We've covered the Acura RSX Type-S since its 2002 launch, showing you what countless others have done with the car, from basic street cars to the $150,000 grocery getters that RealTime Racing runs in SPEED World Challenge. being that the product line will end in 2007, we figured it's about time to do the car justice SCC style. There's nothing like making your own decisions and living with the consequences though, so we finally sweet-talked Acura out of one of the pre-production cars with the 2005 facelift and built it the way we wanted to. In stock form, this was one of the nicest daily drivers you could have. Smooth, comfortable, luxurious, efficient, and reliable. It handled and performed well. Normal people would just enjoy driving it for a couple hundred thousand miles, but how does that build character?
The first thing we did was pave the way for more power -- a lot more. We decided to turbocharge it, but thought we'd skip the Project Focus experience of being fast as hell for two weeks before going straight to it. Even with knock-resistant combustion chambers, you can only put so much boost on 11.0:1 compression and cast pistons, so out came the engine. In traditional OCD project style, we did everything we could, whether we really needed to or not. Mark DiBella of MD Automotive yanked the engine for us. We left the car on MD's lift for way too long while we rounded up Darton sleeves, Crower forged connecting rods, Ferrea valve springs and hardware, ARP head studs, and a Cometic head gasket and took them all down to Cosworth with the engine. Cosworth provided forged, 89mm, 9.0:1-compression pistons then did all the hard work of putting the parts together.
The end result is a 2,140cc K-series engine that revs to 9,000 rpm and will withstand all the boost pressure we can feed it. It's overkill for now, but overkill is good since we have enough blown-up project cars sitting on lifts, and this car will let us learn how to tune and make a mistake or two. You might skip sleeving the block and beefing up the rods until you get seriously stupid about boost, but we hate going back and doing it over and only had one shot to not blow it up.
We picked an off-the-shelf GReddy turbo kit with the optional air-to-air, front- mount intercooler as a first attempt at turbocharging this car, since it would keep us from having to invent too much stuff. Installing the GReddy turbo system is about a three-and-a-half to four-day job, which lined up fairly closely with what Mark DiBella said it had taken him to install it on another car. While the engine was out, we took advantage of the time and installed all the heat shielding wrap on the plumbing and wiring that runs along the firewall, which saved about eight hours (we'd probably still be working on it if we tried it with the engine in place). Just goes to show that even though it's labeled as a bolt-on kit, that doesn't mean it's not a fiddly, tedious project. Thankfully, the only special tools we had to buy were a set of crow's-foot sockets to install the turbo on the manifold.
The returnless factory fuel system was modified with a Walbro 255-lph fuel pump from Lightning Motorsports. Since the factory RSX ECU pulse-width modulates the power to control flow from the stock pump, you must either build a relay circuit or use an alternate ECU to prevent burning out the Walbro pump. RC Engineering 750cc/min injectors also gave us additional headroom to meet our highest power goals. These were fed by an AEM high-flow fuel rail, which provided a convenient place to mount a fuel pressure gauge.
We hit up AEM to provide us with its Engine Management System (EMS) and a lot of help. The 2005 RSX Type-S is significantly different than 2002-04 models, and AEM had not yet finalized its controls of all the systems. AEM's Greg Nakano built an adapter harness to accommodate the different pinouts, and we're currently running an EMS in tandem with the factory ECU -- even though the EMS can be used as a stand-alone controller. This ad hoc engine management meant that the coolant gauge, A/C, speedometer, and odometer -- which are driven by the stock ECU -- would no longer work. Greg showed what a great guy he is by coming to our shop late at night to help us get a rough tune and get the car running the first time.
We initially used AEM's underdrive pulleys for the power steering and alternator. When we found ourselves outrunning the power steering in a slalom, we decided to go back to the stock power steering pulley. We took the opportunity to remove the A/C system but left the AEM alternator pulley in place, because it was too hard to remove with the engine in the car. Bypassing the A/C compressor pulley position left an acceptable serpentine belt path. We measured around the pulleys with string, of course got it wrong the first time, and then couldn't find a seven-rib belt the right length, so we ended up with a 6PK1365 belt (which means six ribs and a length of 1,365 mm). It is the perfect length, and, without the load of the A/C pump, we don't expect the loss of one rib to cause a problem.
We know by looking (plus, everyone has told us) that the stock cat is restrictive and needs to be replaced. We have parts from MagnaFlow to build a replacement high-flow cat system but haven't gotten around to it yet. Initial tuning was hampered by other equipment problems that we've fixed, so it's not perfect for power but rich and safe. We also haven't gotten into the finer points of driveability. Even with the low compression, the extra displacement of this engine makes the GReddy turbo super responsive, with virtually no lag. Everybody who's driven it on the street agrees it's fun so far.
At about 8-psi maximum boost, MD Automotive's Dynojet showed us 249 wheel-hp and 204 lb-ft of torque at the wheels, a significant increase over the 177 wheel-hp and 127 lb-ft of torque provided by a stock RSX Type-S. There's a big dip in power between 6,000 and 7,000 rpm that we need to fix. The torque falls off significantly at the top end, which suggests the car is running into a flow restriction. One place where we already plan to address that is the stock cat.
Next time we write about the engine on Project RSX, look for a high-flow cat, a lot of refinement to the tuning, and turning the boost higher. We're the first to admit that with all the work that's been done on this car, it would be silly if we don't get at least 300 at the wheels on pump gas.