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[Names/Location have been omitted to protect the not-so-innocent and the valuable natural resource we’ve discovered]

Ten shiny SLKs had an exceptional opportunity last weekend on our run to Eastern Washington with warm sunny skies and an optimal road... Everyone got to push their own limit no matter what that may previously have been…

At the driver’s meeting before taking off for an afternoon of spirited driving and wine tasting, our tour leader explained we were about to partake a rare opportunity for some ideal driving conditions. We would encounter a remote plateau in E WA with a 25 mile stretch of newly paved road, straight, primarily flat, farm land, with very few side approach roads, on a warm and sunny Sunday morning. J! Everyone was to travel at their own comfort level speed to arrive at our first winery of the day – we couldn’t miss it as it was the only establishment on this road. We would regroup there when the last SLK arrived.

At the top of the plateau our leader got us up to 105mph. I was in second position enjoying the warm summer breeze top down, windows down. A motion in my side rear view mirror caused me to look and see an AMG55 approaching from behind at autobahn speeds, his hat removed and his hair flying straight out behind him! He flew on past the leader (who later reported he felt a ‘quake’ in the air as he passed) still picking up speed and was gone!

Why didn’t I think of that?” popped into my mind as I downshifted my 350 manual and took off after him. He was but a teal spot in the road ahead when I hit 145mph. Not being a need-for-speed person on straightaways, I thought this was an okay cruising speed, but not as exciting as the last time I was at 140: on the short straightaway of Pacific Raceways between turns 9 and 1. At least there wasn’t a 45° angle turn right ahead! But there was the AMG behind a vehicle as both were approaching a rolling hill.

Timing was such that I arrived on the scene just over the crest of the hill and flew by both vehicles, the AMG driver raising both his arms in the air as I did. He took off behind me and we sailed at 145 for some time. The winery approached so we pulled in. Alone. No other SLKs in sight. We waited.

The group finally arrived and the buzz started. “How fast were you going when you flew by?” they wanted to know. “155,” the AMG driver said, “it governed me”. When he hit 157 he felt a vibration when the ref limiter kicked in and decided 155 was his safe cruising speed.... I’ve been called many things in my life but ‘Danica’ was a new one…. One 300/auto owner beamed, “I’ve never had it above 100 before so I took it up to 101mph”. Everyone had their opportunity to push it in ideal conditions while remaining in their own comfort zone.

Next we took a more controlled drive along a scenic river, returned to the winery to do some sampling and then, joy of joys, got to do it all over again! As we left the winery, I was across the highway taking photos of the group as they exited the beautiful entrance gate and sign. Everyone took off, I snapped a pic of my beauty by the sign, hopped in my 350 and got to play catch up! Wow! Doesn’t get much more fun than that!

AMG was at the front of the pack and it wasn’t long before I caught sight of him. I poured it on. I was going to see what a 350 was governed at. We’re on the last flat straightaway of the plateau and I’m hugging his bumper doing 160. But I have to keep letting up. [Strange feeling I might add: putting the pedal to the metal, yet not going any faster, and when I did let up it continued at 160. I had to let up even more to get it to settle down.]

“So, why do I have to keep letting up with a 55 in front of me?” I wonder with the miles flying by us.

“Is he vibrating at 157 again?” I’m as smooth at 160 as I was at 145 as I was at 80.

Am I governed a few miles faster because I have a manual?” 160 is 6000rpm in 6th gear and I redline at 6400. But, he has 7 gears…

“Now’s my opportunity to find out!” I pull out and pass a 2006 Mercedes-Benz SLK AMG55 doing 160 – pedal to the metal – on a warm sunny Sunday morning in June!

Epilogue
I hopped out at the meet point and eagerly asked AMG driver, “were you letting up when I went by? Were you vibrating again? What rpms were you at? I was smooth at 160…” He told me he had let up, he didn’t feel the need to cruise that fast that long. He didn’t look at his rpms.

So. We’re both governed at 160mph.

I knew I couldn’t do much more anyway – when you hit the redline in a manual it shuts down, releases the clutch. A guy in the group says when he’s in his auto, shifting manually and hits the redline the car takes over and shifts into the next highest gear. Hence, manual drivers are continually looking at rmps while racing and auto guys don’t need to…

Noteworthy
The first time I hit 120mph in my little SLK230k manual in the middle of Montana I was amazed at how smooth the ride was. It felt no different than 70 on the freeway. Only motion was pavement imperfections. When I hit 160 last weekend I recall looking at the speedometer to convince myself I was actually traveling that fast. It sat down, hugged the road, was tight and responsive. These automobiles are perfection on the road, on the right road! The only negative I can see would be the false sense of confidence it may give someone with little or no training…

Reflection
I never got the opportunity to start side by side with the AMG. In previous runs following another SLK AMG55 from a stop I was unable to drive flat out in the lower gears, 1-4. Assuming she was flooring it (and that’s a pretty safe assumption with her) I always had to let up and wait for her car to shift. I suspect the autos shift up at lower rpms than I take my manual which is right up to redline. She did, of course, pull away in the higher gears at higher rpms because of her brute hp.

