slk55er

NOTE: I ran with my '14 CLS63 AMG -S rather than an E-series, but I believe this may be of interest to this forum.

SUMMARY: It was a challenge to coordinate the Race Start (RS) sequence with the sequence of the “Christmas Tree” start lights. In a pressure situation (as in an elimination run), without a LOT of prior experience with RS, I’m not convinced the marginal benefits of the RS launch is worth the risk of a failed run. And any benefits of the RS mode may be offset by slower reaction time.

RESULTS: At an elevation of 3000 ft. and air temps of 95 - 100 degrees and a completely stock ’14 CLS63 AMG S-package, my best quarter mile elapsed time was 11.8 seconds at 118 mph — very impressive for a stock 4-passenger vehicle with air conditioning, AWD and which even parallel parks itself! At sea level and cooler air temperatures, I’d expect mid-11 times and 125mph could be achieved.

DETAILS: On the weekend of 6/6/14, our local Lions Club and Blackrock Motorsports sponsored drag races on the runways of the “old airport” in St. George, UT. Saturday included elimination runs and trophies, but I went out on Sunday which was a “Test and Tune” day. We had a mix of street rods, diesel pickup trucks, motorcycles, rice burners, NOX rides and sports cars. I was able to make 11 or 12 runs between 10am and 3pm. I blew at least 2 runs myself and the CLS63 shut down on 2 other runs. But I finally figured out how to coordinate the 1-2-3-4 RS sequence with the Christmas Tree (details below.)

OK, I’ve had a lot of road racing experience — probably 8,000 laps or more as a student, racer and instructor over the past 28 years on most of the major road courses in the US (Watkins Glen, Rd. Atlanta, Rd. America, Tulsa, Laguna Seca, Infineon, Miller Motorsport park, Las Vegas, etc.) plus a lot of time on some local tracks. But until last weekend, I had never run on a drag strip with a Christmas Tree. So part of the challenge I faced was to become comfortable with the drag strip staging and start sequence.

Throughout the day, I was mostly concentrating on the RS function and I never really had time to work on anticipating the green start light to reduce my reaction time. I mostly launched when I saw the green, rather than anticipating it. Consequently my reaction time was at least a half second or more longer than that of some of the more experienced drag racers. But in most cases the incredible capabilities of the CLS made up for my inexperience. (I surely surprised several Corvettes.)

I spent the first 20 minutes or so just observing the staging and start of other vehicles. On one run the brown street rod in the photo of our tech inspection took a sharp left turn 50 yards or so down the track, narrowly avoiding the vehicle in the other lane. This gave me some second thoughts about the safety of the event, but thankfully there were no other incidents during the day.

Previously I had practiced quickly setting up and initiating a RS so while observing the Christmas Tree, I pretended to launch the CLS, quickly counting 1-2-3-4 as follows:

1 — Right hand on the transmission mode selector dial, Left foot hard on the brake pedal
2 — Rotate the transmission mode selector clockwise to “RS”
3 — Click the right paddle to confirm a RS
4 — Right foot on the throttle pedal to the floor, taking the engine to 4000 rpm.

Then wait for the green light to release the brake.

Here is how I coordinated all of this with the staging sequence and Christmas Tree:

Prior to entering the staging area, make sure the engine is warmed with the oil temp displayed in white letters rather than blue (about 200 degrees.) Select the AMG transmission/suspension setting or simply select S+. Depress the button to put the suspension into “Sport Handling Mode.”

Now I’m ready to creep into the start box — watch for the 1st white light, then the second white light, indicating that I am properly staged and ready for the countdown yellow lights. As soon as the 2nd white light turns on, quickly execute Steps 1, 2 and 3 (brake hard, rotate dial, click paddle.) Hold off on Step 4 ‘cause the vehicle in the other lane may not yet be staged, but as soon as the yellow countdown lights start, put the throttle to the floor (Step 4.) Anticipate the green launch light if I can without a false start or wait for the green light to lift my left foot to release the brake. Hold on, keep the throttle on the floor and enjoy the awesome ride.

It took me several runs to realize that I needed to hold off on Step 4 until the yellow countdown started. On two runs, the CLS shut down after launch into a limp home mode, possibly because I had held the 4000 rpm too long waiting for the countdown and green lights. After the shutdowns occurred, I tried a simple start without using the RS settings — bring the engine rpm up a bit with left foot on the brake and wait for the green to tromp the accelerator as one would do if there were no RS feature. (When not in RS mode but the brake applied, engine rpm appears to be limited to 1000 rpm.)

