BMW Z4 Modification Guide

By on 22 June 2021 / Leave a comment Updated on: 22nd June 2021

Those that love performance cars also often love to modify them. Taking a car and putting your own stamp on it, making it an extension of your personality. While the BMW Z4 was well engineered and performed exceptionally from the factory, it doesn’t stop anyone wanting to enhance and improve every aspect of the drive. Every manufacturer has their limits, both in budget and design freedom that limit the possibilities of a car, something easily unlocked in the aftermarket.

Power upgrades, handling improvements and style changes can all be implemented to great effect. A BMW Z4 with all those extra flourishes and extras will be that bit more exciting to drive, turning every mundane journey into an experience. This handy guide is designed to help split up the mods available and present how they will enhance, improve or change the driving experience of your BMW Z4.

Power Upgrades

The first place that most modifiers will turn to is increasing engine power. Tuning the engine to increase power and torque output will give instant gratification, improving straight line performance and often vastly changing the character of a vehicle. More power often leads to more noise, more excitement and an increased thrill with every press of the throttle pedal.

BMW Z4 E85/86 (including Z4M) 2003-2009 Power Upgrades

Stage 1 (10-20hp increase)

ECU remap – A remap of the car’s electronic brain. No hardware changes are required, as this upgrade simply reprograms the cars computer with optimum values for timing, fuelling and ignition. An ECU remap allows the car to make the most of high-quality UK fuel, with some maps also adding a few extra revs to increase the reach of each gear.

A stage 1 ECU remap will not only increase power and torque but will change the driving characteristics of the car. Electronic adjustments to the ECU can allow for more progressive power delivery, removal of torque limiters and more to enhance the engines performance and increase driving pleasure.

Stage 2 (15-30hp increase)

Air filter/ induction kit – A simple modification to release some extra power and induction noise at the same time. Whether a simple performance panel filter (placed in the factory location) or cold air induction kit, the idea of this modification is to increase maximum airflow into the engine. This increase in air allows for more fuel to be fired into the engine, creating a bigger combustion and more power. The lesser restriction of airflow is also what creates the increase in sound.

Performance exhaust system – Usually most obvious from the extra noise being emitted and larger/ more exotic tailpipes. Exhaust modifications help increase the flow coming out of the engine, lessening restrictions and allowing for power to be increased as a result. Performance exhaust systems come in many shapes and sizes, use our handy guide to performance exhausts for the BMW Z4 to help make the right choice.

Stage 3 (30+hp increase)

Internal engine modifications – Getting more seriously into engine modifications will require internal components to be replaced. These mods are geared more towards those with good mechanical knowledge or a big enough budget to have professionals perform the upgrades. Camshaft upgrades are a common step, giving increased peak power and a more aggressive torque delivery. Past this, owners may look towards increasing compression ratios or increasing engine volume, though this requires machining work and at this stage owners are more likely to find better performance gains through forced induction.

Forced induction (supercharging/ turbocharging) – The holy grail of performance modifications for naturally aspirated cars, such as the E85/E86 BMW Z4. Forced induction introduces compressed air into the engines intake, via either a turbocharger or supercharger. This vastly increases the efficiency and, when mixed with extra fuel, can create huge increases in performance (at least 30% in most cases).

Introducing these further modifications will also require supporting hardware such as a larger fuel pump, more efficient radiator and improvements throughout the cooling system. It is also recommended that those looking towards stage 3 mods should consider brake upgrades to help rein in that extra power.

BMW Z4 E89 2009-2016 Power Upgrades

Stage 1 (10-100hp increase)

ECU remap – A remap of the car’s electronic brain. No hardware changes are required as this upgrade simply reprograms to cars computer with optimum values for timing, boost pressure, fuelling and ignition. This allows the car to make the most of high-quality UK fuel, with some also adding a few extra revs to increase the reach of each gear. Unlike earlier Z4 models, the E89 can gain huge power through a simple remap thanks to the detuning of lower models from the factory.

A stage 1 ECU remap will not only increase power and torque but will change the driving characteristics of the car. Electronic adjustments to the ECU can allow for more progressive power delivery, removal of torque limiters and more to enhance the engines performance and increase driving pleasure.

Stage 2 (30-120hp increase)

Air filter/ induction kit – A simple modification to release some extra power and induction noise at the same time. Whether a simple performance panel filter (to replace the standard item) or cold air induction kit, the idea of this modification is to increase maximum airflow into the engine. This increase in air allows for more fuel to be mixed also, creating a bigger combustion and more power. The lesser restriction of airflow is also what creates the increase in sound.

