• BenzBoost member reviews his Renntech 2012 CLS550 4Matic (all whee drive) ECU tune software + before/after dynograph

      I just want to relate my experiences with a recent RENNtech ECU tune for my 2012 CLS550 4Matic. I've been researching and considering a tune for a year now, but medical concerns have been a much higher priority. My goals may be different than others... I don't race at all, but simply wanted a reliable and efficient street tune. I wasn't worried if I didn't have the most horsepower... I crave usable street torque. In the end, there were many qualified tuners to choose from, but I selected RENNtech based their years of experience, excellence in engineering, and close relationship with Mercedes Benz.

      Since I have some decent mechanical skills, I opted to remove the ECU myself. This operation is extremely simple to accomplish... provided you can find the battery first (they hide it well). Once the ECU was removed, I sent it to Florida on a Monday afternoon and it was back on my doorstep in Massachusetts by 9:00am on Wednesday. Reinstallation was a snap and the Benz easily roared back to life. Altogether, there was not much down time on the vehicle.

      The initial shakedown cruise was next. In local city driving, there were no adverse issues... it was comfortable and docile in traffic. But when I hit the expressway on-ramp... oh yeah, I began to smile. And squeezing the throttle to merge and change lanes was impressive... it definitely was a new beast. For some strange reason, I remained somewhat skeptical, yet highly intrigued... I wondered just how much the dyno would reveal?

      Fortunately, I had the foresight to do a base dyno nearly a year ago. Recently, I returned to 'Enhanced Street Performance' (ESP) for another Dyno Day. Although the main focus of the day was devoted to Corvettes, the group of guys welcomed me and ESP was first class with their professional service. The dyno used here is a Mustang 1100-SE AWD chassis dynamometer. Though I have no proof, I'm told that measurements on the Mustang Dyno are traditionally about 10% less than a Dynojet. Furthermore, the guys also indicated that this particular dyno was even lower than other Mustang dynos they have tested on. All in all, since this was the same dyno for my base numbers, the overall gains should be accurate.

      Setting up my CLS550 4Matic, the traction control was turned off and the pulls would be done in 4th gear... same as last time. The first dyno run was somewhat uneventful... the tranny was difficult to hold gear and kicked down. With some slight initial feathering, the second pull sounded great and everyone was eager to see the results. I was ecstatic when the huge projection screen spit out the uncorrected readings... 426 horsepower and a whopping 515 lb/ft of torque!

      I could be mistaken, but I don't believe there have been any dyno postings from a CLS550 4Matic in the past. Since this is an AWD vehicle, I estimate drivetrain loss at between 15-20% (though MB is very efficient). Therefore, I feel crankshaft figures are a good 500HP and over 600 lb/ft of torque... utterly amazing on a conservative Mustang dyno.

      Overall, I'm extremely pleased with RENNtech and highly recommend dealing with technical advice from Lenny or sales aspects with Tomas. I'm not sure if medical science will note this, but my RENNtech tune also helps to cure my disability... every time I slam down the throttle.



      RENNtech ECU Tune:

      Before & After Results:

      Dyno Day Video (mostly Corvettes):

      This article was originally published in forum thread: RENNtech ECU Tune: The Cure For What Ails You started by 427 View original post