By on May 16, 2011

One of the most consistent and valid criticisms of GM’s product development, even in the post-Lutz era, is the class-leading weight that so many new GM products carry around with them. To a number of industry observers, the lingering weight problem that so many of GM’s cars struggle with is a sign of corners cut in the design process. GM’s cars may look, feel and drive better than they did five, let alone ten, years ago, but clearly the battle for truly “world class” products isn’t over.

And now we’re getting some of the first indications that GM is taking the weight issue seriously, as GreenCarCongress reports that GM’s engineers have pulled 13 lbs out of its 3.6 liter direct-injected V6 simply by redesigning its head. Given that the 3.6 is already one of GM’s better engines, and is used in a huge number of its vehicles, that’s a solid first step as The General takes on the battle of the bulge.

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52 Comments on “Head Games: GM Drops 13 Lbs From Its 3.6 V6...”


  • avatar
    Bridge2farr

    Yes, they replaced a cast iron manifold, bolts, gasket and heat shield with a single aluminum casting. Saves 13 lbs., eliminates potential for gasket failure and improves mpg. In the case of Camaro for example, mpg highway now 30 mpg.

    • 0 avatar
      highdesertcat

      My first experience with weight savings was when I bought a 2011 Tundra 5.7 to replace my 2006 F150 5.4. Yeah, I could tell the difference. Thirteen lbs ain’t much but every little bit helps.

  • avatar
    gslippy

    The article says they integrated the exhaust manifold with the cylinder head, eliminating several components including the exhaust manifold.

    I love sweeping quotes such as this: “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.”

    No mention of the impact on cost or reliability. Hope no consumer ever has to replace one of these things.

    • 0 avatar
      aspade

      +1. If this was the no brainer they’re presenting it as then what does that say about the engineers who came up with the pig iron first edition?

      • 0 avatar
        Bridge2farr

        I’m gonna guess you are “glass half empty” type?

      • 0 avatar

        It says that the engineers didn’t have access to the advanced casting capability that allowed them to cast in complete porting to combine the exhaust ports. Your logic would belittle the Wright Brother for not starting with a 747…

        Seriously, this is a very difficult casting and to pull it off in a production environment (hundreds of thousands of copies) is a pretty big deal.

      • 0 avatar
        aspade

        The LLT is what, all of four years old? Hardly the Wright flyer.

        Honda did the integrated manifold on the J V6 five years before that. Bleeding edge then maybe, at least by the standards of what you can put in a sub $25,000 family appliance. But not in 2008 – all the more so for a motor that spent its first two years in $40,000 Cadillacs and Acadias.

      • 0 avatar
        SP

        Hmm, this is a very interesting idea.

        However, I have concerns about the reliability.

        And a recent commenter on the original GreenCarCongress article made a very good point about increased cooling demands (to keep the aluminum intact) that could hurt the thermal efficiency of the engine and, ultimately, steal MPG.

      • 0 avatar
        Steven02

        @SP
        I read that comment on the article, but am confused by it. The engine has existing exhaust ports already on it. They are aluminum. Now, it has 1 port, still aluminum but bigger. I am not sure if there is much of any extra cooling requirements.

      • 0 avatar
        SP

        @Steven02

        It took a minute for me to reason out why, but he’s right …

        There will be a much larger cooling requirement. Read the comment by Vento97, one or two threads below this one.

        Exhaust is already flowing in the aluminum exhaust ports, of course … but the surface area of aluminum exposed to the hot exhaust is relatively small. Keeping the exhaust in the head longer means the head will pick up a lot more heat from the exhaust. You have to shed that heat, or it will destroy the head.

        A ceramic coating would seem to be a no-brainer, as it would keep more heat in the exhaust gas instead of the aluminum head. The engineers aren’t dummies, so they have probably looked into it.

    • 0 avatar
      outback_ute

      Ford has done the same thing for the 2.0 Ecoboost, where they get an advantage from controlling exhaust temperatures into the turbo – perhaps GM will do the same?