Performance exhaust system – Usually most obvious from the extra sound being emitted and larger tailpipes. Exhaust modifications help increase the flow coming out of the turbocharger, lessening restrictions and allowing for power to be increased as a result. Performance exhaust systems come in many shapes and sizes, use our handy guide to performance exhausts for the BMW Z4 to help make the right choice.

It is recommended to have any turbocharged car remapped after these modifications, as they can vastly affect the airflow through the engine, requiring adjustments to set values in order to have a reliable vehicle with the most power possible.

Stage 3 (100+hp increase)

Larger turbocharger – A limitation of most factory vehicles is the size of the turbocharger. Smaller turbos allow for quicker spool, limiting lag and increasing fuel economy. Big power though, requires a large turbocharger. These are expensive purchases and may require further exhaust modifications to fit, meaning consulting a professional is wise if you are inexperienced with turbocharger upgrades.

Internal engine modifications – Big power levels and large amounts of boost pressure put increased stress on internal engine components. Factory parts were not designed or built to handle huge increases in power and hence, can begin to deteriorate and fail with extreme performance modifications. Common upgrades include forged pistons and conrods, giving extra strength and preventing serious engine damage in highly modified vehicles.

Fuel system upgrades – Big power turbocharged cars need lots of fuel, much more than small (yet efficient) factory units can maintain. Kiss fuel economy goodbye, big fuel pumps will fire mass amounts of petrol towards the engine, in order to keep up with demand. This may increase cabin noise slightly too.

Again, like at stage 2, a remap will be required at this junction, in order to maximise the engines output and run safely with all the new hardware.

BMW Z4 G29 2018-Present Power Upgrades

Stage 1 (40-70hp increase)

ECU remap – A remap of the car’s electronic brain. No hardware changes are required as this upgrade simply reprograms to cars computer with optimum values for timing, boost pressure, fuelling and ignition. This allows the car to make the most of high-quality UK fuel, with some also adding a few extra revs to increase the reach of each gear. Unlike early E85/86 Z4 models, the G29 can gain huge power through a simple remap thanks to the detuning of lower models from the factory.

A stage 1 ECU remap will not only increase power and torque but will change the driving characteristics of the car. Electronic adjustments to the ECU can allow for more progressive power delivery, removal of torque limiters and more to enhance the engines performance and increase driving pleasure.

Stage 2 (40-100hp increase)

Air filter/ induction kit – A simple modification to release some extra power and induction noise at the same time. Whether a simple performance panel filter (to replace the standard item) or cold air induction kit, the idea of this modification is to increase maximum airflow into the engine. This increase in air allows for more fuel to be mixed also, creating a bigger combustion and more power. The lesser restriction of airflow is also what creates the increase in sound.

Performance exhaust system – Usually most obvious from the extra sound being emitted and larger tailpipes. Exhaust modifications help increase the flow coming out of the turbocharger, lessening restrictions and allowing for power to be increased as a result. Performance exhaust systems come in many shapes and sizes, use our handy guide to performance exhausts for the BMW Z4 to help make the right choice.

It is recommended to have any turbocharged car remapped after these modifications, as they can vastly affect the airflow through the engine, requiring adjustments to set values in order to have a reliable vehicle with the most power possible.

Stage 3 (100+hp increase)

Larger turbocharger – A limitation of most factory vehicles is the size of the turbocharger. Smaller turbos allow for quicker spool, limiting lag and increasing fuel economy. Big power though, requires a large turbocharger. These are expensive purchases and may require further exhaust modifications to fit, meaning consulting a professional is wise if you are inexperienced with turbocharger upgrades.

Internal engine modifications – Big power levels and large amounts of boost pressure put increased stress on internal engine components. Factory parts were not designed or built to handle huge increases in power and hence, can begin to deteriorate and fail with extreme performance modifications. Common upgrades include forged pistons and conrods, giving extra strength and preventing serious engine damage in highly modified vehicles.

Fuel system upgrades – Big power turbocharged cars need lots of fuel, much more than small (yet efficient) factory units can maintain. Kiss fuel economy goodbye, big fuel pumps will fire mass amounts of petrol towards the engine, in order to keep up with demand. This may increase cabin noise slightly too.

Again, like at stage 2, a remap will be required at this junction, in order to maximise the engines output and run safely with all the new hardware.

Chassis, Handling and Brake Upgrades

Power modifications are great for straight line performance but for an all-round increase, owners need look no further than chassis and handling mods. Particularly important for owners that regularly take their Z4 to track events, where stopping and turning are equally or more important than acceleration.

