E89 Z4 Track-ready Sleeper Build

[Asbjorn]

New aux radiator is ready. Cant wait to install and test it out on track.

	Old aux radiator	New aux radiator
Height	341mm	same
Core thickness	40mm	52mm
Core width	approx 540mm	approx 640mm
Coolant	1) 50/50 coolant water 2) 100% BMW coolant	50/50 coolant water
Configuration	1) Parallel to CSF radiator 2) Series after CSF radiator	Series after CSF radiator

Also decided to get at set of EBC orange stuff pads. I want to see if they offer better heat resistance compared to the PB race pads. I have been very happy with the PB race pads as a dual purpose street and time attack pad, but they do occasionally fade on track during longer stints, especially when worn.

Thirdly I intend to swap back to race-catted down-pipes to lower EGTs and ensure cat longevity as highlighted to me by @RSL. Since the car cannot pass annual inspections when running only race-catted down-pipes, I will need to add high-flow mid-pipe cats as well.

Finally I desperately need a better FMIC solution. The 7in nonHD cooler already causes power reduction on track, and it isn't even summer yet. It is ridiculously troublesome to import a new 7in HD FMIC into China, so I intend to send my 7.5 HD cooler to a workshop and have them grind off the upper stepped part somehow. It must be possible.

 

[Traf]

Like your build bro ! Have you thought of deleting the roof mecanism?
When you say you use 100% coolant do you mean this coolant ?
Cause IIRC this should not be used without mixing with water, also water is better at transporting heat than this.
I believe race cars use 100% water with some kind of anti corrosion additive.

 

[Asbjorn]

Like your build bro ! Have you thought of deleting the roof mecanism?
When you say you use 100% coolant do you mean this coolant ?
Cause IIRC this should not be used without mixing with water, also water is better at transporting heat than this.
I believe race cars use 100% water with some kind of anti corrosion additive.

View attachment 26490

Yes 100% means I did not add any water to the above BMW product. I believe the benefit of running 100% coolant in racing applications is higher boiling point. The disadvantage is that if it leaks on track, it takes longer time to evaporate (I guess due to the higher boiling point).

Here's a comparison of one hot lap, starting from a cool down lap. New coolant/new iat = 100% coolant. Old coolant/iat = 50/50

datazap.me | Asbjoern | Temp comparison log

datazap.me

As you can see, the peak coolant temperature is about the same.

I have heard some race cars use water and some use 100% coolant. But most of them have very large radiators so it doesn't matter in terms of cooling performance.

 

[Traf]

Cooling system is under pressure anyway, boiling point will be higher than 100c.
Coolant is harder to pump also, frankly i can't see any reason to use 100% coolant.

As for your logs, peak temps are the same but it seems after it heats up, 50/50 temps a generally lower.

 

[RSL]

Always interested to see how these changes actually perform in the real world, looking forward to results.

 

[Asbjorn]

New coolers went in today. Unfortunately my supplier made a mistake, and used the same core thickness as previously. As I didn't want to wait one additional month to have a new one made, it went in as is. The new size offers two advantages. Firstly it is 18% wider, offering better cooling by itself. Secondly the core now has almost the same width as the condenser and CSF radiator, so the end-tanks no longer hinder air-flow to those coolers.

Auxiliary Radiator	Old	New
Rows	31	33
Core dimensions	540 x 341 x 40mm	640 x 341 x 40
Change		18% larger
Configuration	Series	Series
Coolant	100% Coolant	50/50 coolant water

We also installed new oil coolers on both sides. The one on the passenger's side was a bit too large, pushing down on the front bumber. Any hit to the bumper would have been felt by that cooler. I did not feel comfortable about this.
Then, for reasons of symmetry and unknown mental disorders, the other oil cooler on the driver's side (that works with the semi-dry oil sump system) was enlarged as well...

The total increase in oil cooler area is 6%, while the number of rows was doubled. I am not sure which oil cooler design is best, but I had to go with the new style to get the exact height I wanted.

Passenger's side	Old	New
Number of rows	15	25
Dimensions	290 x 210 x 50mm	290 x 184 x 50mm
Change		12% smaller
Driver's side	Old	New
Number of rows	10	25
Dimensions	290 x 136 x 50mm	290 x 184 x 50mm
Change		35% larger

Old

New

 

[Traf]

I'm about to add a aux cooler for the coolant too, it's starting to get hot and i see temps climbing a bit high.
Do you see frost where you live ?

