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991 Porsche PDK Drivetrain Into a 993

Updated: May 23, 2022

In case you missed our tech session on “991 Porsche PDK drivetrain into a 993”, here is a recap of what we discussed. -The Idea (why?) -What’s required to install the drivetrain from a 991 Porsche into a 993 Porsche. -Mounts -Cooling system -Exhaust -Electronic engineering to control drivetrains (MOTEC and HTG GCU) -Engine technology in new Porsche engines, specifically the 9A1 engine -Transmission technology

Idea (The Why?) Behind me is “Treiber” (Trybar), Treiber is a 1997 911 993 Porsche. The owner of Treiber came to me with a unique request, he simply wanted a PDK gearbox installed in the vehicle and he mentioned, ‘We have to do something about the power of the engine.’ After throwing around some numbers, I presented to my client the idea of installing a naturally aspirated 400HP 9A1 engine. He was thrilled with the idea and couldn’t wait to see the final product. First up is mounting the drivetrain After removing the original engine and transmission, it was time to see how the 991 drivetrain fit in the 993 chassis. I quickly noticed that the original engine was much bigger than the 991 engine and it was the opposite on the gearbox, as the PDK was much bigger than the 993 tiptronic gearbox. Once the gearbox and engine were put into place, it was time to fabricate mounts for both of them. And once the drivetrain was in place, the cooling system could take shape. Cooling System The Porsche 993 cooling system uses air and an oil radiator to cool the engine. A 991 Porsche cooling system uses water with radiators to cool the engine. We chose to mount 2 radiators up front in the bumper, due to the best air flow across the radiators. 1 radiator takes the place of the oil radiator and the other is mounted behind the ac condenser. After the radiators were mounted, fabrication of aluminum pipes for the hot coolant going to the radiator and the cooled water coming back to the engine were completed. We used as much aluminum piping as possible and only used rubber hose for connecting points, making the cooling system as reliable as possible. Next up the exhaust system.

Exhaust The client requested loud exhaust that also had the option to be quiet at times. We chose to use factory 991 catalytic converters and 993 factory mufflers but with the option of bypass valves, making it loud when the drivers choose. Being a Fabspeed dealer, we opted to use their valvetronic kit. Fabspeed supplied us with helical technologies valve cutouts, these are the same units used on all exotic vehicles, Porshce, Ferrari, ETC. Helical technologies valve cutouts are very high quality and are made in England. Electronic engineering to control drivetrain components We will be controlling the engine with a MOTEC M142 ECU and the transmission with a HTC GCU. These 2 ECUs will communicate on a CAN bus connection. The 2008 and newer Porsche CAN bus system operates at 500kbps. A CAN bus system uses 2 wires, 1 is can low and the other wire is can hi. These wires need to be twisted together to insure transmission/communication stability. The twisting of the wires eliminates interference from voltage spikes, frequencies, etc. A 120ohm resistor is required at the end of each bus connection to terminate the signals. Free feel to examine the transmission harness laid out on the table. Engine Technology The 9A1 has cutting edge technology engineered in its roots. Starting its life in 2009, Porsche was ready to make an engine that had a better following than its predecessor. The challenge that all engine engineers have is making an engine that takes the fuel and burns it as efficiently as possible to produce the most usable power, while still making it cost effective to produce as well and as reliable as possible. Because an engine is simply an air pump and cannot change the ratio of how gasoline burns with oxygen, they simply designed an engine that can vary the amount of air the engine consumes electronically via the ECU. The modern 9A1 engine family has 2 types of variable valve timing. Variable valve timing controls how high and how long the intake valves stay open, which in turn controls the engine’s air intake. One stage is variable lift. It’s like having 2 different intake camshaft profiles, one with small lift (just enough to open the intake) used at idle and below 2500 rpm, and the other profile a very high lift for wide open throttle driving. These are electronically controlled via the ECU with an electronic solenoid. The second type of variable valve timing is the changing when the intake valve opens in relation to the engine’s intake stroke. By changing the timing to a retard state, it limits the amount of air that the engine can pull into the cylinder. On the flip side, by advancing the intake camshaft, it allows the air to get a running head start to fill the cylinder, which is required at high RPMs. To maximize all the airflow that passes through the throttle body, Porsche engineers have fitted a butterfly valve inside the intake manifold. This butterfly valve changes the volume of the intake manifold. When the valve is closed the plenum has small volume for light load and low rpm, on the flip side when the engine requires a larger plenum for conditions of heavy load and high RPM, the ECU opens the butterfly valve. Like most modern engines, the 9A1 is a direct injection engine. You’ve heard the term thrown around, but what does it mean? Direct injection is simply that. The fuel injector is placed in the combustion chamber, right next to the spark plug tip. The fuel pressure in a direct injection system runs up to 3000 psi, around 60 times higher than port fuel injection. Some advantages of this are better cooling, more efficient atomization and full control of injection timing. When the high pressure fuel is released on the intake stroke, it has an extreme cooling effect in the engine, which lowers the detonation chances and in turn acts like a higher octane fuel. D.I engines are able to run higher compression ratios, higher boost pressure on turbo engines and ultimately higher specific output on 93 octane. The last cool future on the 9A1 is the oil system. While the typical engine has a mechanically set oil pressure with a spring and pressure relief system, this engine’s oil pressure is electronically controlled.

Advantages of computer controlled oil pressure:

  • Less drag ,

  • Increased power output ,

  • Increased fuel economy,

  • Increased engine protection,

  • Because it takes horsepower to pump oil, varying the amount of oil pressure can make an engine more efficient.

  • The 9A1 engine has a 4 stage dry sump system.

Transmission Tech

  • 7 speed forward gears,

  • 1 reverse gear

  • All gears have physical teeth, like a manual transmission

  • 2 clutches inside the front of gearbox, separate torque from engine to gearbox

  • All PDK have clutch oil cooler, some have clutch oil cooler and gear oil cooler -The concept of a dual clutch gearbox was invented by French engineer Adolphe (a-doll-f) Kegresse (Kaygris) in 1939. ZF gearbox company was founded in 1915. ZF produces gearboxes for auto, marine, rail transport and aviation (even the 993 tiptronic gearbox has a ZF 4 speed) Jay

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