Water-cooled Exhaust Manifold = More Power, Less Emissions


integrated exhaust manifold

The future may be electric, but the venerable internal combustion engine still has a lot of tricks up its sleeve to help keep it relevant in the global marketplace. One of the most interesting new features to start showing up in recent years is this: the integrated exhaust manifold.

The basic idea behind this new exhaust manifold tech is pretty simple. You take the usual tubular exhaust manifold that’s bolted to the cylinder head of almost every internal combustion engine (ICE) ever created, and you take the head itself, and cast them out of a single piece. At the same time, a few clever water channels keep coolant flowing around the integrated exhaust manifold (IEM) to keep it cool.


Integrated Exhaust Manifold Cooling

That cooling liquid transfers heat from the exhaust to the rest of the engine. While a technology that increases engine heat may seem like the opposite of what you’d want in a performance engine, the warm coolant spreads across the block and gets the IEM-equipped engine up to temperature much more quickly than a conventional ICE. What that means for you is faster interior warmup times in winter, and better engine oil flow. That translates to better fuel economy, lower emissions, and vastly increased engine longevity.

If you’re smart, you’ve already dumbed that down in your head to “an integrated exhaust manifold makes cold starts pretty much go away”. If you think that, you’re right- but wait, there’s more!

To explain the integrated exhaust manifold and some of the gains tech like this can have in extended-range plug-in hybrids (vehicles that spend a lot of time in a “cold start” condition, in other words), the guys from Engineering Explained put together a great, 6-minute long video that explores the IEM found in the latest turbocharged Volkswagen engines. You can check that video out, below …


Engineering Explained | VW’s Water-cooled Exhaust

… then let us know what you think of the IEM’s potential to squeeze a few more percentage points’ worth of efficiency from the good-ol’ internal combustion engine in the comments section at the bottom of the page.

Source | Images: VW and Engineering Explained, via Jalopnik.

About the Author

I’ve been in the auto industry 1997, and write for a number of blogs in the IM network. You can also find me on Twitter, at my Volvo fansite, or chasing my kids around Oak Park, IL.

  • Leeper

    Interested to see how this pans out. I do question how this effects catalytic converter efficiency, also the extra heat of the manifold would seem to really require increased cooling workload. Bigger cooling loop requirement, stronger fans, and increased wear on pump and the coolant itself.

    • Cat efficiency is temperature dependent, which is why so many (all?) cars have a secondary air pump to recirculate hot exhaust gasses into the cat at cold startup. The cat needs heat. This brigs the heat to the cat.

      • Leeper

        Right, so wouldn’t decreasing exhaust temperature impact the function of the cat? Or is the temp drop not to the level of impact? I can’t wait till most cars just have batteries. The part reduction in the exhaust system alone is mind boggling.

        • Integrating the manifold into the head allows the manufacturer to put the cat like, right up the engine’s a**. Everything gets to operating temp more quickly than with a tubular header design … is how I understand it, anyway. LOL!!

        • kevin mccune

          Ford used to cast the intake manifold into the cylinder head on certain inline engines, I am waiting for the “Adiabatic ” engine , Smokey Yunick had some success with His efforts. You by now realize that the manufacturers and the oil industry are bedfellows , no ?

        • I think it makes the cat hotter because it’s right up against the head/block, even if the exhaust is cooler.

  • Ed

    Add water-cooled exhaust manifolds to the list! A good business lesson for everyone is to never underestimate the staying power of incumbents…nor their unwillingness to embrace big technology change!

    • kevin mccune

      I have dreamed of a camless engine since the 70’s it makes perfect sense to me .

  • Ed

    Really clever…and may well be very important with 48V mild-hybrid start-stop systems, since getting the catalytic converter back up to temperature quickly is important, too. This should allow a close coupling of the converter to the exhaust, without letting inlet temperatures get too high. Me thinks(?)

    • kevin mccune

      You have a point, a good way to help keep a start -stop engine close to operating temperature .

  • Joe Viocoe

    Awesome that they are still finding ways to inch up the mpg.
    But it still is diminishing returns… Getting 1 or 2 more mpg while there exist a huge leap to 138 mpge on the road.