Is it possible for our Project TSX to skin an E46 M3 on the track? We posed this question in our first installment of Project TSX back in December 2004 and we're still exploring the idea. So far, we've changed out the stock suspension, wheels, brakes and tires, all in effort to wring some M3-like handling numbers out of the Acura. Part II involved the installation of a few bolt-on parts; including intake, exhaust, headers and a Hondata K-Pro ECU. These mild modifications netted us 184 wheel-hp.
Ulitimately, our TSX could probably nudge the M3 in handling numbers, but horsepower is another story altogether. It would be tough, considering the difference between 3.2 vs. 2.4 liters is night and day. Sure, Project TSX can keep most cars honest with its streetable, naturally aspirated engine, but to beat BMW's rocket chariot, the TSX's power output needs to be upped.
We're convinced the plan is still realistic. So, Project TSX went back to Skunk2 for a barrage of modifications designed to inject some much-needed horsepower into the 2.4-liter. To help keep build costs down, we chose to keep the stock bottom-end intact. Hence, all the work done was designed to improve flow and raise volumetric efficiency at higher rpms.
An M3 will put down roughly 280 wheel-hp out of the box. All the bolt-ons in the world won't get Project TSX near that kind of output, so we had to get serious work done on the head and turn our motor into a hybrid K24A2 with K20 parts.
HeadworkSkunk2 started with a standard 30-, 45-, 60-degree three-angle valve job on the intake and exhaust valve seats. The exhaust ports were radiused below the 60-degree cut to better transition into the ports.
The majority of the head work consisted of porting the K24A2 head. Since the stock engine only spins to 7100 rpm, the head was designed to deliver more low-end response and torque, which meant smaller ports to increase flow velocity through the head. That's all fine on a stock car, but when the rev and flow range are stretched higher, the port profile has to change significantly. The valve guides were also ground down to minimize restrictions.
Skunk2 replaced the stock valves with lighter one-piece forged valves with hardened tips. Though valve size and compression were not altered, springs and retainers were replaced with slightly stiffer double-wound coils and titanium retainers to perform better at higher speeds and reduce reciprocating mass.
Bolt-OnsEven with the significant porting, Skunk2 felt its Stage 1 RSX camshafts and stock RSX cam gears best fit the flow and engine speeds that Project TSX was capable of. We switched to RSX hardware because it was designed to operate at higher engine speeds and raise the powerband. The RSX cam gear has a wider range of i-VTEC cam phasing, from 0-50 degrees BTDC, compared to the TSX cam gear, which had only 30 degrees of cam advance. The added range of i-VTEC operation lets us retain the K24's low-end torque, while making more power up top.
We threw on all the bolt-on parts we could from Honda's RSX parts bin to keep the car driveable with its new lungs. Honda spent a lot of money designing and casting manifolds that are versatile in response and flow; we'd be stupid to not take advantage of that.
Skunk2 chose to use the intake manifold from the Japanese RSX Type-R, or K20A. K20 manifolds generally have shorter runner lengths designed for increased flow at higher rpm, which fits our bill. According to Skunk2, the manifold from the K20Z found in the new Civic Si is worth 6 to 7 hp just as a bolt-on.