Callaway Of the Month August '05
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C36 Part IV – Pushing the Envelope, Callaway Corvette C36
Following the excitement in our last installment of Lance Miller’s Carlisle Callaway C36, our journey took us to various shows and tracks around the country testing and driving Callaway’s latest advances with this groundbreaking project for the C6 Corvette market.
The last time we visited with Callaway Cars, revisions were being made to the components installed on the C36 in preparation for production. While in Old Lyme, we witnessed the installation of the Callaway 6.8 Liter all aluminum powerplant that now resides between the frame rails of the car. Based upon the Corvette racing engines used in the 24 hours of LeMans racing series, Callaway’s clean room assembly process installs specific components to make 550 horsepower at the crank with this new engine.
These components begin with a heat treated G.M. Motorsports aluminum block with 6-bolt steel billet main caps, billet crankshaft and connecting rods with specific lightweight aluminum pistons for the package, specified at a 10.5:1 compression ratio. Callaway also uses unique, proprietary rings for positive oil control in the assembly. CNC ported LS2 casting cylinder heads are used. However, they are fitted now with larger diameter valves for additional flow and special alloys are used in the hardware, including titanium, for lighter weight and greater durability. Callaway also installed their specific camshaft and, while the profile is rather aggressive, it was designed to be emissions compliant and works in conjunction with a set of higher ratio roller rocker arms for increased lift in the valvetrain.
Being one of the first to swap out an engine in a C6 Corvette, Callaway’s Car Production Shop Manager, Wayne McCurdy shared some of the secrets. “Removing the engine, while relatively straightforward, is done by dropping the engines cradle and attached front suspension components along with it”, McCurdy offered. Callaway Cars has a unique cradle to hold the assembly and then finds that lifting the car off the assembly is the best way to approach this. McCurdy said, “ It comes out much the same as the C5 Corvettes engine did”. With the installation of the 6.8 Liter engine simply a reversal of the process, it wasn’t long before the installation was complete and time to test out the new big cube engine package.
Connected to the car still, was the Motec Advanced Dash Logger (ADL), C36 Part 3, Corvette Enthusiast June 2005. Recalling that the ADL has the capabilities to monitor and capture data from multiple sensors during testing, this equipment would continue to show its value during chassis dynamometer testing. Callaway Cars took the C36 to the chassis dyno facility soon after installation for initial testing and during our follow-up visit, we would be returning to the facility.
Arriving in Old Lyme at the Callaway shop, Wayne McCurdy and I departed for the dyno facility with the C36. During our drive, I realized that while most of the car was the same as before, there seemed to be an absence of noise from within the car – specifically, resonance. McCurdy explained the production pieces of the various components were now fitted to the car and one in particular; the Callaway cat-back exhaust was one of them. During our last visit, we had commented on the attractive “V-pattern” muffler cans under the tail of the car. Since then, Callaway has continued development of the exhaust system to maximize flow potential and minimize backpressure for peak performance. In addition, they have also reconfigured the muffler volume to defeat undesirable resonances while achieving the desired acoustic signature. The result is a refined exhaust note under all throttle conditions, without the resonances afflicting other designs. As we proceeded to the dyno facility, we continued our conversation without ever having to elevate our voices or strain to hear one another.
Further into our drive, the weather changed quicker than I had ever seen before, bringing additional excitement. It went from overcast, to rain, to snow, with flakes the size of silver dollars, all within approximately ten minutes time frame. It was during this part of the drive, the car introduced me to another C6 feature, a message on the dash warned of the potential for freezing roads on the driver’s information display – very cool.
Arriving at the dyno facility, we allowed some time for the tires to dry off as we strapped the car down to the equipment in preparation for our test session.
Preparing to collect the information as the C36 ran on the dynamometer, I noticed McCurdy hooking up another piece of test gear. Tapping into the factory connector on the harness, he had connected G.M.’s Tech 2 hand held scanner to capture additional data during the runs. Capturing data from 51 different sensors already within the C6 Corvettes wiring harness and sensors, this would allow the engineers at Callaway to evaluate additional information obtained that day.
Testing for much of the morning and continuing into the afternoon, McCurdy transferred the data as it came in, uploading it onto a laptop computer or taking notes by hand as to how the car performed. With a full day of data captured, it was back to the Callaway shop for review of the numbers. Gathering information with both the Tech 2 and Motec ADL allowed for more accurate comparisons to be made with runs from the previous dyno session. Back at the shop, the engineers then reviewed the performance of the car throughout the RPM range, looking at the various sensors and seeing individually where one might be adding too much of one thing, or cutting back on another parameter. During the review of the data, I quickly picked up that one of the parameters being looked at, was the much talked about “torque management” and the related timing curves that it controls. By monitoring items such as this, the Callaway engineering team has the capability to make and edit changes to the PCM, allowing the C36, and future cars to make the most out of their packages, overcoming hurdles such as torque management.
