This is a two stage project on 2008 Mitsubishi Evolution X GSR involving Tomioka Racing Exhaust Manifold, Widemouth downpipe, test pipe and the all new Sigma Turbocharger.

Official engine power and torque rating of 2008 Evolution X GSR are 290 HP and 300 pounds-feet respectively. We all know that those numbers slip when measured to the wheel horsepower and torque. Typical power and torque drop on dynapack dyno are 20%, so realistically we are looking at 232 whp and 240 pounds-feet of torque. This particular unturned Evolution X GSR achieved 245 whp and 241 pounds-feet of torque.

2008 Mitsubishi Evolution X GSR Stock Dyno

The first stage of the test were the installation of the tubular exhaust manifold and widemouth downpipe. The second stage installations were Tomioka Racing Sigma Turbocharger, High-Flow fuel rail and test pipe. Other supporting modifications included larger fuel pump, 1000cc fuel injectors and aftermarket lower and upper intercooler piping and Turbo inlet hose.

The Tomioka Racing tubular exhaust manifold for the Evo X is constructed from stainless steel 304 materials with larger piping diameter. The exhaust manifold is guaranteed to increase the exhaust flow efficiency of the 4B11 engine. The bolt-on exhaust manifold comes complete with gasket for easy installation. The mirror finish of the Tomioka exhaust manifold adds a stylish upgrade from the cast iron factory exhaust manifold.

Exhaust system upgrade is not complete without the addition of downpipe. The Tomioka exhaust manifold needs a matching downpipe to meet its increased exhaust flow.   The Tomioka Racing widemouth downpipe replaces both the factory housing and downpipe. The downpipe styles a wide-mouth opening bolted to the turbo exhaust housing and a 3-inch piping connected to the factory test pipe. In Tomioka style, the downpipe is constructed from stainless steel 304 materials and mirror finish that exhibit quality and top-notch craftsmanship. The downpipe comes complete with gaskets and hardware to bolt-on to factory Evolution X.

When the header and downpipe were installed on the GSR, it was ready to get tuned on the stage 1 upgrade. During the initial dyno pulls, the car ECU was definitely thrown off by the increased exhaust flow. With a little bit of tuning, this GSR achieved a peak power of 320whp and torque of 340 pounds-feet of torque on Dynapack dyno. The red arrows show the efficiency gained from the exhaust manifold and wide-mouth downpipe installation with engine tuning. The turbo spool is greatly improved with substantial gain on the low RPM power and torque.

With the success of stage 1 upgrade it was ready to move on to stage 2 modifications. Tomioka test pipe for the Evo X is a straight-through design constructed from stainless steel 304 materials. As in Tomioka tradition, the test pipe is bolt-on and comes with all hardware necessary for installation. To complement the larger turbo and 1000cc fuel injectors are the Tomioka Racing high flow fuel rail which supports up to 650 HP applications. The fuel rail is constructed from high quality aluminum and comes with all the necessary hardware for bolt-on installations.

The last mod on stage 2 is the Tomioka Racing Sigma Turbo.  The journal bearing turbo is rated at 550hp with upgraded 21 PSI (1.5Bar) actuator. The Sigma turbo has larger compressor inlet and outlet diameter of 61.4mm and 82mm respectively with 58.8mm and 67.1mm turbine wheel diameter. More value added feature is the ported and polished exhaust housing which comes standard with the Sigma Turbo.  All of this with the turbo 100% bolt-on!

With all the parts installed on the GSR, it was ready for the stage 2 dyno tune. With a very safe tune and on 91-octane pump gas the GSR achieved peak power of 362 whp and 306 pounds-feet of torque.

The GSR experienced turbo lag and loss of torque compared to the stock turbo but it gained substantial top-end power with the Sigma turbo. With a slight aggressive tuning, the GSR managed to hit 379 whp and 331 pounds-feet of torque on Dynapack.

Evo X GSR with Aggressive Tune

Finally on 100-octane gas, we stopped after the GSR hit almost 420 whp at 27 PSI of boost with stock camshaft. It was an exciting dyno runs for one day!

Evo X GSR with 100 Octane

Full potential of Tomioka Sigma turbo is not yet realized. With higher lift and degree camshaft, the GSR will meet or exceed the spool time of stock turbo and gaining higher top-end power along the way. Another important bottleneck is cooling. The GSR had reached the optimum cooling from the stock front mount intercooler. A more efficient intercooler is definitely needed to match the full potential of the Sigma turbo. After all of that is achieved, the Evo X GSR will truly be a sleeper with a quality & affordable turbo!

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