      Improving flow with this design is impressive, but the exhaust header aftermarket will not be impressed!

    • 0 avatar
      L'avventura

      IEM (integrated exhaust manifolds) are fairly common. Honda, for instance, has them on Accords V6s, Insights, CRZ, etc. There is no negative impact to cost or reliability.

  • avatar
    don1967

    A GM V6 with 13 pounds shaved off does not exactly fill me with confidence. At best it recalls the problematic head gaskets of so many aluminum-head GM V6s over the years, and at worst it screams “Chevy Vega”.

    • 0 avatar
      Bridge2farr

      Please draw the correlation between a early 1970′s 4 cyl head gasket and today’s 3.6L exhaust manifold?

      • 0 avatar
        don1967

        The Vega’s sleeveless aluminum engine block was touted as a weight-saving bit of technology, but went on to become one of GM’s worst powertrains ever.

      • 0 avatar
        highdesertcat

        Amen to that Don. I’ve known several people who replaced the Vega engine with a junkyard 265, 283 or 305. It didn’t save any weight but it did make the old Vega GO! Worthy trade off.

      • 0 avatar
        Steven02

        don and highdesertcat,
        You guys should watch the video to see what is going on. Much less critical than what you guys are thinking. This eliminates a gasket by removing a component, integrating that component into the block. Watch the video and go look at the pictures at the Green Cars link.

      • 0 avatar
        highdesertcat

        Steven02, I did watch it and I am all too familiar with the Saturn 4-cyl because we had a 1996 Saturn for my daughter. The engine blew the headgasket at less than 50K miles, flooded the crank case with antifreeze which thoroughly blended with the engine oil. What a mess! Even though I fixed it myself, the engine was never the same after that because of premature bearing wear and we had to retire it (trade it in) for a 2000 Civic which my daughter still drives today and every day with over 200K miles on it. It’s good that GM addresses the weight issue but it is even better than GM puts more R&D in their engineering stages, leading to better engines. A whole slew of GM engines would have been better had they incorporated this integration technique earlier.

    • 0 avatar
      vento97

      The most common materials used for exhaust manifolds are cast iron and stainless steel. When you glance at the exhaust ports on an aluminum head, notice that the hot exhaust gases travel a very short distance before exiting the aluminum head – for good reason. You want the hot exhaust gases evacuated from the aluminum component as soon as possible to minimize the possibility of heat damage.

      The GM integrated manifold with its longer-length runners means the hot exhaust gases have to travel a longer distance inside the aluminum component before being evacuated from the cylinder head. Anytime exhaust heat hangs around too long inside of an aluminum head – especially one without some sort of ceramic lining – VERY BAD things tend to happen – like warping….

  • avatar
    alluster83

    This is a step in the right direction for GM. The new engine also raises the HP on the Camaro to 323. GM should leverage this engine across the board and save a lot on development costs, designing etc. This new LFX 3.6 can be the made the only V6 in GM’s stable. Of course if there is a design flaw it will affect all the models and be such a nightmare.

    • 0 avatar
      Steven02

      Designs are like that with todays cars. That is why when there is a recall, it will effect 8 different models from 4 different years. Happens with all manufactures.

    • 0 avatar
      vento97

      If this casting process turns out to be more expensive than the original external manifold setup, the GM bean counters will kill this design DEAD!

  • avatar
    carguy

    Ed – this maybe somewhat off-topic but un-muted auto play video advertising (three of them on a page no less) are really annoying.

    • 0 avatar
      KixStart

      Generally, +1.

      Today, however, TTAC doesn’t seem to like either of my browsers (Safari, IE). I’m pleased that I don’t have annoying ads blaring through the speakers but the story-linked video isn’t working either. And the page for the Auto Auction story doesn’t render properly.

      • 0 avatar

        Yeah, those auto-play ads are rogues according to our ad team… they shouldn’t be there. If you see (er, hear) one, please drop a quick note to our contact form, as this might help the ad guys track the issue down. In any case, please accept my apologies… I’ve had to turn off my sound today to stop the annoyance.

