E89 Z4 Track-ready Sleeper Build

Asbjorn

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Feeling super excited about getting Hankook tires for the first time today. They are replacing my old pirelli 245 slicks.

Specifically got Hankook F200 race scrubs in 250-640-18 square on 9J et30. These are the medium compounds, and I intend to use them for the next local dry time attack competition, hopefully already this weekend.

IMG_20191217_162956.jpg


So crossing fingers the new semi-dry oil sump is up for the task. We have done one third and final revision of the baffle, and while chances are slim, it would be such as an achievement if it is finally "track-ready" now without an accusump.

IMG_20191214_170423.jpg
 
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Asbjorn

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As this build thread is now 9 pages long, and almost two years old, I felt the need to make a new thread here to sum up my experiences and recommendations towards building a track-ready Z4 from scratch. I tried to keep it short and focus on the concepts rather than specific products and brands.

Coming back to my last post, the Hankook slicks I mentioned ended up doing this to my brake pads...

IMG_20191221_185755.jpg


I was a bit disappointed with these race scrubs though. Front was good, but rear had no almost no, and I wasn't super competitive in the end. Will need to pony up for new slicks next time rather than race scrubs. Should also get some 10J wheels so I can run wider rubber. Fortunately I was able to do better during a wet time attack where street tires was used last weekend.

And speaking of disappointments, my semi-dry oil sump system is still not able to keep oil pressure above 80psi during left hand hairpins. The only idea I have left is to make the sump deeper around the pick up and then extend the pick up.

On the positive side I am still pretty happy with my cooling setup.

Data from dry time attack, the last lap:
Peak coolant: 210F / 99C
Peak oil: 258F / 125C (2nd oil cooler turned off by mistake)
Ambient: 70F / 21C

Data from wet time attack, three fast laps:
Peak coolant: 215F / 102C
Peak oil: 262F / 128C
Ambient: 64F / 18C

Since I already have a thermostat controlled DCT oil cooler, inspired by a comment from @houtan, I could consider converting to an MT radiator. This would increase the cooling available for the engine by 10% or so (from 2800cm2 to 3100cm2 totally including aux coolers). For Z4s without aux radiators, converting to an MT radiator would mean an increase in 16% of total area (from 1800cm2 to 2100cm2).

In order to keep the functionality where hot coolant is still used to heat up the DCT, I would simply connect the old inlets with a straight hose like this:

n54.jpg


Not sure if doing this makes sense though. The engine will run a bit cooler at the expense of the DCT running a bit hotter. If I study a log like this one, where the DCT oil cooler is already running, it sort of makes sense to give up some DCT cooler towards the engine.


Anyway, here are some pictures from the latest time attacks at Guangdong International Circuit as well as Zhuhai International Circuit. Took home two podiums which wasn't too bad after all.

mmexport1577667024011.jpg


IMG015321.jpg


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mmexport1578238108131.jpeg
 

Asbjorn

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Decided to make a new one pager to explain the build:

page01.jpg


Right now the car is grounded until workshops open in China again. The roof is stuck halfway open. Hopefully it is just a broken wire.

When that is fixed, I will focus on the following work:
- Replace rod-bearings as maintenance
- Try to make the sump deeper and add a dipstick
- Get some proper 10J or 10.5J wheels to run a wider square setup

Nice to haves if I have time:
- Have a custom insulated auxiliary tank built for the water injection and outside spray systems. Right now I am just using the washer fluid tank with a plastic bag expansion to increase volume. The water gets pretty hot because the containers are right next to the turbos, and the ice cubes I add before track sessions don't last long.
 
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Asbjorn

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Stay safe over there....

Thanks man!

Good news is I got my roof fixed. Fault code A68C (similar as A68B, sensor problem). Was just a broken wire from opening too many times - a USD 20 fix.

Mechanic said it might be a good idea to replace the hydralic oil after so many years. Any thoughts?

IMG_20200207_192348.jpg
 

Lurcher

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Could never hurt - but this leads into thinking about a pump rebuild as preventative maintenance. I've had my top start to open (and stop) where I needed to give it a slight "push" to get it to keep opening, but vary rarely (relays already swapped). No leaks or water intrusion, so now that I've moved (finally) and have all my tools back, I'll probably start by looking at the fluid levels and if there is a way to do an "easy" fluid swap...
 
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Asbjorn

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Since China is still much on hold, I decided to dive a bit more into how much HP my car is actually making. As of now, I have two BQ maps, one for RON98 (time attack) and RON95 (endurance + street).