 

[Asbjorn]

I'm about to add a aux cooler for the coolant too, it's starting to get hot and i see temps climbing a bit high.
Do you see frost where you live ?

You generally don't need upgraded coolers for the street. What temps do you experience? My dct cooler and driver's side cooler is basically only activated for track driving. How do you plan to install an auxiliary radiator?

And yes my car occasionally sees frost, which is also why I need to run oem thermostats now. Coolant and oil heats up just fine even with upgraded coolers as long as the oem thermostat and OEM temp set points are untouched.

No matter what you do, please don't get the csf rad. It doesn't help based on my testing, and there are reliability issues according to others.

 

[Traf]

I have a oil2water exchanger, i see water going well above 110 and oil above 125.
I need to beef up the cooling system, not gonna run a CSF rad, aux rad will do the trick.

 

[SamJB]

Absolutely no problem!

Another short update on the build:

Modified driver's side muffler

I find that the Z4 35i sounds much better from the passenger seat when a friend drives it top down. Ever since I experienced this for the first time, I wanted that sound on the drivers side. Now, since the muffler is much smaller on the passenger side, and even has an exhaust valve, I figured these must be the reasons for the difference in sound. I also assume the 35is has a different drivers' side muffler with less sound dampening to amend some of this.

Now how would one solve this problem then? One option would be to get a used 35is muffler. Another option would be to get a set of aftermarket mufflers, but who knows how they sound? A third option would be to cut open the drivers side muffler and simply modify it inside. However based on my experience driving with the golf-tea mod for just one day, I definitely still want the exhaust to be able to quiet down on highways.

The best solution then? Probably just getting another used passenger side muffler, and see if it can be installed on the drivers side, running an extra vacuum line.

And so I did:

View attachment 21585


View attachment 21586


View attachment 21584


View attachment 21583

Now the only problem with this setup is that the muffler had to be turned up-side down. Hence there is a risk the exhaust valve actuator hits something some day. But otherwise I am very happy with the result. Car sounds noticeably meatier when the valves are open. Now I just need to wait for the rain to stop, so I can get the top down and enjoy it.

I was looking at doing exactly this to my 35i when I came across your thread. Could I ask if there's any problem in a reduction of exhaust flow when running with both actuators closed?

The vacuum line runs up to a small solenoid valve in the left hand side of the boot, I'm thinking it would be possible to wire that solenoid up to a switch in the cabin so you'd have a fully switchable exhaust using factory mufflers. My only concern is that there might be too much back pressure caused by the small pipes that all of the exhaust gas' would have to go through when the actuators are closed. If you've had no problems however then it could be worth doing?

 

[Asbjorn]

I was looking at doing exactly this to my 35i when I came across your thread. Could I ask if there's any problem in a reduction of exhaust flow when running with both actuators closed?

The vacuum line runs up to a small solenoid valve in the left hand side of the boot, I'm thinking it would be possible to wire that solenoid up to a switch in the cabin so you'd have a fully switchable exhaust using factory mufflers. My only concern is that there might be too much back pressure caused by the small pipes that all of the exhaust gas' would have to go through when the actuators are closed. If you've had no problems however then it could be worth doing?

When the actuators are closed, yes there is too much back pressure. No problem during normal cruising, but at WOT boost builds much slower than normal. Im down like 5psi at 4k rpm. WOT log here:

datazap.me | Asbjoern | BQ v20 with air leak sound

datazap.me

Never tried pulling to red-line with actuators closed, because it just feels wrong. All you can hear is intake noise. No exhaust haha.

But the actuators should not be closed at WOT. Normally they should open as you start to step on it.

Mine had problems opening sometimes. I do not know why, and I do not know if it was a problem my car already had before I installed the muffler. But it was certainly there after I installed the muffler. Especially when going WOT from low RPM, the actuators would just never open. Then I could release the throttle and step on it again, and they would open properly.

