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2014 Chevrolet Camaro Z/28 - The Inside Story Interview

How GM built and tested the most extreme Camaro ever

Rick Jensen Jan 14, 2014
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If you bleed GM performance like we do, you were blown away by the 2014 Z/28’s introduction. When the new Z took the stage at this year’s New York International Auto Show, it joined an already stellar Camaro lineup that includes the LS, SS, 1LE, and ZL1. With the race-ready Z/28 slated to roll off the Oshawa line in early 2014, Chevrolet will dominate the Mustang at all trim levels, on all roads—and on all tracks.

You may have noticed that the “slash” is back. “Z/28” is the General’s latest alphanumeric riddle (it applies to the 2014 model…and the 1960s one…but not the slash-less 1970s-2000s Z28s…got that?). Z/28 joins ZR-1 and ZR1, LS-6 and LS6, and many other vehicle and engine names that we enthusiasts (and GM, for that matter) can’t seem to keep straight. But as Z/28 hearkens back to those heady days of high-revving, sharp-handling 1967 Camaros on SCCA circuits, this track warrior is clearly worthy of those Z/28 badges.

How worthy? The 2014 Z/28 is powered by a high-revving, dry-sump LS7 with an integral liquid-to-liquid engine oil cooling system. It wears massive carbon-ceramic brakes, 305mm gumballs at all four corners, an aero package, and a precision-tuned suspension with high-tech race dampers.

The Z/28 went through an “intensive lightweighting program”: In addition to weight removal from unsprung components, the interior sound deadening and trunk carpeting was tossed, the rear window got thinner (3.2mm) glass, a smaller battery was used, and the tire inflator kit was tossed (except for RI and NH-bound Zs). Lighter rear seats and no trunk pass-through save weight, too. Engineers wanted to remove the entire audio system, but had to keep it for the seatbelt warning chime—so it has a grand total of one speaker. Air conditioning is an option, a manual trans is standard. Even the manual-adjustment Recaro buckets are light. Combined, the Z/28 is 100 pounds lighter than an SS, and 300 pounds lighter than a ZL1.

The hard numbers are befitting of a true race car: 500-plus horsepower/470-plus lb-ft of torque, which could translate into high-3-second 0-60 sprints, and low 12s in the quarter. 1.5 g in deceleration, 1.05 g in lateral acceleration. And while “downforce at track speeds” is all of the aero info that GM is releasing at this point, you can count on significant aerodynamic enhancements, as well.

We were just as hot and bothered by those parts and specs as you were, and wanted to learn more about Z/28’s backstory. So we connected with Darren Bohne, the Assistant Program Engineering Manager for Z/28 and all-around good guy, who told us how the most extreme Camaro ever built was born.

2014 Chevrolet Camaro Z 28 LS7 2/6

GM High-Tech Performance: We heard that your team made nearly 200 changes to the Z/28 to improve its track performance. What was the main focus of those changes?

Darren Bohne: The Z/28’s focus on lap time is a three-pronged approach. Go, stop, and turn. The driveline, combined with the brakes/wheels/tires, is able to make this car the fastest track Camaro ever. When you look at the parts list that makes up the unsprung mass, we touched every one of the part numbers, except for things like lug nuts. And we even asked the question: What can we do to make the lug nuts lighter?

GMHTP: Compared to a 2014 Camaro SS, how does Z/28’s suspension and chassis differ?

 Chevrolet Camaro Z 28 3/6

DB: When we started engineering the Z/28 we looked at every part of the chassis; the biggest changes were going after unsprung mass in the tires, wheels, and brakes.

In addition to their individual performance benefit, the smaller tire/wheel package allowed us to bring the car’s center of gravity down 33mm compared to an SS. By using Multimatic’s DSSV (Dynamic Suspensions Spool Valve) Dampers with increased spring rates, we’ve developed a very track-focused package that delivers on the promise of being the most track-capable Camaro ever.

GMHTP: Can you provide some insight on how the Multimatic spool-valve dampers were chosen for the Z/28?

DB: On the ZL1, we have MR [dampers] for their great ability on both the street and the track. But with the specific focus of the Z/28, we chose to go with a passive damper that was tuned for one thing—the fastest lap times. Multimatic’s DSSV dampers fit the bill, and they also have mass-related benefits.

GMHTP: What were your team’s expectations for the DSSV dampers, and how were they dialed in at the track?

DB: We knew that Multimatic’s DSSV dampers had to give us very precise wheel control throughout the operating range, as well as be stable over long track sessions.

 Chevrolet Camaro Z 28 Recaro 4/6

GM and Multimatic engineers spent time together using computer modeling and 4-post testing to determine the correct valve before ever going to the track. Instead of trying to flow fluid through a standard shim, the DSSV dampers allow us to control fluid flow through a calculated valve opening that can be adjusted for piston speed. This gives us very tight control over the dampers.

From there, the team headed to the track to make any necessary fine-tuning adjustments to get the most out of the car. The DSSV dampers gave us independent control over the low speed and high speed operating range. In addition, they’re not susceptible to significant changes due to temperature, so you have consistent handling, lap after lap.

GMHTP: Speaking of trick race-ready parts: Can you describe how the 15.5-inch front/15.3-inch rear Brembo carbon-ceramic brakes (CCMs) affect the overall feel of the Z/28? What was it like track testing with them?

