2013 Shelby GT500 Chassis Development - Total Package

The RevLIne

We now have the full scoop on the 5.8-liter V-8's rev limiter. The engine makes maximum power and redlines at 6,250 rpm, so normally there is no need to exceed that speed.

Given the 5.8's frenetic piston speed, staying at redline or below is a good thing. Occasionally, however, it's beneficial to over-rev a gear for a brief period, say to avoid shifting in the middle of a corner during an open-track, or for SVT to set a 0-60 time without shifting into Third...

For such occasions SVT has provided for up to 7,000-rpm over-rev bursts. As soon as 6,250 rpm is exceeded, a clock begins in Copperhead, and it allows up to eight seconds at 7,000 rpm as long as the rev limiter (fuel shut-off) is not reached. After eight seconds at 7,000 rpm, the PCM will drag rpm down to 6,250 and hold it there indefinitely.

What if you want to immediately return to 7,000 rpm? As John Pfeiffer, an SVT electronics specialist, explains, "It's a weighted timer, so it counts up if you are above (redline) and it counts back down if you are below (redline)."

"If you don't exceed the limit, you are good, but you've consumed some of your buffer. If you're in for three (seconds) and you are out for three, you have your full eight back. If you are in for three and you are out for two, then you only have seven left."

And what if you do bang off the fuel shut off?

"It will slowly bring you down to 6,250 if you stay in it, and it won't exceed 6,250 until you hit the reset conditions, which are 15 seconds below 6,000 rpm and at least one excursion below 5,000. It's set up around a shift, right? We don't want a guy to sit there; you're not doing yourself any favors."

Electronic Assist

As electronic aids proliferate, it is difficult to compartmentalize the handling, braking, steering, and other systems because they are now conjoined by electronic aids.

As a quick example, selecting the GT500's Sport shock setting does more than crank up the compression and rebound. It also changes the brake bias a little rearward to help turn-in, retunes the ABS, mutes the Advance Track stability control for less intervention, turns off nibble control in the EPAS electric steering assist, automatically selects the Sport steering setting--and texts the highway patrol for all we know.

Just kidding with that last one, but electronics are more intertwined than ever in the new GT500. And they help, especially for those new to 662hp cars. SVT recommends drivers new to a track do so with all aids in place (the so-called Key-On mode).

As confidence is gained, the Sport mode allows generous amounts of smooth aggression while maintaining a vigilant safety net in the background--good drivers never invoke it. Full-Off remains an option for elite drivers, although we find they rarely switch off intelligently tuned stability control systems such as the GT00's.

Track Cooling

Chevrolet has been keen to point out its Camaro ZL1 comes with engine, transmission, and differential coolers as standard and that the GT500 Ford makes them optional. SVT answers with a desire to keep GT500 pricing lower, and with the stock oil-to-water engine oil cooler the '13 GT500 has all the powertrain cooling it would ever need for all street and dragstrip driving, plus much of the typical open-track road course work. So why force perhaps 98 percent of GT500 customers to pay for and lug around weighty, excess cooling capacity?

For the other two percent, SVT offers the Track Cooling package. It puts air-to-oil coolers on the engine, transmission, and differential, and removes $2,995 from your automotive budget.

In our 5.8 engine article in the March '12 issue, we showed how engine oil cooling was swapped from water-to-oil to air-to-oil with Track Cooling. In this article, we're detailing the transmission and differential coolers.

All GT500 transmissions castings have a provision for oil cooling, but only the Track Cooling cars get the machining to accept the necessary hose fittings or the oil pump. The pump lives in the bottom front of the gearbox and is driven full-time off a tab on the countershaft. Furthermore the system has no thermostat, so the system is active whenever the engine is running and the clutch pedal is off the floor. Thin synthetic trans fluid means there are no issues with congealing oil on cold days.

The differential cooler plumbs its inlet and outlet through the back cover, and adds an electric pump mounted on the bodywork immediately above the rear axle, and an air-to-oil cooler mounted behind the right corner of the front fascia. The pump is purposely located close to the axle for the shortest possible suction line, which helps avoid cavitation.

A small temperature sender embedded in the differential cover senses the axle lubes temperature; the main ECU determines when to activate the pump based mainly on lube temperature.

SVT notes that the typical driver will never activate the differential cooler--it simply can't be done at legal highway speeds. Only hard road-course or sustained beyond-legal high-speed driving can get things hot enough.