Is factory turbocharged performance superior? Can an aluminum block deliver the goods? Making the most of the SR20DET engine has been the focus of the D'Garage Silvia S15 project car from day one. With the introduction of our KA vs. SR Challenge, taking the head start that the SR20-powered S15 has and ramping up to further distance it from the KA-powered 240SX is now top priority. After four Test & Tunes and water/methanol injection, the SR20DET last generated 403 horsepower to the wheels. In addition, a JIC Magic suspension setup by Jon at Ziel Motorsports helped to improve the S15's footwork.

As the last of Nissan's factory-turbocharged, four-cylinder engines, the SR20DET offered good horsepower capability and extensive aftermarket support. As for strength, some stock block examples have eclipsed the 500 whp mark with only a head gasket upgrade and the right turbo, fuel system and cam upgrades. Of course, reliability at these power levels and beyond can be addressed with the proper selection of upgraded internals. With this game plan nearly all of the SR20DET's deficiencies can easily be addressed.

SR24DET Block Party

Many SR20 tuners never go beyond an 87mm cylinder bore. This avoids the cost of re-sleeving of the block with aftermarket ductile-iron sleeves. However, it also means that the displacement increase is just about 47cc. Due to its generous cylinder bore spacing, an SR20DET when properly re-sleeved can support bore sizes up to 92mm (94mm for naturally-aspirated applications) with reliable performance. A 92mm bore SR20 will gain 289cc in displacement. When teamed with a 91mm stroker crank, the SR20DET can tip the scales at a 2,420cc displacement (more than a stock KA24 and just 23cc shy of a +1mm-bore KA24DET). Benson's Performance Engine & Machine will resleeve the SR20 block with Benson Signature Gapless Sleeves bored to 92mm. A custom set of Mahle forged-aluminum pistons will fill the cylinders while Carrillo forged connecting rods will link the pistons and the TOMEI POWERED 91mm stroker crankshaft. This new displacement of 2,420cc is an increase of 422cc (21%). Soon, our SR24DET will no longer have a displacement complex as it will be within one percent of Jeren's KA24DE.

Head Games

The later variants of the SR20DET (1995 and up) featured a revised cylinder-head design with variable cam timing on the intake side. This improved low- to mid-range torque production, adding power where the SR20 was lacking. To further improve airflow in and out of the cylinders, higher-lift, longer-duration camshafts must be employed along with valvetrain improvements. Our cylinder head will be hand ported and the combustion chambers reshaped for the 92mm bore by TOMEI POWERED before receiving a full complement of TOMEI POWERED valves, springs, retainers and solid lifters. Since the factory valvetrain relies on rocker arms with self-adjusting hydraulic lifters, there is no need to adjust for valve clearance when used with mild cams. But the shortcoming of this valvetrain is the potential for the rocker arm to be thrown from its position on the lifter, leading to catastrophic engine damage. For high-lift/long-duration camshafts and a higher redline, the solution is to switch from hydraulic lifters to solid lifters. This requires shimming of the rockers in order to attain proper valve clearance. But the reward is well worth the effort, as maximum engine speed will now be limited by the rotating assembly and not the valvetrain. TOMEI POWERED 270-degree camshafts with 12.5mm lift will actuate the valvetrain and facilitate increased airflow in and out of the cylinders.

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