Liam's Z4C race car project

[Liam22]

Here's a build thread for my Z4 3.0si Coupe race car.

For the last 4 years I've been racing a Mazda RX8 in 750MC Roadsports and Club Enduro.


Before that I did 10 years in the Production BMW Championship (E30 320i).


Since the engine went pop in the RX8 last summer (after 30 races I might add) I've had an itch to go up a class in Roadsports. Always liked the Z4 coupe, and when I was searching the market for cars able to get to 240bhp/ton (@flywheel) it was by far the most interesting option. Not the cheapest though... I couldn't believe how much low mileage cars were going for.

Eventually I found this late 2007 example, with 107k miles on the clock and my ideal spec. No cruise, no satnav, no parking sensors. But piano black trim and nice wheels that I can sell to help fund the build. I paid £6500.


My plan for the build is this:

1. Brakes, suspension, bushes, all fluids, etc
2. Take it for a run around the Nurburgring while it's still road legal
3. Strip, roll cage, race safety equipment

I've decided not to take it back to a bare shell, mostly because it's just too much work. I do everything myself (except welding and painting) so I need to be sensible about how much I take on.

So let's get started!

 

[Liam22]

Since the RX8 sold I've been researching upgrade options and stockpiling parts. There are parcels arriving every day at the moment!

The first job was a simple oil service. Had some difficulty getting the car safely up onto axle stands until I realised that the front crossmember is accessible after removing the undertrays. I'll be cutting a hole in the undertray for quick access to that jacking point before it goes back on.

While the engine oil was draining I inspected/cleaned the DISA valve and both VANOS solenoids. The sound generator is a hideous thing. I'm going to look into a direct hose from airbox to throttle body so that I can ditch the entire sound generator, but that can wait until I strip the interior.


The K&N panel filter got replaced with an OEM paper filter. I'd sooner replace the air filter every 6-7 races than worry about keeping the K&N properly oiled.

 

[Liam22]

Next up, front suspension removal.

Things were going very well until I tried to remove the OSF brake disc. What sort of idiot re-fits a rounded-off, allen head, disc retaining bolt? I tried hammering in an oversized Torx bit, but the bolt was already cheese and it quickly became fully circular.

So out with the drill bits…

Other than that, everything else has come apart fairly easily. Although I'm having horrible E30 flashbacks of removing front control arm ball joints. Is there still no way of doing this without splitting the boots?


The tapered springs also meant that my spring compressors could only get hold of the middle coils which wasn't enough to take all of the tension off the damper. Thankfully, by the time I loosened the top nut off, it was almost out of tension and didn't explode

ARB is also off. I bought an E46 M3 convertible (27mm) item to go back on when the bushes arrive.

Just the steering rack to remove from the front end now. I want to remove the electric motor and run it as a manual rack to see if I can live with it like that. I can't see the motor though… where's that hiding?!

 

[Mr Tidy]

I'm going to enjoy reading how this develops!

Particularly looking forward to seeing how you sort the steering - I assume you're thinking of HPAS instead of EPAS? Or will you run it without PAS - might be OK on a race car.

My E91 has an N52 engine but HPAS, and it's just so much better than the EPAS on my Z4C so a conversion would be very tempting.

 

[buzyg]

Good start. Interesting read too. Enjoy your new project. Especially :driving:

 

[philbo909]

cracking project, looking forward to seeing how it goes on
plenty of people on here would buy the sound generator of you I'd imagine. worth sticking it on.
the 19" wheels really dwarf the brake discs, they look so small, mine's only on 17" at the moment and they fill the wheel

 

[Jembo]

Great thread... looking forward to hear how you’ll get on... trust you know to poly the RTAB’s & maybe even add RTAL’s

 

[Doddsy]

Duck lake view put a post on Instagram under the zed shed recently about converting his EPAS. Might be worth asking him.

 

[Mr Tidy]

Yes, but dlv has a pre-facelift so it has the M54 engine.

Liam22's Coupe is a facelift with the N52 engine, so it's not going to be quite the same.

 

[Doddsy]

My bad for some reason I thought DLV had a facelift car

 

[TomK]

Great thread... looking forward to hear how you’ll get on... trust you know to poly the RTAB’s & maybe even add RTAL’s

Definitely DON'T poly the RTABS would be my advice! Ruins the handling imo.
Limiters on oem rtabs yes.
I've done both back to back.
GuidoK will be along shortly to tell me I'm wrong no doubt....
But really since #racecar the correct thing is to monoball it.