Coilovers

The ultimate in suspension upgrades. Coilover suspension replaces the entire spring and damper unit, often also including adjustable top mounting plates. This overhaul of the suspension system can give vast upgrades in grip, adjustability and also shed weight with some lightweight materials.

Adjustability of ride height, dampening and camber is often included, allowing you to dial the car into whatever scenario it is being used in. This makes Coilovers highly effective for vehicles used on the racetrack but can also give great performance and lowered looks on the road.

Coilovers can be tricky to decide upon, thanks to the hundreds of variants available for the BMW Z4. Take a look at our BMW Z4 coilover guide for further information.

Lowering Springs

While coilovers are highly effective, they are also largely expensive and can compromise ride comfort on the UK’s famously pothole-ridden roads. Lowering springs are not only cheaper than coilovers but can be paired with standard shock absorbers, creating an almost OEM-level of ride and comfort at a lowered ride height.

Bringing your Z4’s height down by a reasonable amount will still improve looks and give the desired lower centre of gravity, enhancing grip and driver enjoyment. Replacing worn-out springs is something many BMW Z4 owners will face as their car gets older, meaning a replacement with lowered springs is a very viable option.

Our guide on BMW Z4 lowering springs can give further information regarding the benefits and amount of ride height you can chop off, just with a simple spring set.

Strut Braces

Though not obvious from the outside of the vehicle, strut braces and body strengthening can also provide a substantial upgrade to the Z4’s handling characteristics and balance. Favoured by many track users, increased bracing adds extra stiffness to the vehicle, between the suspension mounting points. Increased stiffness and less slack in the steering can enhance turn-in speed, while the decreased body roll gives more confidence through the corners.

Strut braces are a great first handling mod, often requiring just a few simple tools and often can be fitted without removing other parts. Strut braces are available for the front, rear and underside of the BMW Z4, check out our BMW Z4 strut brace article for some more helpful insights and the best products on the market.

Big Brake Kits

Last but by no means last, rounding out the best BMW Z4 chassis mods is a big brake kit. Thanks to it’s sports car credentials, the Z4 comes equipped from the factory with a substantial braking system for a standard car. However, as soon as the mods begin and power/ handling are enhanced, the standard braking system will likely show itself as the first weak link.

Having the ability to stop quickly is not simply better for performance but could also make for a safer car to drive. Old braking components will wear and deteriorate with age, blunting their performance. A big brake kit however, such as those featured in our Z4 big brake kit article, will massively increase stopping power and improve longevity for repeated high-speed braking scenarios.

Though a large outlay is required, there is no better method of improving the braking system than getting a well designed and engineered big brake kit.

Bodywork Upgrades

If your car is travelling fast, you better make it look the part too, right?

The BMW Z4 is undoubtedly a well-designed car from the factory, with a long bonnet and wide rear haunches but a few extra little dashes of flare never hurt anyone…

Spoilers

The most obvious choice for BMW Z4 owners looking to make a statement and set their car apart from the crowd. No BMW Z4 thus far has been offered with a factory spoiler, not one large enough to be noticeable anyway. Thankfully, the aftermarket has responded and there are lots of options to choose from.

There are multiple styles to suit your particular Z4 from small edge spoilers to ducktail-style and motorsport inspired offerings. Our BMW Z4 spoiler article takes you through the do’s and don’ts as well as some of the best BMW Z4 spoilers on the market.

Conclusion

Modifying a car is not always about making it go faster, louder or harder. Sometimes a modification can be purely to improve the experience of every drive or increase the wow factor. Whether on a small or large budget, there are modifications out there for every car lover and most can be implemented with a few basic tools on the driveway at home. There is also nothing like the feeling of new BMW Z4 performance parts arriving in the post, the term “like a kid at Christmas” immediately springs to mind.

It is important to inform your insurance before performing any modifications to ensure you are covered and also check UK road laws to ensure you are compliant. The aftermarket for BMW Z4’s is huge and growing daily for the newer G29 models. Big power, exciting handling and looks to kill are only a few turns of a spanner away, what are you waiting for…

If you liked this article, please share, leave a comment below and check out our other exciting articles.

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Jack Gill

Car journalist and fully qualified mechanical engineer, Czok’s newest contributor and long-time automotive writer. Lifetime passion for all things automotive, from new supercars to rusty old hatchbacks. If I’m not behind the wheel, I’m likely under the bonnet or browsing the classifieds. Having spent over 5 years in the automotive industry and under the bonnet of my own car at home, I want to share the knowledge and learning that I have gained, with others without the time to study or the expertise, who just want their car to get them from A to B every day. We aren’t all interested in trawling through endless internet pages and forums. I aim to gather all the information up and roll it into a quick summarised format, to give only the information you really need.

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