Heritage: Dodge Caliber SRT4®
The Caliber SRT4 formula matches a powerful four-cylinder engine to a stout six-speed manual transmission to result in strong, reliable power. Aggressive styling cues inside and out are backed up by capable power, precise handling and phenomenal braking ability. Despite its short production run, the Caliber SRT4 enjoys a following as loyal as all others in the SRT family.
Production model years: 2008-2009
Caliber SRT4 Technologies
The Dodge Caliber SRT4’s 2.4-liter turbocharged engine, equipped with cutting-edge technologies such as variable valve timing, forged connecting rods, composite exhaust runners and high-temperature exhaust valves, was designed from the outset to be a robust expression of modern performance. Strong, reliable, effortlessly powerful and inherently economical, the turbocharged World Engine lives up to its name.
"The base 2.4 engine was a joint program, but the turbo engine was very unique and that was all done here," explains Jim Wilder, who served as Lead Synthesis Engineer on the Caliber SRT4 program. "There were thousands of hours of dyno runs. The calibration was all done at Chrysler. In fact, we had early Neons upfitted with these engines and transmissions to start development work before Calibers were even available."
SRT-specific parts — a specially machined block to increase cylinder head flow, a custom-tuned free-flow air intake matched to a massive intercooler and a Global Powertrain Engine Controller designed by Siemens — complement the robust crankshaft and camshafts shared with the base Caliber. The result is reliability, even when putting out 285 horsepower and 261 pound-feet of torque.
"The turbo is probably slightly bigger than what we needed, but at the time we were developing it, we were targeting 300 horsepower and 300 pound-feet of torque," Wilder explains. "The torque curve is really fat. It peaks at 265 lb-ft in third gear, and it’s a flat line across a very wide RPM range. There’s a lot of pull there."
Competitive sport compacts aren’t just about power, however. In a light car like the Caliber SRT4, engine responsiveness and feel are just as important as output.
"It revs to 6500, and it’s a free-revving car," Wilder says. "Second and third gear pulls are a lot of fun in the car. Once the car is rolling, it really hauls the mail."
Outstanding Ride, Handling and Capability
Sport compacts are expected to sacrifice a measure of ride comfort in favor of the ability to handle at the edge, but the Caliber SRT4 achieves a unique balance.
"The philosophy of the car was that it was a different vehicle from a Neon," Jim Wilder, Development Engineer explains. "It was a little more of a grown-up car than a Neon. Maybe that offended some people, but the Neon was pretty rough, pretty raw — and that fit a good market. This car was a little more refined. We put more ride in the car than the Neon had, just to give a little more of a pleasant everyday experience."
Not to say that the Caliber SRT4 is soft. Despite the visual impression of a high center of gravity, the Caliber SRT4 can corner with extremely capability. Revised suspension knuckles, thick front and rear sway bars and performance-tuned dampers eliminate body roll, while a limited-slip differential keeps power delivery in check.
"There’s a balance between front and rear braking," Jim Wilder, Development Engineer explains. "Front braking is way more important than rear braking. The front’s doing the majority of the braking." For this reason, the base Caliber’s rear brake calipers were re-used for the SRT4. The front brakes, however, demanded special equipment.
"We looked at what we could find off the shelf in the company stores, and what we ended up with was an LX-platform caliper," said Wilder. "You’ve got a 3200-pound car that’s got the brake caliper from a 4000-pound car. We’ve got a ton of brake on the car, and the braking is outstanding. At the time, the fade performance we got was second only to Viper. That’s a pretty high benchmark. Anytime you can say you’re second to Viper, that’s pretty good ground to be on."
To minimize brake noise and dust, special street pads were fitted. Official braking benchmarks and measurements were always recorded using these brake pads, but for serious performance-minded enthusiasts, Mopar provided an even grippier solution.
"We’ve also got an optional pad that we offer through Mopar that’s basically an LX police car pad," Wilder says. "It’s a very aggressive compound, and the initial bite on the pad feels fantastic. It’s a bit noisier and there’s some brake dust involved in it, but for the person who wants an extra oomph from the brakes, we’ve got something on the shelf."
Aggressive and Functional Exterior
In line with SRT tradition, every menacing extractor on the Caliber SRT4 serves a functional purpose.
"The front’s very aggressive," Jim Wilder, Development Engineer says. "It’s got a lot of Dodge character in it. But when you put a 300-horsepower engine in place of a 180-horsepower engine, you need to get more air to it. You need to cool the car. We’re sticking a big intercooler in the front, so we need to get more air to it. You start sculpting big holes to get lots of airflow in. And then you start lowering the front fascia to get drag and lift numbers that are a lot better for a high-performance car. You move your way to the side, you put side sills on it — it looks like a body kit."
As with every other SRT vehicle, intensive aerodynamic development dictated the final shape of the rear spoiler.
"We actually spent a lot of money putting this spoiler on, and a lot of wind tunnel development to get the lift balance right," Wilder explains. "That architecture isn’t particularly great for rear lift, so you put a spoiler on the back and you get the air to do exactly what you want it to do. We closed off the rear fascia, too, to reduce drag."
The Caliber SRT4’s lasting impact, however, is not merely visual.
"You work on a car for three or four years, and it becomes your baby," Wilder said. "You get attached to it. When you see one, you get a smile. It’s nice to see them out there. We haven’t forgotten about them. That group is a strong part of the SRT community, and they’re a very important part of the SRT brand, too. We thought about that group as we were developing the car so we could come out with a higher performance brake package, a higher performance suspension and the Mopar Stage 1 calibration for them. Those are the things that we as engineers really fought for. It was uphill battle trying to get resources to develop a lot of those. I was involved with the Stage 1 calibration’s final validation. It was pushing rope sometimes to get that stuff to happen, so the fact that we could get it out there and give the customers exactly what we in our hearts and minds knew the car wanted and needed — it’s very satisfying."
Race-Inspired and High-Performance Interior
Dodge Caliber SRT4s were factory-fitted with two types of seats. Seats equipped with side airbags were essentially borrowed from the base Caliber and re-covered with unique SRT-monogrammed upholstery. Performance seats, on the other hand, were aggressively bolstered and unique to the SRT4.
"The performance seat was modeled after the Viper," Jim Wilder, Development Engineer says. "We got a ton of high praise for the comfort of that seat. When we were at the track with those cars, we didn’t put race seats in them. That’s the seat that we used. The bolstering’s great. It was pretty unanimously agreed upon that that was probably one of the best seats we’ve done."
The base Caliber was well-known for its innovative "MusicGate" speakers, which flipped down from the rear liftgate. However, interior engineers took the SRT4’s audio system to the next level with a little help from Kicker.
"We upgraded speakers," Wilder says. "We added a subwoofer in the back. The tune in the audio system was a big step up. Not only did Kicker do a lot of tuning, but we had some in-house audiophiles — one guy in particular — that did a ton of hands-on EQ work on that car. It really is a good system."