E89 Z4 Track-ready Sleeper Build

F87Source

Corporal
Oct 14, 2019
134
Canada
stfts are back in the single digits and post shift flatlining is gone. Looks good to me, save for the boost spikes on shifting which can't be cured.

Only thing that annoys me is that cyl 4 sometimes gets corrected heavily (-7deg) post shift. I happens maybe every third pull or so. The correction starts just before the shift, then goes down the stairs post shift. In daily (slow) driving I also notice cyl4 is often the first one to see any corrections. Re-gapping and swapping plugs and coils has made no difference. Even tried installing brand new plugs. I don't think it was doing this one year ago when looking back through logs.
I see, hope you find the cause of the remaining issues.
 

Asbjorn

Lieutenant
Mar 10, 2018
686
European, based in China
Custom "sleeper" dampers installed!

Today we finished the installation of my new made-to-spec adjustable dampers. They took one month to produce and one day to install.

Before: Koni FSD, stock springs front, eibach pro-kit springs rear
After: Custom-dampers, exactly the same springs.

before-after.jpg


Super happy with the result. Before the front was much lower than the rear due to running max'ed out front camber. Now the front is still 5mm lower than the rear, but visually the car is much more balanced. There is much less scraping and much less "the tires might dent my hood"-anxiety. And most importantly. Much more sleeper!

IMG_20200419_183732.jpg
IMG_20200419_183043.jpg


And I know what you are going to ask. Do those blue stickers on the adjuster knobs come off, to make the dampers look even more OEM? Yes they do. Absolutely they do.

IMG_20200419_182912.jpg


So basically the front damper has a longer housing in order to raise the front of the car. The piston has the same length, because it was designed to work with the stock spring.

The rear dampers were designed with a shorter piston compared to the KONIs in order to match the Eibach pro-kit springs, and align the rear suspension with the rear damper curve. The KONIs were made for stock rear springs. This also means there is now less suspension travel available at the rear compared to the front. This should help keep the shorter Eibach spring better in place. I have had one of the rear springs shift a bit on one occasion with the KONIs.

The new dampers also offer much more force compared to the KONI FSDs which were becoming quite comfortable. I had the rear dampers made with higher damper force compared to the front in order to match the stiffer Eibach springs, and accommodate for the power, track application and weight distribution of the car. (ie I wanted less understeer, more oversteer).

Below are the damper compression/rebound curves as provided by the factory (stiffest setting).

mmexport1586922489937.jpg

(Rear, 1338N, -843N @0.314m/s)

mmexport1586922493128.jpg

(Front, 938N, -605N @0.314m/s)

Both dampers are adjustable in 10 steps. The softest setting is already stiffer than the KONI FSDs. There is less weight transfer in all directions, and I can run a softer sway bar setting without loosing steering responsiveness. When I turn up the stiffness the car really gets on its toes and wants to play. Im pretty amazed how much work dampers are able to do. Can't wait to try them out on track.

Oh and today we also swapped in a #4 nozzle as recommended by you @F87Source as the #5 375cc nozzle was a bit oversized for WI.
 
Last edited:

Asbjorn

Lieutenant
Mar 10, 2018
686
European, based in China
Decided two sets of BMW 293 wheels wasn't enough and ordered a third custom set in 4x 18in 9.5J ET35 forged. I wanted to go 10J square, but felt it was too risky up front.

Last year, although I did well in the rain, I was not satisfied with my tire setup for dry time attack. I was using a set of super cheap and heavy cast 9J et30 wheels in combination with used slicks in 245 or 250 sizes. Most of my competition was running new slicks in 265 or even 285 sizes.

WeChat Image_20200516225104.jpg


This year my first time attack will be in June at an event where they only allow semi-slicks. Due to the limited tire options in China, it is pretty well known that Hankook z214 is the fastest semi-slick you can choose. However most of my competition will most likely show up with cup2 or trofeo r. I would also say that the track layout favors cars with good power and braking rather than those who are mainly setup for cornering.

In below picture z214 is on the right, ventus td is in the middle and rs4 is on the left. I am thinking about getting the TDs in 265 or 285 medium compound because then I can drive them to and from the track. z214 is only sold in 245 or 275 medium compound and cannot really be driven to and from the track I think. If anyone has any experience with these, please let me know.

WeChat Image_20200516225045.jpg


As for power it is going to be hot and humid here in June. The competition is mainly M2-M4s, many tuned.

We added an extra 60cc nozzle to spray at the FMIC and lower radiator area behind it. I dont think it will help much, but looking forward to see what kind of temps the car will reach during the competition. I am also thinking to just go with the 16psi tune instead of the 18psi tune to keep timing corrections at a minimum. Might give better power in the end.

