your figures on the new facelifted E-class are correct, 184 hp.mine were 5 hp short.
From what I have read and asked around (and had a talk with my mechanic that specialises in turbocharged engines ) the standard ecu will allow for more boost as per carlsson without a secondary ecu or reprogramming.
Problem is , you are bound to have pre-kcocking and other harmful effects under a constant strenuous load or in hot temperatures...
That's where the k-box used by kleeman seems attractive. Ideally, the factory ecu should be re-programmed but only mkb seems able to do that and these fellows are way overpriced and do unecessary changes to the engine.
I will explain further :..
Apart from upping the boost through a new pulley ,there are two major constraints with the m271 engine.
The first and critical one is that horrendous charge cooler. Eaton kompressor engines are generally more susceptible to high temperatures than turbocharged engines when increasing the boost, and the stock plasticky chargecooler makes it no favours in the case of the slk.
Having run various cosworth cars in various stages of tune over the years ( a quite different car than the slk but fun) I can vouch for pro alloy
for making some of the best intercoolers around. They have some excellent cores and custom make whatever you want depending on the boost the car will be running etc.
In our case the chargecooler will need to be sent to them in order for them to measure and produce an intercooler that will fit in place as the original one and perhaps be a little bigger if space allows it.
The kleeman conversion I have in mind , SLK 20 K2 Performance kit + Header 235 HP / 325 Nm (you can see it at kleeman.dk ->webshop runs 0,2 more boost than stock, that is 0.8 bar.
Anyway the first critical step is taking care of the extra cooling needed, You will notice that various tuners quote a difference of +10 HP with or without a new intercooler (i.e from 195 to 205). Due to a denser mix ,etc etc...
The second item that needs attention is the headers of the m271, that are pathetic and allow for very restricted airflow.
In my experience it would be much better to go the whole step towards getting the performance kit plus headers ,rather than one step at a time.
Kleeman quoted me 235 hp with 325 NM torque (no idea at what revs) which sounds probable. There is of course the downpipe with the precatalyst to take care of ,and the exhaust system ,but that is another story.
I am trying to find whether the m271 engine in the slk has a steel head gasket or one of those horrid paper ones they used to have,that will perplex matters if more boost is applied and longevity is necessary.
But taking into account that the 1.8k engine could do 193 hp from the factory, with a mediocre chargecooler and a very restrictive header , 220-230 sound very probable and without much trouble if the necessary peripheral components are uprated.
The M271 engine runs out of puff after 5000 revs, so the conversion will give the necessary top end. You can certainly do the pulley and secondary ecu conversion first, but in my book the stock chargecooler has to go, even if you were running a stock engine...Belgium may not be as hot as Greece, but more efficient cooling makes for a better and more reliable engine every time. Chargecoolers are a sorry solution,but cheap compared to a decent intercooler.
The M111 engine in the previous slk r170 needed an uprated water pump,this does not seem to be the case in the m271 used in the slk r171. (Although it is probably a plasticky one like all german manufacturers seem to use nowadays)
Since this is getting a bit technical and some people may be averse to tuning, if you want to compare conversions and problems of tuning the engine in our slk, contact me via PM (unless we have support of our forum members
). I have been very aggressive the past three weeks trying to track down all available options and possible problems.