BMW S85 Tuning

"All you need to know about tuning the BMW S85 engine!"

This pages aim is to examine the world of S85 tuning and outline the greatest upgrades. BMW S85 are good project engines and with carefully picked tuning parts like ECU maps, turbo improvements and camshafts you will dramatically improve your driving fun.

History, Power & Specs of the Engine

The S85 is a naturally aspirated V10 and was the first and only production V10 engine BMW produced.

  • S85B50
  • 373 kW (500 bhp)@7,500 rpm
    520 nm (384 lbft)@6,100 rpm

Tuning the BMW S85 and best S85 performance parts.

Best S85 tuning mods

When talking about the best best for your S85 engine, we are going to concentrate on the mods that give the best power gain for you spend.

Significant gains on the S85 can be made from camshaft upgrades. Altering the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the torque and power output.

Fast road cams commonly boost the power across the rev range, you could sacrifice a little low down power but your top end will be lifted.

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

In a car used daily, really you should, ideally aim to match your torque band to your typical driving style.

I'd be surprised if you find a S85 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.

Each engine responds better to mild camshaft durations so set your engine up on a rolling road.

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

Longer valve durations can alter the bhp 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: Sports exhaust manifold, Fast road camshaft, Remaps/piggy back ECU, Panel air filters, Intake headers, drilled & smoothed airbox.

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

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

The S85 engines make great tuning projects and thanks to their popularity there are quite a few choices of mods and tuning parts around.

ECU mapping should help to establish the full potential of all the mods you've fitted to your S85.

(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 the outcome often differs on the mods you've fitted and the condition of your engine.

It is vital to any tuning job to force fuel and air into your S85

Intake headers flow the air during the suck phase from the air filter and allow it to be fed into the engine cylinders.

The size of bore and shape and flow rate of the Intake can make a noticeable change to fuel atomisation on the S85.

Commonly we find the plenum chambers are ripe for a performance upgrade, although a few makers provide reasonably well designed plenum chambers.

Increasing the S85 valve size, getting port matching and head flowing will also boost performance, this will make space for increasing the performance increase on other tuning mods.

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 S85

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

You'll commonly see there is a limit in the air flow sensor AFM/MAF on these engines when a lot more air is being drawn into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting bhp at a much lower level.

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

Fuelling

You will need to ensure that the engine is not starved of fuel so should look at the fuelling when you start exceeding 20% of a bhp increase.Most tuners we speak with say to over specify your injector capacity.

The rule of thumb is to add 20% to the flow rate when specifying an injector, this allows for injector deterioration and allows you some 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.

Exhaust

You only need to upgrade your exhaust if the current exhaust is creating a restriction in flow.

On most factory exhausts you'll find 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.

Sports exhausts generally help improve air flow from the engine but avoid an exhaust that is too big or you could very well end up with a reduced flow rate. So generally speaking, keep to 1.5 to 2.5 inches as a rule of thumb.

Typically exhaust restrictions can be located the filters installed, so adding a faster flowing high performance aftermarket one will improve air flow, and rather than doing an illegal decat, will keep the car road legal.

Weak spots Issues & problem areas on the S85

The S85 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 S85, 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 S85 engine please join us in our friendly forum where you can discuss tuning options in more detail with our 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 modifications 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 S85 articles which are continually updated.

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