I’m not a need-for-speed-girl. I get no exhilaration going fast on straight flat roads. I get my adrenaline pumping when going fast around corners. Skill and car performance figure into it. You know those orange diamond signs on roads and highways? The ones with a bending arrow and a suggested speed? Do you realize your SLK can safely take any of those corners at twice the posted speed, given correct weather/pavement conditions...? So, anyway, after this run I will chuck this adventure up to “Been There Done That”.

Were this an actual encounter, these might be the two SLKs who shared this experience. ;)
 

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Discussion Starter #3
two of us out of spec?
we're not trying to set any land speed records here.
just fun times~
~d
 

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aka John
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At 155, I'd suspect that your speedo's are all going to be wandering a little. Both the '55 and the '350 are electronically limited.

Last time I tracked my 350, I was clocked at 140 when my speedo said 142 - on stock 17 inch tires and rims. I knida blew it off, as I was not really paying attention to my speedo to be honest!

It's hit or miss on the electronic limit - some of the SLK's are absolutely, 100% hard limited, some are not. The limit is a setting in the ECU, and can be changed / removed / etc with the right tools. I've looked at 5 different SLK's (one manual '350, three 7g '350's, and my '55) and the limit was there on all but one of the auto '350's.)

I'm second guessing myself, but I *think* it's actually set in kph at 250, which is a hair over 155 - I'm stuck in the jungle with no way to check at the moment!

I also don't know for sure technically how the limit works - if it's simply rev limiting by cutting fuel flow, there's got to be some slop in the system as well - so maybe a tail wind helps! :) Maybe Dan can shed some light on this for us?

If you are coming to Vegas, I suspect that the tool to remove said limit will be available - just need to sort out a place to verify! :)
 

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After the modifications, I did 290kmh on the highway but there was a slight incline in the road. I am sure if I didnt run out of road I would of hit 300kmh or so because at 290kmh my RPM was in the 5,000 range.
 

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I know my car is unlimited from the factory. Should reach 170 mph given the right roads.
 

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Thanks for taking the time to write that up, a great read! I wonder what a 55 could do with no limit on it? I'm waiting for the 55 to come out with a manual!
 
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I know that basically from the start of 171 production the 155 gentleman's agreement was on its last legs so it makes sense that new 171's are unlimited but i can't seem to figure out the logic they used on the earlier models since some seem to be limited at a fraction above 155, others are limited higher and others have nothing, nobody seems to be able to give me an answer on it either.

But anyways i digress, at the limit the ECU will look at the signals from the pedal and check if the requested throttle will take the car over the limit, if it will then the engine is held at the maximum speed allowed based on the sensed road speed, going with gravity or wind assistance and throttle edges towards closed but working against them and it opens up more to keep the road speed at the limit, it does not brake like cruise control.

Its quite clever really because its not just killing the throttle then throwing it full open again.
 

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I was told that the top speed of an SLK350 manual can reach is 168 if all things are in it's favor. The gearing would take the engine beyond redline to go any faster.
 

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Maybe we can do a tech day with dltslk to swap out his automatic for a manual!

: )
 

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This was discussed awhile back but a quick summary:

Top speed for most SLK 55s is limited at 155 mph. Depending on options, market, and year, the car can come de-limited from the factory. 175 mph is possible on the road with stock body. Gearing for the SLK 55 allows up to 198 MPH.
 

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Maybe we can do a tech day with dltslk to swap out his automatic for a manual!

: )
Then you might run into the problem when I bought my '88 Fiero GT, 5-speed, with the idea that I would drop in a twin-turbo Cadillac Northstar V8... Sometimes the computers are so matching the engines to the trannys that to remove the auto would make the engine go into LIMP HOME mode.

A 60 HP "emergency mode" SLK55 might get a bit depressing. Stunning fuel economy with the stick, however!
 

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How can I tell if the limiter has been turned off by the factory?
 

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This was discussed awhile back but a quick summary:

Top speed for most SLK 55s is limited at 155 mph. Depending on options, market, and year, the car can come de-limited from the factory. 175 mph is possible on the road with stock body. Gearing for the SLK 55 allows up to 198 MPH.
I thought the "Nurburgring" or "LeMans" package (030?) raised the limiter to 175 MPH. Also, I read that 191 MPH was the top speed reached by a stock bodied car with the limiter taken off, on a test track.

I can only imagine feeling the rear go "a little bit light" at those speeds!
 

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Maybe we can do a tech day with dltslk to swap out his automatic for a manual!

: )
I guess we can use the manual tranny out of your 911!:splif:
 

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We wouldn't want to use that garbage in the 55! Brabus is claiming 191 on their SLK package.
 

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How can I tell if the limiter has been turned off by the factory?

Well, there's this track down the road.........


Seriously, not sure - I know that with DAS in "engineering" mode I can see the limit. I *think* I could read it with "normal" DAS, but I'm not 100% sure - and I'm positive I could not change it.
 

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I'm all for getting rid of the limiter, but just remember to make sure your tires are rated for those 150+ speeds! A blowout would be disastrous.
 
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