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GM develops integrated exhaust manifold cylinder head for 3.6L V6 direct injection engine; improvement in performance, fuel economy, emissions and noise

The reduced complexity of the design of the new integrated exhaust manifold cylinder head (bottom) compared to the old (top). Click to enlarge.

GM has combined the exhaust manifold with the cylinder head into a single aluminum casting in the 2012 Camaro 3.6L direction injection V6, achieving both better fuel economy while reducing emissions.

Each integrated exhaust manifold cylinder head (a V6 has two) replaces a cast iron exhaust manifold, six bolts, a gasket and a heat shield and three bolts. By eliminating this joint, the potential for a gasket failure is eliminated. The change reduces engine weight by 13 lbs. or 6 kg per engine. Reducing mass helps improve fuel economy; the 2012 Camaro 2LS model is EPA-estimated at 30 mpg US (7.8 L/100km) highway.

Extensive simulation and bench testing was performed to perfect cylinder-head airflow. Intake airflow is improved 7% with the use of larger intake valves (38.3 mm v. 36.9 mm), which are primarily responsible for an increase of 11 hp. Exhaust flow is 10% better than the previous V6.

With the catalytic converter closer to the engine exhaust point, the emissions reduction process begins sooner, resulting in lower emissions. The new cylinder heads decrease the overall width of the engine by 4.6 inches (117 mm) for significantly more packaging space in the engine bay, making underhood work easier. Due to less surface area, the new design contributes to a 1 decibel reduction in engine noise at idle.

Reducing engine mass of this magnitude doesn’t happen often. Engineering usually looks for reduction in terms of grams not pounds. It’s just like removing a set of golf clubs from your car when you don’t need them—ultimately it saves fuel. When combined with other mass reductions, the customer will see better fuel economy over time with better performance.

The new, patented design benefits the customer in all the key areas without any tradeoffs. Emissions, performance, fuel economy, and noise all improve with the integrated exhaust manifold.

—Ameer Haider, GM assistant chief engineer for V6 engines

Tom Sutter, Chief Engineer for GM V6 engines, describes the cylinder head design change and the integrated exhaust manifold.


Neil Blanchard

It would be very interesting to see whether they could reduce the fuel consumption, possibly by reducing the displacement of the engine; rather than increasing the performance. A smaller engine would weigh less even, and so would also help efficiency even more.



A high performance 4-cyls could do the job with less weight and fuel.


Sometimes you need the v6. Low end power for one..



Agreed, but I think this just exemplifies what is possible with all the new design tools that are available to engineers and fabricators. Just five years ago, such a complex project would've been a no-go.

Ceramic coating that exhaust manifold would pay HUGE dividends in reducing the air intake temperatures, engine coolant load, and the specified size of the coolant system.

Tim Duncan

This is interesting design architecture, but alas there are many good reasons for historic designs. I would like to know how the overall heat rejection to the coolant system is effected. To keep the Al in contact with the exhaust alive over the long run, those areas will need more cooling than if they were cast iron. I would not be supprised if this more than eats the fuel savings from 13lbs weight reduction? Does anyone have AL exhaust experiences? I like the idea of ceramic coatings, the AL casting will do its own Alumina coating but that is not a great thermal barrier. What specifically did you have in mind? Long term durability and cost are ommitted from the published evaluation criteria. Directionaly this will be cheaper to build the first time, more prone to failure and definitely more expensive to fix when there are failures. It is not clear there is any linkage at all between the new architecture and the improved HP. But the HP and Wt savings combo will be great for the Camero!! Nice packaging improvement, that is quite amazing on a mature engine platforom. So on balance very interesting, but as an engine designer I do not agree this is a product of new tools. Mostly just engineers responding to cost and performance cues in their market.


Good point on the aluminum. AL is usually a horrible material for exhaust systems though I don't recall exactly why. I remember a member over on e90post experimenting with an aluminum cat-back exhaust a few years ago and having to pull the exhaust off after about two weeks.


Reduced complexity V6s is beyond oxymoronic. $4 fuel will require more 4 and 5 cylinders.


It is probably the sum of a couple of advantages that count. Emissions (except NOx) at high load are reduced when fuel enrichment is reduced. This is ”all the fashion” for the moment in spark ignition engine development. The new 1.8 liter TFSI engine of the VW group also has integrated manifolds, one of the first examples with turbocharger.

Insulation is interesting. Ceramic coatings are difficult on AL. A cast-in port liner is possible. Porsche had such an engine in production a long time ago (turbo 4-cyl). However, this was a 2-valve engine. With siamese exhaust ports, as on a 4-valve engine, this is probably beyond what we could do to day. A complete integrated manifold with coating or cast-in lining appears impossible.

An interesting feature would be to use a skewed valve layout. If you mirror left and right hand layout, you could have shorter ports and better exhaust flow for the cylinders at the end of the cylinder head. Exhaust port length is also reduced and thus, also heat loss. Some diesel engines already use a skewed valve layout. However, for practical reasons, you must reduce the valve angle and this would be a disadvantage for gasoline engines. Most diesel engines already have zero valve angle, so in this application, it there would be no compromise. However, the heat loss is a considerably drawback for diesel engines.

For turbocharged V engines, the turbocharger could be more easily mounted in the V bay of the engine with integrated exhaust manifold. Look, for example, at the effort BMW had to make to accomplish mounting turbochargers between the banks their new V8 gasoline engine.


Not a new design. Honda has been doing this on V6 engines for years with great results.

However, tuned intake and exhausts are part of a modern high performance engine. Eliminating that tuning by using a log style combined exhaust manifold is going in the wrong direction. I feel it's better to properly tune and downsize.

We could just as easily make an integral intake manifold, with just a hose clamp needed. And, then we would be right back to the designs of the 1930's. With Siamesed ports and one simple inlet and outlet.


"Just five years ago, such a complex project would've been a no-go."

AFAIK, Honda has been using this in their V6 since 2003. P


It might have been a no go for GM.


The idea of aluminum exhaust manifolds bugs me, but only because I have the mental picture of molten engine parts on the one hand, and the lost possibility of the engine cooling jacket being used to make medium-pressure steam for a bottoming cycle engine on the other.

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