Modifying and tuning the BMW S65

Modifying and improving: "BMW S65 Tuning"

BMW S65 Tuning Guide

"Modifying and tuning the BMW S65 engine!"

Now we will review and look at S65 tuning and point out the ultimate mods that work. BMW S65 are good project engines and with carefully picked sports upgrades like ECU maps, turbo improvements and camshafts you will definitely enhance your driving opportunities.

When talking about the ultimate parts for your S65 engine, we are going to focus on the modifications that give the best power gain for you spend.

Significant gains on the S65 can be made from cam upgrades. Altering the cam profile alters the intake and exhaust durations on the engine and can dramatically change the power band and power output.

NB: Fast road cams commonly boost the performance across the rpm range, you could sacrifice a little bottom end bhp but your higher rpm power will be higher.

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

A Race cam makes it harder when on the daily commute.

You should ideally match your engines power to your cars usage so for a daily driver stick with a shorter duration S65 cam

Different S65 engines respond better to less aggressive camshaft durations so set your engine up on a rolling road.

The ECU mapping and injectors and fuel pump also have an effect on the torque gains you'll get.

Extending exhaust or intake durations can alter the torque 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.

Our top 7 top upgrades for your motor, and we will break these into stages and discuss them in detail for you.

  1. Map Tunes - remapping, via either OBD port, or piggyback ECU's and aftermarket ECU's can all make decent gains
  2. Fuelling Pump Injectors - You'll need to match the greater air flow with more fuel to unlock the power
  3. Turbo upgrades - Improving the intake charge with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex especially where conversions are required).
  4. Suspension Upgrades - always improve your cars handling, tuning is not just about engine mods
  5. Brake Upgrades - Even before adding power improve your cars brakes to effectively stop the car
  6. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
  7. Exhaust - as with intakes it helps to remove a restriction in the exhaust, cats are the usual bottleneck

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

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

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

Stage 3 mods: Competition cam, Adding or Upgrading forced induction (turbo/supercharger), Internal engine upgrades (head flowing porting/bigger valves), Engine balancing & blueprinting, Twin charging conversions, Crank and Piston upgrades to alter compression.The S65 engines are great to work on and we note that there is a lot of upgrades and performance parts out there.

ECU flashing should help to to establish the full potential of all the parts you've done to your S65.

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 depend much on the parts you've fitted and the condition of your engine.

It is the whole point to any engine performance tuning task to force air into the S65 engine

Headers transmit the air from the filter and allow it to be pulled into the engine cylinders with fuel for the squish phase.

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

Design and flow characteristics of the Plenum can make a large change to fuel atomisation and engine efficiency on the S65.

On popular production engines intake headers are in dire need of aftermarket tuning parts, although some makers provide reasonably well designed intake headers.

Larger S65 valves, doing some S65 port enlargement and head flowing will also raise performance, the fantastic side effect is it will make space for a greater performance increase on other upgrades.

S65 Turbo upgrades

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 a separate 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 S65

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.

If your motor is fitted with a turbocharger tuning parts are more reliable and we find turbo charged engines are made using many forged and stronger components.However you will find an engines have weakspots

See where you'll find these limitations and upgrade to better quality crank and pistons to utilize the power.

We've seen car owners spending a loads on turbo upgrades on the S65 only to see the engine literally blow up on it's first outing after it's been enthusiastically driven.

Bigger upgraded turbos commonly suffer low end lag, and smaller turbos spool up much more quickly but don't have the peak rpm bhp gains.

In recent times the choice of turbos is always developing and we now see variable vane turbos, allowing the vane profile is altered according to speed to lower lag and increase top end performance.

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

It is common that there is a limit in the air flow sensor AFM/MAP on the S65 when considerably more air is being sucked into the engine.

We see 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited power at a much lower level.Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large torque gains, although more complex to setup. We have this article covering twinchargers if you want to read more.

S65 Fuelling upgrades and mods

You will need to ensure that the engine is not starved of fuel so should pay attention to the fuelling when you start going beyond 20% of a bhp increase.

It is important to be generous with your injectors flow rate.

The accepted safe increase is to add 20% to the flow rate when fitting an injector, this accounts for injector deterioration and affords a bit of spare capacity should the engine need 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..

S65 Exhaust upgrades and mods

You should look to upgrade your exhaust if your exhaust is creating a restriction in flow.

On most factory exhausts you'll see your flow rate is still 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 out of the engine but avoid an exhaust that is too big or you may end up will reduce the flow rate. Stick to one and a half to two and half inches as a rule of thumb.

Usual exhaust restrictions can be located the catalyst and filters installed, so adding a higher flowing race alternative will help avoid this restriction.

S65 Issues & common problems

The S65 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the S65, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your S65 engine please join us in our friendly forum where you can discuss tuning options in more detail with our S65 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 really like hearing from our readers, and hearing about which upgrades were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our S65 guides and tips are kept up to date.

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