Z4 3.0 Track car build

O

oalloyd1

Member
Hey all,

I'm new here and have just bought my first Z4 as a track car build project. She's a beaut and even has a hard-top which should help with some rigidity (there's teh first mod sorted then :thumbsup: )

Z4.jpg

I'm not very rich right now so looking to do it on a budget. My initial thoughts for improvements once I have given it a shake-down at my local track are;

1. E46 330 brake upgrade (325mm / 320mm) front and rear with extra brake cooling through foglight removal and trunking
2. Shorter ratio diff
3. Coilovers
4. ARB's
5. Camber arms
6. Track tyres (RSR's or similar)
7. Square set-up and lightweight wheels (Pro-race 1.2's preferably)
8. Full geo set-up

No plans for extra BHP yet but a remap would be good to increase the torque slightly.

Any tips on sourcing good used parts would be appreciated plus anything I should check for specifically when preparing the car for the track.

Cheers in advance, i'm looking forward to contributing and sharing my experiences on this jouney,

o :)
 
Are you putting an LSD in, or just shortening the standard open diff?

I'd also recommend putting in a decent bucket seat, to stop you sliding around everywhere.
 
Replace the RTAB's with a proper balljoint http://www.bimmerworld.com/Suspension-Steering/E46-E36-3-Series-and-Z4-Rear-Trailing-Arm-Bearing-Kit.html.

Replace the lower rear upright bush with the same bearing used in the top (as per M3/Z spec).

Install offset Z4M TCA bushes to increase castor.

buy as many different thickness front anti roll bars that fit a Z4, reinforce AR bar mounting points and run the bar in Delrin bearings with adjustable pick ups for the drop links.

reinforce the turret mountings and rear damper mountings with plates.

LSD essential and bin the rear anti roll bar.

Remove the ABS pump and plumbing, install a bias adjustable pedal box and Aeroquip the car front to back.

Lighten the damn thing, waaay to much crap in a Z4 for the track, don't need AC, CD changers, Satnav, carpets, sound proofing, uber heavy seats, strip out the hood and motor if your using a hard top, any weight high up is a big no no, get your seat as low as you can cope with and throw way any plastic trims and covers that don't work for a living!

After that you can start getting radical and reset the geometry to suit the tyres :evil:
 
Don't bother with camber arms, you need camber plates for the front. It's not hard to get decent camber on the rear but the front doesn't give much even with the pins out.
 
Cheers guys, some great tips!

Id like a race seat too but worried the subframe / mountings will be too high and I need all the headroom I can get as am 6 foot 5!

How hard would it be to fit an E46 M3 rear end? LSD is attractive..

Will engine ad gearbox poly mounts make a good difference?

Cheers, more feedback on other areas too would be appreciated - Was thinking bigger radiator and water pump with metal impellar as well as an oil cooler too? Are these easy to fit?

Cheers,

o :)
 
Lovely looking Z4 OP - I do like them in Merlot. :thumbsup:

Interesting project you are embarking on - I'm looking forward to updates!

I can't see where you are based from your profile, but there are a couple of forum members in the Surrey area who do track-days in their Coupes so you could do worse than see what they reckon (next planned meet should be 18 June). Both have taken a trip to Birds for a Quaife LSD, but it's a 4 figure price-tag so assuming that it fits an E46 M3 rear end might be a cheaper option!

If you are thinking of bigger brakes, it might be worth getting upgraded discs while you are at it - I know one of the Coupes has just had a set of drilled and grooved Tarox discs fitted as standard ones got way too hot.

This year a new race series for 3 litre Z4s started up, so a visit to a meeting might let you get some useful information. It's also a shame you missed the visit to Gary Feakins Racing at Aldermaston, Berkshire back in March as they prepared some of the cars for that series, but you never know what a phone call or a visit might produce!

Sorry I can't provide any first-hand advice, but good luck with your mods. :thumbsup:
 
E46 m3 rear end will fit. As for a diff you need to get a LSD I have an M Factory diff in mine and love it. I fitted mine myself fairly easy job if your handy with spanners. And there are a few of us hear that have done it and will help with advice.

M3 front ARB will fit just buy the correct bushes. I have done both with polly bushes in most places and limiting washers on the rear trailing arm bushes coilovers and a good geometry set up. The car handles great now.

Don't underestimate how much the LSD will help not only getting power down and being able to rotate the rear of the car. But also front end turn in.

Take weight out also look into swapping the electric steering to hydraulic. Check the cooling system over it's a bit of a weak link on the m54 as is the oil pump. If you going to be doing lots of track days. On early m54 engines the gear that drives the pump has been known to come off. Usually after prolonged high revs. It's thought that engine harmonics can cause the retaining nut to loosen. But I have never known it happen on a z4 not sure if there was a redesign??

Good luck with this it sounds a fun project. Fair few people on hear really know there stuff and are very helpful.

If I where you I would ditch the hard top and buy a LSD. Plus track days with the roof down are great :thumbsup:
 
Great responses guys, thank you!

I still have a standard E46 M3 front ARB in my shed - Could anyone advise what parts I would need to fit this to my car? Also, no rear arb? Would I just be better off getting a full H&R front and rear ARB kit? Costs £300+ though which i'd rather spend on half decent coilovers.

With regards to cooling - Has anyone fitted an uprated radiator to theirs or fitted a different water pump? Does the standard Z4 one have the dreaded plastic impeller?

Also, would anyone recommend fitting a new oil pump as a precautionary measure or just take the sump off to check the toque of the retaining nut described?

I take it if I fit an E46 M3 rear end it will be all the suspension, arms etc too of will the Z4 stuff attached to the M3 subframe and diff? Are all the subframe mounting points the same for E85 vs E46 M3?

