Fans of the Civic Si disappointed with the EP3 were encouraged to see Honda step up with the next version of the performance compact. The rollout of the Si Concept at the Chicago Auto Show this past winter got tongues wagging and minds racing around the HT offices.
Honda is proposing a 200-hp i-VTEC plant (no doubt a K) with an 8000-rpm redline mated to a close-ratio six-speed gearbox transmitting through a limited-slip differential. Bad-ass.
In light of such tantalizing news, current-generation Si owners may feel like they got the short end of the stick. The three-year-old EP3, in spite of its bad rap, has earned a loyal following that has found ways to improve on the model's shortcomings. Head and engine swaps, particularly of the JDM variety, are especially useful in bridging some of the performance gaps, and the hearty K-series crowd has found other aftermarket ways to pump up the virility of the K20A3.
Less known is how to bring the gearboxes up to snuff. Nikos Stoufis, the administrator and owner of K20A.org, explained the process of converting the five-speed EP3 and base-model RSX manual transmission into a six speed. It involves combining base RSX/EP3 Si and RSX Type-S gears. The routine requires previous understanding of Honda transmissions, but is fairly straightforward for folks comfortable around a gearbox.
James Farrar, proprietor of Fearless Racing in Houston, Texas, first pitched the idea to Stoufis, then performed and documented the swap for HT. Farrar scavenged some parts from a broken Type-S tranny sent by Import Auto Salvage in Marion, N.C. What he couldn't recycle from the busted box, he picked up at a local dealership.
List price on all the parts we used was a little over $1,000, and that includes new third through sixth main and countershaft gears along with their respective synchros. Folks can pick up an RSX-S transmission used for around $800, but keep in mind that it's just that--used. Most of the parts that could go bad in a used gearbox can be replaced in this upgrade.
For the sake of comparison, consider that you can buy a used K-series Type R transmission for around $2,000. That would be about the total price if you bought a used Si gearbox, bought all of the parts at retail price, and paid someone to rebuild it.
• 10mm six-point socket
•14mm hex socket
•12mm six-point socket
•3/8-inch impact gun
•14mm six-point socket
•Snap ring pliers
•12mm hex socket
•Special driver, Honda
Make Me a Match
James Farrar's shop has specialized in Honda since 2000, and after years of working on K-series trannies, one day he had that familiar Honda tuner's revelation. He noticed how similar the internals were across platforms. After playing with some parts, he figured out how to do the swap we have here. He also learned much about the interchangeability of gearboxes mated to K-series motors.
For example, EP3 Civic and DC5 RSX/JDM Integra gearboxes all use the same case. Additionally, all differentials and ring gears across EP3 and DC5 lines are interchangeable. Other combinations are possible as well. Farrar says portions of the TSX's guts, namely the gears, will also work in the Si/RSX-S gearbox.
In theory, you could buy a TSX, Type-S or R main shaft and the matching first and second counter gears, in addition to the other parts for this EP3 trans project, and build your own complete S, R, or TSX box. Even with all new gears and synchros, the build should cost less than buying a used Type-R transmission abroad.