If I had a dollar for every time someone asked me when I was going to swap in a SR20DET engine into my 240 I would be a rich man. Okay, I'm exaggerating but the point is that everyone thinks that if you own a 240SX you need a SR20 in it...the faster the better. And can you imagine the reaction of these people when I tell them that I plan on building the stock KA engine and turbocharging it? It is as if I am performing a sacrilegious act on my car and I shouldn't be allowed to own a 240.
Don't get me wrong, I will be the first to tell you that the SR20DET is an awesome engine. But I feel the KA24DE can be an equally powerful engine with some work. The last time I checked, an SR20DET changeover cost anywhere from $2,000 to $2,500. With that money you get about 200 to 220 flywheel horsepower, which equates to about 170 to 180 horsepower to the rear wheels. Most SR20DET enthusiasts will often times add an upgraded downpipe, high-flow air filter, exhaust and a piggy-back fuel computer. With those upgrades the engine should generate around 250 to 275 horsepower to the wheels. If you want to generate any more power beyond that you will need to upgrade the head gasket, fuel system and turbocharger, which can add up to a couple thousand dollars. We felt instead of spending money upgrading to an SR20 engine we could fully build a KA24DE engine from the ground up to withstand boosted duty.
We decided to add some performance upgrades to Project Silvia while we searched for products for our boosted engine. Our first avenue for more power was to increase the exhaust flow. Although future plans are to turbocharge the KA engine, we found a used GReddy tubular header at SP Engineering. It came from one of the employees who installed a SR20DET power plant and no longer was using it. Although GReddy no longer offers the header, we wanted to check out how well the header works. We expected the long tubular runners and 4-1 collector to increase mid- to top-end power of the engine. On the dyno, the GReddy unit performed like a champ pushing the power output of the KA from 136.3 to 141.1 horsepower. Peak torque also rose from 145.6 to 152.2 lb-ft. The GReddy manifold produced power exactly where we thought it would, from 3750 rpm to redline. The largest power increase we witnessed was at 5200 rpm with an increase of 7.8 horsepower.
Anticipating the future turbocharger, we wanted to find an exhaust system with large diameter piping to expedite the increased exhaust flow from the turbocharger. Our search ended by selecting the Blitz Nur-spec polished stainless steel exhaust system. The Nur-spec piping measures in at a behemoth 80mm (3 inches) in diameter. If this system doesn't take care of our exhaust needs, nothing will.
We were worried, however, of how loud the system was going to be with the 80mm piping diameter. Fortunately, the exhaust system comes with a silencer and it does a great job of quieting the exhaust note without sacrificing too much power (see dyno chart).
The two-piece exhaust system is constructed from mandrel-bent polished stainless steel piping with a robotically TIG-welded muffler canister and large diameter tip. The system bolts up to the factory downpipe and retains factory the catalytic converter. On the Dynojet the KA posted 146.6 horsepower and 156.1 lb-ft an increase of 5.5 horsepower and 3.9 lb-ft. From 5700 rpm to redline the Blitz system generated 6 to 7 horsepower over the stock system.