E89 Z4 Track-ready Sleeper Build

Asbjorn

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Very nice. So how did you decide to go with the urethane bushings for the rear subframe and diff? Any concerns about squeaking or higher NVH?

Filippo

So obviously I do not know if I made the right choice yet, and while there are plenty of youtube videos out there showing how to install these, the review part is often missing or not relevant to the Z4 case. But here is what I am thinking:

1) Some people have complained about wheel wobble at the drag strip, and while I never drag, in theory additional power also calls for stiffer bushings to maintain response. Most of the vendors I found do not list bushings for the E89 Z4, or directly responded that theirs wont fit. According to realoem, the Z4 differential bushings are not identical to other models, so the PowerFlex products I got was for the E46, and I was prepared to take a loss, or modify them if they did not fit.

2) The M3/M4 has a sub frame that is bolted directly to the chassis. It is of course a completely different car, but apparently it was worth it for BMW M, whatever the trade off was. I often look at the detailed technical pdfs of the M cars to learn what they did and why. Now in my case I am ending up with a combination of stiffer differential bushings, and softer sub frame bushings compared to the newest M cars. A different and more M inspired route would have been to get new OEM differential bushings, and then go all in on the sub frame bushings instead. But I wouldn't know what is better with the Z4.

3) The differential bushings are obviously not turning much, so I am not nervous about squeaks from those. The main concern here is NVH, especially since I am going stiffer than BMW M, and adding the Quaife core which may or may not produce additional NVH. As for squeaking urethane in general, yes it is a concern, which is also why I am keeping them out of the moving suspension. I only installed one urethane bushings at the weakest part of the moving suspension (the outer lower control arm) as well as with the sway bars, and those might start to squeak at some point. This is not a huge concern, because they are easy to replace, and I might go adjustable lower control arm at some point anyway.

4) My subframe still uses OEM bushings front, and only inserts rear. So as with the suspension, I am only upgrading the softest part. Should this turn out to be a mistake, then inserts are easy to pull out again.

I will reply to this post with a review as soon as I have one.
 
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Asbjorn

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And the turbos are finally here

ldkes6N.jpg


As well as the accessories

NAhZCKU.jpg


And about the that wet sump...

Since that oil pan baffle was not obtained, we decided to pull the oil pan and see if we can do some custom work on it ourselves. The plan now is to install an additional oil cooler at the drivers side, with a pump connected directly to the oil pan. The pump is then turned on only on track days, just like the oil cooler fan I installed. We are doing it in this way to ensure that the sump is wetter on the track, and to keep the oil pressure stock while increasing oil cooling. Lets see if it is possible.
 
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Asbjorn

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Here are some pictures of the work done on the oil sump.

CKzP1FA.jpg


DJP27AW.jpg


As mentioned previously we are connecting an oil cooler directly to the now "semi" baffled oil sump using a manually operated pump.

While the engine was out, all valves were cleaned as well.

Ffqp358.jpg


mRqOU5X.jpg


We also installed fresh OEM engine mounts. The engine is going back in the car tomorrow. I decided against stiffer engine mounts due to the added vibrations from the M4 flywheel in low rpm high load situations.
 
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Asbjorn

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Great choice for BOV, I have the same Turbosmart (recirculating) and I am 100% satisfied.

Great to hear. And just to explain: These, together with the OEM intake silencer, have been selected to keep the car stock sounding - ie to adhere to the sleeper goal. Of course the exhaust is louder than OEM, but probably less so than an M4, even after switching to race cats. I will find out this week when the car is assembled back together. FYI this is what my research has shown so far:

  • OEM: Fairly silent, but probably louder than a 3-series
  • De-catted midpipes only: Still on the quiet side, but much better
  • Race-catted, with de-catted mids: To be determined
  • 100% de-catted: Too loud
  • Race mufflers: Too loud

One thing I have noticed is that the car sounds better when sitting in the passenger seat. This is probably because the exhaust flap is on that side. The drivers side muffler is bigger and without a flap. It is both awesome and frustrating that the car sounds so much better when sitting in the passenger seat (with the top down that is). I'm hoping the race cats will solve that by making the whole system a bit louder.
 