As far as I can tell, a stock M4 does 100-200kph in 9.5s. That car is rated at 430ps crank, but puts down +420whp on a US dynojet. Which number is more inaccurate - I don't know.

BQs 6MT Z4 did 100-200 in 9.6s on a 93 tune that measured 410whp on a US dyno.

My car did 100-200 in a little under 9.4s.

mmexport1581684675318.jpg

All these cars weigh about the same plus/minus DCT. The Z4 probably has a bit more drag though. As far as I can see the M3 F80 is 0.1-0.2s faster than the M4 due to less drag. But it is hard to find reliable numbers to support this.

When I load up virtual dyno and my RON98 logs, then add smoothing, dynojet and sae correction I land at 427whp. That doesn't sound too far off I guess.

If that is true, then here's the hp difference between my maps:

RON98 18.5psi / 8deg: 427whp
RON95 16.5psi / 8deg: 395whp

dynojet.jpg



Anyway, here's a collection of dynojet results from other cars. It supports that a 2psi difference (within the effective range of a lites turbo) does indeed mean around 30hp:

Dynojet resultsSourceTune (boost / timing)ACN9193
N54 VTT GC litesLink20psi / 6.4deg486whp
Link18.5psi / 6-7deg (log)456whp
N54 VTT GCLink16psi / 4.5deg450whp
-20psi / 4.5deg480whp
-25psi / 4.5deg543whp
-30psi / 4.5deg568whp
S55 stock M3Link17psi (but trailing off) / 7.5deg421whp
S55 stock M4Link17psi (but trailing off) / 7.5deg424whp

However, the second row, GC lites at +18.5psi, measured 456whp average over 4 runs according to VTT. If my car is not making quite that, it could perhaps be the 200cell race-catted down-pipes eating some power.
 
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CNITUSRJ

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Came here for gc lites review n real world output info esp for tuning with RON98 in China, and pleasantly surprised by your well (meticulously) documented build. 🤩
 

Asbjorn

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Came here for gc lites review n real world output info esp for tuning with RON98 in China, and pleasantly surprised by your well (meticulously) documented build. 🤩

Thanks for the kind words.

So regarding the GC lites
  • Inlets are specific to the GC-family which is fine. The inlets are larger than stock turbos. I find the combination of stock Z4 air box + vtt GC inlets to be plenty fine for my power. No need for DCI.
  • You don't really want to use the GC-type vtt alu outlets on a track car. Because the outlet for GCs uses silicone couplers near the turbos, and it gets pretty hot down there. So if you go on track, you want to avoid this in my experience. Others will tell you they never had a problem. In the end you have no other option when selecting GC turbos. You need the smaller turbos to get access to outlets that dont use silicone couplers.
  • GC lites are a bit oversized for Chinese RON98. With Chinese RON98 I never got above 21psi. We tried with 20psi but eventually had to reduce to 18.5psi due to the track use and related iats. 20psi might work on street though, but it is still way below what the turbos are capable of (25psi?). I have a snow injection system which I currently use with water only. If one day I decide to do 50/50 water meth, I might be able to do a higher boost map. But for RON98 I would say these turbos are over-sized if your tuner is conservative. If your tuner is more aggressive, one user in here @zcchen runs HP turbos with RON98 as well, and he is running more timing and power than me. My tuner says this is not safe, but I guess it depends who you are... @zcchen says chinese RON98 is at least better than ACN91, and the HP turbos will run lower iat because they are larger. Read more here.
  • GC lites are great in terms of spool and even better in terms of response. All this while still pulling hard to red-line, unlike the stockers. But you can still get even better response by going to smaller turbos. Personally I wouldn't want any more lag than what the GC lites already have with 200 cell catted race down-pipes.
  • The GC turbo manifolds are different from stock. You get more flow with less psi, but with the disadvantage of more heat inside the engine compartment. For track use I would have preferred the stock double-walled manifold in hind-sight.

So all in all for Chinese RON98 a pair of VTT stage 2 or smaller might be a better option for track use. For street and aggressive tuning + WMI you can probably get more from the GC lites or larger.

Feel free to add my wechat: xiongbuli

@Chris@VargasTurboTech please feel free to correct me if wrong.

Maybe @CC-CHN @CC-Z435IS has something to share regarding chinese RON98 as well.
 
