BMW M41 Tuning

"All you need to know about tuning and performance parts on the BMW M41 engine!"

Our aim here is to provide a guide to M41 tuning and highlight the greatest modifications.

The M41D17 is a great diesel engine and with a remap can embarrass similar sized petrol cars.

BMW M41 are good project engines and with the right modifications like ECU maps, turbo kits and camshafts you will certainly maximise your driving enjoyment.

History, Power & Specs of the Engine

M41D17

66 kW (90 PS; 89 hp)@4,400 190 Nm (140 lbft) @2,000
1994–2000

Tuning the BMW M41 and best M41 performance parts.

Best M41 modifications

When talking about the best modifications for your M41 engine, we are going to focus on the tuning parts that give the best power gain for you spend.

Altering camshafts on petrol engines will make a dramatic difference to the engine torque but this is not really the case on diesels. Choosing a higher performance cam profile raises the torque accordingly but you really want a wide power band.

On a road car should ideally to optimize your power band to your preferences.

I would be surprised if you have found a M41 Motorsport cam is a pleasure to live with when on the daily commute, because the lumpy idle will make the car prone to stall and smooth driving at low rpm becomes impossible. If you are developing a track car this doesn't matter as you are in the high end of your RPM range anyway and that is where you want the power to be.

We would strongly recommend a remap on the M41D17

Each engine responds better to less aggressive cam durations so view each engine as unique.

The map and fuel pump and injectors also have a large bearing on the power gains you'll get.

Extending exhaust or intake 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.

Typical stage 1 mods often include: drilled & smoothed airbox, Intake headers, Remaps/piggy back ECU, Panel air filters, Sports exhaust manifold.

Typical stage 2 mods often include: Ported and polished head, high flow fuel injectors, Sports catalyst & performance exhaust, induction kit, fuel pump upgrades.

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

 

Plan your options and then acquire your tuning mods and set yourself a power target to void expensive mistakes.

 

ECU flashing allows a tuner to release the full potential of all the tuning mods you've done to your M41D17.

(In some cases, as the factory ECU is locked flashing is not an option, so an aftermarket ECU is the route to take, and many of these will outperform factory ECU's but make sure it has knock protection and that you get it setup properly.)

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

Pulling more air and fuel into the M41 engine is vital to any engine upgrade project.

Intake headers take the air from the filter and allow it to be sucked into the engine cylinders with fuel for the squish phase.

The size of bore and shape and rate of flow of the Intake can make a big change to fuel mixing and power on the M41.

We often see air intake systems are in desperate need of an upgrade, although a few manufacturers provide reasonably well designed intake.

Increasing the M41 valve size, doing a bit of port work and head flowing will also lift torque, the fantastic side effect is it will make space for a better torque increase on other modifications.

Turbo upgrades

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 M41

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

When your motor is turbo charged mods are relatively easy and most turbo engines use more solid components.

However most engines have weakspots

See where you'll find these limitations and install higher quality crank and pistons to survive the power.

It's not unheard of people spending a lot of money on turbo charger upgrades on the M41 only to have the motor go up in smoke just after it's first rolling road session.

Big upgraded turbo units will usually suffer no power at low rpm, and low capacity turbo units spool up much more quickly but don't have the peak end power band gains.

Thanks to progress the range of turbochargers is always improving and we now see variable vane turbochargers, permitting the vane profile is altered according to speed to lower lag and increase top end performance.

Twin scroll turbochargers divert the exhaust flow into a couple of channels and push these at differently profiled vanes in the turbocharger. They also help the scavenging effect of the engine.

You'll commonly see there's a limitation in the air flow sensor (AFM/MAF/MAP) on the M41 when a lot more air is being pulled into the engine.

Going up you'll find 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited bhp at a much lower level.

Adding a supercharger or additional turbo will make large bhp and torque gains, although more challenging to get working. We have this feature on twinchargers if you want to read more.

Fuelling

When you lift the bhp and torque you will need to increase to the fuel delivery.

 

More bhp and torque needs more fuel. It makes sense to be generous with your injectors flow rate.

As a rule of thumb add 20% to the flow rate when specifying an injector, this allows for injector deterioration and affords some 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.

Exhaust

Only look to boost your exhaust if the current exhaust is actually causing a flow problem and the M41 generally flows really well.

On most factory exhausts you'll find your flow rate is still good even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

Please don't run with the biggest exhaust you can source this will slow up the exhaust flow rate and diesel engines do not need much flow due to the low rpm nature of them. 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 can be traced to the emissions filters installed, so adding a faster flowing sports alternative is the answer. This keeps the car road legal and will flow much better due to it's higher internal surface area and design, so has the added benefit of keeping your car road legal. The alternative decat should be considered an off road only mod, as removing a catalyst is illegal in most territories and regions for road registered cars..

Weak spots, Issues & problem areas on the M41

The M41 engines are generally reliable and solid units, as long as you follow the manufacturers service schedules, and use a good quality oil to ensure longevity. Few problems should happen as long as they are regularly serviced and maintained.

Carbon build up in the head, particularly around the valves which will sap power or create flat spots, this is a larger issue on direct injection engines but should be looked out for on all engines. We have tips on removing carbon build up.

Some of our members have had issues with flat spots or glitches after applying mods and upgrades or tuning, this is not usually related to this engines design, so instead see our article on diagnosing flat spots and problems after tuning which should help you get the bottom of this issue.

Regular oil changes are vital on the M41, especially when tuned and will help extend the life and reliability of the engine.

If you would like to know more, or just get some friendly advice on Tuning your M41 engine please join us in our friendly forum where you can discuss tuning options in more detail with our M41 owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

Please help us improve these tips by sending us your feedback in the comments box below.

We love to hear what our visitors have got up to and which upgrades work best for you on your car. Which helps us keep our guides and tips up to date helping others with their modified car projects. Your feedback and comments are used to keep this page up to date, and help improve the accuracy of these M41 articles which are continually updated.

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