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A key feature of the Flatnose and Package cars was the M64/50S engine - the X88 'Sport Tuning' option, a factory derivative of the 1993 IMSA 3.6 Turbo engine built by Andial for Brumos racing. According to the factory, 155 X88 option engines were built. Ninety-three of these engines went into the 'Turbo S' cars, 51 engines were installed in standard 3.6 turbo models as special order option 'X88' and 11 engines are unaccounted for possibly test engines, sold to dealers as retrofits or sold to customers for race applications.

The 'S' designation is denoted by an understated punch stamp!

Engine Serial Number
Engine Type Stamp

So just how powerful is this engine? Largely generated from the April 1994 Excellence article early speculation turned to myth that the car was really producing 480 to as much as 508 HP. Speculation was that Porsche had understated the actual figures. Porsche always discloses its horsepower and torque figures from the engine bench. Using this method the 'S' engine was rated at 385 HP by the factory in its technical bulletins. Interestingly, most USA MSRP stickers misquoted the rating at 380 HP and some of the earliest USA MSRP stickers misquoted the rating at 355 HP (which was the HP rating for the standard 1994 3.6 Turbo).

The following charts are non-SAE adjusted rear wheel HP dyno runs of a stock X88 engine and an X88 engine modified with bolt on items. The stock engine (see photo of Unidentified USA Car on dyno) produced 305 HP to the rear wheels and the modified engine produced 375 HP to the rear wheels (a 70 HP gain). So what is the answer? Depending on what percentage loss figure you use from crank to wheels the stock unit most-likely produces no more than the factory stated 385 HP at the crank.

  Stock X88
  Modified X88

  The M64/50S engine obtained its increased power from specially modified cylinder heads with different than standard inlet and exhaust ports, upgraded camshafts, modified timing gearwheel and the K27 7006 turbo charger (the K27 7006 has a larger hot side than the K27 7200 in the standard 3.6 Turbo which makes for a 300 rpm later boost onset which lowers back pressure in the exhaust manifold increasing efficiency to make more HP - 7006: inducer/cold 58.5mm exducer/hot 64mm - 7200: inducer/cold 55mm exducer/hot 59mm). Valve timing was advanced from standard for more overlap and richer mixture. Maximum boost pressure was 0.79 to 0.85 bar the same as the standard 3.6 turbo engine (although the onboard computerized boost gauge only reads to 0.7 bar as described in factory technical bulletin '9032-9307').

The following information on the 911 3.6 Litre - Engine with Increased Output - X88 is from the factory technical bulletin 'Xe'.

Engine with increased output - X 88

Part No Part designation Qty

964.105.247.08 Camshaft, left-hand
964.105.246.09 Camshaft, right-hand
911.105.171.02 Spacer flange for LH camshaft
900.067.082.02 Bolt
900.082.072.01 Bolt
930.113.025.03 Gearwheel
930.100.908.03 Gasket set
930.123.003.03 Turbocharger
930.123.121.06 Turbocharger Bracket
964.104.033.22 Cylinder head
930.110.141.04 Flange
930.110.034.05 Inlet manifold

Engine - X88 Type - M 64/50S

Displacement 3600cc (3.6L)
Output 283 KW (385 HP) at 5,750 rpm
Torque 520 (53 kpm) at 5,000 rpm.

Scope of Modifications to M64/50 Engine

Cylinder head intake & exhaust ports modified
Inlet manifold and spacer flanges modified
Modified camshafts
New turbocharger
Turbocharger bracket
Valve timing 1.26 + 0.1 mm (inlet valve stroke in overlapping TDC


VIN# on Engine Case to
Ensure Matching Numbers

Crank Case Part Number
  The 1994 964 Turbo S is the last of the 'x-tronic' cars. Everything that came after was 'OBD' compliant. This means that these are the last of the cars where you can "get away with it" when it comes to engine modifications and emissions standards.

The following photos are of a M64/50S motor as taken during an engine resealing.
The 'Typ 965' Designation
Shows up on the K Jetronic
Engine Before Initial Teardown

M64/50S Long Block
Special Cylinder Heads

Special Cylinder Heads Mounted on Block
Short Block with Cylinders

Short Block
Special Camshafts
Pistons - Note Factory Installed 993 Style Fully Threaded Head Studs on Exhaust Side
40 Pounds of Stock Heat Exchangers
20 Pounds of Stock Cat &
22 Pounds of Stock Exhaust

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