      • 0 avatar
        KixStart

        The video now works for me. Thanks, Ed. I enjoyed watching it.

  • avatar
    KixStart

    “Class-leading weight.” LOL.

    The Cruze is a nice car but it’s some 3100 lbs. A Corolla is less than 2800. I haven’t looked up the new Civic but last year’s was under 2700lbs. Across the board, GM vehicles do seem to be 5 to 10% heavier than the competition. This is additional raw materials, energy to manufacture and a certain drag on city fuel economy.

    That the Cruze manages to make 42mpg (in Eco form) is impressive but when one notices the weight, one wonders if GM was designing to the test and if real-world driveability will suffer and/or real-world fuel economy will not be quite so impressive.

    • 0 avatar
      KixStart

      But praise where praise is due… I’m pleased that they were able to find 13lbs of weight to cut. Perhaps the new head and manifold also cost less to manufacture? Win-win?

    • 0 avatar
      tced2

      Every platform project should have as one of its goals: Reduce weight of finished car by 10% from previous model. Reducing weight has many benefits: better handling, reduced fuel consumption, potential savings of raw materials…although raw materials may have to be higher-tech and higher cost…

    • 0 avatar
      indi500fan

      I’m getting mid 30s on my Cruze Eco automatic. Mostly in town,
      On the 50 mi trip to my dghtrs house, which looks a lot like the EPA highway test, I regularly get 42 mpg. Quite impressive.
      As for the Corolla comparisons, the Cruze is MUCH quieter, so a bunch of the ballast is sound deadening. That’s a big reason I bought it.

      • 0 avatar
        SkiD666

        Most of GM’s new vehicles are heavy because of thick glass and sound deadening and the fact they are usually ‘tweeners’ (larger than the competition).

      • 0 avatar
        KixStart

        I should have explicitly said that there might be good reasons for the difference in weight. The goal is, after all, sales and profit, not making some arbitrary number in any dimension.

        indi500fan, I trust you’re not taking the computer’s word for your mileage? Or, if you are, it’s because you’ve verified it’s accurate?

    • 0 avatar
      tech98

      GM has had this problem for decades, another aspect of their penny-pinching, corner-cutting, accountants-rule-engineering mentality.

      Years ago Car and Driver had a letter to the editor explaining that GM cars were far heavier than their competitors because GM’s Board of Directors were huge fans of The Dukes of Hazzard, and demanded that all GM vehicles bear several hundred pounds of ballast in order to maintain a suitable flight profile when launching over creeks…

  • avatar
    Zackman

    I sure hope this is a good thing and doesn’t cause any unforeseen reliability issues, but it is a step in the right direction. If problems do occur down the road, my wish is that GM would offer an extended warranty until any bugs are worked out. I get very nervous about any new concept for engine components – lab testing, no matter how extensive, often doesn’t translate accurately into real-world realities.

    I wish when something like a video on a topic doesn’t work or refuses to load, a classic test pattern like NBC used to use would at least be entertaining to look at!

    As far as the annoying audio ads, I hate them as well as the pop-ups that appear on the bottom of photos. I suppose TTAC needs to pay the bills like the rest of us, so I’m O.K. with them – I just don’t like them.

  • avatar

    My recollection is that the Saturn Sky and the Pontiac Solstice were about 400 lbs heavier than the Miata. That was enough to make me dismiss the GM twins.

    • 0 avatar
      SVX pearlie

      The Sky, etc. are also considerably *larger* than a Miata. Much higher beltline, etc. They are not small cars.

      • 0 avatar
        Quentin

        Larger for what purpose, though?