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Oct 24, 2016
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GC lites are a great track turbo, but you want to leave more margin in a turbo on the track, not less i.e. small turbo run extra hard simply won't last as long as the duty cycle any turbo sees on the track is much more severe than street driven usage. I would chose any of the GC family over any of the stage 1/2 family every single time. The GC aluminum outlet is fine for this application. I would definitely recommend ceramic coating the manifolds to help with heat management, but if you're making a track car heat management should be towards the top of the list of things you're addressing regardless of the turbo you choose. I also recommend anything you can do to raise octane is always preferred; WMI will lower EGT's (heat) and everything runs happier/cooler, the trick is to not get greedy with power output.

-Chris
 
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CNITUSRJ

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Your build is really interesting as I had previously set out with a very similar goal for my Focus ST before getting the 1M last fall. Eventually settled for a well sorted street car due to heat management headaches and bought a dedicated track car with friends for Beijing Golden Port race track.
 

F87Source

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GC lites are a great track turbo, but you want to leave more margin in a turbo on the track, not less i.e. small turbo run extra hard simply won't last as long as the duty cycle any turbo sees on the track is much more severe than street driven usage. I would chose any of the GC family over any of the stage 1/2 family every single time. The GC aluminum outlet is fine for this application. I would definitely recommend ceramic coating the manifolds to help with heat management, but if you're making a track car heat management should be towards the top of the list of things you're addressing regardless of the turbo you choose. I also recommend anything you can do to raise octane is always preferred; WMI will lower EGT's (heat) and everything runs happier/cooler, the trick is to not get greedy with power output.

-Chris
100% agreed on everything said.

Not only with reliability being improved on the turbo by having more head room, but when you run in the turbos efficiency range and with lower boost pressures you have cooler iats and egts.

Running e85 helps alot as well, if you have access to it.


And just like chris said, dont get too greedy with power. A car that can put the power down well (i.e. useable power) will out perform a car with a really high power output that can't put down the power. Remember neat and tidy racing lines = fast, sloppy drifting lines = slow.
 

Asbjorn

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100% agreed on everything said.

Not only with reliability being improved on the turbo by having more head room, but when you run in the turbos efficiency range and with lower boost pressures you have cooler iats and egts.

Running e85 helps alot as well, if you have access to it.


And just like chris said, dont get too greedy with power. A car that can put the power down well (i.e. useable power) will out perform a car with a really high power output that can't put down the power. Remember neat and tidy racing lines = fast, sloppy drifting lines = slow.

Totally agree

I am not sure what 18-19psi for GC lites means in terms of VTT stage 2 twins, but if that is too little headroom for those on track, then I must take back the recommendation for chinese ron98.
 

F87Source

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Totally agree

I am not sure what 18-19psi for GC lites means in terms of VTT stage 2 twins, but if that is too little headroom for those on track, then I must take back the recommendation for chinese ron98.
Yeah im not sure either since I have little to no experience with the N54. Maybe if you dont have any options just add some octane booster for the track. The issue is temperatures at that point.
 
Oct 24, 2016
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GC's will make same power as Stage 2 on a couple less pounds of boost so you can gain a little there too. We have some Stage 2/2+ family out there doing track duty, just not wrung out as hard as full GC's could be.

Chris
 

Asbjorn

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Recently Im feeling excited about a few upcoming mods:

1) Custom dampers
I currently run Koni FSD dampers in combination with stock springs front and Eibach pro-kit springs rear. Let me first list the advantages of this setup
  • Comfortable. FSD basically means the dampers are soft over pumps (high frequencies) while harder than stock in turns (low frequencies)
  • Balances the car away from understeer, due to the up-rated rear springs.
  • Reduces squat as caused by the torque which is x1.5 over stock, again due to the up-rated rear springs
  • Not too low, but much care is still needed when entering basement parking lots etc.
  • Great reliability - no problems during the three years I have had them.
Disadvantages of current setup
  • The front is really too low, both in and by itself, and compared to the rear. The main reason for this is that I run around negative 3 degrees of camber up front. Even with stock front springs, the ride height is impractical in China, and it also looks a bit silly. With stock camber, the is no problem, but I'm not going back to that. I love how the car feels with lots of camber, both on street and track, and eventually it will also allow me to run wider wheels.
  • The dampers are not adjustable. And you can only adjust so much, even with modified adjustable sway bars. Sometimes I get a bit of under-steer on corner exit, which is a front rebound issue, and especially at high speeds, I get a lot of weight transfer on track. And in general I would like to be able to adjust the balance even further, as well as overall to accommodate anything from rain/street tires to full slicks.
So what were the options?
  • New stock dampers. An often overlooked option. Dampers wear over time, and new OEM dampers should outperform used ones by a good margin. They probably wont be cheap, but the quality is there. This is something you would want to consider on cars that were designed from factory to do what you want to use the car for. My car did not come with adaptive suspension, and even if it did, it would be running comfort suspenion in DSC=off, which is not ideal.
  • Bilstein B16 - way too low
  • KW V3 - still on the low side, and probably also a bit on the comfortable side for use with slicks and high hp. Clubsport seems to be a better choice, but then that is an even lower coilover package, and not available for the Z4 off the shelf
  • Ohlins - only really 3DMs kit would make sense, and I couldn't convince the dealers local to me to do any of that. I also have M4 friends who had ohlins and went to clubsport later. Also, as mentioned, I actually want to raise the front of my car.
  • Koni yellows - probably great, but rear dampers are not adjustable with the Z4 kit. Also the lead-time was long.
  • High-end custom coilovers. I don't know. Dampers are a wear item, and what they do at the end of the day is really simple. Paying exorbitant amounts of money for high-end 4-way dampers just because they are labelled "motorsport" seems super unreasonable to the engineer in me. Yes more adjustability is always great, but not at any cost.
  • Normally-priced custom dampers. Alright then...

