[t0pless]

As someone that tracks their car, I’ve really enjoyed taking this car and finding out some of its limitations. I wanted a trackable street car, and not the other way around. I find this formula similar to how the M division takes BMWs- a livable daily that can be competitive at the race track without much modification. I’ve placed first in my run group (intermediate/advanced point by) a handful of times, and the car is competitive with GT350s, caymen GT4RS, 911 GT3s, Machs, and other track oriented cars. For what I spent on the car, it competes with other cars 2x its price.

I’ve gone through several racetracks this season and will continue throughout the rest of the year. Between each track event, I would build on areas I felt that would need improvement. I started with engine mods and slowly worked on other components as I realized horsepower plays a much smaller role than I imagined. I also didn’t want to constantly switch out parts depending on street vs track, so finding parts that serve dual purpose was difficult.

With that being said, this build isn’t about high horse power, ultimate track build, or car show clout. If the M division did work on this car, I’d imagine it would look similar to what I made. All components still work as stock, maintaining all creature comforts, and no compromised ride comfort.

Engine:
BM3 stage 2 OTS
BM3 flex fuel kit
Wagner tuning intake manifold
AA catted downpipe
Akrapovic axle back exhaust

Brakes:
M550i front and rear brakes
- 374x36 front rotors, 370x24 rear
EBC blue brake pads
ATE 200 brake fluid

Suspension:
KW DDC coilovers
Verus camber plates
SPL traction arms
aFe front sway bar medium stiffness

Alignment
Front: -3.5 camber, 0 toe
Rear: -2.4 cambe, 0.22 total rear toe

Wheels/tires
Apex VS5RS
Front: 19x9.5 et25 275/35/19
Rear: 19x11 et 40 305/30/19

Engine:
The car really woke up from just a tune and downpipe. It’s not like the car ever felt slow, but cars these days keep getting faster and faster. To me, it seems clear that BMW built the b58 with the intent to tune and throttled it down to not encroach S engine power. My favorite addition was the flex fuel kit which automatically detects the % of ethanol in the fuel. For those unaware, ethanol has a higher octane rating which allows you to run more boost and advance the timing. Stage 2 OTS on 91ACN fuel puts the car roughly 420-430HP w/ downpipe. With e50 mix, the car is doing around 480-500whp.
At this power level, the traction can be a little unruley with stock tires.

One issue I did encounter running e50 on the track is the turbo is now outside of its efficiency range. At high RPMs, the turbo is doing about 23PSI and essentially just blowing hot air. Charge temps can exceed 400F. With a stock intake manifold, the car would start to pull timing after a couple of laps.

Enter the Wagner intake manifold. This manifold works wonders to keep IATs down. There are periods which the manifold managed to cool the charge temps over 200F, and temps remain between 110-125F with e40 fuel and several laps. I can’t recommend this intake manifold enough- it’s one of the most affordable, offers port injection, and compatable with the stock charge pipe.

Brakes:
This is a tough one. I first took out my car at Willow Springs, which is essentially a track that tests how big your balls are. It’s all about long sweeping turns and keeping the pedal down. There are a few areas, like turn 1, which bring straightaway speeds of 140+mph down to about 70-80mph. I went here with stock brakes and pads for my first go around, and the car faded pretty quickly. For stock sizes, the car has a bunch of pad and rotor options. For those that are track rats, I actually recommend to stick with stock sizes and just upgrade pads and fluid.

Those interested in the retrofit, I have a write up on the Supra forums.

https://www.supramkv.com/threads/big...catalog.21024/

The reason I chose to upgrade the brakes from the m550i are two fold- larger brakes means higher heat capacity. Higher heat capacity means more resistance to fade. The major downside to this is that this size is heavily limited on brake pad options. I still standby this upgrade as it was essentially free after selling the stock parts, and the car performs really well with just EBC blue pads.

Suspension:
This is by far my most favorite (and most expensive) mod. The car is fairly undersprung for track use and the dampers are too soft and lazy. They made for great canyon drives, but it was far to wallowy in anything technical.

Enter KW DDCs.

Game. Changer. I swear if anyone has the opportunity to ride in some good coilovers, this would be everyone’s first mod. While KW doesn’t publish their spring ratings, the car is much more on its toes. DDC is probably the best available STREET coil, and handles track duty very well. There are better track coils (KW club sport, MCS, etc). But they all remove factory EDC. In comfort mode, it’s maybe 0.5x more stiff than stock sport mode. In sport mode, it’s now about 2x more stiff. It’s far from an unbearable ride, and actually turns the car less GT like and into more sports car. The spring barrel and perch are also much more narrow allowing for more aggressive offsets, camber, and tire profile.

The front uses McPherson struts which doesn’t allow camber adjustment from factory. In other words, you get what you get. Stock ranges from -1.6- -2.2 degrees, which is actually pretty aggressive for a stock car. Even still, I’ve gone through several tires that would get shredded from the lack of camber. Camber plates are a cheap and easy way to add more camber and the Verus camber plates were great for this.

The factory alignment is just okay. There is some minor bump steer from the rear factory settings, but not nearly as bad as what the early model Supras were complaining about. The race alignment settings are what all the Supra track suggest, and the car feels extremely stable, with a slight understeer due to the front sway bar. I had the car corner balanced and sits at virtually 50-50 to my weight.

