I don’t know whether you would consider this an upgrade or a downgrade, but swapping the CLK55’s front rotating assemblies for a set of CLK320 brakes and wheels will definitely make the car quicker at the dragstrip.
I’ve been running the heavy 18″ Mercedes-Benz E55 wheels on all four corners of the CLK55, which look great, but they aren’t be best for drag racing. Each corner weighs-in at over 50 lb, leaving a lot of room for improvement. The factory CLK320 wheels are the hot ticket for drag radials on the rear, but they also make a good low-budget “front runner”. They only weigh about 13 lb each (because they’re forged), and at 7″ wide you can fit a fairly narrow tire on them. I bought a pair of inexpensive V rated 205-60/16 tires that can be used as daily drivers, while still saving a good amount of weight for the track.
I took the CLK to a bracket race event at the Woodburn Dragstrip on Father’s Day last weekend. The car performed flawlessly in the heat, running some pretty consistent times. Ultimately I won the class by going three rounds with good lights and good dials.
Phase I (Baseline testing) of the CLK build has been completed ahead of schedule. Yay! This is good because driving a mid-13 second “race car” is a little tedious when your daily driver is a low-11 second beast. I’m ready to get on to bigger and better things, but first let’s see how the baseline testing went.
I came up a fair bit short of my goal of running a 13.20 at full-weight, only managing a best of 13.58. A 13.20 might be possible on a really cold day, on a nearly empty fuel tank, and with the spare tire and passenger seat removed, but I haven’t got time for that! I’m ready to call this phase done and get on to the weight reduction.
The 2002 CLK55 that I recently bought came with a set of aftermarket wheels that just didn’t work for me. They were Katana GTM wheels, which look fantastic on the company’s website, but the 18×7.5 wheels didn’t have enough “dish” to look proper on the CLK. The fronts were OK, but the rear wheels had improper offset and were tucked way too far inside the fenders, giving the car an anemic look. Of course it doesn’t help that the 7.5″ wide wheels will only support a 225-40/18 tire.
I decided to solve this problem by killing two birds with one stone. I could sell the Katana wheels and recoup some of what I paid for the car, and I could clean out my garage just a little by putting my old factory E55 wheels on the CLK.
A very common place for a vacuum leak on the E55’s is that port on the rear of the supercharger with a strange multi-piece plug in it. I assume that port is used for the brake booster on cars that don’t have the SBC system, but it is beyond me why the engineers at Mercedes-Benz decided to make a three-part plug to fill it instead of using a simple rubber plug. This is especially strange since there is an existing Mercedes part that seems to work perfectly.
I was at Mercedes Benz of Portland today, trying to get a new plug for my car since the old one is leaking. For some reason the parts diagram on the computer only shows two of the pieces required. It was clear that it would not work without that third piece, so after some head-scratching the parts guy said “Hey, I’ve got an idea!” He ran into the back and two minutes later came out with a plug for the windshield washer on a CLK320 (part number 210-987-00-45) that is the perfect size for the port in the supercharger!
If you own an M113k-powered Mercedes-Benz you know that keeping the intake air charge cool is one of the biggest headaches of the platform. Any supercharged engine will have increased IATs due to the compression of the charge, but the M113K engine suffers more than others because of the size and placement of the intercooler. The intercooler is relatively small, and it sits under the supercharger, in the “V” of the engine. Heat soak is all but guaranteed after each high speed run.
Things get especially bad at the dragstrip because the car spends a lot of time in the staging lanes with no airflow over the heat exchanger, effectively rendering it useless until you start a pass. By then it’s too late and your IAT’s have likely climbed above 90 degrees, which is where the computer starts to pull timing.
There are various ways of dealing with this issue, such as a larger heat exchanger, larger circulation pumps, or methanol injection. I decided to go a different route and use my A/C to cool the intercooler water, courtesy of Kincaid Performance’s Killer Chiller.
I took the CLK to the Woodburn Dragstrip for the first time today so I could get some baseline numbers on the car while it is still full-weight and 100% stock. While not the numbers I was hoping for, I did learn a few things and started the process of getting to know this car’s personality at the track.
If you are looking for better traction for your E55 you have come to the right place! The hot ticket for cutting your 60′ times is a set of Hoosier DOT Drag Radials mounted to OEM Mercedes CLK320 wheels.
The rearward bushings in the front lower control arms of the W208 CLK are known to wear out rather quickly. They are “loose” by design, having an air gap around more than half the perimeter of the bushing, meaning there is only about 2″ of rubber holding the outer shell to the inner sleeve. This not only leads to premature failure, but often leads to vibrations in the car, even when the bushings are new. I’m sure the Mercedes engineers had good intentions, but in practice these bushings have been a sore spot for many CLK owners. You can replace the factory units with aftermarket polyurethane bushings from Powerflex if you want a performance and reliability upgrade.
This typically happens under hard acceleration and can cause a lot of expensive damage to the car. The rear subframe is held in by four bolts, and it always seems to be the rear two that have the problem, never the front two. This makes sense, since under acceleration the rear end is trying to squat while the front end rises due to the torque imparted on the chassis by the drive axles. The front half of the subframe, ahead of the axles, is pushing up into the body, while the rear part, behind the drive axles, is pulling down on the body. With 516 ft-lb of torque available from even the stock engine, those two rear mounting points tend to fatigue and fail when you least expect it.
Adding the large-diameter washers is the key to this fix.
The fix is pretty straight forward, especially if you do it before it becomes a problem. It’s a simple matter of replacing the factory rear subframe bolts with a pair of new bolts with nuts and large washers on them, creating a “sandwich” that is much stronger than the original setup. Adding the large-diameter washers is the key to this fix. They spread the load out over a much larger surface area than the original mounting bosses, thereby making it nearly impossible to tear them out of the body. My car has over 180 dragstrip passes on it, all on sticky Hoosier drag radials, and the bolts have held strong. Continue reading “E55 Subframe Bolt Replacement”→