Brabus SL55 K8
For the vast majority of people, the 476-bhp SL55 AMG is fast enough. After all, any car capable of accelerating from 0 to 100km in under 5.0 sec. and on to over 200 mph once you remove the limiter, should be as fast an anyone would want to go, even on the autobahn.
Apparently not, for since this fastest-ever production Mercedes-Benz was announced, some of Brabus' best customers have been on the phone asking when the power upgrade for the SL55 AMG will be ready.
The result is the Brabus K8, which made its first public showing at Geneva in March. I was the first to drive the car after its return to Germany and came away stunned by the depth and breadth of its performance.
Think about it. The standard SL55 AMG packs a supercharged 476 bhp and 516 lb-ft (700Nm) of torque under its sleek bonnet, but the Brabus K8 version raises the stakes to 530 bhp with 572 lb-ft of torque at 3470 rpm.
The K8 blasts to 60 mph in 4.4 sec., but right now its top speed is limited to 188 mph because of tire speed ratings. On special 18-in. tires the car should reach 206 mph, but such rubber is not yet widely available for a car of this weight.
The 188 mph I achieved came easily, though, as I swept up the autobahn A31 from Bottrop, heading for the Dutch border. Traffic was light, and within minutes I found a clear stretch of road where I could open the car up.
As fast as the stock SL55 AMG is, the extra urge of the K8 conversion is simply astounding. Even in fourth and fifth gears, the speedometer needle climbs round the scale almost as fast as its counterpart on the tachometer. The other eyeraiser was that the AMG Speedshift even kicked down a gear when I accelerated from an indicated 155 mph, bringing the engine back into the meaty bit of the torque curve for maximum possible acceleration.
At close to 200 mph, things happen both very fast and very slowly at the same time. If you relax and look really far ahead, the horizon appears to be reeling in and yet it stays put. Your peripheral vision tells your brain that the world is whizzing past at an immense rate, but that horizon never actually gets any closer. It is a very strange feeling, quite different from the one you get in an aircraft where there is no long strip of tarmac connecting your relative position with the horizon. It is almost like being on the fabled event horizon of a black hole.
The punch is the back is not so much explosive as compulsive. The more you feel it, the more you have to have it. It gives you real seven league boots in the way that a powerful jet plane does. There is simply so much surplus thrust there for the asking, you are almost surprised that a mere road car can contain it safely. It shows just how good the basic SL chassis is with its clever ABC suspension.
Using the AMG 476-bhp supercharged motor as a base, Brabus set out with a 10%-plus gain in power and torque in mind to make the K8 conversion worthwhile. "We use new ventilated pulleys on every single component in the system to make sure all the relative gearing is correct and the belt is kept cool, as belt life is governed largely by heat stress," he explained. The cooling capacity of the engine is also increased by 50 percent to keep charge air temperatures low and the engine healthy.
"At the factory 0.8 bar boost, the IHI supercharger consumes 91 bhp at peak revs," Jorn continued. "We run 1.1 bar boost on the K8 conversion, and now the system consumes 106 bhp but gives back even more. We claim 530 bhp, but as you can see from the dyno chart, we got 548 bhp on this particular car. Bear in mind that manufacturers have a 5% tolerance on output, and that falls broadly into this area."
At the time I drove the Brabus K8, I also learned that the forthcoming 476-bhp bi-turbo 5.5-liter V12 engine for the S600, CL600 and SL600 has prompted AMG to revise the specification of its supercharged 5.5-liter V8. After making just 100 cars with the 476-bhp engine, the SL55 AMG now has 500 bhp. "So we will increase our K8 to 550 bhp," Gander reported.
The Brabus K8 has so much raw, yet totally refined, power that it seems pointless to own it unless you live in a place where you can use the power. More so because using it is addictive, and the awesome performance is so natural and so effortless, it seems almost churlish not to indulge yourself. An indulgence? No, it is simply one of life's great pleasures.
Scandinavia is not exactly noted for its activity in the automotive world, so when I was recently invited to drive a new SL500 equipped with a supercharger system from Danish Mercedes tuner Kleemann, I was as curious as I was excited.
european car reported on a pair of Kleemann cars in the Dec. 2001 issue, but this was the first time I had driven a Kleemann-modified car, and I did not know what to expect. Approaching the drive with anticipation and an open mind, I came away absolutely stunned by the experience, because this car did exactly what was claimed for it, and more.
A great advantage is that the invitation came from Holger Mohr, owner of Kleemann's new German importer, based in Bruggen, on the German border with Holland. We say that because, of course, most of Germany's autobahnen have no speed limits, whereas Danish roads do. And from what I hear, the Danish police lack a sense of humor.
The compact supercharger is made for Kleemann by Swedish AutoRotor, and is a twin-screw positive displacement unit with low internal friction.
The secret is cool air and low boost. Thermal stress puts a limit on reliability, so Kleemann approached heat as the root of all problems. Once you have too much heat at the air intake, you have a cascade effect throughout the whole engine. Then you need a lower compression ratio to avoid detonation, but this blunts throttle response. Then you have to run higher boost to get the power and torque, but the higher the boost, the more heat you get and the closer you run to detonation. It all goes round in a circle.
Kleemann set out to develop a special intercooler system that would effectively reduce the temperature from the supercharger from 100C to no more than 25- or 30C above ambient air temperature at the inlet manifold. This allows the stock compression ratio to be retained, cutting out a lot of expensive internal engine work. It also means that the conversion is easily reversible should you decide to sell the car in standard form.
The innovative intercooler comes from Laminova, another Swedish engineering firm. It is so efficient that at full power it can dissipate nearly twice as much heat from the charge air as the comparable AMG unit. Laminova claims net horsepower gain is higher and is achieved on lower boost pressure. In fact, the other reason the stock compression ratio can be retained is that the Kleemann car uses just 0.45 bar of boost compared to 0.8 bar on the 476-bhp SL55 AMG.
On the SL500 the 5.0-liter V8 goes from 306 bh48% torque increase!
The Kleemann SL50 K starts and drives around town with a 5.0-liter normally aspirated V12 up front.
There is no supercharger whine to speak of, and throttle response is instantaneous, the boosted motor revving sweetly to the redline in each gear, aided and abetted by that strong column of air in the induction. The M-B V8 is a very smooth engine, but it somehow seems smoother still with the supercharger on top.
Where the power of the stock engine peaks at 5600 rpm and gently falls away, the Kleemann motor charges past 6000 rpm smoothly and with real vigor in every gear. Even at well over 250 km/h, acceleration is strong, and the car does not take long to top 300 km/h.
I drive dozens of modified cars every year, many of which are very good indeed. I approached the Kleemann concept with an open mind and was rewarded with a result that stacks up against the very best anywhere. Without pulling any punches, it is one of the best aftermarket supercharger installations I have ever driven.