From the pages of SCC Magazine
Hybrid How-To: 2002 Civic Si : K20A2 RSX Type-S Engine
Concerns:
A security chip in the key must match the code in the ECU. Once you swap to the Type-S ECU, you'll need to take the car and documentation showing you acquired the engine legally to a Honda dealer to have the key code put in the ECU. Other than that, this swap is as straightforward as it gets.
What and Why
When Honda introduced its 200-hp Civic Type-R to the world, it forgot about the United States. Here, the top-shelf Civic is the 160-hp Civic Si. Nice car, but a ho-hum performer compared to the punch delivered by its steroid-infused, Type R badge-festooned, 146-mph brother. Fortunately, Honda saw fit to place the Civic Type R's sauce, the 200-hp 2.0-liter powerplant and rifle-bolt six-speed gearbox, into the U.S.-market Acura RSX Type-S. The drivetrain of the Civic Type R right here in the United States? It was too obvious for us to ignore. Especially when you consider the entire RSX Type-S drivetrain is a direct bolt-in swap for the 2002 Civic Si chassis. And it had better be, aside from the intake manifold, the base non-Type-S RSX engine is identical to the one found under the hood of the Civic Si.
Picking the Chassis
The latest Civic platform was introduced in model year 2001 without a hatchback or an Si in the lineup. Surprisingly, Honda adopted a MacPherson strut suspension up front on the new chassis in place of the previous double-wishbone layout. Better chassis stiffness and faster steering were part of the new package, too.
The year 2002 saw the introduction of the Civic Si, a new hatchback body style with a five-speed shift lever sprouting from the dashboard and a 2.0-liter engine stuffed under the hood. With its distinctive minivan-meets-sneaker bodywork and 160-hp mill, the Si certainly stands out from its earlier Civic siblings. But the Japan-only Civic Type R spoiled us. Edgier, quicker, and a much more engaging drive, the Type R is really what the Si should have been.
Picking the Engine
Pumping out 200 hp at 7400 rpm and 142 lb-ft of torque at 6000 rpm, the engine from the RSX Type-S (K20A2) is actually quite similar to the K20A3 in the Civic Si. They share the same 2.0-liters of displacement, bore/stroke, block, head, valves, and intake manifold. However, a whole slew of internal guts and external bolt-on bits are radically different between the two.
For starters, the RSX's K20A2 boasts 11:1 compression pistons, dual valve springs, and a tri-y header with larger primaries than the Civic.
Perhaps most significantly, the K20A2 employs a more sophisticated i-VTEC system in conjunction with more aggressive cams. There's a lot of confusion of the differences between the two engines' i-VTEC systems, so here's the straight poop. On both cars, i-VTEC really consists of two features: VTC (Variable valve Timing Control) and VTEC (Valve Timing and lift Electronically Controlled). VTC, in both cases, is simply a hydraulically controlled adjustable cam sprocket that varies intake cam timing on the fly depending on engine speed and load. VTC does not affect the exhaust cam. It's the VTEC portion of these systems that differs. On the K20A2 (RSX Type-S), VTEC means there's a low-rpm set of cam lobes and a screaming, high-lift, long duration high-rpm set of cam lobes both carved into the same camshaft. At about 6000 rpm, the rocker arms stop following the wussy little low-rpm cams, and start following the big ones. This is the system that made VTEC synonymous with high-output, 8000-rpm monsters.
Unfortunately, the K20A3 (Civic Si) uses a completely different system that happens to share the VTEC name. At low engine speeds, the two intake valves operate with different cam lobes--one valve gets the "primary" lobe (33.925mm lobe height). The other valve gets a wimpier "secondary" lobe (29.638mm lobe height). When VTEC mode kicks in at 2300 rpm, both valves start following the primary lobe. That's it. No high-rpm kick, no screaming, no high output. In the meantime, the exhaust valves always get shoved open by a 34.092mm lobe with no tricks at all.
With the two engines sitting together on the floor, we picked up on some notable external differences between them as well. In addition to the different cylinder heads, the RSX has a cast aluminum oil pan (the Civic's is stamped steel) and a small oil cooler at the base of the oil filter.
The Si shifter cables hook to the RSX transmission without modification. The shift mechanism, however, isn't designed to move far enough to reach the six-speed's reverse gear. Putting a notch here, as shown, allows you to reach reverse.