        Dimension Miata Sky
        Length 157.3 161.1 in
        Width 67.7 71.4 in
        Height 49.0 50.2 in
        Headroom 37.4 38.4 in
        Hiproom 50.6 50.6 in
        Shoulder room 53.2 52.7 in
        Luggage volume min 5.3 2.0 cu.ft
        Luggage volume max 5.3 5.4 cu.ft
        Weight 2480 2965 lbs

        So, while it is a few inches longer, wider, and taller, it has no advantage in passenger space and is considerably worse in cargo space (top down). Why should it get a pass for the extra near 500lbs if it doesn’t make good use of the extra LWH? MSRP was considerably higher than the Miata, too. The Sky and Solstice were just 2 more classic Bob Lutz sports cars*: pretty but no attention to detail.

        * First gen Viper and Prowler are classic examples of this. The Viper burned your legs because they ran the exhaust under the super wide door sills and the Prowler could fit a V8 in the engine bay, IIRC.

  • avatar
    PenguinBoy

    At a first glance, this looks similar to the integrated exhaust manifold on the Mopar Pentastar.

  • avatar
    Greg Locock

    ” simply by redesigning its head”

    writes someone who has never designed a single thing for serious production.

    It may amuse the dilettantes to learn that the cylinder head is probably the most complex part of the engine.

  • avatar
    LeadHead

    Not really anything spectacular. The Chrysler Pentastar has integrated manifolds, and several other engines do/have had them as well.

    The GM 3.6 still isn’t all that impressive when you consider the Chrysler 3.6 Pentastar makes 305HP without direct injection.

  • avatar
    Andy D

    An integrated aluminum exhaust manifold. How long have they been in appliance vehicles? How have they held up so far? Wabbout a turbo? Like somebody bringing up the Vega. I too, am leery of big aluminum castings. A buddy of mine bought one new.It didn’t last 20K miles before the engine had lost so much compression, it would barely start. At the other end, BMW had problems with sulfured gas melting the V8 blocks when it turned into sulphuric acid during combustion. If Detroit, or any other car maker, wants to reduce weight, lose weight, get rid of the gadget-try. Manually operated windows, cabled operated HVAC, manual seats weigh much less than their powered parts. A basic dash, with gauges instead of electric everything.

    • 0 avatar
      vento97

      I hear ya – GM is taking a HUGE gamble on this. The first hint of a recall related to the integrated aluminum exhaust manifold has the potential to cause severe damage to GM’s reputation – almost to the point of irreparability.

  • avatar
    golden2husky

    Didn’t the old 200 inline Ford Six have an integrated intake manifold back in the day?

  • avatar
    Tosh

    Where’s the CERAMIC integrated block AND cylinder HEAD I was reading about over 20 years ago?! This current future is pretty disappointing so far (except for cell phones and internet).

  • avatar
    Morea

    Well, a 2-minute google patent search turns up a patent (1,190, 252)

  • avatar
    Morea

    Well, a 2-minute google search turns up US patent 1,190,252 filed in 1909 by Fiat that shows an integrated, water cooled exhaust manifold.

    The bigger question is how much heavier will GM’s cooling systems need to be to handle the extra heat load. Heat that once went into the air or out the exhaust pipe will now go into the cooling system. 13 lbs off the engine, but 13 lbs added to the cooling system for no net change?

  • avatar
    GarbageMotorsCo.

    Did they fix the timing chain stetching problems? That should be their priority.

  • avatar
    Bridge2farr

    “Couldn’t make it any worse than the last 40 years of their reputation.”
    It’s gems of wisdom like this that make this site so interesting

  • avatar
    geozinger

    I’m wondering how long it will be before the automotive engineering community re-embraces the monobloc again? Especially with today’s advanced casting techniques as compared to the turn of the last century’s methods, this could be a reality. Just think, less parts, less chances for assembly or part failure, less cost, probably less weight, too…

  • avatar
    Ducky

    This has been done in the Honda K24 engine, starting with the TSX.

    It’s not so much the reliability I’m concerned about- the design is fairly compromised in terms of exhaust gas flow (most of the gains they made were on the intake side), and most of the heat of the exhaust is actually dumped inside the cylinder head. More importantly, any Camaro enthusiasts that wants to swap on aftermarket headers for a significant power increase are in for a big disappointment.


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