In last month's installment we were able to pump up the KA24DE engine using an AEM intake, a DC Sports race header and an AEM EMS system. Although some might say the power output might be a far cry from the more potent SR20DET, the KA is more than capable of propelling the Nissan up to speed. From our research on the KA engine, however, we were surprised to find a number of owners keeping the so-called "truck" engine rather than performing the swap. Additionally, because the SR20DET conversion has been done a thousand times over we wanted to see the true potential of the KA. Our eventual goal is to fully build the engine with stronger rods and pistons, and to port and polish the cylinder head. We hope to have a sheet metal intake manifold made and also have a custom tubular turbo manifold fabricated for the 240SX. But that's down the road. For now we need to address a more important issue hindering the true performance of the Nissan: the suspension.
In its current state, our 240SX handles like an all-wheel-steering car without having any control of the direction of the rear two wheels. Even at freeway speeds, the car feels like it will lose control at any second when going around a slow sweeping turn. In all honesty, we should have addressed this issue before pumping up the power of the vehicle - but the horsepower bug got the better of us, and we were waiting for the Peak Performance rear suspension arms to come in.
First on the agenda was to replace the tired rubber bushings on the 240SX with stronger and stiffer polyurethane bushings from Energy Suspension. Any vehicle that has gone beyond its tenth birthday should strongly consider upgrading the rubber bushings with new polyurethane pieces, or, at the very least, new rubber bushings. If you enjoy taking your vehicle on a "spirited drive" on occasion, polyurethane is the only way to go. Keep in mind that the Energy Suspension polyurethane bushings are much cheaper than the factory rubber pieces. And, with over 25 years in the polyurethane formulation business, and nine U.S. patents to their name, the company has done its homework. For vehicles that see occasional track time, the Energy Suspension products are a no-brainer - as rubber bushings are too soft for ultra sticky R-compound tires and have too much flex for the suspension to work properly. Polyurethane bushings are much stiffer, allowing the suspension to function properly under hard driving conditions.
Installing the polyurethane bushings should be left to the professionals, but if you plan on performing the swap yourself you better have at least a 20-ton press to push out the stock bushings. We were fortunate to have Energy Suspension engineers Bill and Jeff help us out and replace the tired stock bushings with polyurethane. The hardest part of the install was removing the rear lower arm bushings from the arm. This required using a chisel to bend the bushing end before being able to push the bushing out on the press. We recommend giving a professional a call to before attempting this on your own, because it was a pain in the rear. The biggest culprit to the sluggish steering was the rack and pinion bushings that were nearly nonexistent. One of the bushings was half torn off and the other had deteriorated into a rubber sponge from a previously leaking oil pan.
Now the 240SX actually responds to the steering wheel, unlike before when there was a short delay. This was probably from the rack and pinion actually moving before turning the wheels. Although the we opted for the complete Hyper-Flex kit that replaces nearly every single bushing, we didn't replace bushings in the rear upper toe arm, traction bar or upper camber arm, because we replaced them with Peak Performance multi-link suspension arms that have spherical rod ends. After the bushings installation we went for a test drive, and we must say that the Energy Suspension pieces provided a huge difference in the handling of the 240SX. Granted, the factory bushings were shot; but the car handles much better than before. We were worried that the polyurethane bushings were going to be too stiff for bumpy roads, but we didn't notice any stiffer of a ride.
For round two we needed to address the knocking between shifts. (I told you the Nissan's suspension was shot.) The knocking sound was the rear subframe hitting against the frame of the 240SX, a fairly common problem with S13 and S14 240SXs. To fix our knock subframe issue, we did our research and found Peak Performance subframe urethane bushings. The urethane bushings do not replace the factory bushings, but are inserts to remove any possible play in the subframe. There are also aluminum subframe bushings on the market, but, unless you plan on drifting the car regularly, we recommend sticking with urethane. A total of eight bushings come in the Peak Performance kit (four uppers and four lowers). The upper urethane bushings are split, so it does not require dropping the entire rear subframe to install them. We found the best way to install the bushing is to work one side at a time. The swap can be performed on the floor using a jack stand and a floor jack, but a lift would make it much easier. We spent about 20 minutes replacing the bushings using simple hand tools.