Modding uprating the BMW S85 engine!

Tuning guide "S85 Modifications"

S85 Modifications Guide

How to modify and upgrade the BMW S85

"Comprehensive guide to tuning the BMW S85 engine!"

Popular tuning sites like TorqueCars are always getting posts about how to improve the S85 from people inquiring about getting more power from the S85 and wanting to know what are the things tuners are recommending when it comes to S85 modifications. So let us look into BMW S85 modifications and outline the best mods that work on this great engine and point out some potential pitfalls along the way.

The BMW S85 are fantastic to work on and with carefully picked modified parts like ECU maps, turbo kits and camshafts you will substantially enhance your driving pleasure.

This pages aim is provide a guide to S85 tuning and point out the best modifications.

Just because particular upgrades are appear in lots of S85 projects it doesn't mean its worth having, so we'll concentrate on the greatest upgrades that will give your S85 the best power gain for you spend.

Without us subscribing to the mentality of 'if it's shiny and makes more noise it must be good' you seem to get in many tuning magazines and on car forums'.

S85 induction kits

Improving air intake on the S85

You need fuel and air for an engine to work. If there is too little fuel then it will run lean, if there is a lack of air it runs rich losing power . We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the whole point to any engine upgrade task to get fuel and air into the S85 engine but this has a knock on effect with the air flow sensor.

You'll commonly see there's a limitation in the air flow sensor AFM/MAP on the S85 when loads more air is being drawn into the engine.

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

Air Intake manifolds carry the air during the suck phase from the intake filter and allow it to be drawn into the engine and mixed with fuel.

The bore size, shape and flow rate of the Intake headers can make a large improvement to fuel engine efficiency on the S85.

It's not uncommon that intake are needing a performance upgrade, although some manufacturers provide well optimised intake.

Fitting big valve kits, doing a bit of port work and head flowing will also lift torque, this will permit increasing the torque increase on other parts.

S85 performance cam tips.

Different S85 engines respond better to more or less aggressive cam durations so view each engine as unique.

The ecu map and fuelling also will make differences on the power gains you'll make.

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.

Significant air intake, and exhaust improvements on the S85 can be made from cam upgrades. Changing the cam profile alters the intake and exhaust durations on the engine and can dramatically change the bhp and power output.

NB: Fast road camshafts commonly push up the performance throughout the rev band, you may lose a little low down power but top end will be better.

Motorsport camshafts, push up the top end band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Competition camshaft makes it harder when driving around busy urban areas.

You should ideally match your engines power to your preferences so for a car driven daily stick with a fast road S85 camshaft

Stage 1, 2 and 3 mods for the S85

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

  1. Suspension Upgrades - always improve your cars handling
  2. Brake Upgrades - Even before adding power improve those brakes
  3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
  4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
  5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
  6. Fuelling - when you've increased power you'll need to match this with more fuel
  7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 S85 parts:

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

Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Stage 2 S85 parts:

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

Stage 3 S85 parts:

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

Plan your options and then find your modifications and set yourself a power target to avoid disappointment.

A remap should help to to establish the full potential of all the upgrades you've done to your S85.

You will typically expect to see gains of approximately 20-30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but power output often differs on the upgrades you've applied and the condition of your engine.

Turbo modifications on the S85

To get a turbo working on a NASP engine there is a lot involved, from lowering compression ratio to improved fuel supply and mapping, so we have found a great guide to helpavoid the common pitfalls or end up with an unfinished project because you were not told what you were getting into by doing this on the 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 excellent power gains.

If the engine is fitted with a turbo parts are relatively easy and you'll see that turbocharged engines use many forged and stronger components.

There are tuning limits for every engine, with some being incredibly solid and some just sufficiently able to handle stock power

It is important to find these restrictions and fit stronger pistons, crank and engine components to survive the power.

We see many car owners spending a loads of money on turbocharger upgrades on the S85 only to watch the motor go up in smoke soon after it's been completed.

Larger turbochargers will usually suffer a bottom end lag, and low capacity turbochargers spool up more quickly but do not have the peak rpm torque gains.

Thanks to progress the world of turbochargers is always developing and we commonly find variable vane turbochargers, where the vane angle is altered according to speed to lower lag and increase top end bhp and torque.

Twin scroll turbochargers divert the exhaust gases into 2 channels and flow these at differently angled vanes in the turbo. They also boost the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large performance gains, although more difficult to get working. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the S85

You will need to ensure that the engine is not starved of fuel so must ramp up the fuelling when you start going beyond 20% of a bhp and torque hike. We strongly recommend you to be generous with your injector capacity.

As a rule of thumb add 15% when specifying an injector, this accounts for injector deterioration and affords a bit of spare capacity should the engine require more fuel.

Don't forget that different fuel grades will usually require different settings, a high octane fuel will burn more efficiently than lower octane fuel for example. A car will trim fuel supply to keep within the ideal air fuel mix but at the extreme ends you may need to adjust your injector capacity, or the mapping or you'll get flat spots and potential lean or rich fuel issues..

Recommended S85 performance exhaust upgrades

We'd only recommend you look to increase your exhaust system with an upgraded one is if the current exhaust is creating a flow problem.

On most factory exhausts you'll see the exhaust flow rate is good even on modest power gains, but on a serious tuning project with a big boost in power you will certainly need to get a better flowing exhaust.

Sports exhausts increase the flow of gases through the engine.

But if the exhaust is too big, ie: it's over two and a half inches diameter, you will lose a great deal of the flow rate and end up sapping power and torque.

Typically exhaust restrictions come around the catalyst installed, so adding a better flowing sports alternative will help avoid this restriction.

Decats (NB:catalysts reduce harmful engine emissions) is illegal in most countries and regions.

Faults issues and things to look out for on the S85

Like most engines an S85, should have few issues if it gets properly serviced and looked after.

We cannot stress enough the need for oil changes with the correct grade of oil on the S85, failure to do this will exacerbate engine wear, on a tuned S85 this is more important than ever and close attention should be paid to your maintenance schedule.

If you are interested in learning more or getting impartial tuning advice for your S85 why not pop over to the forums at TorqueCars where you can chat about S85 tuning options and read about others projects who may be planning to do similar modifications on their S85.

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