 

[TomK]

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[firebobby]

This looks interesting. You will get many ££££s back from interior parts, the seats will sell easy, multi function steering wheel, trim parts. All the removed parts will find new homes on here.

 

[Jembo]

Great thread... looking forward to hear how you’ll get on... trust you know to poly the RTAB’s & maybe even add RTAL’s

Definitely DON'T poly the RTABS would be my advice! Ruins the handling imo.
Limiters on oem rtabs yes.
I've done both back to back.
GuidoK will be along shortly to tell me I'm wrong no doubt....
But really since #racecar the correct thing is to monoball it.

Another topic almost as divisive as Whippy vs Stubby or Couoe vs Roadster... polying the RTA’s change the way the @rse handles, some love, some loathe & some creak

 

[AveZ4coop]

Looks exciting, shall be following this with interest.

 

[JonLeeper]

Great thread... looking forward to hear how you’ll get on... trust you know to poly the RTAB’s & maybe even add RTAL’s

Definitely DON'T poly the RTABS would be my advice! Ruins the handling imo.
Limiters on oem rtabs yes.
I've done both back to back.
GuidoK will be along shortly to tell me I'm wrong no doubt....
But really since #racecar the correct thing is to monoball it.

Another topic almost as divisive as Whippy vs Stubby or Couoe vs Roadster... polying the RTA’s change the way the @rse handles, some love, some loathe & some creak

I've just had all of the bushes replaced on my Z4C with poly. . Mainly the purple road spec but I got Rogue Engineering RTABs. I also had the Rogue rear strut mounts, a b12 kit and new anti-roll bars at the same time. I'm not 100% sure which has made the lost difference ebut the car is transformed.

 

[Jembo]

Definitely DON'T poly the RTABS would be my advice! Ruins the handling imo.
Limiters on oem rtabs yes.
I've done both back to back.
GuidoK will be along shortly to tell me I'm wrong no doubt....
But really since #racecar the correct thing is to monoball it.

Another topic almost as divisive as Whippy vs Stubby or Couoe vs Roadster... polying the RTA’s change the way the @rse handles, some love, some loathe & some creak

I've just had all of the bushes replaced on my Z4C with poly. . Mainly the purple road spec but I got Rogue Engineering RTABs. I also had the Rogue rear strut mounts, a b12 kit and new anti-roll bars at the same time. I'm not 100% sure which has made the lost difference ebut the car is transformed.

Doing that is about 80% of the way there, the other 20% being the geo & what you’ve done with the front.

Suggest u Check your drop links, especially the rears as they take a lot of abuse, though other than the tie rod ends think ur a long way there

One last suggestion is to consider removing the tailgate in its entirety, replacing it with a fibreglass replica& a monster spoiler - if u remove one of the grass struts you’ll see just how much weight is in it

 

[Liam22]

Interesting discussion about rear trailing arm options. I've ordered Strongflex sport bushes to replace most of the rear end. PowerFlex black series for the front control arm. Rear control arms will be replaced with adjustable items with spherical bearings.

Started to disassemble the rear today. I'm sure I'm doing things in the wrong order, but I'm slowly getting there. Couldn't believe how much of the boot needed to come out just to get to the damper top mounts. Currently debating whether I can keep the drive shafts attached to the trailing arms when they come off the car. Any guides for this? As usual, the TIS leaves me frustrated.

 

[Liam22]

Slowly getting to know how the rear corners fit together.

I *am* going to try to keep the driveshafts connected to the trailing arms. Any tips on detaching the cables that route through the trailing arm? Other than that it's about ready to drop.

Still haven't figured out how the rear wheel alignment is adjusted...

 

[JDavis21]

Still haven't figured out how the rear wheel alignment is adjusted...

That should become quite obvious once you have the trailing arms and brackets off :wink:

Whereabouts in Cambs are you? Happy to lend a hand if there's any two man jobs as I'm quite interested to see the end result!

As for bushes, I'd recommend the Millway Motorsports kit over anything poly - although poly arb bushes will have to do.

Below is my R53 MINI Challenge car that I ran for three years, spherical mountings all round improved predictability no end.