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.
-Cooling system
-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.
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)

Speed Density Motorsports will be hosting an advanced tech session on February 6th, 2021.
Want to know what it takes to swap a 991 Porsche PDK drivetrain into a 993? And have you ever wondered why it hasn’t been done before? We will be covering in detail just what is involved in installing a 9A1 Direct Injection 400HP 3.8 flat six Engine and a 7 speed PDK Gearbox into a Porsche 993 chassis. Maximum number of attendees is 30, reserve your spot soon! Email us at sales@speeddensitymotorsports.com for more information and to reserve your spot.
Look for the follow up with all the details discussed during the session! Jay

A look back onto 2019.
In the beginning of 2019, we set some lofty goals. We had our eyes set to achieve 1200-1500whp for our 996 turbo. Looking to break past the 200+mph ½ mile trap speed, we knew we had to have a power plant producing between 1200-1500whp. To help with traction at this power level we continued testing on our SDM 996 4WD controller. We believe this product will be a game changer for the 996 Turbo chassis. The SDM 996 4WD controller worked flawlessly and we had full traction even with the factory Michelin Pilot sport tires all the way up to 180mph! We chose a VW VR6 engine swap into a Porsche 911 chassis. This included fabricating engine mounts using the factory engine plate from the 996 turbo, and designing and building an intake manifold to fit in the tight engine bay and still flow the volume we needed to make well over 1000whp. To complete the air flow path we fabricated a turbo manifold, mounted a large 8385 turbocharger from Precision Turbo and finished it off with a Syvecs ECU for the increased fuel, air and spark control. Another obstacle we had to overcome was combining a cooling system from the VR6 engine to mate up with the 911 radiators. The VW VR6 is based mostly for FWD transverse configurations which made the task a little daunting. Once we had a game plan for all the systems in March of 2019, we were ready to get the project going.

Fast forward to the beginning of June 2019, and things were looking up. The long block was assembled, intake and turbo manifolds were done, exhaust system was completed, the fuel system was 90% done. But as of a few days before our race day in Colorado the engine still had not fired and the cooling system and intercoolers piping were incomplete…and so the long days continued. Thanks to 17 hour work days, we were finally able to get the car fired up, the cooling system completed and pressure tested, the intake pipes fabbed and we performed an initial break in on the engine. Once the engine saw operating temp, the engine oil was replaced with a high grade racing oil from Valvoline and we were ready to set the 911 chassis on the Dynamometer rollers.

June 20th was a big day. As with any fresh new builds, the car experienced a few mechanical odds and ends repairs. While sorting through issues we were able to produce 824whp and 564wtq on the dyno. This power was made on wastegate spring pressure, 22psi. With one of the issues, being unable to control boost via the ECU, the boost unfortunately was stuck at 22psi until further notice. We knew that in order to make around 1200whp we needed to increase the airflow of the engine to a boost pressure in the 40’s and in order to run 200mph in a half we needed around 1200whp. Because we were racing June 22nd and 23rd in Colorado and being located in the middle of TN, we had to load up and start heading out. We were able to diagnose and find the issue of boost control while on the road at a hotel one night. We found that there was no power to the wastegate solenoid, causing it to be an open circuit. We quickly rerouted a power source to the wastegate solenoid and we now had boost control via the ECU.

We arrived at Colorado Spring Airport safely and were able to make our first pass. While going down the track, it was quickly apparent the engine was breaking up/misfiring and all the fuel and air that the turbocharger was packing in the engine wasn’t being burned correctly inside VR6 air pump. We found that the excessive heat from waiting in the stages lanes prior to the run caused the ignition coils to show their age. Upon further inspection, we found small cracks forming at the base of 4 of the 6 ignition coils. The original 996 Turbo coils had failed. What seemed like a hopeless race weekend quickly turned around. A gentlemen who was a technician at the Porsche of Colorado Springs Dealership had dropped by to check our car out. Long story short, a few hours later we had some brand new 997 Turbo coils in our VR6 engine and we were back up and running. With the ignition system and the wastegate fixed we were able to make our first clean pass. The boost pressure yielded roughly 30psi, confirming that we had successfully repaired our boost control and the new 997 coils were making sure that all the fuel was being ignited in the VR6 air pump. At 30psi we estimated the engine was making a little over 900whp, to propel the 3500lb 911 chassis to a speed of 179mph in a half mile. Looking at the logs for our 179mph run, the turbocharger was only producing the following boost per gear: 1st-14psi, 2nd-28psi, 3-5th-30psi.

Being our first time racing at high elevation with the lack of air pressure we quickly learned a thing or two about large turbochargers. As you increase in elevation, the atmospheric air pressure decreases. What this means in terms of turbochargers is simply that they multiply air from atmospheric to desired boost set by the wastegate spring. Therefore, if you start with less atmospheric pressure, the turbocharger requires a faster shaft speed to develop the same pressure as it would at a area with higher pressure such as sea level. We were able to make another clean pass at around 30psi yielding a speed of 180 in the half mile.

