• Jan 21, 2008
BMW's twin-turbo 3.0L inline-six has been a rousing success, with nothing less than a Wards 10 Best Engines award sitting in its trophy case. The praise is understandable and well-deserved, as the engine uses a combination of forced induction and direct injection to serve up a torque curve that's far beefier and flatter than what should be expected from a engine of its size. So what next for the propeller brand? Simple -- take similar technology, add it to the company's 4.4L V8 and toss in a dash of unconventional packaging to make everything fit.

BMW put its latest jewel on display at the 2008 Detroit Auto Show, and we snapped some shots of it to give you an idea of why this engine is so special. We've included those photos in one of our galleries, and below the fold, we've thrown in a few observations.



Undoubtedly, the most unique feature of the 4.4L TT is the packaging of the turbochargers in the valley between the cylinder banks.



This is made possible by the swapping of the intake and exhaust ports in the cylinder heads, with the exhaust now exiting towards the middle. This allows the turbochargers to be mounted in the valley with minimal plumbing, which means less bulk, lower weight and better efficiency.



Immediately after exiting the turbochargers, the exhaust gases enter the catalysts. It's important to keep the cats as close as possible, as the exhaust carries heat that is required for the converters' operation.

Packaging the cats in this location underneath the hood must present some interesting insulation challenges!



Instead of expensive variable-vane technology, each turbo makes use of fixed geometry and relatively simple wastegates.



Each compressor is fed via a black oval-shaped duct, as shown above.



Between the compressor outlet and the intake manifolds lie a pair of air-to-water intercoolers, one for each bank. Such an intercooler reduces packaging volume and tract length compared to a top- or front-mounted air-to-air heat exchanger.

Immediately downstream of the intercoolers lie a pair of electronically-controlled throttle bodies.



Below each centrally-located coil-on-plug (COP) assembly resides the direct injector, along with the feed lines and fuel rail. It's presumed that piezoelectric injectors are employed here, which are fast enough to allow several injection events per combustion cycle.



Each fuel rail gets its own fuel-pressure regulator. The operating system of this system is yet unknown, but we're guessing that it's similar to the 200 bar (3000 PSI) that is used in the engine's direct-injection predecessors.



Dished pistons are used to lower the compression ratio, with a compact ring package to reduce crevice volume and frictional losses.



The net effect is a peak of 400 HP, with 450 lb-ft of torque delivered between 1750 and 4500 RPM. In a sport sedan such as the 5 Series, this engine will likely erase fond memories of the musclecar era, and even in portly SUVs such as BMW's X5 and X6, the result should still be rather impressive.


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  • 48 Comments
      • 7 Years Ago
      GM's got a new 4.5L V8 TD on the way.

      They ought to hustle to get it into some high-end cars right away. Give BMW a run for their money.
        • 7 Years Ago
        "High end" GM cars do not compare to BMWs in any dept., sans hp and tq ratings.
      • 7 Years Ago
      The motor can surely make more than 400hp/450tq, but probably pushing the turbos past their good efficiency range. Seeing how max torque is reached at a low 1750 rpms, those turbos are sized on the small side for quick spoolup and response, not topend power.

      With regards to BMW and their previous mindset of avoiding turbos, I think it's much the same mindset that Honda had. There's a certain elegance and bragging rights from making lots of power NA. It's not easy making 100hp/L NA! It's MUCH easier to just toss some forced induction on a motor to make power. But in this new age of emissions and mileage, forced induction makes a lot more sense. What do you think of when you hear Ferrari, Honda, and BMW? Think think of screaming street motors that rev to 8400-9000rpms and make over 100hp/L NA. And now, all three of them are going turbo; things change.
      • 7 Years Ago
      The packaging of this engine, ie reversed intake and exhaust with turbo in the V, is very similar to the new 4.5L Duramax diesel that GM is releasing on the next few yrs. Putting the turbo in the V significantly reduces the installed width of the engine.
        • 7 Years Ago
        i have looked all over that article on the new 4.5 diesel and i cant find anything regarding the reversed intake exhaust setup. are you sure that engine is exhausting in the V because the pics sure look like an intake manifold right where it should be.
        • 7 Years Ago
        i have a twin-turbo V6 with the turbos in the traditional location. You can't even see them from above. They do not protrude out wider than the heads do. This might narrow the width of the engine down at the bottom, but it doesn't reduce the overall width. Is there really a need for the block to be narrow down there?

