With the swap essentially completed (you can check out modified.com to read the previous articles) and our K20A2 installed and running, there were two remaining tasks before the DC2 could make its maiden voyage around a track. First up, a proper flowing exhaust system needed to be built and then the car needed to be tuned.
There are plenty of bolt-on exhaust systems available for the Integra chassis, but most of them are for the B-series engine, meaning they will need to be shortened in some way to mate to the K20's header. Secondly, most measure 2.25-2.50 inches in diameter, and to maximize power output on a K, everyone recommends a 3-inch system. If you can live with the noise (and there's plenty of it) then there's no reason to go with a smaller-diameter exhaust.
I turned to John Veloso, head of R&D from Vibrant Performance, for the custom exhaust build using only Vibrant components. We were able to source some T304 stainless steel mandrel-bent tubes with various bends and lengths as well as a StreetPower flat-black muffler and 3-inch resonator (these are a must if you want to fly under the radar). To keep the emissions clean, a round metal core catalytic converter was thrown into the pile of parts we ordered from Vibrant, which has quickly become the leader in fabrication components. The variety of parts now offered by Vibrant is incredible. No matter the job, whether it's exhaust, intake, intercooler piping or something custom, Vibrant has it.
Building an exhaust on a FWD car isn't as straightforward as simply running some pipes back and you're done. Due to all the bends and the need to route everything over the lower control arms, it can actually get quite complex. Without proper measurement and clearance, you're almost certain to have some piping hit the chassis. Watching John and Mike Hackett work, I could quickly tell I wouldn't experience those issues. They measured everything precisely and even redid some bends to ensure it would all fit. It's a little-known fact that stainless steel can expand up to 1 inch at the tailpipe when it's hot. Remember that when you're building your own system because it might not bang when it's cold, but on a track you'll have that annoying racket.
With the exhaust finished, the note the muffler emits is very tolerable at idle and cruising. Once you get on it, the sound is more pronounced and almost sounds like a race bike. Thankfully, and probably due to the good construction of the StreetPower muffler, there's no annoying raspy tone at cruising or WOT. That's one thing I couldn't live with.
Church Automotive Tuning Few shops are as synonymous with tuning Hondas as Church Automotive out of Long Beach, California. Shawn Church is a tuning wizard and knows the best ways to extract as much power as possible from a K-series engine. Armed with a laptop and his trusty Dynapack dyno, Shawn got down to business as I observed and tried to pick up a thing or two about tuning. But before any adjustments could be made, a baseline run was done to see what the engine was making in its current state. To our surprise, it actually produced good peak numbers: 215.5 whp and 167.2 ft-lbs of torque.
Since Project DC2 will be used mainly at the track, I really didn't care about making high peak numbers. Instead, smooth power delivery and a good torque band were priorities that I expressed to Shawn. I'll leave the bragging rights to the guys who want them-I want a solid, reliable tune so I can thrash on the car and not have to worry about it exploding, and that's exactly what I got.
Not only was Shawn able to improve horsepower and torque throughout the entire rpm range, but he also made and extra 12.8 whp and 6.7 ft-lbs of peak power. Just look at the dyno chart and the results speak for themselves. What's more interesting is that VTEC will engage as low as 3000 rpm, depending on throttle position and load. There's no more waiting for the power to hit at 6000 rpm-it's linear and pulls hard as soon as I mash the pedal.
The initial test drive after the tuning session cemented that. The K20 that I always wanted has finally arrived. Untuned, there was no urgency in the power delivery; now it comes on strong and begs to be revved. Shawn also upped the limiter to 8600 rpm over the stock 8200, which is still safe on the stock valvetrain.
It's been a long road traveled, but I'm finally satisfied to say that the K-swap is complete and I now have a very capable powerplant and chassis in my garage. Next up is getting the car to a track day for a review of how it drives and handles.
Before I wrap this up, many people have asked me whether the swap was worth all the hard work and trouble. For me, yes. The K20 has, hands down, the most potential of any naturally aspirated motor on the market. It definitely wasn't a cheap venture, but if you can afford to do it right and not cut any corners, go for it. You'll never regret it.