• Mar 15, 2007
Lotus, the company that made its name on "adding lightness" and clever engineering, is at it again. This time, it's the engineering wing of the Group Lotus concern. Lotus's efforts have been directed at banishing seperate exhaust manifolds. We groaned when we heard the news, and assumed it to be a very discouraging development. Then we got to thinking -- with this type of cylinder head, you'll never have leaky manifold gaskets again. That's a big plus for those of us who keep our cars forever and are persnickety about fixing all the little stuff that happens along the way. After a decade of heat cycling, mani gaskets are usually done for, and on today's tightly-packaged powerplants, removing the manifold is no treat. Add in the requesite broken studs and frozen fasteners, and you've got a veritable jamboree weekend. Looking further into it, the integrated manifold makes a good case for itself.
[Source: Lotus via Paul Tan]

We won't argue that it'll be at least slightly more difficult to open up the exhaust ports in search of every ounce of power, and it will likely turn out to be a lot more difficult. That said, the Integrated Exhaust Manifold is really aimed at OEMs and Lotus Engineering likely doesn't give a flip about enthusiasts. It will take a little while for this to trickle down to everyday cars, let alone into the grease-stained mitts of performance junkies. As unexciting as it seems, there's performance gains to be realized.

First, and most in keeping with the Colin Chapman legacy, the IEM will reduce weight. Lotus has developed their IEM technology to be manufactured out of aluminum, so it's off to the slag heap for those old cast iron beasties. Reducing weight is like free horsepower; or you could think of it as free gasoline. Less mass is just plain good. Another performance gain comes from the reduction of underhood temperatures. Engine compartments these days are hot environments, but the IEM can significantly reduce the heat level. Like marine engines, which pump raw water through their exhaust manifolds to keep engine room temperatures managed, the cooling system is integrated into the IEM. By capturing the heat in the exhaust, engine warm-ups are faster, meaning passengers have heat more quickly, a comfort and safety improvement. The catalytic converter can basically be mounted where the old manifold and downpipe used to be, which reduces thermal losses before the cat, and speeds light-off. Faster light-off means reduced emissions. Keeping the engine bay cooler reduces the temperature of air in the intake ducting, as well as helping the HVAC do it's thing more efficiently. As usual, efficiency equals both eco-friendliness and performance.

"Siamesed" exhaust ports that combine in the head or block are nothing new - the Ford Flathead V8 had a single port for the two center cylinders in each bank; and the exhaust ports all went through the water jacket. That's not to say the IEM is a copy of the old V8-60, it's way more high tech. The Lotus IEM will offer fewer underhood failure points, which bodes well for reliability. The technology will also yield a cost reduction, which will equal money that can be spent elsewhere. Some packaging efficiency gains are also envisioned. We think the real news here is the faster catalyst lightoff; Lotus claims it's up to 20%. The faster you can get those emissions systems scrubbing, the easier we can all breathe.


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    • 1 Second Ago
  • 15 Comments
      • 4 Years Ago
      Integrated exhaust manifolds might be a decent idea for reducing cost...only for the engine.
      I dont completely buy Lotus' argument that cat light off occurs sooner. In fact during cold starts, due to the cooled exhaust, the light off can get delayed causing an emissions issue ( with hydrocarbons, not NOx).
      Also, all the additional heat that is dumped into the coolant has to go somewhere, and guess what the cooling system in the car has to work that much harder to compensate-translation : Engine saves cost but the cooling system gets more expensive. It would need a more powerful fan at the very least killing charge margins and if it does not, even climate control might suffer as a direct consequence. I guess it is supposed to help charge air temperatures, but in modern turbo engines, the charge air is cooled anyway(more cost to cooling systems) so it does not really get up to the same temperature as underhood.
      It definitely helps at high operating temperatures.

      • 7 Years Ago
      it is definately a novel idea, but one of the keys of engineering a car is that components will fail. Ill take a grease fitting over a "lifetime seal" ball joint any day. ditto for lifetime fuel filters, etc. Cars could be built in single pieces - they're not built like that because only certain parts fail at any given time. Especially considering that Lotus are designed for the track, this integrated manifold will see a tough life, and it would seem that it would be mroe liable to crack - but if/when it cracks, it looks like it has integrated cooling as well: youre engine will overheat, ruin your cats, o2 sensors, not to mention gaskets, possibly hydrolock, water pump, etc. But, if it can be done effectively, I think this could be a great idea.
      • 7 Years Ago
      This could make turboing the car easier also, all you need is an adapter plate, not a full manifold... however this doesn't give you the option to use a tubular equilength mani for a high end kick in the pants turbo or a header should be building an all motor car...
      • 7 Years Ago
      BMW's N54, no.

      More like Honda's R18A1 in the civic and the J30A4/5 in the Accord

      I like to see Lotus try for an inline5 integrated exhaust manifold.


      Don't race car engines go the otherway, aren't the ports bifurcated? Individual holes per exhaust valve.
      • 7 Years Ago
      Sounds like a great idea as long as you don't plan on swapping them out for something higher flowing. I guess that wouldn't be a problem with a Lotus but with something more mainstream it may not be favorable.
      • 7 Years Ago
      I'd rather deal with replacing a bad gasket than replacing an entire cylinder head...eventually, the exh manifold could crack, then you are stuck buying a new head (well, maybe a shop can weld the crack, but who knows). Anyway, I'm not sure if it is the greatest idea, only time will tell, right?
      • 7 Years Ago
      It will take awhile to trickle down to everyday cars?? The Honda Accord V6 model has had the integrated exhaust manifold since 2003, when it made Ward's 10 Best Engines list. And then the Acura TL has had it since 2004, when it was the best selling luxury car of that year. And now I believe the universal Civic R18 engine has it as well.
      • 5 Years Ago
      I've always been a fan of lotus tech.
      • 7 Years Ago
      The American Motors Rambler 195.6 cubic inch displacement sixes had this feature from 1939 through 1965 when the engines were finally discontinued.

      Nothing new under the sun?

      The engines were even available with an aluminum block (with iron cylinder liners) from about 1958 through 1965, $30 extra cost. This lightened up the front of the car so that nobody except an 85 pound granny might need power steering.
      • 7 Years Ago
      1976 Chev 250 six cylinder - same thing.
      • 7 Years Ago
      Yes the integral exhaust manifold is going to be congested, regardless if Lotus makes it.
      For optimal effect you pair match A & C and B & D in a 4 cylinder firing order (A B C D) that would be the outer two and the inner two.

      It is not impossible with an integrated exhaust manifold, but is not worth the effort.
      It is so much easier to just do this.
      http://www.nissannews.com/multimedia/nissan2007/bw/07-MY07Sentra-29.jpg
      • 7 Years Ago
      i would have to see one to have an opinion but it seems like it would comprimise airflow. exhaust manifold allows you to manage airflow in the best possible way that you can fit in the engine bay. this "new" setup restricts that to what you can fit in the head. im not sure how it would weigh less either, i mean the head still has to dump the exhaust into another tube so its not like you can just subtract the weight of the exhaust manifold. you just moved your failure point to another gasket. all that weight added to the head would make the engine top heavy, hurt center of gravity and handeling.

      doesnt seem to me to be obviously better, maybe useful for certain applications.
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