Tuning the Vauxhall U20SED

"Comprehensive guide to performance tuning the Vauxhall U20SED engine!"

We are frequently getting posts requesting information on the best tips for U20SED upgrades. So let us look into Vauxhall U20SED mods and outline the best upgrades on this great engine and point out some problems along the way.

Let us provide a guide to U20SED tuning and outline the best modifications for your car. Vauxhall U20SED great bases for a tuning project and with the ultimate upgrades like ECU maps, turbo improvements and camshafts you will increase your driving opportunities.

Just because particular mods are popular with U20SED owners it doesn't mean it is good, we will recommend only what we regard are the best mods that will give your U20SED the best value for money to power increase.

Altering your U20SED cam will make a dramatic difference to the engine power band. Choosing a higher performance cam profile raises the power band accordingly.

NB: Fast road cams usually bump the power over the rev band, you may lose a little low down power but top end will be higher.

Motorsport and race cams, bump the top end band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Motorsport camshaft makes it harder when driving in heavy traffic.

You should ideally match your power band to your driving style so for a road car stick with a fast road U20SED camshaft

Different U20SED engines respond better to less aggressive camshaft durations check your engine on a rolling road.

The map and fuelling also have an effect on the power gains you'll achieve.

Longer 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.

U20SED Tuning Stages

Stage 1 U20SED modifications: Panel air filters, Drilled & smoothed airbox, Fast road camshaft, Intake headers, Remaps/piggy back ECU, Sports exhaust manifold.

Stage 2 U20SED modifications: fuel pump upgrades, high flow fuel injectors, Fast road cam, Sports catalyst & performance exhaust, Ported and polished head, induction kit.

Stage 3 U20SED modifications: Adding or Upgrading forced induction (turbo/supercharger), Engine balancing & blueprinting, Twin charging conversions, Internal engine upgrades (head flowing porting/bigger valves), Competition cam, Crank and Piston upgrades to alter compression.

Review your options and then buy your upgrades and set yourself a power target to avoid costly mistakes.

A remap will help release the full potential of all the tuning mods you've done to your U20SED.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but power output will depend much on the tuning mods you've carried out and the condition of your engine.

Forcing air into the U20SED engine is the whole point to any engine tuning job.

Headers flow the air from the air filter and allow it to be drawn into the engine and mixed with fuel.

The size of bore and shape and flow rate of the Plenum can make a large improvement to fuel mixing and power on the U20SED.

Most intake are crying out for a performance upgrade, although a few manufacturers provide fairly well optimized intake.

Larger U20SED valves, doing some 3 or 5 angle valve jobs and porting and head flowing will also lift performance, and more importantly will allow you to get a greater performance increase on other tuning parts.

Turbo upgrades for the U20SED

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 U20SED

The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes superb power gains.

When an engine is fitted with a turbocharger modifications are going to net you a larger power gain and you will discover turbocharged engines are built with harder and stronger components.

There are tuning limits for every engine, with some being very over engineered and some just sufficiently able to handle stock power

Research these limits and install higher quality crank and pistons to handle the power.

We see many car owners spending a lot of money on turbo upgrades on the U20SED only to watch the engine block explode when it's completed.

Large upgraded turbos will usually experience low end lag, and low capacity turbos spool up much more quickly but do not have the top end torque gains.

In the last 10 years the market of turbo chargers is always moving on and we commonly find variable vane turbo chargers, permitting the vane profile is altered according to speed to lower lag and increase top end performance.

Twin scroll turbo chargers divert the exhaust flow into two channels and direct these at differently angled vanes in the turbocharger. They also increase the scavenging effect of the engine.

It is not unusual that there is a restriction in the air flow sensor AFM/MAP on the U20SED when loads more air is being fed into the engine.

We note 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 more challenging to setup. We have this feature on twinchargers if you want to read more.

Uprating U20SED fuel injectors

You will need to ensure that the engine is not starved of fuel so should pay attention to the fuelling when you start exceeding 20% of a torque increase.We strongly recommend you to be generous with your injectors flow rate.

As a rule of thumb add 20% capacity when specifying an injector, this takes into account injector deterioration and provides a little spare capacity should the engine require 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 U20SED performance exhausts

You may need to replace your exhaust if the existing exhaust is actually creating a flow problem.

On most factory exhausts you should find that the exhaust flow rate is fine 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 biggest exhaust you can source this will reduce the exhaust flow rate - the best for power gains are usually between 1.5 to 2.5 inches. It is the shape and material more than the bore size.

Common exhaust restrictions are traced to the emissions filters installed, so adding a higher flowing high performance alternative will help avoid this restriction.

Problems and issues to look out for on the U20SED

The U20SED engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the U20SED, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your U20SED engine please join us in our friendly forum where you can discuss tuning options in more detail with our U20SED owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

We need your help to complete and improve this page, so do give us your feedback in the comments box below.

We really like hearing from our readers, and hearing about which parts were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our U20SED guides and tips are kept up to date.

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