Depends what you want to achieve: Track specific gains, power, aesthetics or make it drive like it was when it was new?
TBH a refresh of elements will make a huge difference to start with.
- Suspension for one, inevitably, whether its low milage or not it will be past its best, struts often loose air, suspension is crashy as is but can be much worse, springs are renowned for snapping and this is because the struts arent doing their job. A good fully adjustable kit will make a huge difference.
- Brakes are also a big one, stopping power increases lap times. A bigger brake kit and braided lines loads of options. Good tyres and lighter wheels are probably the best place to loose weight and add stickiness. Decreses unsprung mass and rotational inertia makes a big difference in turn in and braking.
- Steering feel is a big one too, you could retrofit the hydraulic steering from the Z4M to the car which will make a huge difference in feel.
- Add an LSD will completely transform the car and with suspension, brakes and wheels will make it feel a much more direct connected car to drive.
- Putting in a set of carbon race seats will reduce the weight of the car considerably. Pretty sure heated electric seats in the Z are around 50kg for the pair and for going quickly the sports seats arent great.
- You could introduce a much smaller lighterweight battery to further reduce weight.
- Exhaust system
- Air intake, with the exhaust system you can remap to get a better power curve car breathes better etc
You could easily spend 10k doing the list above with good components.
The thing about spending 10k is that your unlikely to see it back, even with the mods you add they wont add value. If they do it will be to a very niche audience when the Z4 is already super niche. So worth knowing that going into it. If its a keeper then no worries but another thing to think about is buying something more specific to the needs your after than making a Z4 into a sharper tool.
Adding power is another thing altogether, 300ish hp is a pretty good number in a stiff car and getting some driver training will well improve your speed far more than power. Loads of options super chargers etc but they are costly and need a lot of fine tuning its not just plug and play as far as im aware. A few people here have done it so im sure they will chime in.
Again depends what you want to do with it.
Could buy an M but again the Ms will need quite a few of the above elements to get it to be more focused as they suffer the same issues. Suspension, brakes, exhaust and air intake. They just have the nicer aesthetic elements and of course the S54 which is an awesome engine.
North West Surrey
