BMW S65 Tuning

"All you need to know about performance parts and tuning the BMW S65 engine!"

When BMW unveiled the S65 engine, it marked a significant chapter in the rich history of high-performance BMW powertrains. Crafted with precision and engineered for adrenaline junkies, the S65 debuted as the heart of the iconic M3, spanning the E90, E92, and E93 series from 2007 to 2013 proving to be the heart and soul of the ultimate driving machine.

This supersmooth & supertorquey V8 engine not only succeeded the revered inline-six S54 but also brought a fresh surge of power to BMW's M division.

The S65, a 4.0-liter V8 marvel, stands out with its impressive output—delivering up to 414 horsepower at a thrilling 8300 rpm and 295 lb-ft of torque.

It was designed to embody the M philosophy of high-revving engines, mirroring the characteristics found in Formula 1 racing engines of the era.

The peak torque might seem modest by some standards, but it's the high-revving nature that defines the S65, allowing drivers to experience an exhilarating push as they ascend the rpm scale. Indeed it is rare to see a V8 with such a wide powerband, with most seeming quite lazy in comparison to the S65.

Throughout its tenure, the S65 received numerous accolades and became a favorite among enthusiasts for its robust performance and distinctive sound. Car shows and our forums show the popularity of these engines and the ever growing availability of parts creates a rich playground for tuners the world over.

This engine not only powered the M3 but also found its way into the limited-production E92 M3 GTS, where it was tuned to produce even more power.

In this article, we dive deep into the tuning potential of the S65 engine, exploring how to enhance its already formidable capabilities and tailor its performance to meet the demands of the most discerning drivers.

Whether it's on the track or the open road, the S65 is a testament to BMW's engineering prowess and a cornerstone of automotive legend.

A BMW S65 gives a fun base for your project and with carefully chosen performance upgrades like ECU maps, turbo improvements and camshafts you will really enhance your driving pleasure.

Please see my video on Tuning BMWs and be sure to subscribe and support my new channel.

History, Power & Specs of the Engine

It was a lovely sounding NASP V8 fitted to the M3. The S65 replaced the S54

Unique in its architecture, the S65 abandoned the typical cross-plane crankshaft of V8s for a flat-plane design, a choice that significantly enhanced its acoustics and throttle response. This engineering decision underscored BMW's commitment to blend daily driving suitability with racetrack-ready aggression.

The S65 was also ahead of its time in terms of technology. It featured a double-VANOS variable valve timing system that optimized engine breathing, and a complex engine management system that finely tuned the balance between performance and efficiency.

Additionally, it was equipped with individual throttle bodies for each cylinder, ensuring that response times were as quick as a flash.

It came as a 4.0l and 4.4 version, both sounded fantastic and perform really well.

• S65B40 (414 hp) at 8,300 rpm 400 Nm (295 lbft) at 3,900 rpm
• S65B44  (444 hp) at 8,300 rpm 440 Nm (325 lbft) at 3,750 rpm

There was also a motorsport version of the S65 named P65B44

Best S65 upgrades

When talking about the best ultimate for your S65 engine, we are going to concentrate on the tuning mods that give the best value for money.

Tuning the BMW S65 and best S65 performance parts. Vanos already enhances the valve timing and gives the best of both worlds in terms of low and top end response, but more adventurous projects will seek the extra gains offered by a more aggressive cam profile, which will work with the VANOS and provide more lift.

The cam profile plays a big part in the engines power output so cam upgrades make quite a large difference. The intake and exhaust durations will alter depending on the chosen cam profile, so large power band gains are on offer for cam upgrades.

Shrick offer a 284 degree cam profile upgrade suitable for everyday road use and also have a 292 degree option if you are after track performance and are willing to upgrade the valve springs.

Fast road camshafts tend to increase the performance over the rev band, you could sacrifice a little bottom end bhp but higher rpm power will be better.

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

On a car driven daily you need to match your torque band to your typical driving style.

I'd be shocked if you have ever thought or claimed that a S65 Race cam is a pleasure to live with when in heavy traffic because low end power will be very lumpy. Competition cams are designed for maximum power at the top end of the RPM range, a place that most daily commutes will not permit!

Some S65 engines respond better to more or less aggressive cam durations check your engine on a rolling road.

The engine timing and fuelling also will make differences on the bhp gains you'll get.

A longer valve duration 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.

Please watch our video which covers the 5 principles of tuning your car. Be sure to keep up with our latest YouTube content and subscribe.

Best mods for your S65

1. Turbo upgrades - A New Turbo is the most dramatic method to improve intake air supply, which permits you to utilize more fuel and make power gains. Although one of the most complex upgrades it does provide the largest gains.
2. Lightened Flywheels - a lower weight flywheel will enhance the engines ability to rev freely. Not a great mod for all S65 engines.
3. Air Induction kits and Sports Exhausts - Please note that on their own these mods will NOT ADD PERFORMANCE for most setups, but they enable you to release power after other mods by lessening the restriction.
4. Fast road Camshafts are are often the best upgrade for an engine, but we recommend they be installed by someone familiar with setting them up on your car and tracking one down may be hard but there is usually a local firm to regrind a stock cam for you.
5. Engine Tunes - A tune/remap gives the most power compared to cost, aftermarket ECUs, and inline Tuning boxes are all alternatives.
6. Flowing and porting the engine head - for larger gains, you will get better flow and make a more efficient engine if you do this to support your other mods.

