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The Porsche Cayenne project finally gets a full day out in the desert.
Porsche built the first-generation Cayenne to prove that an SUV could simultaneously offer excellent driving dynamics and real off-road capability. Unfortunately, the complexity of a big Porsche with a beefy range of engine options, an Aisin six-speed automatic transmission, a transfer case with a locking center differential and true low-range four-wheel drive, plus options like air-lift suspension and electronically disconnecting sway bars led to significant depreciation for the 955 and facelifted 957 Cayennes.
The depreciation curve allowed me to purchase a 2006 Cayenne Turbo last fall, though, at pennies on the dollar. From the get-go, I planned to make some light modifications hoping to transform the SUV into a mild overlander and ski season storm chaser, with additions like knobby Toyo Open Country A/T III tires, a skid plate from Eurowise to protect the dry-sump twin-turbo V8, and a swingout rear spare tire and gas can carrier.
My to-do list continues to grow now that I recently took the Cayenne out onto the Mojave Road to test whether Porsche's original super SUV might ably conquer the relatively technical climb up Paiute Ridge, a route I previously explored in both a Jeep Gladiator Rubicon and my own 1998 Mitsubishi Montero.
In my Montero, I needed to engage my locking rear differential to climb up a few of the rockier sections of Paiute Ridge. But I went on that trip without an air compressor, so I never aired down the LT-metric Cooper Discoverer S/T Maxx tires. In the name of science, then, I felt compelled to drop the Cayenne's Toyos down to the same 38 PSI that I run the Montero—just a bit less than my usual 42 to 48 PSI for ideal fuel economy and road noise reduction of the P-metric tires. All Cayennes equipped with air suspension include a built-in compressor, which makes airing up after off-roading quite easy, so on an earlier trip to a smoother section of desert, I aired down lower still.
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I also used this adventure to test out the OnX Offroad App that I originally used on a recent journey through Joshua Tree National Park. In this case, I downloaded offline maps of the entire Mojave Desert in both low and medium-resolution, then plugged in my target trailhead where the Mojave Road crosses I-95 south of Searchlight, Nevada. I connected OnX on my phone to the Cayenne's aftermarket Sony head unit, which allowed me to run a larger map via CarPlay with a zoomed-out north-south orientation map on the phone. Together, this setup helped me avoid any wrong turns in the hot desert—stay tuned for a full review of the app coming soon.
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I love fiddling with all of the Cayenne's various drive settings. On the drive out to the trailhead, I dropped the air suspension to Low and softened the shocks to Comfort. But once we pulled out into the dirt and rocks, I raised the ride height to High and flipped the shocks between Comfort, Normal, and Sport depending on conditions. On higher-speed washboards, Comfort allowed for smoother driving but in the rockier sections and whoops, Sport actually helped the SUV stay better balanced.
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The climb up Paiute Ridge presents a few sections that I might otherwise avoid without the Eurowise engine skid plate protecting the Cayenne's underbelly. For the first half-mile of steeper terrain, I flipped the transfer case between 4-High and 4-Low to experiment with traction before getting to the tougher stuff. On a hot day approaching 100 degrees with a bit of a tail wind up the hill, the coolant temperature gauge began creeping towards 200 degrees Fahrenheit, even though the engine oil stayed rock steady. Still, I decided to stay in 4-Low just to keep the fluids circulating faster, while allowing the Aisin transmission to shift gears automatically.
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On the gnarliest segments of Paiute Ridge, I popped the gear selector over to Manual mode to keep the trans in second, then locked the center differential. Given the twin-turbo V8's 457 lb-ft of torque, first gear actually produced a bit more wheelspin than I wanted while second kept the ride a little smoother, even at elevated RPMs. Choosing a careful line, I steadily pushed up the rocky trail, trying not to lift off throttle. Though my Cayenne left the factory with neither a rear locking differential nor the disconnecting sway bars, the traction control can squeeze the brakes individually to prevent single wheels from spinning in low-grip situations or when off the ground. And the Jeep behind me said that I got multiple wheels up about 18 inches in the air, multiple times.
The brakes grabbing produced something of a strange sensation, though. On one hand, traction immediately improves. On the other, the shuddering sounds (and feels) a bit jarring. Plus, the braking slows the 5,200-pound SUV down and makes avoiding throttle lift all the more important to prevent unintended stops. My own seat dyno suggested the Montero with a true locking rear diff probably rode up the hardest sections slightly more smoothly, though the Cayenne still climbed up Paiute Ridge without breaking a sweat. Maybe my own skill increased with additional experience since I last visited Paiute Ridge—or maybe the Cayenne's capability made the difference—either way, I reached the top fully impressed. And I might hazard that I could have completed the trail without even using four-low or the locking center differential at all.
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I only felt a couple of impacts on the Eurowise skid plate, none of them significant enough to leave a noticeable mark or dent (at least, that I noticed without climbing under there or getting the Cayenne on a lift). But I felt much more confident knowing that a thick piece of steel protected that Porsche powerplant rather than the flimsy factory underbody trays, even as brush and stray rocks popped up on the day's higher-speed portions and rang out like a drum.
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On the Cayenne's next trip, I plan to air down further to 20 PSI and hopefully experience the full potential of the Toyo Open Country A/T III tires. Compared to the LT-metric Coopers, the Toyos felt a bit smoother at the same 38 PSI, plus they tended to slip less despite the Cayenne's prodigious low-end torque. But those impressions seem in line with P-metric tires that measure 265 millimeters wide versus the 235s on the Montero. I still need more experience airing down the Coopers, too.
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Two Cayenne conundrums cropped up on the trip. The first triggered my fears that online complaints that Porsche's tightly packed engine bay can lead to overheating. But on this second trip where the coolant crept up in temperature with a tailwind, I came to the conclusion that the coolant simply heats up to 200 degrees, as seen above to match the engine oil, without then continuing any higher. I kept my eye on the gauge throughout the day and whenever we turned enough to create a sidewind or headwind, the issue stopped altogether. I figure if the coolant climbs any higher than 200 or if the engine oil starts creeping upward, too, then I need to start worrying.
The other issue involves airing down in a vehicle with a tire pressure monitoring system. The Cayenne's TPMS actually works more reliably than any other I've experienced, so far, but even with the Toyos only aired down a bit, the dash showed the warnings visible above all day which blocked me from checking on the rest of the car's computer readouts. With no cell reception on the Mojave Road—making OnX Offroad's offline maps especially helpful—I never found a way to clear those codes while aired down (and still haven't).
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Throughout 45 miles of off-roading in the Mojave Desert, ranging from the technical climb up Paiute Ridge to soft high-speed sandy roads, the Cayenne performed just about as well as I hoped last October. Next, I plan to add a few more bits of armor from Eurowise and then start working on the cabin buildout for a sleeping platform. In the meantime, after airing the Toyos back up, the Cayenne showed off those impressive on-road capabilities by hauling me home cruising down the hot highway effortlessly at 80 miles per hour with the A/C blasting.
Sources: coopertire.com, onxmaps.com, eurowise.com, and toyotires.com.
Michael Van Runkle grew up surrounded by Los Angeles car culture, going to small enthusiast meets and enormous industry shows. He learned to drive stick shift in a 1948 Chevy pickup with no first gear and currently dailies his 1998 Mitsubishi Montero while daydreaming about one day finishing up that Porsche 914 project. He's written in various media since graduating from UC Berkeley in 2010 and started at HotCars in February 2018.