEM catted downpipes in order to be able to pass annual inspection)
Miltek de-catted midpipes - installed
VRSF race FMIC - installed in May (This was later replaced with 7in nonHD FMIC)
ER charge pipe (DV, Z4 type) installed in May
Turbosmart Kompact DVs w/ Z4 kit - installed in May
CSF coolant radiator - installed in May
High speed oil cooler fans - installed in April, then removed again in July.
NGK 95770 spark plugs - installed in June
S63 injectors - installed in May
Precision Raceworks ignition - installed in July
VTT PCV valve and BMS oil catch can - installed in July.
"Semi-dry oil sump" with additional oil cooler and oil pump connected directly to baffled oil pan - installed in May
n20 tmap sensor - installed in October to avoid occasional 2ABC codes
Transmission DCT
M4 flywheel - installed in April. Adds a form of chatter in certain driving situations, and is not recommended for daily driven Z4s.
SSP DCT oil cooler and oil pump connected directly to the SSP DCT oil pan (turned on at track only) - installed in June
Differential/sub frame
New OEM rubber giubo - installed in May (I wanted the OEM alu version, but wrong part was shipped by ECStuning. Currently waiting for better options to hit the market)
Powerflex subframe rear inserts - installed in May, then later replaced with bimmerworld solid mounts in October
Powerflex diff front and rear poly bushings - installed in May.
Quaife ATB differential - installed in May.
Suspension front
Koni FSD - installed
Eibach pro kit - installed
M front tension struts - installed, later added bearing kit in october
M front wishbones - installed
Ground control camber plates - installed in August
H&R 28mm sway bar - installed in April
Suspension rear
Koni FSD - installed
Eibach pro kit - installed
M RTAB + RTAB limiters - installed in May
Powerflex lower wishbone outer bushing - installed
Powerflex sway bar bushings - installed
H&R 21mm adjustable sway bar - installed in April
Chassis strengthening
CIDEP front strut tower bar
CIDEP lower bar kit (see picture below)
Brakes (changed brake bias from 67/33 OEM to 69/31)
Front PB big 6 pot, 356mm floating, no PB logo, OEM colors - to be installed in March
Rear PB small 6 pot, 330mm floating, no PB logo, OEM colors, E-brake - to be installed in March
EBC yellowstuff - installed in March. Switched to PB race pads for better track readiness.
Redline RL 600 brake fluid - installed
Wheels OEM (car was delivered with cast 293 wheels from factory)
Rear 18inch custom made 293 replicas, forged aluminum, 18x9.5 ET40 (stronger, wider, yet lighter than OEM)
Front 18inch custom made 293 replicas, forged aluminum, 18x8.5 ET35 (ET changed compared to OEM in order to reduce kingpin offset)
Rear tires 265/35
Front tires 235/40
Exterior
None
Interior
Custom made sport seats in OEM color prepared for 4 point racing harness. (These were later removed again, please jump to page 4 to read why)
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