981 GT4 RS - The Car Porsche Never Built

Many years back, Flat 6 Motorsports took a 981 Cayman (base) and swapped a 3.8L X51 engine out of a 991.1 GTS into the modest base Cayman. Adding key elements like a GT4 bumper, 991 Carrera S brakes and JRZ coilovers, the result was an amazing car for it's time. The concept was a GT4 Touring. A recent opportunity arose to purchase another base 981 Cayman.

981 Cayman GT4 RS (4.2L X51) - Flat 6 Motorsports

Humble Beginnings

This car had a salvage title from a rear-end impact. Fortunately, the damage wasn't significant enough to cause any frame or structural damage, just a bunch of broken plastic, lights, etc. The former owner rebuilt the car and added some GT4 bits. The car was enjoyed with about 82K miles on the chassis when the previous owner money shifted the car and caused some damage to the heads. To our surprise, the car ran but after heat built in the engine, the valves were hitting the piston. We knew we needed an engine when we purchased the car. Ironically, we had the 2.7L engine with 8K miles on it that we pulled out of the previous 981 Cayman Build, but...we decided to tear that apart to make a light fixture with!

Getting More Than Deserved

Maybe some would call it an overinvestment, perhaps we should have just purchased a GT4 but, we really enjoy testing parts for clients and building inspiration with what is possible. Our friends over at BGB Motorsports had built the ultimate 9A1 engine for a client. Some circumstances changed and they pulled the engine out of his car after about 10 hours of use. When we saw them post this engine for sale, we said "why not?!"

This engine started it's life as a brand new Porsche 3.8L X51 engine, the same that we had in the previous Project 981 Cayman. However, it was extensively reworked to extract maximum power. It was bored and stroked to achieve 4.2L of displacement, the heads were CNC ported along with a valve job. BGB revised the valve flapping in the X51 manifold and custom integrated a 92MM hellcat throttle body to get more air into the engine. This engine made 460whp on their dyno and is the highest horse powered non-GT Flat 6 engine engine in the world! We had an opportunity to dyno the car on our dyno which produced 457whp which translates to roughly 520HP at the crankshaft. A massive improvement over the 2.7L engine which good examples make 236whp on our dyno.

Piecing It All Together

With the significant investment into the engine, we decided to build a 981 GT4 RS concept. We recently built a 992 Carrera T, that we akin to the GT2 RS Touring so the concept of a street focused but track capable weapon started to drift more towards a true track set-up car. Frankly, if it was a clean spec'd 981 GT4, maybe we wouldn't have gone this far but given the history of the car, we decided to go for it. We liked the Sapphire Blue Metallic paint color but given the fact that we had 3 different shades of it form the previous owner, we decided to incorporate a custom Flat 6 livery. This was inspired by our livery for iRacing. We replaced various missing pieces throughout and under the car. We decided to use a CSF center radiator and use all of the GT4 OEM ducting to give the car as good of an aero balance as possible. We added GT2RS fenders and out back, we replaced the decklid with a clubsport decklid so we could bolt a real wing to the rear hatch. Instead of glass, we went with a polycarbonate rear window to save weight. With over 1/2 tank of fuel, the car weighed in a 2,895 lbs with everything on the car. We also did some subtle enhancements like adding a 991.2 GT3 RS Alcantara GT Sport Wheel (yes, we changed the back plastic cover for the manual version), 981 GTS tail lights and a Raceseng shift knob. Since there is a very long list of modifications, we're just going to list them below. The idea was to make the car as fast and focused as possible.

Engine / Drivetrain