How to Tune Your BMW for More Power

Carpart News

Mar 16th, 2020

How to Tune Your BMW for More Power

BMW has been building superior cars for decades and has consistently produced engines with proven reliability, performance and durability. Although they have made mistakes over the years, as any other manufacturer has, BMW is one of those automakers that have strived for automotive greatness and succeeded.

Bayerische Motoren Werke AG, translated in English as Bavarian Motor Works started in 1916 producing aircraft engines then produced motorcycle engines and farm equipment. BMW became an automobile manufacturer in 1928 with its first offering – the BMW 3/15. Since then, they have released countless iconic passenger cars and supercars, becoming one of the world’s much-admired marques. 

Over the years, BMW has produced thousands of engines from 4-cylinder to 12 -cylinder petrol types and also a host of diesel units. This would be a very long list of engines with multiple variations and upgrades, most of them capable of handling more power with a few aftermarket parts and some tweaking.

From the factory, BMW engines are usually restricted and rated lower than what the base-level engine is capable of producing. This is in part due to regional market restrictions, import tariffs, and the existing demand in the segment where the car belongs.

The Basics – Intake and Exhaust Systems 

The early carburetted engines like the M10 family were basic petrol engines that could benefit significantly with the introduction of more fuel, airflow and improved exhaust. 

These are the basic requirements to produce more power. Replacing the stock Solex carburettors with better ones or replacing jet sizes increases the fuel and air that goes into the cylinder. Quality exhaust headers and open mufflers or tail pipes prevent restrictions for the exhaust gases. 

Those days, however, are mostly gone. With strict emissions controls and our responsibility to avoid the release of harmful gases, these engine modifications are not anymore practical these days.

The most basic and least expensive way of producing more power is increasing airflow and releasing gases effectively. Aftermarket and used performance parts are readily available. The range comes from low restriction air filters like the ones sold by K&N, cold air intakes and ram-air intakes. 

For the exhaust gases, there are equal length headers, cat-back exhaust systems and free-flow mufflers. When doing these modifications, don't forget to add more fuel as the increased air would mean your system will run lean. For older carburetted engines, a simple fuel jet size increase should be enough. For fuel-injected cars, however, race or performance chips, bigger-sized fuel injectors and fuel rails may be needed depending on the amount of power you are aiming for. 

The principles don't change though.

  • Add more fuel.
  • Increase fuel flow.
  • Burn the mixture better. 
  • Release the gases more effectively.

These should be every tuner’s objectives. 

But getting there is very tricky. You can increase your BMW’s power adding a few more kW (or horsepower) for cheap or go all the way to spending several thousand dollars to gain heaps of power.

Forced Induction – Supercharger and Turbochargers 

Forced induction, in the form of either superchargers or turbochargers, constitutes the modifications that give the best power gains. Add-on intercoolers to provide a denser air charge almost always accompany them as the pressurised induction system heats up the air. Of course, increasing the air into the cylinder also requires an increase in fuel and a suitable exhaust system to handle it.

Most BMW engines can handle an extra boost in the single-digit without changing any internal components, but double-digit boost numbers would require changing the pistons, piston rings and cylinder heads. It’s always advisable to know your exact engine model number to find out the internals. If your engine came with low-compression cylinder heads and forged pistons, then you can most probably increase your boost. 

BMW engines that already come turbocharged from the factory can also benefit from increased airflow with larger diameter turbocharger or supercharger systems. This is true with either the petrol or diesel-fueled variants.

Race / Performance Chips

As mentioned earlier, most BMW engines are released from the factory with restrictions. Take as an example the venerable and reliable M50 series that was used on the E34 and E36. The E36 was marketed as the 320i rated at 110 kW known as the M50B20. There are available performance chips that can increase the power by 16 kW or more. More power can be gained from these performance chips by changing fuel injector size. These chips either raise the rev limiter to about 7,000 rpm or in some products totally delete it. 

BMW aftermarket parts specialists sell these parts upgrades either as standalone or packaged with bigger injectors and aluminium flywheels to get the most performance gains. These chips are available for most BMW engines starting from the late 1980s and can still be used for earlier models with the help of dyno tuning and fuel mapping. 

Frequent Tune-Up

Your BMW comes from the factory, more often than not, finely tuned and ready to deliver the power it advertises. As you use your car, power decreases over time due to engine soot, fuel quality and oil lubrication properties. BMW recommends a specific schedule for your maintenance tune-ups, but these are generally given with typical road conditions and their knowledge of the components used in the engine in mind.

Road, climate, driving conditions and fuel quality are rarely typical though, and more frequent oil changes (using recommended or above rated oils, spark plugs and filters) and tune-ups will help retain the power and prolong the life of your engine. 

Filling up your tank with good quality fuels also makes a world of difference in performance. The practice of filling up your tank regularly and not letting it dry out prevents rust from developing. It also prevents sludge and contaminants from being sucked by the fuel pump, which can impede the fuel flow and dramatically decrease the engine's capacity to produce power. 

Other fluids also require maintenance; the gearbox and differentials need proper care.  Whatever power your engine produces, it is quickly lost if the rest of the drive system performs below par. 

One other component which is often neglected but plays a very critical part is your car’s battery. BMW cars require a specific type of car battery to function properly. An inefficient battery can significantly impact your car's performance.

Where to Start

Get a lot of information for your specific car – that’s where. BMW models can have very different specifications, and you have to know what you need to increase your car's power and performance. Carpart.com.au is one of the best sources of information and, with its easy navigation, can give you all the information you need to know including where to buy new aftermarket BMW partshard-to-find auto parts, and oils or fluids. Simply visit our website, fill in the details of what you're looking for in a form, and we will help you in the best way we can. 

Fred Cajulis