After our next pass we realized that because of the lower air pressure and our wastegate solenoid routing being a 3 port, 30 psi was the highest boost we could achieve with this setup. Without access to a 4 port wastegate solenoid and more time at the track, 180mph was the highest speed we were capable of running the weekend at Colorado Spring Airport.

We returned to Middle TN and installed a 4 port wastegate solenoid, got the car back on the dyno and were able to produce 1203whp at 49psi! We had plans to bring the car to another half mile event towards the end of 2019 to test it with the 4 port wastegate solenoid, but we were unable to make it out.

2019 Recap

World’s first 996 VR6 911 Turbo!
180mph in the half mile
Release of the SDM 996 4WD controller
Production of the SDM Billet intake manifold
Prototype of VR6 Billet Valve cover

Stay tuned as we share what we have planned for 2020!

A look back into 2017 with our stage 2 package. With the goal in mind to achieve 175mph in a half mile with a stock 996 turbo 3.6L Mezger longblock engine we knew we had to start with high quality components. This goal of 175mph in a half mile with a 3500 pound vehicle, manual shifted transmission would have to have a power plant producing somewhere in the neighborhood of 750-800 horsepower. To increase airflow into the engine we chose a set of Precision 5858 Turbochargers. These turbocharges are mounted to the engine with a set of custom turbo manifolds built in house. Hanging in front of the turbocharger exhaust inlets we mounted a set of Precision 46mm waste gates. These gates are responsible for controlling turbocharger shaft speeds by diverting a portion of exhaust to bypass the turbocharger exhaust wheel. The waste gates ultimately are the ones responsible for controlling boost being fed into the engine. After the Precision turbochargers spin up to compress atmosphere air, the air is forced throught a set of 4.5″ bar and plate inter coolers. We chose a set of SRM 996 turbo inter coolers, because of there high quality and efficiency. Since an engine is nothing more than an air pump, increasing airflow into the engine requires an increase of fuel. This increase in fuel is responsible for the increase in horsepower and torque that the engine produces. For fuel upgrades we went with a set of 1700cc injectors from Injector Dynamics, a custom twin fuel pump basket with 2 Walbro 480lph fuel pumps and stainless fuel lines with AN fittings. While our stage 2 package is available in a pump/race fuel or E85 configuration, we chose E85 as our fuel source. E85 is a great fuel with an octane rating of around 105 and it burns 30% richer, meaning more fuel to air ratio, which in turns has many benefits. E85 advantages include cooler intake runners, back of intake valves, piston tops as well as cooler combustion chambers. The increased octane rating from fuels such as E85 allow the air pump to compress the fuel without self ignition, which in turns allows higher compression ratios, higher boost levels or higher cylinder pressures with a steady controlled burn of fuel being initiated by the spark plug rather than heat, also know as detention. Responsible for controlling the engine we chose the standalone Syvecs. Syvecs does an perfect job integrating with the factory modules for a seamless operation which behaves just as the factory ECU does, including full operation of instrument gauges. Syvecs has the ability to monitor critical engine data such as oil pressure, coolant pressure, knock activity, air fuel ratios and fuel pressure. We were able to acheive 175.9mph on stock Michelin sport 2 tires.

SDM Billet intake manifold
Fitting a VR6 Vw engine into a 911 chassis was no small task. With our goals to make well over 1000whp, we had to design an intake manifold that fit under the rear decklid and flow enough air to make the power we had in mind. We chose to use a Skunk2 plenum as a starting point and design a lower manifold to bolt to the inline six style head. We designed this manifold to be modular. What we mean by this, is we will be offering this setup in 12 different configurations. The plenum will come with a center feed option and a side feed option. The center feed plenum from Skunk2 has a large volume plenum starting at 5 liters. In our 1200whp VR6 we used the center feed plenum and the Skunk2 2 liter spacer, giving a total intake plenum volume of 7 liters. The side feed is best fitted for transverse drivetrain configurations such found in the Vw Golf, Audi TT and Audi A3 platforms and has a volume of 3.5 liters. With this swap becoming ever so popular in the Audi S4 chassis the side feed or the center plenum could be used.

Tech information on the VW VR6 Engine.
The VR6 block in stock form is a great starting point to produce high RPM horsepower. First off the block is made of cast iron. On the underside it has 7 main bearing caps. The 7 main bearing caps house a very sturdy crankshaft. Because the VR6 is neither a V6 or a inline 6 cylinder engine, it has a very small footprint and overall size is nearly identical to a inline 4 cylinder engine. Spinning at the bottom is a short forged crankshaft. The crankshaft measures a little over a foot and half. These factory crankshafts found in the 2.8 liter VR6 and 3.2 liter VR6 are both forged steel units.

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