Sometimes,? says Hartmut Feyhl, ?I am a little ashamed to call myself a tuner.? Not because the calling itself isn?t noble (how can making cars go faster and handle better be otherwise?), but because so many cable TV shows use ?tuner? to describe most anyone who lowers a suspension using Home Depot C-clamps, or enhances noise, not performance, by bolting on a big, loud tailpipe extension. ?So many of them are parts install-ers, not tuners,? Feyhl says. ?It has become almost a joke.?
There?s nothing funny about the performance or the price of Feyhl?s tuner cars. As president and CEO of Renntech, the Florida company that since 1989 has been among the country?s top Mercedes tuners, Feyhl has a reputation for dogged attention to detail. Renntech modifications typically have the look and feel of a factory installation, not surprising since Feyhl?s childhood home in Germany was located next to the AMG factory, and he apprenticed at the best-known Mercedes mod shop when he was a teenager. By 1986 he had become the technical director of AMG?s North American distributorship, where he built the brutally fast AMG Hammer sedan, a 300E with the weak-willed six-cylinder surgically removed and replaced by a much-massaged 32-valve V8.
Renntech first came to our attention more than 13 years ago (?Hammering It Home,? Jan. 11, 1993), when we wrote about the company?s 600E, essentially a 400E with the engine balanced, bored and stroked to 6.0 liters, bumping horsepower from 275 to 385. ?Think of it as a second-generation Hammer,? the story said, ?taking advantage of Mercedes design improvements since the AMG original.?
Speaking of design improvements: We made a trip to the Renntech shop, north of Miami, to sample a Mercedes CLS55 Renntech. We?ve gone on record as more than impressed by the looks and performance of the chance-taking CLS, and more of a good thing is, well, a better thing. The CLS55 AMG?s 5.5-liter V8 starts with a healthy 469 hp?which, incidentally, Feyhl says is maybe 25 hp fewer than the engine actually puts out?and Renntech?s modifications can take that horsepower to about 650.
Those mods include huge but sanitary top-mounted twin intercoolers, an ECU upgrade, a bigger throttle body and crankshaft pulley kit, and stainless-steel headers. A new carbon fiber engine cover air box had not been fitted to the test car, the final touch of the $37,600 package. Without that piece, the supercharger whine and air intake were louder than Feyhl likes, but we thought it had a nice, means-business sound. The engine?s bottom end, Feyhl says, is plenty strong enough to handle the extra power, as is the five-speed automatic transmission.
Suspension modifications included a lowering module ($1,495) and a toe-link kit (also $1,495) that Feyhl says is needed to help locate and strengthen the rear end, which he says tends to walk a bit from side to side under very hard acceleration. The tire and wheel package ($7,830) included 20-inch Renntech-forged, diamond-cut wheels with P255/30 rubber up front, P295/25 rear. Though Feyhl prefers Nittos, the tires on the tester were Pirellis, because Nitto doesn?t offer suitable tires in these particular sizes. The final performance upgrades were 16-inch, eight-piston Renntech front brakes, which add $7,995. Base price of a new CLS55 is $86,600; mix and match the Renntech goodies, then you do the math.
We told you Feyhl was good; we never told you he was cheap. Much of what you?re paying for is an on-staff roster of engineers and designers, and for Feyhl?s get-it-right philosophy, which also means he will never star in one of those makeover TV series where your car is done in a weekend. Or a week. Or maybe a month.
On the road this CLS55 definitely feels beefier than the stock model. The tires and suspension mods enhance handling but add to a rougher ride that, while never intolerable, is often mildly jarring. We?ve never had issues with the stock front brakes on the CLS55, but these larger units have the same linear feel and would certainly help keep their cool on track days.
While the test car didn?t have it, Renntech offers a carbon fiber interior trim kit that replaces the standard wood, and a carbon fiber and leather steering wheel. Also available is $5,150 worth of front and rear carbon fiber splitters and side skirts, but we think just the lowered suspension and wheel and tire mods do plenty to set off an already handsome design.
Thumbing through the catalog for the CLS, it appears the real bargain might be a $15,900 upgrade kit for the base-price $64,900 CLS500, which boosts the 5.0-liter V8?s 302 hp to 443 via a Renntech supercharger and intercooler, and an ECU upgrade. The company stocks parts and upgrade kits for most Mercedes models, as well as Porsches and several other brands.
We?ve driven perhaps a dozen Renntech tuner cars over the years, and Feyhl?s attention to detail has not wavered, as suggested by an all-star clientele ranging from comedian Jerry Seinfeld to country singer Alan Jackson to actor/whatever Sylvester Stallone. But to be a Renntech customer, it helps to be patient. And rich.
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