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Asbjorn

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We need complete side shot - since it looks like the rear end is sitting off to the side. I want to see just how torn apart eh car really is... I know I'd have a few extra parts taking things to that level

Both front and rear sub frames were out to do differential and turbos at the same time. They are now back in. Did not get any side shots unfortunately.

What is taking some time now is fitting the oil cooler on the drivers side. A lot of custom work is needed, horn needs to be moved etc. But I insist on not installing it in the middle, just in case I need a DCT cooler there in the future.
 
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Asbjorn

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The car is now fully assembled and I went to do the first test drives today. Here are some of the conclusions

Turbos
Very happy with the GC Lites 2.0 and accessories so far. Turbo siren is gone. Top end has opened up, and most importantly, I do not feel any additional turbo lag. I am obviously not maxing these out, and was worried if they were the right choice for my rather conservative power target. But so far I am very satisfied.

Race catted down-pipes
So in combination with stock mufflers and de-catted mid-pipes, the Z4 sounds very aggressive with race-catted down-pipes. Absolutely love it. It has made a huge difference in how well pops, bangs and crackles can be heard.
Fortunately it does not drone, and I think the noise level is OK for road-trips, given that this is a Z4.

Quaife Differential and PowerFlex bushings
I do not have any comments on the ATB differential yet, but as for the bushings they definitely made a difference. I can now hear a slight differential whine, both on and off throttle. I do not mind the sound, and when cruising it is easy to find speeds were it is not audible at all. On the positive side, the drive-train does feel more responsive. There is however a minor clearance problem with one of the new differential bushing as seen below.


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Below are some more pictures of the oil cooler install. I am very happy with the result here.

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The only parts not installed now are the S65 injectors, oil catch can and colder spark plugs. I also decided to order coils via the group buy in the N54 section. All of these should be ready for install in June/July.
 
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Asbjorn

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Asbjørn, did you just switch to the H&R rear swaybar setup? I'm just wondering why you have a clearance issue at the diff mount.

Filippo

Well, it is actually rather a bushing clearance issue. There is no clearance issues with the OEM rear differential bushing. This may explain why this powerflex bushing is not listed as available for the E89 Z4, but only for E46 etc.

Btw, just drove half way across China, and with the stiffer bushings, the diff whine is mainly audible during deceleration. There is also some whine when cruising at a around 70kph and then again at around 130-150kph (louder).
The new exhaust config also has its quiet and not so quite spots in the rpm range.
Fortunately, my experience is that when cruising, the car is fairly quiet between 90kph - 125kph which is perfect for motorway driving in China.
 
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Asbjorn

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that cooler looks like it should work well.

The next track day will show! And just to explain what happened here. The new pump pulls oil from the front bottom of the oil pan, sends it through the cooler and then back to the rear of the oil pan. The engine oil pump draws oil from the middle of the pan, and between the middle and the front, there is now a baffle with a gap at the bottom. So the system basically moves oil from the front of the pan to the middle where the engine oil pump inlet is. When the system is not on, which it basically never is outside the track, the oil can still move back and forth, just not as fast as before.
 

Asbjorn

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So curious - what's the labor rates over in China? My typical shop here (Dallas TX, USA) is $100-120 hr. Dealer is $150.

Well it depends, but the short answer is you can find almost any price you want. The key is to be able to speak Chinese. Some charge by the job, some by project and some sell the parts with a mark up and say installation is included. Prices also depend on which Chinese city you are in, and how skilled the shops/workers are. Needless to say, having anything done by BMW is the most expensive, and their charges are probably similar to western shops. It is also very difficult to get good parts at a discount in China. If I want original BMW parts, I also sometimes have to wait one month for it to be imported. The M4 flywheel and M RTABs are examples hereof.
 

Asbjorn

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Here is a quick video comparing stock and FBO without any additional software tuning.

Sunny day (late 2017): Stock turbos, de-catted mid-pipes, ESS 15psi tune
Rainy day (June 2018): VTT GC lites, VSRF Race FMIC, Race-catted downpipes, de-catted mid-pipes, M4 flywheel, same ESS 15psi tune


The video was made using my Chinese dashcam, and unfortunately the audio quality is rather bad. But hopefully it is possible to hear that the top end has opened up. It is definitely noticeable when driving the car.

As stated earlier I do not intend to run high boost, as it would work against the track-readiness/reliability goal of this build.

I am uploading better videos and audio when time allows.