Tuning the BMW M20

"Comprehensive guide to performance parts and tuning the BMW M20 engine!"

We often are seeing threads asking about the premier M20 upgrades. So let us look into BMW M20 mods and outline the best modifications on this great engine and point out some frequent tuning mistakes along the way.

The BMW M20 make a good tuning project and with the best tuning mods like ECU maps, turbo improvements and camshafts you will positively enhance your driving experience.

TorqueCars will examine M20 tuning and provide tips on the best modifications.

When talking about the top parts for your M20 engine, we are going to concentrate on the mods that give the best power gain for you spend.

Altering your M20 cam will make a dramatic difference to the engine engines power. Choosing a higher performance cam profile raises the engines power accordingly.

NB: Fast road cams normally bump the bhp and torque over the rev band, you may lose a little low down bhp but higher rpm power will improve.

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

On a typical daily driver should ideally to match your power band to your driving style.

I'd be shocked if you find a M20 Competition camshaft is a pleasure to live with when driving around busy urban areas.

Each engine responds better to extreme cam durations than others.

The engine timing and fuelling also have an effect on the power gains you'll make.

A longer valve duration 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.

M20 Tuning Stages

Stage 1 M20 modifications: Remaps/piggy back ECU, Sports exhaust manifold, Fast road camshaft, Drilled & smoothed airbox, Panel air filters, Intake headers.

Stage 2 M20 modifications: fuel pump upgrades, high flow fuel injectors, Ported and polished head, Fast road cam, Sports catalyst & performance exhaust, induction kit.

Stage 3 M20 modifications: Adding or Upgrading forced induction (turbo/supercharger), Crank and Piston upgrades to alter compression, Engine balancing & blueprinting, Twin charging conversions, Competition cam, Internal engine upgrades (head flowing porting/bigger valves).

The M20 engine blocks are great to work on and we note that there are quite a few choices of upgrades and performance parts around.

ECU mapping should help to to establish the full potential of all the parts you've done to your M20.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but figures achieved may vary depending on the parts you've done and the condition of your engine.

Shoving more air and fuel into each cylinder is vital to any engine modification job.

Air Intake manifolds carry the air from the intake filter and allow it to be drawn into the engine cylinders with fuel for the squish phase.

Structure and flow characteristics of the Headers can make a big difference to to fuel mixing and power on the M20.

On popular production engines headers are needing motorsport parts, although a few OEM provide fairly well optimized headers.

Adding a M20 larger valve kit, getting port work and head flowing will also improve power, this will afford you an improved power increase on other tuning parts.

Turbo upgrades for the M20

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 M20

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 a car is turbocharged, tuning parts are going to make more power and you'll see that turbo charged engines are made with better components.

However every engines have limits

Research these restrictions and upgrade to better pistons and crank to survive the power.

We see many people spending a a stack of money on turbo charger upgrades on the M20 only to have the whole thing catastrophically fail soon after it's been finished.

Larger turbochargers will usually suffer low end lag, and small turbochargers spool up more quickly but do not have the high rpm bhp gains.

In recent times the choice of turbo chargers is always evolving and we commonly find variable vane turbo chargers, where the vane angle is altered according to speed to lower lag and increase top end performance.

Twin scroll turbo chargers divert the exhaust gases into 2 channels and feed these at differently designed vanes in the turbo charger. They also improve the scavenging effect of the engine.

It is common that there's a limit in the air flow sensor MAP/MAF/AFM on the M20 when considerably more air is being fed into the engine.

We see 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped bhp and torque at a much lower level.

Adding a supercharger or additional turbo will make large performance gains, although more difficult to setup. We have this feature on twinchargers if you want to read more.

Uprating M20 fuel injectors

You will need to ensure that the engine is not starved of fuel so will need to uprate the fuelling when you start going beyond 20% of a torque increase.It is important to be generous with your injector capacity.

As a rule of thumb add 20% when specifying an injector, this accounts for injector deterioration and allows a bit of 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 M20 performance exhausts

You should look to boost your exhaust if your current exhaust is actually causing a restriction.

On most factory exhausts you'll find the exhaust 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.

Sports exhausts will certainly help air flow through the engine but do not go too big or you may end up will reduce the flow rate. Stick to 1.5 to 2.5 inches as a rule of thumb.

Common exhaust restrictions are in the catalysts installed, so adding a freer flowing race alternative will help avoid this restriction.

Problems and issues to look out for on the M20

The M20 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the M20, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your M20 engine please join us in our friendly forum where you can discuss tuning options in more detail with our M20 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 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 M20 guides and tips are kept up to date.

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