BMW S85: Everything You Need To Know

Winning multiple awards from different International Engine of the Year in various categories seems like a road less traveled for some engine manufacturers, but not for a well-adorned manufacturer like BMW. Debuted in the BMW E60 M5, BMW S85 is a naturally aspirated V10 petrol engine produced from 2005 up until 2010. In its rookie year, BMW’s S85 was nominated and won Best Performance Engine, Best New Engine, and International Engine of the Year for its excellence on M5 and M6 cars. The following year, it bagged the same awards that include Best Engine above 4.0 Liter up until 2008, which eventually, ending S85’s winning streak.

BMW’s previous involvement in Formula One, S85’s engine, was inspired by BMW’s P84/P85 engine installed in the F1 Williams FW27. The S85 engine is the only V10 that is available for sedans. And to flatter the S85s more, the S65 engine took most of its attributes and features from S85s. This engine appears in BMW E63 M6, E60 M5, and Wiesmann GT MF 5. S85 replaced the S62 V8 engine on BMW M5 models, which housed them. However, unlike other BMW M engines, S65s and S85s were not related to a BMW regular engine production.

Engine Specification and Design, and Features

  • Production Run: 2005 to 2010
  • Cylinder Head Material: Aluminum
  • Cylinder Block Material: Aluminum
  • Configuration: V10
  • Bore: 92mm
  • Stroke: 75.2mm
  • Valvetrain: DOHC 4 with VVT 4 Valves per cylinder
  • Displacement : 4999 cc
  • Compression Ratio : 12.0
  • Weight : 530 lbs.
  • Max HP : 507hp
  • Max Torque : 384 lb-ft

BMW S85 is a high revving 5.0 Liter V10 petrol engine designed for power utilization over a wide range of rev band arrays. Its high compression ratio of 12.0, beating previous M3 models, can achieve at least 100 hp/liter while ceiling the redline at 8250 RPM. S85’s cast aluminum block is redesigned, with a bedplate design split at the crankshaft axis; along with its cast aluminum cylinder heads, they were molded to form a 90-degree angle using low pressure. That 90-degree angle helps balance the weight and reduce unnecessary vibrations, especially those are in contact with the camshaft. Pistons for S85s are also made of high-quality heat-resistant aluminum alloy, and it weighs 482 grams that include piston pins and rings.

Installed on most BMW M engines, S85’s also has double-VANOS (Variable Valve Timing) dual overhead camshafts, which vary both the intake and exhaust cam phasing. Its valves are actuated through non-rotating inverted bucked cam followers. Its specific output of 100.0 braking hp per liter ranked highest among naturally aspirated engines, easily produces a peak power of 507 hp at 7750 RPM and a peak torque of 384 lb-ft at 6,100 RPM.

It is also equipped with ionic current sensing for knock sensing that applies a low voltage supply across spark plugs right after the ignition spark can detect misfiring and pre-ignition. Its throttle valve is connected electronically to 10 actuated individual throttle bodies, just like in S65s. S85s has oil-cooled forged aluminum pistons, forged steel crankshaft that has counterweights. Its lubrication system is a quasi-dry sump where the engine has two sumps that hold the oil; the secondary electrical scavenges pump enhances the oil pickup and feeds the oil to the smaller the main sump. Its Engine Control unit is heavily encrypted to protect the software from hacks and modifications.

S85 Tuning and Performance Upgrades

Sometimes, if you are in the zone to think that, maybe, you could upgrade your S85 engine, if you own one, to a more powerful machine- through it’s insanely gorgeous. No doubt that the S85 engine has high power and aggressiveness, and the easiest way to ramp up the horsies a little bit is to buy a cat-back exhaust system, intake system upgrade, and ECU modifications. However, upgrades to this scale could cost you some serious bucks but, you may want a cheaper option, right? Let us say an alternative to cure the itch of performance upgrades, and that is to buy an E60 M5 Supercharger kit. This kit can be installed on stock internals and can boost up to 7psi. And do not forget the ESS connecting rod bearings for an added reliability.

S85 Engine Reliability, Problems, and Repair

As we always say, it does not matter how powerful or exquisite the engine is because there will come a time that some of the parts or components will not be in good condition as they once were. That is why we perform preventive measures to assure ourselves and the engine that we did our best to keep the engine in the best condition. However, problems occur, and we cannot avoid such things. These are some common issues that your S85 engine might suffer:

Connecting Rod Bearing Issues

One of the most common issues not only for S85 but also with S65 V8, which are produced in the same period, is the connecting rod bearing issue. Bearings are like the links that keep the connecting rods held to the crankshaft. If these bearings wear out or are abused, it can lead to a more severe problem such as rod knock, bent rods, or worst, engine failure. Some owners recommend replacing the bearings every 60,000 miles, and you may consider adding to your preventive maintenance routine.

Throttle body Actuator Failure

S85s are not directly connected to the throttle valves themselves, but it is connected electronically to 10 actuated individual bodies. Two banks control these bodies, and those two banks have a throttle actuator inside. The problem is not the actuator but on the internal gears that wear down due to age and mileage. If gears get worn out, it can cause occasional electrical failure and may overheat the engine. You can fix this by buying repair kits that offer new gears.

Valve Cover and Gasket Oil Leaks

S85s have undergone extreme harsh conditions, and rubber-made gaskets are being pummelled with constant heating and cooling cycles resulting in deterioration and cracking. Once it started to have crevices, leakages might follow. Many BMW engines experience this kind of problem as their engines got older, and mileage took its toll on the machine. However, periodically checking your gaskets or covers might be an easier task than replacing them, right?

Summary

Being BMW’s first V10 engine, B85 roared like a madman and embraced its ancestral descent with the right amount of grace and viciousness. Once it hit the streets, you know what’s coming at you. This F1-inspired V10 engine, though it has some minor issues with its rods, actuators, and gaskets, will not change the fact that S85s are dogs in the business even though they came from decades ago. From its fuel economy to the amount of power it gives, you never go wrong with S85s.

We hope that we cleared some clouds in your head and it is our pleasure to help you decide on your next car curiosity.

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