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      04-14-2015, 08:57 PM   #1
BGR
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Z4C Track Build Thread

I posted some tidbits here and there about my plans for the car, but wanted to start an official build thread.

A little about me: I've been racing sportbikes for the last 8 years and instructing the last 3, but just got into track driving in a car last year. I know this Z4c isn't the most typical "track" car, but I love the looks and how engaging it is to drive. It is way more fun and nimble than the 135i that I sold last summer. I've owned a number of sporty cars, but never had a car where the majority of the driving will be track based.

Vehicle
-2007 Z4 Coupe
-One previous owner
-85k on the clock when I bought it

Phase 1 mods, completed 4/14/15
-Breyton GTS-R wheels
-12mm spacers up front, 10mm rear
-Koni double adjustable/H&R springs
-Wheel spacers for the Breyton wheels
-4 new OEM wheel roundels (3hp each)
-SS brake lines/RBF600 fluid
-FrozenRotors slotted front brake discs
-Hawk front pads
-New OEM floor mats (10hp each)


Phase 2 mods, purchased and waiting to install
-M steering wheel
-aFe air filter
-ZHP shift knob
-3.91 LSD from Jim at Performance Gearing


Phase 3 mods, under consideration
-Full coilovers
-8.5" front wheel
-???


Original



With just the wheels




Phase 1, 4/14/15

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      04-14-2015, 08:57 PM   #2
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      04-15-2015, 11:22 AM   #3
bibbly
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i don't want to pee in your cornflakes, but get an oil analysis done and check your rod bearings. although my oil analysis was fine, the rod bearings were into the copper at 47k miles. they really are a sacrificial part.....and much cheaper than crank work/replacement
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      04-15-2015, 11:25 AM   #4
NickyC
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Quote:
Originally Posted by bibbly View Post
i don't want to pee in your cornflakes, but get an oil analysis done and check your rod bearings. although my oil analysis was fine, the rod bearings were into the copper at 47k miles. they really are a sacrificial part.....and much cheaper than crank work/replacement
He doesn't have an S54 though.
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      04-15-2015, 12:24 PM   #5
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Correct. N52 goodness.
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      04-15-2015, 02:55 PM   #6
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Quote:
Originally Posted by NickyC View Post
He doesn't have an S54 though.
I think he saw "Z4C" and "track" and automatically thought M.

BGR: Looks good, but by the time you're done with Phase 3 or 4, you could've just bought a Z4M for the same price. Obviously as an enthusiast you're probably doing it for the fun of modding, not to turn the 3.0si into something that can outperform a stock Z4M on the track. What's the 8.5" front wheel in Phase 3? You just put on new wheels...
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      04-15-2015, 06:31 PM   #7
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Quote:
Originally Posted by Twixboy View Post
I think he saw "Z4C" and "track" and automatically thought M.

BGR: Looks good, but by the time you're done with Phase 3 or 4, you could've just bought a Z4M for the same price. Obviously as an enthusiast you're probably doing it for the fun of modding, not to turn the 3.0si into something that can outperform a stock Z4M on the track. What's the 8.5" front wheel in Phase 3? You just put on new wheels...
The current fronts are only 7.5". My goal is to find another pair of rears like the ones on the car and use them for the front.

Right now I'm at $20k total including car, parts, and install costs. After phase 2 gets installed, this car will be more capable on the track than a stock Z4M, with lower insurance and upkeep costs. And like you said, this is more of a unique, enthusiast project. I've never gone "all out" building a track car so it is fun for me.

Also, for what it's worth, the dealer I bought the car from includes a lifetime powertrain warranty with used cars under 100k miles. I think my rear flex disc and/or center support bearing/driveshaft is on its way out so we will see how easy they are to work with when it comes to
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      04-17-2015, 11:26 AM   #8
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Completed the muffler delete last night. Sounds pretty darn good; almost zero drone and looks OEM from the back.

Compared to the Berk Race Exhaust (basically a muffler delete) on my 135i, this is a touch louder and more raw, likely because there are no turbos muting it. If I had to describe the sound, I would liken it to half of a Ferrari 250 GTO.

Here are some pics, and I will try to get a sound clip tonight.





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      04-17-2015, 11:58 AM   #9
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While you're crawling around under the car, take a look at the front control arm bushings and the rear trailing arm bushings. Depending on the mileage, those may be in need of some attention.

I really like the Tree House Racing front control arm brackets and bushing on my car, but it looks like those are NLA, and Bimmerworld now actually has a slightly cheaper alternative--

http://store.bimmerworld.com/bimmerw...nts-p1301.aspx

They also have a bearing set to replace the rear trailing arm bushings. I don't have any first hand experience with these though.

http://store.bimmerworld.com/bimmerw...kit-p2138.aspx

Before I refreshed the RTABs and put in companion limiters, I got a kind of "wiggle" out of the rear end between when the chassis finished rolling and the rear end took a set. Went away when addressed.

Other track related suspension wear issues I've had over the 90,000 total miles I've put on the car are a rupture in the driver's side strut bearing and the inner ball joint on the same side front control arm-- seems to be more right turns than lefts at the track.

Strut bearing issue addressed by installing adjustable camber plates-- not much to do about the ball joint except replacement.
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      04-17-2015, 12:08 PM   #10
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Are you keeping the original wheels?

Steve
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      04-17-2015, 02:20 PM   #11
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Quote:
Originally Posted by ShakyDog View Post
Are you keeping the original wheels?

Steve
That was the plan for whenever I sell the car. They have brand new tires on them as well.
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      04-17-2015, 02:20 PM   #12
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Quote:
Originally Posted by Karacticus View Post
While you're crawling around under the car, take a look at the front control arm bushings and the rear trailing arm bushings. Depending on the mileage, those may be in need of some attention.

I really like the Tree House Racing front control arm brackets and bushing on my car, but it looks like those are NLA, and Bimmerworld now actually has a slightly cheaper alternative--

http://store.bimmerworld.com/bimmerw...nts-p1301.aspx

They also have a bearing set to replace the rear trailing arm bushings. I don't have any first hand experience with these though.

http://store.bimmerworld.com/bimmerw...kit-p2138.aspx

Before I refreshed the RTABs and put in companion limiters, I got a kind of "wiggle" out of the rear end between when the chassis finished rolling and the rear end took a set. Went away when addressed.

Other track related suspension wear issues I've had over the 90,000 total miles I've put on the car are a rupture in the driver's side strut bearing and the inner ball joint on the same side front control arm-- seems to be more right turns than lefts at the track.

Strut bearing issue addressed by installing adjustable camber plates-- not much to do about the ball joint except replacement.
Great info. Any idea if there are upgradable diff mounts? Since it will all be apart anyway I would like to be able to do those at the same time.
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      04-17-2015, 03:59 PM   #13
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No info on the diff mounts, but if it's coming out, and there's significant mileage on the car, I doubt there's much point in leaving the old ones in.

If you're dropping all that stuff out, it's also a pretty good time to refresh the stabilizer bar end links and bushings too. Access to change out the end links is much easier with the axles and exhaust system out of the way. That stuff doesn't need to come out to do it though.

When you got the diff redone, did you manage a mod or exchange to get a unit with a drain plug? Mine just has the fill hole, so I have to suction out everything I can.
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      04-17-2015, 06:55 PM   #14
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Mediocre video/sound clip of the exhaust. Sounds a lot more raspy in the clip than in person.

(Disregard the safety wire. It is temporary until I get the hanger welded on tomorrow)


Last edited by BGR; 04-18-2015 at 12:54 PM.
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