After I found this problem I pinched the vacuum lines to the actuators, keeping them open at all times. After a few weeks of driving like this, I opened the vacuum lines again, and now they pull vacuum constantly keeping the actuators closed no matter how I drive. Again, no idea why. Something has broken.

Next week I plan to pinch the vacuum going to the solenoid valve, in case it has failed and is leaking. Then I have bought a remote controlled vacuum generator box that I intend to use to open and close the valves from the cabin.
I will be driving with the actuators open 99% of the time, but for long distance high-way cruising, just listening to music with the top up, being able to close them adds comfort. The exhaust is much quieter than stock with the actuators closed, and a bit louder than stock when open. There's a huge differnce, and honestly it sounds a bit silly when they close going from 2nd into 3rd with the OEM control. As it is now, I would have liked them to only close in 7th gear. But since something broke, instead of trying to code that, I will use a manual control.

 

[SamJB]

That's some helpful information, many thanks. That is a huge amount down in fact! I wonder if the majority of the added pressure is from the route gas' are forced to take through the muffler or if it's from trying to cram it all through what must be a 1 inch pipe?
That small pipe could be removed entirely, drill out a larger hole in its place and weld in a full size pipe to have two exhaust tips per muffler?

A great thread by the way, I've also got the M3 suspension components fitted and couldn't believe how much extra mechanical grip the car found with them. The standard Z4 parts must deflex like crazy in comparison.

 

[Asbjorn]

That's some helpful information, many thanks. That is a huge amount down in fact! I wonder if the majority of the added pressure is from the route gas' are forced to take through the muffler or if it's from trying to cram it all through what must be a 1 inch pipe?
That small pipe could be removed entirely, drill out a larger hole in its place and weld in a full size pipe to have two exhaust tips per muffler?

A great thread by the way, I've also got the M3 suspension components fitted and couldn't believe how much extra mechanical grip the car found with them. The standard Z4 parts must deflex like crazy in comparison.

I wouldn't know if it is related to the muffler route or the pipe. But since it is a smaller muffler than the driver's side muffler, yet offers better sound dampening, I assume it is muffler related. On a side note, my driver's size exhaust now sounds ever so slightly louder than the other, and I speculate it is because the pipe is less restricted on that side. There is a small section on the passenger's side close to the differential that narrows down. I want to try and change that.

 

[Asbjorn]

I have a oil2water exchanger, i see water going well above 110 and oil above 125.
I need to beef up the cooling system, not gonna run a CSF rad, aux rad will do the trick.

How do you plan to do aux radiator?
Your oil temp seems more than OK, but your water is a bit high if it reaches 110C during track driving.
If 110C happens on the road going slowly - probably no worries. If the DME detects "ECO" driving, I believe it targets 108C coolant. During spirited driving it targets 90-95C.

 

[Traf]

I will put the rad passenger side fender and use the oil2water exchanger water line.

 

[Asbjorn]

Quick update on the build

EBC orange stuff & slick tires
I took the car to participate in a 1hr endurance race. Had the front rotors resurfaced and installed the EBC orangestuff pads both front and rear. Drove around for 1000km or so to try and bed in the pads. They never started biting on the street. As I entered qualifying I still had no braking, and the brake pedal almost hit the floor a few times. After a lap tor two, the pads would bite at first, scrub off some speed, and then loose all bite at low speeds entering corners. I went around like this for a few laps and eventually gave up on setting a fast lap as I had lost all confidence in the setup.

After that experience I talked to some other drivers, and they told me it is normal for racepads to not bite when cold. Also newly resurfaced rotors don't offer the same friction as polished ones.

Alright, so during the race safety car start, I basically just slammed on the brakes a few times, and suddenly they started biting... HARD! I was on slick tires for the first time as well, and the combination offered absolutely mind blowing stopping power. Holy moly what an experince.

Unfortunately I then got a boost leak (a clamp broke) and misfire on cyl 2 on the second lap... did a few limping laps, and then that was the end of that. Amazing grip, mind blowing braking, no power... I went back to AD08R tires and EBC yellowstuff pads before going back on the street, and I must admit that @barry@3DM was right. In the end you just cant use the same pads and tires on street and track.

