As Mercedes shifted into forced aspiration engines cooling became an issue intake air temperature (IAT), heat soak, and more were only exacerbated by tuning.
Tuning Superchargers or Turbocharged engines often looks at increasing the amount of compressed air into an engine. Compressing air, as we know physics today, will always increase the temperature of the air. An intercooler then cools this air before entering the engine.
Splitting the IC and Engine Cooling Circuits
Certain Mercedes engines may also not have split cooling between the engine cooling circuit and intercooler circuit. As you may imagine one popular upgrade is to split the cooling between the intercooler and the engine. One tuner I will cite later claims this will drop IATs by 7 degrees.
Lower Temperature Thermostat
M157 and M278 engines also run hot, likely for emissions purposes. One way to remedy this slightly is to use a lower temperature thermostat (tstat). A cooler tstat will open before a higher temperature tstat and circulate fluids at a lower temperature.
The factory may want to run at 190 degrees to meet emissions or fuel economy standards which they are graded and taxed against. But the end user may want to run at 180 degrees to preserve for example the life of plastic engine connectors.
This is a mod I will likely go for soon, although it may not be as popular as other mods, I do believe running at lower temperature may decrease risk related to long term reliability of certain parts. This is mod is popular for Range Rovers and other cars running the BMW V8 of the time, please check out offroadrover.com for more information.
Bigger Radiators, Faster IC Pumps
Bigger (aux) radiators are often employed as well. VRP Speed offers a plug and play radiator for $399 for the m157/m278. While a lower temp tstat attempts to run an engine at a lower temperature, if the engine does become heat soaked it may need a bigger radiator, or IC pump to actually hold the temperatures.
VRP Speed offers the IC pump upgrade for a m278 to match the AMG for around $430.
Methanol Injection & Ice Cooling
Methanol injection really needs it's own page under performance too. In general the WWII German war efforts realized that injecting methanol into turbocharged plane engines enabled them to resist knocking and boost much more than they would otherwise be able. Other's have claimed it actually cleans out your engines. Either way it should be a must consider item for every m278 and m157 engine as it adds significant power (>100hp) and may protect the engine. VRP and Weistec both offer blow off valve (BOV)/methanol injector and kits with VRP being cheaper and Weistec perhaps finished better.