VTEC V6-Swapping a Second-Generation Acura TSX Sedan

Following an infatuation period with the third-generation Acura Integra Type R, Ryan Bradfield parked his street version and found a half-built, fully-caged example on the other side of the country. With this shell, a set of tools, a lot of enthusiasm, and an abandoned service station to work, he and his father built the car that would serve him in his road racing foray.

The street car had shown him the ropes on the autocross courses and exposed him to NASA’s HPDE ladder system, but Bradfield wanted higher speeds and a greater level of performance, not to mention the challenge of building a true race car. With a verbal “I jump, you jump” agreement with fellow enthusiast Navin Dhas, he turned his focus toward preparing a car for NASA’s Honda Challenge 2 class. Along with Bradfield and Dahs, Michael Young, and Paul Horsley all entered Honda Challenge simultaneously with the hope of injecting some lifeblood into the series. Within a few years, the H2 class was regularly seeing some 15 racers at events in the Mid-Atlantic Region. Only four events in with the new build, Bradfield suffered a crash at Summit Point Raceway and totalled it. Determined to attend comp school, he purchased another turn-key H2 car from retiring driver Allan Haggai.

That willingness to venture into uncharted water was what urged Bradfield to make a bold new move after five years in H2. He had always liked sedans, and with the growing information on Honda’s range of widely available V6 engines, he looked around for something that would satisfy that craving without deviating from the proven Honda recipe of double wishbones up front and a high-revving VTEC engine he could use in H1. Not much had been done in club racing with the second-generation Acura TSX, but the middleweight had been proven in professional racing at the hands of Peter Cunningham at RealTime Racing, who took this particular platform to success in World Challenge in the early-2010s after several years of developing the first-generation of this car. “[Cunningham] is the one who gave me the confidence to try,” Bradfield declared.

The V6-powered second-gen TSXs only came with an automatic transmission, but there was a quick and easy solution to this. The contemporary Honda Accord, also powered by a similar V6, shared nearly identical subframes, so Bradfield bought both cars.

He began this hopeful build with a four-cylinder manual TSX with a blown motor and a crashed V6-powered manual Accord coupe. Into the TSX went the Accord engine, gearbox, and mechanical steering system to replace the TSX’s electric system. Powertrain conjoined, Bradfield stripped the TSX and refreshed each part before reassembling the car.

To realize the V6’s potential required more mixing and matching. The J35Z6 variant that comes in these cars is also cheap and readily available. The problem is it only has VTEC on the intake side, meaning five camshaft lobes per cylinder. To get a little more power, he pulled several parts off the heads of a J37A2 from an Acura TL AWD variant: one of the few Honda V6s released with VTEC for intake and exhaust. As each bank of the V has a single overhead camshaft, this means each camshaft has six lobes per cylinder.

Thankfully, the heads of these two variants are mostly interchangeable because they share the same head castings. Bradfield plucked the rocker bridges and camshafts from the J37A2 and added a different spring in the oil pump from the J37A2.That was all that was required. With this change, he picked up 15 wheel horsepower across the board.

Bradfield designed the mounts and brackets and mounts in CAD and had cut by with SendCutSend. Along with an intake manifold and throttle body from the same J37A2, ported lower intake runners, a 3D printed airbox, and a custom exhaust from the heads back, he has been able to produce an average 287 horsepower at the wheels. He also designed his own oil pan baffle, which he cut with Sendcutsend and welded into a Honda Ridgeline oil pan, which has a greater capacity than the stock pan.

From the outset, he knew the gear ratios were not suited for a race car, and so a final drive and pinion change was critical. First, he went with a company that offered a custom ring gear and final drive to lower the top speed from 192 to 155 miles per hour, but it broke after four weekends. Then, he went for an OEM alternative. “I learned the gearbox internals were similar to those in the current 2.0-liter turbo Hondas like the Civic Type R and Accord Sport,” Bradfield added. The only problem was the Accord used a different bolt pattern. To enable the new ring gear to mate to the Cusco differential, Bradfield sent the ring gear off the Liberty’s Gears for redrilling. This modification effectively changed the car from a six-speed to a five-speed, but he believes the revised gearing has increased performance. While it was out, Bradfield added strengthened third and fourth gears with parts from RV6 to handle the torque – a precaution he took due to information read on forums, not from personal experience.