So many questions but luckily so many knowledgeable and great people on here - thanks so much guys :)

o
 
oalloyd1 said:
Great responses guys, thank you!

I still have a standard E46 M3 front ARB in my shed - Could anyone advise what parts I would need to fit this to my car? Also, no rear arb? Would I just be better off getting a full H&R front and rear ARB kit? Costs £300+ though which i'd rather spend on half decent coilovers.

With regards to cooling - Has anyone fitted an uprated radiator to theirs or fitted a different water pump? Does the standard Z4 one have the dreaded plastic impeller?

Also, would anyone recommend fitting a new oil pump as a precautionary measure or just take the sump off to check the toque of the retaining nut described?

I take it if I fit an E46 M3 rear end it will be all the suspension, arms etc too of will the Z4 stuff attached to the M3 subframe and diff? Are all the subframe mounting points the same for E85 vs E46 M3?

So many questions but luckily so many knowledgeable and great people on here - thanks so much guys :)

o
Click to expand...


You just need new ARB bushes for it to fit. I haven’t upgraded the rear yet I do have one waiting to go on. If you wait things become available on hear.

The oil pump can be modded to make it safe look it up. I will be doing mine at some point. If you take yours off and send it to me i will mod it for you.
 
Cheers MM! WHat rear ARB will go on? E46 M3 also? I have one of those too.

The oil mod may be useful i'll stay in touch and have also been your comment about LSD - I think you may be right, I should consider biting the bullett..

Have you done the brake-cooling mod yet? Also, will the standard cooling system be ok on track?

Best,

Owen
 
oalloyd1 said:
Great responses guys, thank you!

I still have a standard E46 M3 front ARB in my shed - Could anyone advise what parts I would need to fit this to my car? Also, no rear arb? Would I just be better off getting a full H&R front and rear ARB kit? Costs £300+ though which i'd rather spend on half decent coilovers.

With regards to cooling - Has anyone fitted an uprated radiator to theirs or fitted a different water pump? Does the standard Z4 one have the dreaded plastic impeller?

Also, would anyone recommend fitting a new oil pump as a precautionary measure or just take the sump off to check the toque of the retaining nut described?

I take it if I fit an E46 M3 rear end it will be all the suspension, arms etc too of will the Z4 stuff attached to the M3 subframe and diff? Are all the subframe mounting points the same for E85 vs E46 M3?

So many questions but luckily so many knowledgeable and great people on here - thanks so much guys :)

o
Click to expand...

Standard anti roll bars are designed for use with the softer road springs, if you uprate your springs to a more track oriented setup the AR bars will be too stiff, transferring even more load into the outside tyre and causing carcass deflection resulting in less grip,

The rear anti roll bar unloads the inside wheel causing wheelspin and loss of drive, on both BMWs I have raced (325i E30, 325I compact) the car gave best traction and handling without the rear anti roll bar but with a properly balanced spring set, not aftermarket "kits"

If your using road based tyres then we found a spring frequency of 120cpm (cycles per minute) was the limit, road tyres simply wont take the load race slicks will so you have to limit the weight transfer, in wet conditions we disconnected the front bar also.

If you convert to coilovers that means you can use 2.1/4 or 2.1/2 coil springs on the front which gives you a massive range of rates and lengths to chose from, I'm unclear what you can do on the back as fitting a coilover to the rear means completely changing the loading points for the rear chassis, on our Compact we had springs made to the rate and length required to match the front with a 105cpm front and 110cpm rear then used a combination of damping and adjustable front bar to set the car up for what circuit or hill we were going to.
 
Hey all,

Ok my initial plan of attack is;

1. Complete compression test to check it's ok as a base.

2. If all-clear complete service and check cooling system.

3. Purchase used rear subframe and poly bush it.

4. Purchase used 3.64 diff and get Mfactory LSD fitted.

5. Purchase coilovers (DC racing or Gaz, I can't justify spending more than 700 on them)

6. Purchase full E46 brake set up, suitable pads and braided hoses. Also race fluid at same time.

7. Fit all of the above and replace RTAB's at the same time as well as Z4 M front lower things (dead technical, me) to help camber.

8. Fit E46 front arb

9. Fit team dynamics pro race 1.2 wheels with track tyres

10. Complete geo set-up

Any thoughts,

Cheers!

O
 
If this car is for track use primarily, I would bin the ABS system and use braided lines front to back to eliminate as many joints as possible.

You can make or buy in a bias adjustable cylinder setup for the servo so you can dial the brakes in properly, ABS is fekin awful on the track.
 
Tyre wise if keeping it road legal and driving to and from track try the Yokohama AD08R 's as well priced and work really well wet or dry so no real need for two sets of wheels then to be taken.
Diff wise 3.9 or 4.1 ratios work well ,fit one of these and the car will feel like it's gained another 50 rwhp....quickens acceleration puts you in a nice usable rev range on track , getting good pull out of the corners top end will be reduced but you don't need top speed on track as you have already probably found out.
J C Racing are worth a call about building a diff as many of the BMWRDC use them in the e36 /e46 Kumho cup cars with excellent reliability.
 
The Z4M offset front lower rear bushes are well worth it, they add castor so dynamic camber rather than static but it made a noticeable improvement to mid-corner grip for me. Makes me wonder if I should get camber plates after all as the grip has come from more camber.
 
Steve84N said:
The Z4M offset front lower rear bushes are well worth it, they add castor so dynamic camber rather than static but it made a noticeable improvement to mid-corner grip for me. Makes me wonder if I should get camber plates after all as the grip has come from more camber.
Click to expand...

Only a tyre temperature gauge will tell you how much camber you need, it will be different for most cars and drivers and tracks come to that.

Either way it's important to consider the loads being applied to the top mounts, so if camber is to be increased spherical bearing top mounts may well be required.
 
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