The power steering systems are also different. The Si uses electric power steering, while the RSX's is hydraulic. Finally, the axles differ slightly. The RSX has a larger bearing to support the intermediate shaft, and uses larger splines at the hubs.
The Civic Si steering rack has electric power steering assist, so the stock engine has no power steering pump.
Engine Removal
Like many Hondas, removal and installation of the engine is often best done from beneath the vehicle. Unless your jackstands are 4 feet tall, use a lift.
Under the hood:
1. Disconnect and remove the battery.
2. Remove the plastic cover on top of the intake manifold, the airbox, and intake snorkel assembly.
3. Unbolt the battery lead at the fuse box. Don't forget to unbolt the cable's chassis ground located near the battery tray.
4. Disconnect the throttle linkage and remove the cables from their brackets.
5. Relieve the fuel system pressure and remove the supply hose from the metal fuel line at the engine.
6. Remove the charcoal canister hose and brake booster hose.
7. Unbolt the clutch slave cylinder and the clutch line's mounting bracket.
8. Remove the two shift cables at the transmission.
9. Disconnect the ECU (under the glove box), remove the grommet and harness hold-down tabs, and pull the engine harness through the firewall.
10. Remove the accessory drive belt, the A/C line mounting bolt at the engine, and the two A/C line clips at the subframe.
Where the Si engine (on the right) has an idler pulley, the RSX engine (on the left) has a conventional power steering pump. Fortunately, the Si's idler pulley simply bolts onto the RSX engine.
Beneath the car:
11. Remove the splash pan and drain the coolant, transmission fluid and engine oil. No, not into the same bucket. Remove the lower radiator hose.
12. On the suspension, disconnect the anti-roll bar end-links and lower ball joints, then remove the halfshafts.
13. Disconnect both oxygen sensors and remove the catalytic converter.
Under the hood again:
14. Remove the heater core hoses, then remove the radiator. This is just a precaution to avoid ventilating it with wrenches or engines.
15. If you have a hoist, attach it to the engine and raise it, then remove the nuts and bolts holding the support brackets for the transmission mount and upper engine mount. If not, you will need to keep the engine bolted to the chassis while the subframe is removed.
16. Unbolt the engine mounts on the subframe and position your tool cart--or whatever you have that can support the weight--beneath the subframe. Mark the position of the rear subframe bolts before you remove them, then remove the subframe.
17. Unbolt the A/C compressor from the engine and support it somewhere in the engine bay. This way you won't have to discharge/recharge the A/C.
18. Carefully lower the engine, checking for any interference, connected vacuum lines, coolant or fuel hoses, birds' nests, or lounging hippopotamuses.
Rather than use an engine hoist, Hasport used a homegrown engine cart. Just lower the car over the cart, unbolt the engine from the car, bolt the engine to the cart, then raise the car up and out of the way.
Since the RSX uses larger splines on the hub end of the halfshafts (right), the Civic halfshafts (left) are retained for this swap.
Chassis Prep
The only difference in the wiring harnesses is that the Si harness does not have wiring for the reverse lockout solenoid, and the ground leads at the ECU are different. We used the RSX-S harness, which is ideal for this swap since it snaps right into the Civic. Assuming you can locate a connector for the solenoid, the Civic harness could be used instead if the ground and solenoid leads are crimped and spliced in. Our RSX drivetrain included a harness, so that's what we used.
Like the Si harness, the RSX harness has two flying leads, one goes to the fuse box and battery while the other goes to the ECU. The RSX ECU replaces the stock Civic ECU.
The RSX's downpipe and catalytic converter are larger than the Civic's, and the RSX's cat locates further downstream than the Civic's. Plus, the flange on the RSX cat does not mate up to the stock Si exhaust. Since using the puny Civic Si exhaust on the freer-flowing K20A2 would only choke off dangerous horsepower anyway, your best bet is to have a larger cat-back exhaust made.
Higher output means more heat rejection. The RSX has a coolant-to-oil heat exchanger plumbed in at the base of the oil filter to help offset the increased heat load.
Engine Installation
The RSX drivetrain literally bolts right into the Civic. Just reverse the removal procedure described above and sell the Si drivetrain to someone with a base Civic.
One of the few obstacles of this swap. The RSX catalytic converter is larger, farther downstream, and clocked differently than the stock Civic Si cat and thus will not bolt to the stock Si exhaust. Fabricating a new, larger exhaust more suitable for 200 hp makes more sense anyway, so we dumped the stock exhaust entirely.
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