Ok, got the disclaimer out of the way, and it seems like there is some interest - so here goes.
When you look into the engine compartment, you will see a box by the fuse box that has all kinds of metal tubes running from it. This is the ESP / BAS control module - a smart module that co-ordinates brakes, throttle and transmission interaction, over and above driver input. The objective of this system is to allow the car to accelerate smoothly regardless of the surface; ditto for braking - and keep the car going in the intended direction (yaw control). It is capable of making rapid adjusments to brake power and torque in the blink of an eye. By default it is on. when you push the ESP button on the dash, it does not turn off - it just grants you broader movemnt before intervention. Mercedes pioneered this system and most of the time, it operates unnoticed by most drivers.
All this is controlled by fuse 17. When this fuse comes out, the entire system shuts down. The anti lock brake function is gone; traction control is gone; as is yaw control and torque modulation.Loss of these functions seriously degrades the collision avoidance ability of the car. In effect, it returns it to the technology of 30 years ago. It makes no sense to disable this system under normal street driving.
For performance driving at the drag strip, the autocross, or road circuit, turning these features might make for faster shifts; higher cornering speeds and better threshold braking.
I was supposed to do a day of advanced lapping at Mont Tremblant last Wed., but the hurricane remnants put an end to that plan. I had hoped to run a set of laps with the fuse in and with it out. The lap times would be hard data and my observations, providing I kept the rubber side down, would of added to the experiment.
This morning, I decided to pull fuse 17 and head out onto my favourite back roads for a bit of spirited driving. When my 300C started up, the ESP/BAS light came on and stayed on. Driving out to my favourite twisty 2 lane black top roads, the shifting did indeed seem very smooth. In drive, it seemed to hold gears longer. The intermittant mid range throttle hesitation was definitely gone. Unfortunately, the roads were unusually busy with Sunday drivers enjoying the nice weather. Long ,fast runs were not feasible.
My first test was braking. I used a modest 50 mph with firm pedal pressure.
The car stopped quickly and smoothly with no lock up (I'm running 255/55/18 BFG KDW2's with 35 lbs pressure). Next braking test was at 60 mph with hard pedal pressure. the car stopped straight and quick - again no lock up.
Nex test was threshold braking (used by racers to get max braking without lock up just before a corner). I did this on a straight stretch. I took the car up to 75 mph and wanted it down to 40 mph. I applied full pressure and expected to have to let up at point of lock up. The car was down to 40 mph, again with no lock up.
On to acceleration tests. Car at dead stop. Tranny in drive. Trottle quickly to WOT. Mild wheelspin in 1st; sharp shift up to 2nd - chirp in second; small chirp in third. seemed fast. Next run. Dead stop. Tranny in 1st. WOT. Same reults as in drive.
Cornering. I have a run that is a series of straights with 3 alternating 90 degree curves. Posted speed is 50 mph with 25 mph in corners. I routinely run these corners at 60 mph with the fuse in. I only got one run in. I approached the corners at 75 mph, braked to 50 mph, put on WOT after apex. Car ran smoothly. Did the 2nd and 3rd at 60 mph - no drama - except in the 3rd corner. A red dodge minivan coming in the opposite direction was over the centerline. I had to correct and move over at the last second. again the suspension tolerated this transition with no fuss.
Back home. Turned car off then back on. No error codes - just the ESP /BAS warning light on the lower right corner of the instrument panel.
Analysis? Inconclusive. Roads were dry - the tires very sticky, and g forces not high enough to put the car out of control - at least with my driving style.
The transmission definitely felt stronger. I hope we can keep this thread going - get some other results from experienced drivers; love to see some quarter mile timeslips; and some tech notes from people who understand how all of these systems work.
I still plan to go to the track. In the meantime, I strongly recommend you keep that fuse in place for everyday driving.
:newangel:
