If you’ve ever driven a naturally aspirated SR20 engine, you’ll know that for what they are, they are torquey little buggers. With an 86x86mm boreto-stroke, the SR20 engine is able to both rev fairly high, and produce a decent amount of torque for their given capacity and aspiration. Although not a world beater, the factory motor does have a decent amount of potential; so if you do want to leave the original motor in the hole, there are a few things you can do to get some better numbers. First off, the factory exhaust system and intake is fairly restrictive; replace the exhaust with a mandrel-bent 2.25-inch to 2.5-inch system from the headers back, and the intake with a 3-inch alloy pipe, pod filter and cold-air box. All are a given, as with most naturally aspirated engines, but with the Primera, the real results come from tuning the factory ECU with an aftermarket daughter board, or EPROM. The EPROM acts as a fully tunable ECU and it gets socketed into the factory ECU, so you retain all the nice factory features. Very good gains are to be had once a daughter board has been installed and the best part about it, is once you have upgraded the engine further, you can have it retuned to suit. If you’re after a little more power, but still want to stay N/A, the SR20VE engine out of the Nissan Primera P11 bolts straight in. The SR20VE engine features ‘Neo’, which is essentially Nissan’s version of Honda’s Vtec hardware. We won’t get into immense detail as to how Neo works, but like Vtec, it operates using hydraulic pressure which operates a seperate lobe on the camshaft for a huge increase in valve lift and duration. The camshafts have two different lobes per valve, one best suited to low-rpm torque, and one with a much larger lift and duration to suit high-rpm power output. With the same modifications listed for the SR20DE, you should net a solid 20-30kW more peak power with the VE. If you’re addicted to turbo, and the SR20VE doesn’t give you as much power as you’d like, there is good news for you; the SR20DET engine in multiple variations drops straight in too. The Nissan Avenir W10 SR20DET turbo engine features stronger internals than the SR20DE and is fitted with a small Garrett T25 turbo; these engines produce 157kW (207hp) from the factory and are your cheapest turbo option. The Avenir W11 SR20DET turbo engine is your next best bet — the engine itself received minimal changes — but the turbo was upgraded to a ball-bearing T25, and because of this, power was raised to 169kW (227hp). The ball-bearing turbo on this engine is super responsive, and although it doesn’t make the most power, it sure makes for a fun car to drive. Last, but certainly not least, is the N14 GTI-R SR20DET engine. Featuring quad throttle bodies, a much larger Garrett T28 frame turbo and bigger injectors than the other engines, this is the one to look out for if you’re chasing over 200kW without upgrading to a larger turbo. If you still have the daughter board installed, serious gains can be had with a Z32 afm, 550cc injectors, and a boost controller.