Welwynnick

V12TT engines put a lot of heat into their engine compartments, and owners know all about their water cooled turbo-chargers, air-cooled suspension oil, double radiators, water cooled alternator andcountless heat shields; all the measures necessary to control that heat.

But here’s one that I bet you didn’t know about. I've been doing some big jobs on my car recently, and had the opportunity to take some pictures of things you don't usually see. Like - have you ever wondered what those NACA scoops on the engine under-tray are really for? Meaning: what happened before they were incorporated into Mercedes’final design? What was it that got too hot, and failed too quickly during prototype testing? I always assumed that they were to cool the wheel arches, alongside the turbos, but they're not. The answer might not entirely surprise you:










The V12TT has air-cooled motor mounts.

How cool is that? ;-)

Nick

Shifter

Almost every Benz is like that.

Welwynnick

Look at the things that tend to go wrong with V12TT's like mine:

• Coil packs
• ABC hoses
• Engine mounts
• etc

And look at the things that have heat shields to (try) to protect them from the heat of the turbos:

• Coil packs
• ABC hoses
• Engine mounts
• etc

The engine compartment is a hostile environment, and adding two turbo-chargers seems to have made things a bit too challenging from a thermal point of view - at least for anything that's made of rubber or plastic. The recent trend to fit the turbos in the MIDDLE of the V seems to make this only more difficult.

Well, I obviously have a suspicion that heat is responsible for a lot of our reliability problems. One of the things I'm doing now is to lag all the ABC hoses in the engine compartment with aluminized fibreglass sleeve insulation. I might try that with the charge cooler pipes as well.

Looking closer at the coil packs, it seems they're protected with strange-shaped metal shields, that only cover the centre portion. I'm rebuilding my turbos at the moment, and it's quite apparent why this is, once you remove enough stuff from around the engine. Mercedes have obviously gone to some trouble to protect everything from the heat of the turbos, and they fitted two metal heat shields down each side of the engine, one front and one rear. Since the charge air pipes to the intercoolers have to get past these shields, there are gaps in the shield's coverage. These gaps have to allow the oil feed and coolant return lines to pass as well.

This picture shows two shields, 100 & 110, that clip into the exhaust manifold gasket, and provide some shielding to the top half of the engine. They're cut-away to allow the compressor pipes to get past, and that's where I think the hot air gets through, around cylinder 3 & 4.



This shield gap appears to allow radiated and convected heat from the turbos to hit the respective coil packs directly. The localized metal shield on the coil pack is directly above this gap, so there was obviously a problem to begin with, and ultimately the problem never fully went away.

Unfortunately, metal shields can do their job well, but only if they have a good air gap on each side, so they can both block IR radiation, and segregate the hot and cold air. I don't think Mercedes have quite finished the job.

Nick

WHTEVO

Thank alot for sharing. Let us know how it goes and what things you add or change to help combat the heat issue all these cars have. Good luck.