Wheels and tires:
I can’t stress enough that shoehorning a “wider” tire onto a stock wheel while running stock pressures does not increase straight line grip. I can go on about this, but I highly encourage people to read this article:

https://motoiq.com/how-to-properly-s...performance/5/

Unlike a lot of other BMWs, the z4 chassis has massive wheel wells. I contemplated running square 18s for better sizing availability and affordability, but 19’s just work so well on this car.

[ebirotedu]

Nice write-up. Appreciate the level of detail on your Z’s track mods.

[SMD001]

Great info! Defiant the KWs. Recently did coilovers on my c6 and wish I would have done it years ago.

[tracer bullet]

Awesome work. I certainly love the idea of modding things in a way thinking "they'd have done it this way if they could have".

Glad you like the Wagner intake. I feel like a FMIC swap is almost always a must but of course the B58 doesn't have one. I'll keep the car stock for a while, but - only a while. I could easily see that being a first next step especially if / when a tune goes on.

Also thanks for listing the tire sizes and wheel offsets. I'm guessing no rubbing? Or if any, it's minor? 275's a lot of rubber for a Z4. I would have thought you might hit a limit by then.

Thanks for the write-up, and the pictures. I know that takes time and it's much appreciated. Awesome to see someone racing!

[Top Gon]

Awesome write up!!

Thank you for sharing your build and I’m happy to see ppl tracking and realizing the potential of this car.

You have the exact same wheels that I want in the same color also

1 question. How were you able to unlock the ecu to be able to tune it?

[t0pless]

Originally Posted by Top Gon

Awesome write up!!

Thank you for sharing your build and I’m happy to see ppl tracking and realizing the potential of this car.

You have the exact same wheels that I want in the same color also

1 question. How were you able to unlock the ecu to be able to tune it?

I have a 2020 MY so it only required a bench unlock. Most sources say only bench unlock for build dates before 06/2020. There have been some reports of May builds requiring FEMTO, and July builds having bench unlock only. Something like MHD will be able to tell what unlock you’ll need if your build date ends up being an oddball.

[t0pless]

Originally Posted by tracer bullet

Awesome work. I certainly love the idea of modding things in a way thinking "they'd have done it this way if they could have".

Glad you like the Wagner intake. I feel like a FMIC swap is almost always a must but of course the B58 doesn't have one. I'll keep the car stock for a while, but - only a while. I could easily see that being a first next step especially if / when a tune goes on.

Also thanks for listing the tire sizes and wheel offsets. I'm guessing no rubbing? Or if any, it's minor? 275's a lot of rubber for a Z4. I would have thought you might hit a limit by then.

Thanks for the write-up, and the pictures. I know that takes time and it's much appreciated. Awesome to see someone racing!

Things heat up fast with a turbo. Water to air is just so much more efficient and uses less space. The stock intercooler isn’t that bad, but it will still pull timing at stock power levels if your doing successive pulls or even canyon driving. I’ve heard of stock Supras hitting 140+F IATs on the track, and that’s when the car pulls significant timing.

Here is a log on the track. This is after several laps, 80F ambient temps in Vegas. You can see that charge temps hit 400F and yet the IATs are extremely stable at 118F. This is below the threshold where the car will start to pull some timing, which would be around ~125F. It’s really doing a bang up job cooling down a turbo operating outside of its efficiency window.

The Wagner is an excellent proposition.

No rubbing with the setup. I know of people running square 295, and some people even have done larger on the Supra. I can’t imagine that working without coil overs, perfect offset, and a lot of camber.

[Top Gon]

Originally Posted by t0pless

I have a 2020 MY so it only required a bench unlock. Most sources say only bench unlock for build dates before 06/2020. There have been some reports of May builds requiring FEMTO, and July builds having bench unlock only. Something like MHD will be able to tell what unlock you’ll need if your build date ends up being an oddball.

Ahh lucky you have the 2020.
I and many others are completely uninterested in shipping the eco across the world lol. So we’ll just wait for a solution stateside to happen hopefully eventually

[Balr14]

Thanks a lot for the info on the Wagner intake!
A quick question: Does the Akrapovic axle back exhaust contribute anything to performance?

[t0pless]

Originally Posted by Top Gon

Ahh lucky I have the 2020.
I and many others are completely uninterested in shipping the eco across the world lol. So we’ll just wait for a solution stateside to happen hopefully eventually

You should be able to bench unlock actually. Build dates in 2020 should actually be 2021 model years, which would require femto.

Something like MHD would be able to verify what you exactly need. However, you can also pull out your ECU and verify the ECU build date, which is actually what matters vs the chassis build date.

[t0pless]

Originally Posted by Balr14

Thanks a lot for the info on the Wagner intake!
A quick question: Does the Akrapovic axle back exhaust contribute anything to performance?

It’s about 20-25lbs lighter, but virtually nothing you’d be able to feel. The Supra boys say the stock exhaust really isn’t a bottleneck until like 650HP+, which I could agree. The titanium does give it a more unique sound!

[Top Gon]

Originally Posted by t0pless

You should be able to bench unlock actually. Build dates in 2020 should actually be 2021 model years, which would require femto.

Something like MHD would be able to verify what you exactly need. However, you can also pull out your ECU and verify the ECU build date, which is actually what matters vs the chassis build date.

I have a 2023. No chance

I made a typo on my response 🙃