S65 Tuning Stages

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

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

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

ECU mapping helps release the full potential of all the parts you've fitted to your S65.

(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 NA (naturally aspirated) engines, but figures achieved usually depend much on the parts you've fitted and the condition of your engine.

It is the aim to any engine performance tuning project to force more air and fuel into each cylinder

Intake manifold flow the air from the air filter and allow it to be pulled into the engine cylinders with fuel for the squish phase.

Shape and rate of flow of the Intake manifolds can make a big improvement to fuel atomisation on the S65.

We often see air intake manifolds are begging for aftermarket parts, although a few manufacturers provide well optimised air intake manifolds.

Adding a S65 larger valve kit, doing a bit of port matching and head flowing will also lift power, and significantly will permit increasing the power increase on other parts.

S65 Turbo & Supercharger upgrades

NA (naturally aspirated) 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 S65.

We have seen a few projects where a supercharger was added, and these are relatively easy to setup and map compared to a turbo, pushing power towards the 650hp region.

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

There are tuning limits for every engine, with some being over specified and some only just able to handle stock power and the S65 is actually pretty well tuned from the factory in it's naturally aspirated form but proves to be a formidable base for a tuning project.

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

It's not unheard of car owners spending a lot of money on turbo charger upgrades on the S65 only to see the whole thing throw a rod when it's been completed because the owner cheaped out or was overly optimistic on the stock engines strength..

You'll commonly see there is a limitation in the air flow sensor AFM/MAF on these engines when loads more air is being fed 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 and torque at a much lower level.

Adding a supercharger or additional turbo will make large power gains, although harder to setup. We have a twincharger power adding guide if you want to read more.

S65 Fuelling Mods

Don't dismiss the need pay attention to the fuel system when you are increasing the bhp and torque - it makes the car more thirsty. It is important to over specify your injector capacity.

DeatschWerks offer various fuel upgrades for the S65, with injector options from around 550cc to 1000cc proving popular upgrades depending on your project needs and tuning.

Bosch motorsport injectors have also proved quite popular and are available in a range of outputs.

Fuel injectors are only part of the equation though, the fuel pump itself will need to supply enough fuel to maintain fuel pressure or you'll end up with annoying flat spots or running problems.

As a rule of thumb add 20% when specifying an injector, helps cope with injector deterioration and allows some spare capacity should the engine need more fuel.

A BMS JB4 port injection system will offer more fuelling flexibility and permit the use of alternative Ethanol based fuels.

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.

S65 Performance Exhausts

You should look to increase your exhaust if your current exhaust is actually creating a flow problem.

On most factory exhausts you'll find your flow rate is good 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 can usually air flow from the engine but do not go too large or you might just stuff your flow rate and make things worse. So generally speaking, keep to a size of 1.5 to around 2.5 inches to maximise flow rates, and this should take into account the amount of air your engine is moving.

Typically exhaust restrictions are in the catalysts installed, so adding a faster flowing race alternative such as a sports catalyst pretty much removes this restriction, thanks to it's larger size and surface area, and will effectively raise the performance to levels you would expect without having a catalyst installed, but keeps the car road legal.

Weak spots Issues & problem areas on the S65

The S65 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.

Don't drive it hard until it's warmed up and don't drive it like a high revving turbo car on the redline all the time and it'll last forever.

Gaskets on the valve cover can leak a little oil, you might even smell burning oil as it drips over the hot engine. The heat from the engine causes this and is not a major cause for concern.

Regular oil changes are vital on the S65, especially when tuned and will help extend the life and reliability of the engine.

There was a rob bearing wear issue that led to a few engines failing, this problem is not as common as you'd think looking around, but it is very well documented. If the engine has a tick tick noise at tickover or at low to mid rpms get this checked.

Throttle bodies can fail, and you'll get the EML and DSC lights come up if you didn't realise the car was in Limp home mode.

Rough idling is often down to a faulty idle control valve, which can also cause cold start issues and misfires when under load.

If you would like to know more, or just get some friendly advice on Tuning your S65 engine please join us in our friendly forum where you can discuss tuning options in more detail with our 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 articles which are kept updated and constantly revised.

If you've enjoyed this page we would be very grateful if you could share a link to it on your favourite forums or on your social media profiles, it helps us keep going.

Please Check out my YouTube channel, we're regularly adding new content...

Click to accept YouTube Cookies & Play.

This article is flagged for an update, so please pass on specific tips below that I can include. All articles, and content was written by me, Waynne Smith TorqueCars founder. Some outlines are just too general so I appreciate your feedback and suggestions. This entry was filed under BMW. You can leave a response below or join our forum to discuss this article and car modification in detail with our members.

If you liked this page please share it with your friends, drop a link to it in your favourite forum or use the bookmarking options to save it to your social media profile.