"It's a racer's dream!"
If you're familiar with the ultra-high-performance '12 ZL1 going on sale this spring, it shouldn't surprise you to hear those words from Tony Roma, ZL1's Program Engineering Manager. What should surprise you is that Tony wasn't talking about the ZL1--he was talking about the Chevy Volt.
Specifically, Roma was waxing poetic about the Volt's high-output water pump, which his team snatched from the GM parts bin to test on the supercharged, 6.2-liter LSA's intercooler circuit. The 556-horsepower LSA had gotten the nod for ZL1 duty--it was a dream engine for anyone who lived and breathed Camaro. But Roma's team had no intention of leaving good enough alone--after all, this mill was going into the baddest, most powerful Camaro ever. So Team ZL1 took one look at it, and then jolted up the Chevy Volt's pump with some extra voltage.
"The Volt's water pump is super efficient, super high-output," Roma explains. "We slapped that thing in there and hot-rodded it up: It runs at 50 watts in the Volt--we turned it up to 80 watts. And we found that starting with a really high-flow water pump on the intercooler's air side helped it end up being more efficient."
Efficiency and world-class, all-around performance were two attributes targeted by the ZL1 team from the very beginning as they set out to bring supercar technology and performance at a sports-car price. And they used nearby rival Ford and its GT500 as the benchmark.
"We felt that before the ZL1 came out, the GT500 was the class of the field in this market," Roma says. "We were definitely looking to redefine the segment."
However, the ZL1 team also had to keep an eye on the project's budget; besting the GT500 on the street and at the track was the goal, but they also had to keep the ZL1's price tag competitive. So the team stopped thinking like a car company, and started thinking like racers.
"Planning the ZL1 was not much different than what anybody who's building a high-performance car goes through," Tony reveals. "If you go buy a Camaro SS, have X number of dollars for performance upgrades, then start flipping through a performance catalog, you want to get the best components that you can afford, right? We did the same thing for the ZL1--we just did it on a really large scope and at a high level. So at the beginning, all of us racers sat down with pen and paper and said, 'If this part doesn't make the car go faster, it's not in.'"
While some items like the Corvette ZR1's 638hp LS9 engine were too pricey to be considered, the team was able to include most of the desired performance components (including the Cadillac CTS-V's powerful LSA V-8), and still hit the price point. Items not crucial to performance, like the interior, were put on the backburner.
"We saved money in lots of ways," Tony states. "We have only one forging for both the 5- and 10-spoke wheels. And we used just one new coupling for the rear halfshaft for both the inboard and outboard sides. That's just a couple examples of many in the ZL1 that people won't ever see. But when you look down the spec sheet, the important stuff is there, like an all-new diff and an integrated cooler to keep it cool. We took care of the big stuff, and then got conservative with things that people will never notice."
LSA Fitment"The LSA wasn't much trouble to put in the Camaro," Roma says. The ZL1-spec LSA engine is only slightly different than the CTS-V's, with all internals exactly the same as the Cadillac-spec mill. None of its mods caused any significant problems for the Camaro engine bay--after all, the fifth-gen car was designed for the LS3/L99 V-8s of similar dimensions.
The team's biggest issues were the lid under the cowl, and the added length from the extra belt track for the supercharger.
"We had to use the CTS-V's alternator and water pump for the main belt track, as well as an idler where the power steering pump would be. We also had to move back the A/C compressor to the CTS-V and Corvette position, so the ZL1 has a unique one. This change made room for the V's supercharger belt track in front."
The ZL1's exhaust manifolds are of the LS3 design, but they're high-grade, cast stainless steel with stress relief cuts between the cylinders to deal with the LSA's higher temps. They link up with a 2.5-inch stainless exhaust system featuring a dual-mode muffler setup.
The wiring is different due to more sensors, and the CTS-V's/ZR1's E67 ECU is utilized, since the extra inputs are needed for the supercharger. Feeding that thirsty blower is a high-volume fuel pump, which sucks premium unleaded from a tank with an additional fuel pump pickup for those high-g corners.
Intake/SuperchargerTo maximize airflow and power, the team added a secondary air inlet to the lower box on the air cleaner. A unique air filter with shallower pleats lowers the restriction. Computational Fluid Dynamics (CFD) was used to optimize the design, and the LSA's throttle body position allowed a lower-restriction duct.
While there were no changes to the 1.9-liter supercharger's four-lobe innards, gains were made thanks to the shape of the lid. The ZL1's LSA engine has a 9.1:1 compression ratio; its SAE-certified power and torque ratings were made at 9 psi boost.
IntercoolerMuch of the ZL1's power increase over the CTS-V's 556 hp comes courtesy of efficiency gains found in the LSA's air-to-liquid intercooler.
"Compared to the CTS-V, the intercooler brick had to be pushed forward in the ZL1," Roma explains. "And because we ended up redoing the whole thing, we decided to optimize it."
The team analyzed the tube-and-fin cooler's water flow rate on both sides, the water flow rate through the tubes, and the airflow rate at the other side. The brick's dimensions and its fin pitch were optimized for pressure drop on the air side, as well as on the water circuit. And the pump and heat exchanger sizes were adjusted--the former thanks to Chevy's "hot rod" Volt.
"The ZL1's intercooler is incredibly efficient, and it keeps the intake air temps in the range where the engine keeps making great power," Roma says proudly.