Callaway Cars is continuing their fine tuning on this package, pioneering the way for future C6s and with the components installed in the C36, they will have eclipsed the recently released Corvette Z06’s 7.0 Liter, 500 horsepower mark!
On the road again…
During the course of our visit, we amassed a few hundred more miles of seat time during our testing and evaluation in this incredible machine. As mentioned earlier, the exhaust note is right on the money and with the gas pedal down, the C36 simply pulls! Thrusting its occupants back into the sculpted leather seats and emitting an authoritative growl, this car under acceleration lets you know it’s time for business!
Taking a trip up the highways of Connecticut, for the return drive, we decided to let the C6 GPS Navigation system determine our return path. Entering our destination, the GPS plotted our course after instructing the system to avoid highways or major roads, resulting in a tour of Connecticut’s most serene backroads. Rowing the short throw shifter through the gears, we continued on through the twists and turns the small roads offered, challenging at times, the C36 answered the call every time. While the additional power from the 6.8 Liter engine is quite obvious, some other changes in character about the C36 came forth during our drive as well.
Rounding the corners and easing through series after series of switchbacks, the C36 dynamically feels far more taut than before. Keeping in mind that many of the enhancements that Callaway Cars has done with the C36 are related to controlling the additional power. They have strived for total balance and control of the car’s power. Coil over shocks and larger diameter anti-roll bars with specific bushings and links were the parts working the hardest during our spirited drive, with the huge 14 inch Callaway / Alcon brakes bringing the car’s speed down in an instant, and showing zero signs of fade during repeated use.
During the drive, I came to the conclusion that Callaway Cars may have constructed the most balanced feeling car ever produced, and certainly the most balanced of any I have driven.
When it comes to evaluating a vehicle at its limits, the two main types of testing are steady state and transient. Skid pad testing is an example of steady state testing, where a vehicle is brought to its performance threshold and maintained at that level. Skid pad results represent the ability of the vehicle to utilize the available traction. Slalom testing is an example of transient testing, where the vehicle is forced to react to a series of predetermined inputs, or in this case forced to follow a prescribed course. Slalom results are a gauge of the level of control that a vehicle maintains in its ability to respond to changing direction. In the real world case of driving a vehicle, transient testing more directly relates to the feel of the vehicle, the sense of response and balance that the vehicle relays to the driver.
It is the driver’s reaction to the transient response of the vehicle that develops their impression of the real world feel. We call this the “seat of the pants” results. After spending a few thousand miles in the C36 before and after the suspension updates were made, I can tell you that it is a far better car in both smoothness and control compared to stock.
Keeping in tune with Callaway Cars testing philosophy for gathering data on all gains or improvements of performance in their cars, the C36 was also tested on a closed course at a vehicle test facility. The test courses are designed and set up exactly like the courses used by national auto publications such as Car and Driver Magazine. The identical course layouts allow Callaway Cars to directly compare their results with those of various vehicles tested by magazine staffs. Callaway performed the testing of the C36 in both stock and Callaway trim on the skid pad and the slalom course.
While the testing was conducted under less than optimal conditions, during the dead of winter, the Callaway team was still able to quantify and report their results. Given that the tests were run during a cold day (34 degrees Fahrenheit), the C36 picked up a modest improvement of .01g on the skid pad. The Callaway suspension upgrades yielded .91g, compared to the Z51 suspension package performance at .90g. As the skid pad testing was completed, the team headed for the slalom course, where the C36 really shined!
The C36 with the Callaway suspension package executed the seven cone, 600-foot slalom course 3.8 mph faster than with the OE Z51 equipped suspension! While the Callaway suspension upgrades get most of the credit for the improvements, the Callaway lightweight alloy wheels and Pirelli P-Zero tires were instrumental in obtaining those stellar numbers.
With this round of testing and validation completed, Callaway Cars will continue to fine-tune the programming for the 6.8 Liter powerplant in search of even greater power. In the meantime, Callaway Cars has recently revised their entire website (www.callawaycars.com), allowing for a virtual tour of everything they offer for your new C6 Corvette, and where to purchase and then have the components installed – Check it out!
© 2005 Christopher Chessnoe
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