So I ordered locally produced custom dampers, according to the following requirements
  • Adjustable in 10 steps both front and rear
  • Front: 15mm longer damper base to raise front ride height. Shock travel matched to stock spring.
  • Rear: Shock travel matched to Eibach lowering springs. Valved for harder base-dampening.
  • Black color - because sleeper.
Can't wait to see the result in April.


2) Exhaust flap valves
After reading this post on zpost, I realized the vacuum valve controlling the two exhaust valves on my car is probably broken. Currently I just run the valves open all the time, as the system hasn't been working for months. This is great on track, but not so great for highway cruising. For longer trips I even prefer to have the mid-cats installed to reduce the noise.

I ordered a $30 kit consisting of a new vacuum valve and a remote control box with remotes to open and close the valve. My idea then is to have the new valve work as stock, but with the option to have it open 100% of the time with the remote. Lets see if that logic can be wired up. I would not want the flaps closed at all times, because I run two exhaust flaps, and with both of them closed, there is way too much back pressure for any kind of boost as seen in this log.


3) Separate water-methanol fluid tank for injection use
Currently I have two snow performance systems on my car. One is used for charge pipe injection (375cc) and one is used for spraying in front of the radiator and DCT cooler. They both take water from the wind screen washer fluid tank, which has been expanded with an additional tank for extra capacity. Problem is, I cannot add methanol to this tank, because the fluid is still used for wind screen washing. Another problem is that the fluid gets warm being inside the engine compartment, right next to the GC lites cast manifolds.

The situation now is that I do not use the outside water spray on the street. On track I have access to plenty of ice cubes, so that is not a concern, and I still use it there occasionally. I also do not use the water injection on street, because I don't really push the car much in day-to-day use, and my car is tuned for pump gas anyway. I feel like it doesn't make sense to inject hot water either, as there is no octane in water, and if it doesnt cool iat and egts, whats the use?

So a bit wrong how I installed these then...

After some thought, I have decided to add a new fluid tank in the trunk. This fluid tank will then be used for permanent water-meth injection, and only that. Since the fluid wont get nearly as hot, it even makes sense to just use pure water when access to methanol is limited.

The enlarged water tank in the engine compartment can then continue to serve its dual purpose using pure water.


Alright, that was way too much text that no-one will ever read. My next post should contain pictures with the actual results. Im still planning to change the rod-bearings and enlarge the oil sump somehow, but fortunately my oil filter was 100% clean when we checked it again recently.
 
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F87Source

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Very nice! Since the water tank is in the engine bay condensation won't be a huge deal for you. That means you can either put distilled water icecubes into the tank to make the water really cold, or you can out reusable ice packs in (down side to reusable ice packs is that you lose water volume).
 
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Asbjorn

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Talk to me about the current Koni's FSD - saw them as an option, and without wanting to go lower - running out of aftermarket choices (Bilsteins 6/8/12s are options too (and still non-adjustable)).

FSDs are upgrades over oem in that they offer similar comfort, but with harder damping for cornering. They excel at crusing. If you run upgraded power you still want uprated rear springs though, as the Konis simply aren't hard enough. I think they are a perfect match for smaller engine Z4s, but thats just an assumption.

I believe KONI is introducing a new brand called active which are red dampers. Im not 100% sure, but I believe those are replacing the FSD type. As for the yellow ones, it seems they have stopped production for Z4, and are just emptying the stocks.