DB: The best CCM brakes feedback came from our drivers after their first few test sessions. With their output capability paired up with the Trofeo R tires, some of our best drivers were taking the Z/28 so much deeper into the corners than they thought possible. The first time into the corner, the guys felt pretty good braking between the 2 and 1 markers. By the end of the session, they were coming back in and saying, “Did you know you can wait until .75 to brake?!”

GMHTP: So…305/30ZR19 PZero Trofeo R tires at all four corners. Can we get some backstory on those steamrollers?

 Chevrolet Camaro Z 28 Brakes 5/6

DB: The Trofeo Rs have been a really good match for the hardware on this car. With the braking capability of the carbon-ceramics, along with the aggressive aero package, we needed a tire that would really stand up to the test. We looked at some other tires that were a close fit for the Z/28, but in the end, we went with the Pirelli for its performance.

And the tires gave us a surprise: Originally, we were going to fit the Z/28 with even larger, 325mm rear tires. However, in testing we found that the 305mm tires were actually faster, because they were a better fit for the balance of the car.

GMHTP: How did your team get the Z/28 to 1.05g in lateral acceleration? Was the huge handling difference mostly thanks to the 305mm tires?

DB: The lower center of gravity and the 305mm tires were a big enabler to get that 1.05g lateral. Also, the alignment settings have been adjusted to work best with the tire package.

GMHTP: What can you tell us about Z/28’s aero bits?

DB: The Z/28 incorporates a lot of serious aero content. We’re not ready to talk about specific numbers here, but I can assure you that the things we have done to this car have really added to the performance.

From the aggressive front splitter, to the fender flares and extended rocker panels, all the way back to the rear spoiler and functional diffuser, we have made sure that we manage the air to get everything we can from it. We have a great aerodynamics team on this program, including a former fighter pilot, and he has been militant about making sure that we get the air where it needs to be to get the fastest lap times.

GMHTP: How much of the aero package was based on an existing GM vehicle like the ZL1, and how much was created especially for the Z/28?

DB: We learned a lot on the ZL1—it not only shows up on the Z/28, but also on the 2014 LS and SS models. For example, adjusting the balance of the grille openings allows us to more efficiently use the available airflow for cooling and drag.

GMHTP: Where did the Z/28’s track-ready trans/diff coolers come from? Are they new or existing parts?

DB: With Chevrolet having such a strong performance lineup, we were able to pull many of the parts together from existing parts bins and make little to no changes to them. One of the coolest new parts that I am excited about is the rear differential cooler. The ZL1 has an incredible differential cooler setup, and we wanted to make sure the Z/28 would, as well.

I had an outstanding designer spend some time looking at the ZL1 and find a way to come up with a similar package for the Z/28 using the transmission fluid to cool the rear differential. However, the ZL1 has a unique differential. The great thing about the Z/28 diff cooler is it’s integrated into the rear cover of a standard SS differential. So for the guys who are spending time on the track in the SS or 1LE Camaros, we hope to offer this as an accessory to them as well.

GMHTP: Did Z/28 need any additional reinforcement or bracing due to the heavy lateral loads?

DB: We started with such a great platform on the Camaro that we didn’t have to add any structural enhancements. With the SS, 1LE, and ZL1 already going through the extremes of the 24-hour testing, we are very familiar with what this car is capable of.

GMHTP: Is the Performance Traction Management system the same calibration as other GM performers like ZR1, or specifically tailored to the Z/28?

DB: It is the same in function, but calibrated specifically for the application.

GMHTP: What changes had to be made to the Z/28’s engine bay/hood to fit the LS7?

DB: The main changes to the engine were the exhaust manifolds. The current Z06 manifolds wouldn’t clear the framerails, so the powertrain team did an outstanding job of coming up with high-flow, 3 into 1 manifolds that fit the Camaro engine bay.

GMHTP: Tell us about the little, non-visible things built into this Z/28 that will really make a difference in overall performance?

DB: The things you haven’t seen yet are items like the springs and bushings. We increased stiffness anywhere from 100-400 percent on the various components to get the most out of them at the racetrack. While this may be too aggressive for some people as a daily driver, the mission of this car is clear.

GMHTP: Is there any specific racing class (SCCA, etc.) that the Z/28 is optimized for? How do you see it being used by owners—will any of them street drive this monster?

DB: Currently, there is no specific SCCA class for the Z/28. We are working to get some of the parts homologated for racing, but there’s nothing to announce yet. We believe most will be used by weekend track warriors who want a street-legal/track-capable car they can drive to the track, run some laps, then drive home. Z/28 will be too track dedicated for many people to drive as a daily driver, but you certainly can.

Special thanks to Darren Bohne and Monte Doran of GM for their assistance with this article.

2014 Cheverolet Camaro Z 28 6/6


SPECS

Engine: LS7 7.0L V-8, 427cid, 11.0:1 compression

HP/TQ: 500/470

Drivetrain: TR6060 6-speed manual (2.66 First gear), 3.91 rear gears with limited slip differential and cooler

Suspension: Z/28-specific adjustable monotube shocks, progressive-rate springs, stabilizer bars, bushings

Brakes: Brembo 6-piston fixed front calipers, 15.5 x 1.4 in Carbon Ceramic Matrix front rotors; 4-piston rear calipers, 15.3 x 1.3 in Carbon Ceramic Matric rear rotors

Wheels: 19x11 front, 19x11.5 rear

Tires: Pirelli PZero Trofeo R 305/30ZR19 front, 305/30ZR19 rear

Curbweight: 3,720-lbs (estimated)

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