Deep in the troubled hearts of many hot-rodders lays a two-part desire that often leads to trouble. The first part involves making machines do things they were never designed to do, outsmarting factory engineers with frugality and mechanical savvy. The second part is all about embarrassing people who spent a lot more to go fast, or who feel smugly secure because they did. From these dark desires are monstrous sleepers born -- even from as humble a creature as the 2000 Hyundai Elantra.
Since you're already looking for tips on upgrading your little Elantra, you've already noticed how hard performance parts are to come by. The Elantra is one of those cars that never exactly developed a performance following; few Korean cars have, particularly those from this era. Few -- but not "none." Today, Hyundai is rapidly developing some real street credibility with cars like the Genesis and Veloster, and that all started with the 1996 Tiburon. The Shark was Hyundai's first real stab at grabbing a piece of the burgeoning sport compact market; the Tiburon wasn't a supercar, but Hyundai was serious enough about it that they quietly tapped Porsche for input on the suspension design. The Tiburon is the reason that a certain degree of aftermarket support grew up around the 2.0-liter G4GM Hyundai Beta engine -- the same one used in the 2000 Elantra.
Beta Engine Horsepower
The bad news is that the Beta engine's cylinder head was never really designed for performance use; it has a number of sharp turns and odd kinks in the intake and exhaust ports, and porting them will only help to a certain extent. That's going to limit naturally aspirated horsepower compared to more performance-oriented four-cylinders like contemporary Hondas'. A cold-air intake, cat-back exhaust and computer tune will get you about 120 to 125 wheel horsepower. Those experienced with fabrication have been known to cut the intake manifold runners, and polish and shorten them to boost high-rpm horsepower; matched with a set of reground performance cams and a larger throttle body designed for the Tiburon, all this might get you 180 to 200 horsepower. But that head is ultimately going to limit power potential without a little extra help.
Do a quick web search on "Elantra turbo," and you'll probably wind up finding something like the RX Racing Street Demon kit on eBay. These kits are basically universal kits with a custom manifold and a few extra bits designed to fit this engine. They're very cheap at less than $2,000, but most of the parts are Chinese and you'll get what you pay for. If you're shopping for a good turbo kit, it pays to go with one engineered for your car. As of 2013, Australia is home to one of the few companies offering a custom-built turbo system for the Elantra, and a specialist like Silverwater Automotive will offer the kind of customer service and experience-based help you just won't get with a Brand X Auction House kit. A 7-psi turbo kit will get you about 200 horses, and shouldn't require any other major mods. If you opt for a bigger turbo, consider a set of forged 8.8-to-1 pistons like those sold by CP mandatory equipment.
There's always nitrous; the Beta engine is known to take a 75-shot of nitrous oxide without breaking, and some have reported using upward of 100 to 150 horsepower's worth. The transmission is safely good for up to about 200 horsepower without modifications, but a big hit of nitrous is going to put it closer to breaking. Shedding weight is always good for speed, but the market isn't exactly flush with carbon fiber parts for this car. Your only real options here involve removing things like interior parts, the spare tire and soundproofing; you can replace them with racing seats and spray-on truck bed-liner to keep things both civil and waterproof. Available lightweight aftermarket wheels will help you shed both curb weight and rotating mass, which will help in all aspects of performance. A few manufacturers, including Koni, offer adjustable shocks and stiffer lowering springs for this chassis.