ashutt

For CLK55 owners, I wanted to pass on some information I think is of value. Last night, I installed the AutoMeter Digital Pro Shift Light System ("DPS"). A few people, mostly 1999 CLK 430 owners who do not have the manual shift capabilities of our cars, have asked why would you install this an an automatic car like ours. Below are my reasons why:

First, for my car, which has a SpeedTunning ECU upgrade (93-94 octane setting, raised redline & speedlimiter removed), the car will up shift at 6,000 RPM in automatic mode. However, in manual mode the redline was raised to 6,400. Thus, on my car the manual mode shifting allows for a longer period of time in the gear and results in more HP and TQ in lower gears such as 1-4th.

Second, when at the road course track, it is usuful in manual mode to shift around 6,200 RPM because there is a time delay between hitting the shifter and the gear change, in order hit the maximum RPM shift point of 6,350 while avoiding the 6,400 redline cutoff. If you hit redline the injectors will shut-off for an instant to protect the engine, which is not optimal for racing. One thing you don't want on a long sweeping corner is the car to downshift in automatic mode and throw off the balance of the car. Thus, I would manually shift the car. To assist in this process, the DPS has a Four-Stage Shift-Lite setting for each gear as well as Progressive Shift Light Technology which warns of approaching shift and over rev. This is excellent for a road course track where you would be manually shifting mostly between 2nd (80 MPH at 6,400 RPM) and 3rd (122 MPH at 6,400 RPM) gear because you will know where your redline is without having to look (it is almost impossible to keep the correct line on corners while trying to find the RPM range).

Third, when at the drag strip, it is important when power braking to have the car at the optimal RPM of 1,500 to 2,000 (this may change depending on your tires, setup and weather conditions) so as not to generate excessive tire spin off the line. The DPS has a Launch Lite Feature for precise launch RPM with minimal driver distraction. You set it to the RPM range you (i.e 1,700) want and it will light up green when within -/+ 100 RPM of the target range. If exceeded it will flash red. If you have every tried to power brake the exact RPM while watching the light tree and the road at the same time, you will appreciate this feature. At the strip I would let the car automatically shift itself. Also, there is a Peak RPM Recall feature that will show the highest PRM reached during the run, which is useful for determining if you are shifting optimally.

Installation:
Install of the DPS at first appeared to be a problem but turned out to be pretty easy. After looking in the engine bay, I found the spot to run wires directly into the cabin. It turns out there is a round black rubber plug to the left and down from the drivers side fuse box. Just pull it out and that is it.

From the cabin, you must remove 4 or 5 screws that hold up the footwell top panel but that is easy. Once you pull the panel down you will see the hole into the engine bay where the rubber plug was removed. The hole is about 1" wide so there is plenty of room to run wires or hoses as needed.

There are four wires to hook-up. If anyone goes this route I can assist you with the process. Cost was around $170.00 shipped from Sumit Racing.

ItalianStallion

I completely understand and think its pretty cool.

benzmodz

Peak power and peak torque are never at redline or anywhere near it in most production Mercedes.

blackbenzz

Its a good idea but when shifting manually it takes sooo long from the time you shift until the car actually shifts. It drives me nutz!

ashutt

I notice quick shifts in my 55 so not sure if the 430 is different? Downshifts are vitually immediate, which is where a lot of track time is spent.

As to peak HP and TQ, with the ECU upgrade, I am expecting to shift the thresholds higher towards redline for max power. I am having the car dynoed on the 21st so that will tell where the power band is for sure. What I notice is that the car pulls very hard all the way to redline and in automatic mode shifts right at the old redline in each gear, so I assume this is by design for max speed and power.

blackbenzz

Thanks for the info, I also have a CLK55. If you have ever driven an SMG you would know how extremely slow the manual shifting in our cars is. Down shifting is not that bad but upshifting (which is why you installed the light in the first place) is extremely slow!

ashutt

Well for me, the shift light purpose is three fold. One, it is to utilize the launch lite feature when power braking for a launch off the line. Two, it is to indicate how long I can hold a gear before having to up shift at the track. Three, it is to indicate when to upshift at the optimal point. I will use the dyno to indicate where the max HP is in each gear and then set my shift point slightly below that mark accordingly.

To be honest, I understand that there are faster manualmatic shifting systems out there but for me (having driven race transmissions with race clutches), I don't see a significant difference in shifting times once I have put the car in aggressive mode from having entered the WOT point. Shifts come pretty quick up and down for me while in the power band- I really like the 2nd and 3rd gear. Not as fast as a manual but much safer on the transmission since a power shift or missed shift is not really as big an issue.

ashutt

Here are some pictures of the DSP installed in the car.