Uncommon Performance: Dodge Spirit R/T, Shelby CSX, and the K Car Legacy

The lowly K car. It’s the platform that pulled Chrysler out of bankruptcy in the early ’80s, and which was stretched, sliced, and diced to underpin everything from hatchbacks to minivans, but it’s rarely earned anything resembling respect on the performance scene. Those in the know, however, can peel back the frumpy styling of these box-like compacts and appreciate the potential lurking under the hoods of a pair of its number from later in that decade: the Dodge Spirit R/T, the Shelby CSX.

These bright spots on the extended K (dubbed the AA platfrom) and the shrunken K (the P platform), alongside more modest turbo K-car fare in an otherwise econo-oriented line-up, showed just how committed Chrysler was to turbo technology in an era where other automakers were still reluctant to embrace forced induction. 25 years later, this unusual group of sedans, coupes, and convertibles are screaming deals for anyone willing to tweak their unique four-cylinder drivetrains and extract surprising amounts of horsepower for very little money.

Check out these tips on how to best benefit from the uncommon performance found in the Dodge Spirit R/T and the Shelby CSX.

From The Factory

At the end of the 80s, Chrysler was selling four different entry-level cars all sharing the same K-car platform and available turbocharged drivetrain. In the Dodge showroom there was the Dodge Spirit and the Dodge Shadow, while Plymouth dealers had the Acclaim and the Sundance. The Spirit and the Acclaim were sold as sedans, while the smaller Shadow and the Sundance were offered in hatchback and convertible editions.

The latter two were introduced as 1987 models with the ‘Turbo I’ four-cylinder motor available as an option. Originally offered as a 2.2-liter unit delivering 146 horses and 170 lb-ft of twist, by 1989 its displacement had grown to 2.5-liters and it was retuned to provide 150 horsepower backed by a stouter 190 lb-ft of torque.

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Right from the beginning, however, it was also possible to order a very special version of the Shadow/Sundance hatchback that had been tuned by Carroll Shelby. Dubbed the Shelby CSX, this sleeker two-door model was sold for a two year period with 175 horsepower and 175 lb-ft of torque from its 2.2-liter, intercooled ‘Turbo II’ four. It also featured numerous suspension upgrades as well as rear disc brakes. The CSX produced two variants: the CSX-T (a rental special downgraded to the Turbo I drivetrain) and the CSX-VNT, a fresh-for-89 edition of the car that stepped up to the Turbo IV’s 15 psi and 205 lb-ft of torque at 2,100 rpm (while leaving the 175 horsepower rating intact). Only 500 VNTs were ever sold, and every CSX came with a 5-speed manual gearbox.

The somewhat larger Spirit and Acclaim initially went the V6 route in their top trims, making use of a 141 horsepower, 3.0-liter Mitsubishi-sourced unit when they first went on sale in 1989. A 2.5-liter, 150 horsepower Turbo I four-cylinder engine, however, was also available for both, asking, but not forcing buyers to take a chance on this relatively new replacement for displacement.

By 1991, the real jewel in the Dodge Spirit crown was unveiled: the R/T. Equipped with a 2.2-liter Turbo III four-cylinder, Lotus-designed 16-valve head, forged pistons, crank, heavy-duty rods, and a five-speed manual transmission, the car was good for a startling 224 horsepower and 217 lb-ft of torque, making it the go-to sleeper for Mopar fans. Chrysler marketed it as the ‘fastest sedan in the U.S.’ at the time. The Spirit R/T, which could hit 60-mph in less than six seconds, would last until 1992.

From The Aftermarket

There is a respectable community of tuners still focused on the Turbo I, II, and III engines thriving online, with build threads, FAQs, and Facebook groups all out there waiting to be discovered by anyone who wants to squeeze more performance from their K-car. For those who want to stay streetable, but who desire better top end and acceleration from their car, the easiest path forward is to increase peak boost to 20 psi to 25 psi from the 9 to 12 psi offered stock.

“The CSX and the Spirit R/T are two completely different animals when it comes to turbos,” says FWD Performance’s Cindy Lindsay, a prominent figure in the K-car tuning scene. “The CSX with the VNT turbo is pretty great because there’s no boost lag, but it’s undersized, which leads most people to the Garrett T3 turbocharger from the Turbo II cars. You don’t want to go too big, so that leaves stuff like the tried-and-true 50 trims, the Garrett GT series, or the Turbonetics Super 46 or Super 50. There’s a very specific flange on the Chrysler Turbo II that requires an equally specific turbine housing, and there’s only so much you can do there. The Spirit R/T platform, on the other hand, has a T3 flange, which makes turbo sizing almost infinite. Most people go with a Holset HE351 from a Cummins turbodiesel, with Garrett GTX and Precision turbo options for those who want better spooling.”

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You’ll also want to install larger fuel injectors, a new head gasket and head bolts, a 2.5-inch exhaust, a wideband O2 sensor, and a remapped computer that can manage the boost and fuel you’ll need. Turbo IV cars should also install a blow-off valve, since there isn’t one there from the factory. Properly executed, you’re now close to 300 horsepower at the crank with these mods.

If you want to move beyond a street fighter and start tapping into the full potential of these engines – think 400 wheel horsepower – you’ll want to invest in a boost controller, a 3-inch exhaust, a ported intake and exhaust manifold, larger throttle body, and of course a larger turbo (although not so large as to introduce too much lag into the equation).

“The intercooler is a huge bottleneck on these cars, so you need to move to some kind of front-mount intercooler as quickly as possible,” says Cindy. “For engine management at all levels, we offer different stages of calibration for the ECU, where we reprogram and replace the chip in the stock unit, as well as a 3-bar MAF sensor and 40% larger injectors that put you in the 55 lb range. It’s a plug and play setup.”

If you’re thinking this sounds a lot like what you’d have to do to most forced induction engines to gain power, you’re right, although the Mopars happen to be blessed with excellent heads, pistons, and cams that aren’t a liability when increasing boost. There are even cars out there running 600 horsepower at the wheels at 30 psi on Turbo III motors.

On the transmission side, automatic cars do best with a V6-spec rebuild and a trans cooler, while a 555 or 568 manual gearbox is a necessary upgrade for manual shift cars in the 400 horsepower range. A Turbo III clutch is another helpful addition, but axles can remain stock without issues. When it comes to suspension there are a host of aftermarket shocks and springs available for the car, and polyurethane bushings are recommended.

In addition to FWD Performance, Forward Motion, Inc also still caters to 2.2-liter and 2.5-liter turbo Mopars, although with each passing year the emphasis is less pronounced on the older cars.

From Left Field

With so much potential on offer from the Dodge Spirit R/T and Shelby CSX (and with junkyards filled to the brim with Turbo II Shadows and Sundances) there’s really not a huge cult following for bizarro-world swaps out there in box-land. No V8 shenanigans here, although there is a dedicated contingent out there installing Dodge Neon SRT-4 drivetrains into these older cars, replacing one turbo four with another, more modern iteration of the same concept.

In addition to reaching out to the vendors mention above about your K-car project, it’s also worth visiting the Turbo Mopar and Turbo Dodge forums for advice. If you’re comfortable dipping into the Internet’s way-back machine, you can also find fan pages for these cars with detailed, although in some cases dated, technical information about them and their drivetrains, such as HH Scott’s Turbo II resource, Allpar, and the performance section of the MiniMopar.net site.

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