Some of you may have seen my tales of turning my ‘07 Mercedes C230 Sport 6-speed into a daily driver that can thrash an autocross and can eventually head to the track. A lot has changed since I last posted about it, so here’s a quick catch-up. I’d like to do a full write-up, so expect that soon.
So, the suspension is done. Aside from a sway bar link that eventually came loose, these somewhat clueless hands did the job. The result you see above is induced via adjustable Koni Yellows, H&R lowering springs, an adjustable H&R rear bar and a CLK63 Black Series front sway bar. Just as I was hoping, the outcome is a car I daily to work in comfort and feel equally as comfortable in blasting down a backroad at good speed. Eager to get it out to an autocross to see the true fruits of my labor.
Aside from basic maintenance in the form of plugs and whatnot, the biggest milestone recently came in the form of the intake manifold replacement. Boy did that snowball, but I’ll give the quick-and-dirty of the project below.
The M272 has a pretty clever intake manifold, with adjustable swirl flaps (electronically-controlled) that help to provide low-end grunt and open to breathe up top. The catch is, they fail all of the time. In a best case scenario, the tiny actuating arm (plastic) snaps, inducing a check engine light and a loss of power somewhere in the rev range as the flaps are unable to actuate as intended. This was the case with my example, as it is with many of these engines.
The arm can be replaced with a metal unit for a certain repair, but the worst-case scenario is that the bushings on these flaps can wear over time. If you’re extremely unlucky, the plastic swirl flaps can fall into your engine. We don’t want that.
As I knew the route I was going with this car, I saw the opportunity to both upgrade and increase reliability, so I did it. This came in the form of fitting the composite intake manifold from the Mercedes SLK350 Sport.
The SLK Sport had the 3.5 M272 (also found in W204 C-classes) along with this intake manifold, some clever cams, and basically a handful of other goodies to make them a true performance roadster. As an added benefit, these intake manifolds are relatively a direct bolt-on for ALL M272s (yes, even my tiny 2.5L). And better yet, this is a traditional intake manifold; no failure-prone swirl flaps. So while it does decrease low-end torque, it massively helps top-end power. And it never breaks.
So I jumped into it with way too little knowledge. Everything goes together easily, but I hadn’t properly researched exactly what parts surrounding the manifold needed to be upgraded to make everything fit (spoiler; it needs an 82MM throttle body from a CLK550, an intake air deflector from the same car, and a tune if you want to do it safely). This took me a couple of weeks start to finish as I was waiting on parts, the unfortunate consequence of not doing enough research on parts needed during a pandemic.
All said and done, the flap sensors for the stock manifold were of course left flapping around in the engine bay. I elected to go with an ECU tune via OETuning to delete the sensors and to tune for the additional air being delivered.
I added K&N drop-ins and the car runs great. Behaves way more like a traditional NA twin cam, blasting through the top of the rev range. I love it, and all said and done, it’s an easy mod to increase power and reliability for only a little bit more than buying another stock manifold like everybody else typically does.
There is very little information on what is needed to do this on ANY of the M272 engines on the internet, let alone the 2.5L that I have in my W203 as the few people that have done this typically do so on the bigger engines in the W204. This irritated me at various points as I struggled through, so I put together two YouTube videos for anyone else that tries to replicate this in the future; the first explaining how to get the manifold in, and the second walking through exactly what parts are necessary. If you have an M272 and think this may be for you, or if you just want to listen to me ramble about this lovely V6, the videos will be linked below. All said and done, this car is one of very few, if not the only one, running this manifold on the 2.5 in the country.
In anticipation of my upgraded muffler arriving soon, I hacked off the stock muffler this weekend just out of curiosity. Although loud, this engine sounds phenomenal. I’ll see if I can get a video together of that as well, as despite being a bit embarrassed of taking such a hack route in what is otherwise a decently-clean build, this car sounds excellent.