There was very little difference with and without RS. Here are the results of 3 runs in the afternoon (when it was 99 - 100 degrees), Number 7 and 9 are with RS, Number 8 is without:

Run 7 — Time to 60 ft = 1.84 s, Time to 1/4 mile = 11.96 s, Speed = 115.7 mph
Run 8 — Time to 60 ft = 2.18 s, Time to 1/4 mile = 12.38 s, Speed = 115.4 mph
Run 9 — Time to 60 ft = 2.15 s, Time to 1/4 mile = 12.23 s, Speed = 117.3 mph

These times are longer without RS; however there is another aspect to this. I’m not sure how “reaction time” was measured at this event. I know that professional racers get times of 1 or 2 tenths of a second, but the shortest reaction time I observed among all competitors at this event was 0.72 seconds by an experienced drag racer. My measured reaction times were typically between 1.3 and 2.0 seconds, but even if I was waiting for the green light and worrying about the RS Sequence, I know it was not anywhere near 2 seconds until I released the brake in RS mode.

But interestingly, the SHORTEST reaction time I had was in Run 8 — WITHOUT RS — by at least 0.3 seconds! So it is possible that there is some delay in RS mode which undermines the benefits of the RS launch. In a head-to-head elimination drag race, an additional 0.3 second reaction time with RS could lead to elimination, even if the ET is quicker than the competitor’s ET. Anyone seriously competing should spend a lot of time experimenting with and without RS, particularly considering the extra coordination of the RS sequence with the Christmas Tree as I’ve described.

I really enjoyed the day experimenting with this wonderful vehicle. As you would expect, it received many favorable compliments from drivers and spectators who were surprised and impressed by this beautiful beast. It is truly a privilege to own and drive this CLS. Hope this was helpful.

LJMartin

I've only used RC once. It was on warm black top. Upon launch it went about 5 feet and bogged down really bad and then took of like a bandit leaving long black marks till I let off in 3rd or 4th gear. Was the black top the reason for the bog or is there another explanation.

Chocofishez

Thanks for such a detailed review! Race start certainly seems faster to me, but I agree that the procedure takes too much time. I'd prefer a push button that skips the dial turn and paddle confirmation.

Also I have noticed that you must have an oil temp above 100 C in order for race start to engage. Not always possible on the street!

How high were you revving it on your non RS runs?

Patric

Nice write up Gordon. My car has a momentary bog on brake release in R.S. before launching hard also. I think it has to do with the small clutch pack instead of a high stall torque converter a lot of high performance drag cars run. I assume you were driving around the water box?

slk55er

I don't believe the black top surface would cause any bog down as you describe. An immediate perfect launch is a lot to ask of our street vehicles. The bog down might be cured with a slight adjustment or reprogramming. I did not experience any noticeable wheel spin. I suppose that in the required Sport Handling Mode this is possible 'cause I believe there is limited or no "traction control." Perhaps the limiting factor in your runs was the traction provided by the tire and the bog down was more a result of limited traction rather than the RS programming. Hard to know.

Frankly, I was not watching the tachometer during runs, just letting the vehicle shift as programmed. I assume it was reaching redline prior to each shift.

Yes, I drove around the water puddle that was put down for some vehicles with slicks for their burnouts. (I was running with the original Pirelli P Zero tires in stock sizes.) Many of the participants used the water to clean and warm their tires. The most tire smoke (and crowd pleaser) was generated by an stock underpowered Ford pickup which was running the quarter mile in 19 seconds at 79mph! But the guy surely know how to burn the rear tires.

slk55er

After some discussion with event organizers, we concluded that "Reaction Time" is measured from the time the Green Light turns on until the front wheels completely leave the start/staging box. That is, until the front wheels no longer interrupt the beam associated with the frontmost edge of the start box -- the beam that indicates the vehicle is staged and ready for the yellow countdown (but not too far forward, still in the box.)

Generally, the yellow lights are sequenced a half second apart. One can expect about a half second or a little less delay in human reaction time and another half second or so for the vehicle to respond. So in order to "anticipate" the Green, releasing the brake in RS mode or mashing the throttle in S+ between the next-to-last and last yellow light would be an appropriate starting point. As I indicted in my initial post, I never go to the point of anticipating the Green.