MENUTuning the Vauxhall Z20LEH
"Comprehensive guide to tuning the Vauxhall Z20LEH engine!"
We often are getting posts about the best Z20LEH modifications. So let us look into Vauxhall Z20LEH mods and outline the best modifications on this great engine and point out some common pitfalls along the way.
The Vauxhall Z20LEH have loads of potential and with the right performance modifications like ECU maps, turbo improvements and camshafts you will definitely maximize your driving fun.
Let us examine the options for your Z20LEH tuning and provide tips on the greatest upgrades.
When talking about the optimum parts for your Z20LEH engine, we are going to concentrate on the upgrades that give the best value for money.
The cam profile plays a big part in the engines power output so cam upgrades make quite a large difference. The intake and exhaust durations will alter depending on the chosen cam profile, so large torque gains are on offer for cam upgrades.
NB: Fast road camshafts commonly boost the power throughout the rev band, you may sacrifice a little low end power but the high end rpm power will be better.
Motorsport and race camshafts, boost the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.
A Race cam makes it harder when in heavy traffic.
You should ideally match your engines power to your preferences so for a road car stick with a fast road Z20LEH cam
Some Z20LEH engines respond better to more aggressive cam durations so view each engine as unique.
The engine timing and injectors and fuel pump also will make differences on the power gains you'll achieve.
Altering valve durations can alter the power band and on most engines the exhaust and intake durations do not need to match, although most cams and tuners use matched pairs there are some advantages to extending the intake or exhaust durations.
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Guide to the best Z20LEH tuning mods & Upgrades
- ECU Map Tuning & Remaps
Some cars may require a piggyback ECU's or aftermarket ECU's to change the OEM map, but remapping is the most vital step of your tuning project to fully maximise your mods. Expect 10-20% on NASP engines and 30-40% on turbocharged units.
- Strengthen Your Engine
Tuned cars will show up weaknesses, typically in the turbochargers, clutch and internal engine components. Whilst most engines can cope with mild tuning mods, TorqueCars recommend that you upgrade the internal components before these weak spots manifest themselves.
- Mods that Remove a Restriction
A restricted intake or exhaust will have an impact on your performance, so use a better flowing air filter/induction kit and better flowing exhaust (sports cats where legal are a good option) whenever your tuning creates a flow restriction. Turbo engines also benefit from intercooler upgrades as these resist heat soak for longer periods of time.
- Mods that Improve Fuelling
Every tuning project will aim to increase the air supply, but fuel supply is just as vital and will need to match the air the engine can utilise, a fuel pump and injector upgrade are usual mods, but also in many cases the fuel regulator will need improvement.
- Mods to Provide better Airflow
Increasing the air supply is just as essential as improving fuelling, we suggest you look at head mods (flowing and porting, 5 angle valve jobs), fit bigger valves, fast road cams and forced induction upgrades (adding a better flowing turbo) to improve air intake.
Z20LEH Tuning Stages
Stage 1 Z20LEH modifications: Intake headers, Panel air filters, Sports exhaust manifold, Remaps/piggy back ECU, Drilled & smoothed airbox, Fast road camshaft.
Stage 2 Z20LEH modifications: induction kit, Fast road cam, fuel pump upgrades, Sports catalyst & performance exhaust, Ported and polished head, high flow fuel injectors.
Stage 3 Z20LEH modifications: Competition cam, Engine balancing & blueprinting, Adding or Upgrading forced induction (turbo/supercharger), Internal engine upgrades (head flowing porting/bigger valves), Crank and Piston upgrades to alter compression, Twin charging conversions.
ECU flashing allows a tuner to fully realize the full potential of all the tuning parts you've done to your Z20LEH.
It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but the end result usually differs on the tuning parts you've done and the condition of your engine.
It is the aim to any tuning task to pull fuel and air into your Z20LEH
Intake carry the air from the filter and allow it to be drawn into the engine and mixed with fuel.
The bore size, shape and rate of flow of the Intake manifold can make a noticeable change to fuel atomisation and engine efficiency on the Z20LEH.
It's not uncommon that plenum chambers are begging for an upgrade, although some car makers provide decently flowing plenum chambers.
Fitting big valve kits, getting Z20LEH port enlargement and head flowing will also increase bhp and torque, & more importantly will raise potential for raising the bhp and torque increase on other mods.
Turbo upgrades for the Z20LEH
NASP engines need quite a lot of work when you add a turbo, so we have a separate guide to help you take into account the pros and cons of going this route on your Z20LEH
The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes excellent power gains.
When your motor has a turbocharger mods are going to make more power and we find turbocharged engines are made using stronger components.
However you will find an engines will need better parts at higher power limits
It is important to find these limitations and fit stronger pistons, crank and engine components to handle the power.
We see many guys spending a loads of money on turbo charger upgrades on the Z20LEH only to suffer the indignity of watching the whole thing throw a rod on it's first outing after it's been finished.
Bigger capacity turbos commonly experience no power at low rpm, and low capacity turbos spool up much more quickly but don't have the top end power band gains.
In the last 10 years the world of turbos is always increasing and we now see variable vane turbos, permitting the vane profile is altered according to speed to lower lag and increase top end bhp and torque.
Twin scroll turbos divert the exhaust gases into 2 channels and flow these at differently designed vanes in the turbo charger. They also help the scavenging effect of the engine.
It is not unusual that there's a limit in the air flow sensor MAF/MAP on the Z20LEH when loads more air is being pulled into the engine.
You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited performance at a much lower level.
Adding a supercharger or additional turbo will make large torque gains, although harder to get working. We have this guide to twinchargers if you want to read more.
Uprating Z20LEH fuel injectors
When you improve the torque you will need to increase to the fuel delivery.
More torque needs more fuel. 
It makes sense to over specify your injectors flow rate.
As a rule of thumb add 20% capacity when specifying an injector, this allows for injector deterioration and gives a little spare capacity should the engine need more fuel.
We think this one is common sense, but you'll need to match your fuel injector to the type of fuel your car uses as well.
Best Z20LEH performance exhausts
You should look to boost your exhaust if the current exhaust is creating a flow problem.
On most factory exhausts you'll see your flow rate is ok even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.
Note that with the largest exhaust you can get you'll slow the exhaust rate - the best exhausts for power gains are usually between 1.5 to 2.5 inches. It is the shape and material more than the bore size.
Usual exhaust restrictions are in the catalysts installed, so adding a faster flowing sports alternative will help avoid this restriction.
Problems and issues to look out for on the Z20LEH
The Z20LEH engines, if regularly serviced and maintained, are generally very reliable and have few issues.
Regular oil changes are vital on the Z20LEH, particularly when the engine has been modified and is putting down more power than the manufacturer intended.
For more information on Tuning your Z20LEH engine please join us in our friendly forum where you can discuss tuning options in more detail with our Z20LEH owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.
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We really like hearing from our readers, and hearing about which tuning mods were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our Z20LEH guides and tips are kept up to date.
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