There have been weak points. The first set of brakes, designed for the lighter first-gen TSX, were not suited to the task, so he turned to Paragon Brakes for a custom 356 mm x 36 mm front rotor and a set of six-piston calipers, which have performed well enough not to require the addition of ducts. Paragon’s R7 pad worked well enough, but he wanted to try something from EBC’s revamped lineup. The more aggressive SR21 initially caused a lot of ABS intervention. The current SR11 sintered pad has better feel, bite and lifespan. The stock rear brakes have been more than adequate, though it goes through rear pads fast.

Bradfield used the same spring split front to rear as he did in the Integra, adjusted for the greater weight. Bradfield started the build with a set of STANDARD Racing coilovers. The current rates are 1,300 pounds and 1,000 pounds, front and rear, respectively, and he admits to over-springing the front slightly to support the heavier nose. After a season of tinkering with the STANDARD setup, he’s now working with Shaftworks on a set of custom Penske units, hoping they’ll be better suited to control the movements from the big sedan.

The car has been limited mainly from the lack of support from the aftermarket, which has prompted Bradfield to innovate a few items, namely a rear sway bar. He devised a splined sway bar for the rear measuring 1.25 inches in diameter with .120 wall thickness. The splined components are weld-on units from FDF Raceshop.

It rotates eagerly enough, and the longer wheelbase, as well as the 9 Lives Rear Wing, offer certainty at speed. Up front, he adapted a splitter from a popular FK8 Civic Type R from Racebred Components. The balance is friendly and encouraging.

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Ryan Bradfield’s custom rear sway bar in action.

The TSX V6 has ample torque – about 250 pound-feet at just 5,100 rpm, and needs to be treated accordingly.  “I used to use the throttle in the Integra like an on-off switch. This one needs to be modulated,” he elaborated.

Power-down characteristics have been improved through a Cusco RS 1.5-way LSD, which is a motorsports product made in a few small batches. “Interesting bit of history – these only exist because Honda hired Cusco to build them for Honda’s World Challenge efforts back in the day. They actually raced a similar V6 and transmission combination in Accord Coupes. Procuring one was not easy, but Gerzybear Performance, a shop specializing in Honda V6 supercharger kits, had recently started making them. Thankfully, he’s been able to run this rare item without issue.

Once the power is administered cleanly, he gets to minimize his shifts. The motor isn’t peaky; forcing a shift between 6,500 and 7,500. Shifting is less frequent than it was in the Integra, and the TSX’s sixth gear is not used, not even at VIR.

Interestingly, the car’s lap times at faster tracks like VIR are, compared to the H2 front-runners, relatively quicker than they are at tighter, more technical tracks. This isn’t just straight-line performance, but composure in the high-speed sections that embolden Bradfield. “I like a neutral car, one that’s safe and forgiving. This one gives you that reassurance and doesn’t surprise you.”

This performance was on full display at the 2024 Hyperfest, where he entered the HFGT race, sharing the class with Larry Chen and qualified second. Ahead of him was Wyatt Foster in a DC2 prepared by Kaizen Autosports. After capitalizing on a collision between Foster and another driver, the only two ahead of him, Bradfield brought home the win. He had proven his sedan among some stiff competition and even beat the model of car the TSX replaced. Everything had come full circle.

More important than the hardware was the inspiration he drew from running in a field 40-deep. “I’ve gotten a little lonely in H1,” he admits. “I hoped that ‘if you build it, they will come’ would bring in more folks, but I haven’t had much luck there.” Now, the aim is to improve the TSX in the ways that are necessary and cost-effective so that he can compete in a fuller field of Super Touring 4 cars. Aside from the aforementioned roll center adjustment and improved shocks, he hopes to trim what little fat is left. “I’d like to use some carbon, but the price of building one-off carbon panels for the TSX is hard to justify. In ST4 this year, the new Toyo R tire will replace the Toyo RR he ran previously. Bradfield believes the grippier tire will make up for the sedan’s shortcomings. He’ll change from the 295/255-section tires he’s used in his Honda Challenge efforts to a set of 275/255s. Early testing has proven the setup to be faster at Summit Point by 1.5 seconds in similar conditions. The balance is also quite manageable, thanks in large part to the new sway bar.

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“I’m excited to dice it up in ST4 in 2025. We have a few guys who will be joining the class in the Mid-Atlantic and we’ll share some cross-over events with NASA Northeast where the ST4 class is strong. If it can perform there, I’ll know that taking a leap of faith with this car was well worth it.”

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