BTW, I noticed my brake pedal gets very hard after parking overnight. I had the same issue a year back. Then it disappeared somehow. Now it is back. It really puzzles me. My brake fluid is a bit overfilled (pushed the pistons in to install the new pads, so the fluid level went above max). Wondering if that could be the reason.

Yellow vs Orangestuff:

Pirelli slicks

The new coolers
Well I see a small improvement overall for both oil and coolant temps, but the underlying problem is still there. Temps rise slowly but surely if I push the car on track.

The AC definitely also gives up earlier now with the bigger radiator in front of the condenser. The fan and compressor is working overtime during slow city driving, and on track I loose AC when coolant hits around 105C. Fortunately no problems when just cruising on highways.

Anyway, one day I should install an auxiliary radiator where one of the oil coolers is now.

AiM Solo 2 DL
Laptimer with datalogging - awesome device. I use it to display lap-time and coolant temp on track. Also the LEDs on the sides light up according to my predictive lap time so I can see if I am ahead or behind mid-lap.
It is currently OBD connected which I found isn't ideal. It needs to be CAN bus connected to be able to log brake pressure etc on a E89 Z4.

Anyway, first up is diagnosing what is causing this new hiccup:

datazap.me | Asbjoern | v22

datazap.me

 

[derekgates]

Fantastic update! Looks like some learning experiences were had.

Looks like fun out there.

 

[Asbjorn]

So the hiccup shown in the log above turned out to be a loose spark plug in cylinder 2. All plugs were replaced 1000km ago, and it probably wasn't tightened properly at that time. Of course the problem only decided to show up during lap 2 of the endurance race. Not two days before. Not when during WOT logging. Not when we installed the plugs. No on lap 2. Sure.

Then due to extreme incompetence during troubleshooting, we swapped injectors without replacing injector seals. Now my fuel trims are off. Car has been driven like this for maybe 2hrs in total, so hopefully no permanent damaged has been done. Tomorrow new seals go in and hopefully the head survived. Definitely not getting much sleep until then...

In the meantime I had this made

This is my old VRSF 7.5 HD intercooler with the stepped part now removed. This FMIC is to replace my current 7in nonHD "china" FMIC which has turned out to be a surprisingly bad performer - even though I run relatively low power. Naturally, I then wanted the 7in HD FMIC because it fits perfectly below the auxiliary radiator, while offering better cooling compared to the nonHD 7in. However, given that I am based in China, and the HD versions apparently aren't produced here, this was just easier...

 

[Asbjorn]

So it seems the car survived the injector stunt. All index 12s are now back in with new compressed seals.

Alright, I have now confirmed that EBC orange stuff is a much better 1hr endurance pad than PB race pads. They feel absolutely fantastic as soon as you get enough heat into them. They dont work on street though.

I have a reoccuring problem where chargepipe clamps keeps getting loose as soon as I am near a track. I have decided to try out the revshift motor mounts, but not sure what the lead-time is. I have also ordered poly rtabs to replace my current M rtabs with limiters. This because the rear end feels a bit wobbly on braking and hard acceleration, and the rtabs are the only big rubber bushings left on the car.

As for other next steps, I still have a major cooling bottleneck. As pointed out by @Bnks334 I need better ducting to the coolers. I would also like to try and run a helper coolant pump. I would then switch this on together with the DCT and oil pan oil pumps whenever I enter a track. On the road I would then keep it off in order to avoid the problem where my AC stops working because the condensor behind the first radiator doesnt get enough cooling. I have bought a 3600L/h pump with 38mm aluminum in/outlets. I have also bought another 25row cooler that I intend to install in front of the oil cooler for the semi-dry oil sump.

Here's my idea on how to run the system. When the helper pump is off, water wont pass through it. If the OEM pump is off and the helper pump is on, the water will just run through a closed loop.

Do you see any issues with this setup?

 

[Lurcher]

More fluid flow only helps if the system is capable of the heat leaving due to air flow, or you get heat soaked. I know you went bigger radiator (caused other issues). Did you ever look at the higher wattage fans from the 1 series? I know some guys trim the plastic in front of the intercoolers thinking no big deal, but it's a high pressure area, but that only works when the car is moving. Sealing up any openings allowing air to leak around the radiator will help, but probably have that covered already. That's the extent of my CFD knowledge....

Getting to that point of needing hood vents.....