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.
- ECU can pull power when oil, coolant, IAT… is hot
- Maintain power under successive pulls
- Optimized calibrations for more active cooling ramp-up
View cooling kits →
Lower Temperature Thermostat
M157 and M278 engines 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.
I have reached out to some people who have had a lower temp tstat and said it was not beneficial. None the less, UPD offers a lower temperature tstat for the m157 which will likely fit the m278 as well for $399.
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.
Active Cooling Calibrations
Tuners are able to command pumps to operate sooner and ramp up faster. There may also be some coding options that can help in certain situations.
Interchillers
Interchillers cool air using the cooling power of the AC unit.
Cutting and Porting
Many of the vent areas on Mercedes are blocked off for efficency, however, these can be modified to take advantage of fake vents as real vents. Some people may also cut to increase cooling for specific performance upgrades such as fender cuts and porting to increase brake cooling.
Common questions about cooling upgrades
Is upgrading cooling necessary for street use?
Maybe not for mild tunes. But for sustained pulls, heavy boost, or hot ambient temps, it’s critical to prevent power rollback and protect turbos.
Will I need new calibration?
No but after installing any cooling parts, we typically suggest it because for IAT correction, and knock maps to unlock headroom safely.
Does this affect emissions / warranty?
Cooling upgrades are generally off-road/aftermarket but they should not alter emissions especially if stock thermostat settings are used. Please check local laws.
How complex is the install?
Moderate to advanced — requires front bumper removal, routing lines, bleeding, and possibly relocating sensors. Our kits include instructions.
Can I install parts piecemeal?
Yes — start with the biggest bottleneck (e.g. intercooler). But matching your tuning map ensures safe operation across all upgrades. However, when going from an M278 style solution to an M157 you may want to consider that M157 parts will be using AUX coolers that may not be used in M278 solutions. Therefore aux coolers, or workarounds for the provisions may be needed.
