Porsche specialist Karl Wilen, owner of Rennsport KC, splits his time between building and maintaining road-race cars and street cars.Karl Wilen uses a torque wrench to tighten oil pan bolts on a 911 after checking for signs of IMS failure.Rennsport KC replaces failed or failure-prone intermediate shaft ball bearings (right) with an IMS Solution oil-lubricated plain bearing.

‘Porsche Doc’ has Rx for reliability

RennsportKC applies preventive maintenance regimen to Porsche street and race cars

Grandview, Mo.—In the punishing racetrack environment, even a small part failure can ruin the day of a driver who may have spent $10,000 to compete at a weekend event.

“Mileage on a race car is tenfold what it is on a street car, in terms of the abuse the parts take,” said Karl Wilen (pronounced “Willen”), owner of RennsportKC. “So if it’s 1,000 miles on a race car, it’s like 10,000 miles on a street car.”

Staying on top of preventive maintenance — with keeping fluids fresh at the top of the list — is key to reliability on the street or on the track, he said. (Rennsport, German for “racing,” is generally understood by U.S. enthusiasts to apply specifically to Porsches.)

Wilen splits his time between the care of street cars and road-race cars, applying to each what he’s learned from the other in preventive maintenance and part failure analysis. About 25 weekends out of the year, he travels to races either driving a team’s hauler or flying in for total support of what maintenance a team may need, from simple brake replacements to engine or transmission swaps. Porsches are his specialty, but he’s also the crew chief for PF Racing, a Harrisonville-based team that races a Ford GT4 Mustang in IMSA.

It’s not uncommon for Wilen to spend four to five hours prepping a car for each race by checking the torque on each suspension nut and bolt, changing brakes and fluids, and looking for any leaks.

Wilen, who works alone, said he has a “soft spot” for 944s, although he doesn’t see as many of them in the shop anymore.

“I bought my first Porsche when I was in chiropractic school. It was an old 944 Turbo, and it probably should have gone to the junkyard, it was so bad. But I couldn’t afford to pay anyone to fix it, so I had to learn how to work on it, and pretty much everything on it broke. I took that car down to the bare chassis more than once rebuilding it.”

While still in school, he became friends with the owner of Imagine Auto, a now-closed local Porsche tuning shop.

“When I graduated, I was working for a doctor during the day doing chiropractic, and then working at the shop at night after hours. We were doing big-modification, big horsepower-style builds up to 1,000 HP — and not a lot of daily maintenance.”

Adopting the handle of “Porsche Doc” on various Internet forums, he later became lead tech and shop manager, seeing chiropractic patients at night, before devoting his efforts full-time to his automotive passion. A friend in 2011 guided him to the building that would become his own shop’s new home, a former vintage-Porsche racing shop with 5,000 square feet and a 2,000 square-foot storage mezzanine.


Pre-purchase inspections avoid costly repairs

Wilen advises customers to have him perform a pre-purchase inspection (PPI) before they’re stuck with an expensive problem.

“The problem with Porsches is people get emotionally attached before they ever buy the car,” he said. “So you have to kind of walk them off that ledge and back to the reality of the cost of things. If one of these motors fails, it can cost anywhere from $20,000 to $35,000 to replace. The $500-$600 it takes to do a pre-purchase inspection might save you tens of thousands in the end.”

One common failure point in certain 911 and Boxster engines, which he detects by finding metal in the oil, is the intermediate shaft (IMS) bearing, which is “a sealed greased ball bearing, and in an oil environment, that doesn’t work. Oil seeps past the seal and washes the grease out. There are a lot of different factors, from thrust, to heat, to oiling issues, but that’s a big one.”

It’s a common concern during a PPI, and it’s also something he fixes with the “IMS solution,” jointly developed by LN Engineering and Flat Six Innovations as a permanent fix, replacing the roller ball bearing with an oil-fed bushing. As one of a few shops certified by the IMS Solution manufacturer, he said he does about 15 of those retrofits a year.


Custom alignments can reduce tire wear

Wilen aligns race cars with a string aligner and pays a shop down the street to use its alignment machine for street-car alignments.

“On these newer 911s, the cars are so fast and so powerful that they’ve dumbed-down the alignment a bit to keep the car very stable, but it’s at the expense of excessive tire wear. A new 911 gets 10,000 miles on a set of rear tires before the inside edges are bald. We can make some modifications that make it handle a little better — a little more aggressive - and sometimes get better tire life.”

At $105 an hour, Wilen figures he’s cheaper than the dealership and many independents. Some have told him he’s leaving money on the table.

“But I like offering a good product, at a fair price, without the ‘Porsche tax.’ There are clientele for whom money is no object: ‘Just fix the car, and fix it right.’ And then there are guys who are, ‘Man, this 996 is the first Porsche I’ve ever owned; I can finally afford a Porsche.’ So, we’re going to try to make this ownership as affordable and pleasant an experience as possible.”

Parts & People

Parts & People is published monthly by Automotive Counseling and Publishing Company, Inc., a Colorado corporation, P.O. Box 18731 Denver, CO 80203, 303-765-4664. President-Lance Buchner. Founded by Lance Buchner and Dave Lucia.