        See pics at this article. BMW's V10 has lots of space for turbos under the heads.

        http://www.autoblog.com/2008/01/10/corvette-zr1s-ls9-inspired-by-bmw-m-v1/
        • 7 Years Ago
        ohc or ohv?

        the ohv V6-8 has much less room under/next to the head so it might make more sense in terms of reducing the overall width in that application
        • 7 Years Ago
        I was basing my comments on this article http://www.autoblog.com/2007/06/15/gm-announces-clean-diesel-v8-for-pickups-and-the-hummer-h2/
        among others. I do think it simplifies the packaging especially where a single turbo is used on a V type engine.
      • 7 Years Ago
      Wow, that is some bizarre packaging!

      Knowing how heavy turbos, manifolds, catalytic converters, intercoolers and all the associated plumbing and braketry is, doing it this way must shift the centre of gravity of the engine way up! This should definitely stay SUV-only.

        • 7 Years Ago
        the weight is just the begging, its a really tall engine and THE HEAT, MY GOD THE HEAT!

        the friggin cats would be right up against the back of the hood, everything in that area (hood, paint, windshield wipers motors and lines, wiper nozzles and lines, electronics, brakes) all of that stuff has to be able to handle EXTREME HEAT

        there would almost be fewer problems if you mounted the engine upside down. there is certainly a very long list of very good reasons that NO ONE has EVER had a v8 exhaust in the valley and intake on the outside.

        all of this trouble for better turbo response? hardly seems worth it.
        • 7 Years Ago
        naggs- you know how the Germans love their heated wiper nozzles.
        • 7 Years Ago
        ...and the front/rear weight bias.
      • 7 Years Ago
      Take that ZR-1 !
      • 7 Years Ago
      Just seems awfully complicated......... Not the route I would go as an engineer. The more complicated something is the higher the failure rate
      • 7 Years Ago
      I really love the fact that BMW is now going with Forced induction. It wasn't that long ago when they were talkin about how they only believed in NA to defend themselves as to why Audis and MBZ had more power on their cars. That is what you would Call "Hypocrites."
        • 7 Years Ago
        Back when BMW owners were crapping on Audis (like S4s), my Audi A6 was already making full torque (more torque than the 540i made at full song) at 1850 RPM. So don't tell me things have changed now and you suddenly can have a flat torque curve when you couldn't before.

        I think you're wrong about it being a change in technology. It was just BMW owners' snootiness and bias and now they are forced to sing a different tune.

        Turbo lag existed then, and it exists now. The 335i has lag, the Veyron has lag and this will have lag too.
      • 7 Years Ago
      Remember the EU pedestrian safety regs are raising the distance of the hood to the engine anyway; the engineers have plenty of height to work with in a sedan now as long as the engine is pushed back.

      The EU ped laws were (I think) 18" between hood and hard point in the front? Might be wrong on that number, but it's a lot of space ... which is why you're seeing the new tall nose designs like the new MB C class.

      Once they clear that ped zone, the engineers have tons of space to work with now. Just a nightmare for the designers.
        • 7 Years Ago
        Alconel is softer than iron, but it's still harder than a pedestrian's body is. With the turbos sticking up, the hood will have to be raised further to get clearance from the turbos.
        • 7 Years Ago
        Why did I type alconel when I meant Inconel? I'm losing it.
        • 7 Years Ago
        also, between the turbo + cats and the hood you will need a butt load of heat shielding.

        more weight and more height
      • 7 Years Ago
      I agree with spdracerut, and I know things change. But like i said, they are still hypocrites all the same. Btw i don't think I've ever heard Honda and Ferrari Scoff at using turbo chargers, since I know there have been many Ferraris that have turbos. The one that comes straight to my mind is the ferrari F40.
      • 7 Years Ago
      Unconventional packaging, ummm.........I don't like the sound of that! You better take out another morgage on the house and offer up the kids as slave labor because when you have to bring that "unconventional" package in for a repair.......it's gonna cost ya! You know because it's "unconventional"
      • 7 Years Ago
      I could be wrong but I could swear that I heard the next M5 was going to have a turbo V8. Could this be it?
      • 7 Years Ago
      I am assuming a couple of things here, the first being that 400hp is being way conservative, I would more believe it to be like 450 possibly even higher. The second thing I am also assuming is we are looking at the next M3 motor mind you this is further down the pipe line but I could see it making it's way into there with even more power, I believe even if they release it with 400hp its only to make it so they have room to improve upon its numbers later on in production and have ad's like "now with more power"
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