WeChat Image_20200516225025.jpg


As I mentioned over in the accusump thread, we also replaced the rod bearings (which actually looked fine at 150.000km), and removed the lower part of the baffle wall in the oil sump. Since I have never seen any problems with oil pressure dropping during acceleration, even on stock cars, there wasn't really any reason for the wall to be there, even if it had a one-way door.

IMG_20200512_234341.jpg WeChat Image_20200516225116.jpg

Finally we also added an oil dip stick. Should have done that years ago.
 

F87Source

Corporal
Oct 14, 2019
134
Canada
Decided two sets of BMW 293 wheels wasn't enough and ordered a third custom set in 4x 18in 9.5J ET35 forged. I wanted to go 10J square, but felt it was too risky up front.

Last year, although I did well in the rain, I was not satisfied with my tire setup for dry time attack. I was using a set of super cheap and heavy cast 9J et30 wheels in combination with used slicks in 245 or 250 sizes. Most of my competition was running new slicks in 265 or even 285 sizes.

View attachment 37784

This year my first time attack will be in June at an event where they only allow semi-slicks. Due to the limited tire options in China, it is pretty well known that Hankook z214 is the fastest semi-slick you can choose. However most of my competition will most likely show up with cup2 or trofeo r. I would also say that the track layout favors cars with good power and braking rather than those who are mainly setup for cornering.

In below picture z214 is on the right, ventus td is in the middle and rs4 is on the left. I am thinking about getting the TDs in 265 or 285 medium compound because then I can drive them to and from the track. z214 is only sold in 245 or 275 medium compound and cannot really be driven to and from the track I think. If anyone has any experience with these, please let me know.

View attachment 37786

As for power it is going to be hot and humid here in June. The competition is mainly M2-M4s, many tuned.

We added an extra 60cc nozzle to spray at the FMIC and lower radiator area behind it. I dont think it will help much, but looking forward to see what kind of temps the car will reach during the competition. I am also thinking to just go with the 16psi tune instead of the 18psi tune to keep timing corrections at a minimum. Might give better power in the end.

View attachment 37783

As I mentioned over in the accusump thread, we also replaced the rod bearings (which actually looked fine at 150.000km), and removed the lower part of the baffle wall in the oil sump. Since I have never seen any problems with oil pressure dropping during acceleration, even on stock cars, there wasn't really any reason for the wall to be there, even if it had a one-way door.

View attachment 37788 View attachment 37787

Finally we also added an oil dip stick. Should have done that years ago.
If I were you I would put the water sprayer's in the middle because the water coming out of the nozzles are so finely atomized when you're driving the wind just forces the water to hit the side of the coolers and not reach any other part.
 

F87Source

Corporal
Oct 14, 2019
134
Canada
Funny you would say that. We actually had it in the middle, then moved it to the side.

View attachment 37829
Yeah, because there is so little water that comes out of these nozzles and it is so finely atomized the wind will just blow it onto the radiator the moment it leaves the nozzle and you really wont get much water distribution far over to the opposite side of mounting. That is why you should mount it in the middle because it will give it a better chance to spray more of the cooler.

But the best mounting position is to have the nozzle opening pointed directly at the cooler parallel with the direction of air flow so the wind will help distribute the water instead of fighting it. The best way to achieve this goal is to get 90º fittings because you get cleaner hose runs, then place the nozzles so the spray pattern will get as much coverage as possible (your intercooler sprayer is mounted properly and like I described). This is what I have done in the past with inter cooler water sprayers, otherwise the water sprayer was really ineffective at high speeds because the air rushing in was just making it hit only one part of the intercooler.


Sorry I forgot to mention this to you earlier lol.
 
  • 1Like
Reactions: Asbjorn

Asbjorn

Lieutenant
Mar 10, 2018
686
European, based in China
Was trying to figure out what tire size to go for today. What I know is that
AD08r 265 on 9.5J ET40: No robbing rear
F200 250 on 9J ET30: Tiny bit of robbing rear (marks on outer plastic fender liner).

Then I started comparing thread width, section width and diameter only to get super confused. For instance AD08r in 285 has a more narrow thread width than 265 and almost same as 250 slicks.

tire-sizes.jpg


EDIT:

Talked with Hankook China. They actually recommended against 285 on 9.5J. So its either 265 or 275.

Another small update is that we increased the angle a little bit on the spoke design.

mmexport1589893455309.jpg
 

Attachments

Last edited:
Thread starter Similar threads Forum Replies Date
Lurcher BMW Z 3

Similar threads


Top