AutoblogGreen

AMG shouldn't simply adopt existing technologies in a defensive move to reduce the CO2 emissions of its models in the NEDC driving cycle. It's customers are hardcore petrolheads who would perceive their beloved performance brand as having gone soft. No matter what the actual specs, to them "electric hybrid" translates to "Birkenstock crowd" so they want no part of it.

A more interesting approach would be to use not one large ICE but two small ones - e.g. two small inline threes with inertial compensation and sequential turbos (cp. Mahle's demonstrator, a 1.2L mill rated at 163hp). Both engines would deliver power to a single robotized transmission via two non-concentric - and therefore easily cooled - dry clutches. One engine would support the even gears, the other the odd ones.

At low power levels, one engine would be shut down and fired back up during the next gear change event. No electric power is required for this, just additional torque from the already active engine. There would be no torque interruption tot the wheels, but the process might take a full second to complete. During freeway cruising, it may become necessary to switch between the engines in order to keep them both hot enough. Fortunately, the ratios of sixth and seventh gear will anyhow be very close to one another, so the change in engine pitch would barely be noticeable.

When very high power levels are required, both engines would be active but run at different speeds. The active gear ratios should yield harmonious engine orders or the sound will be unpleasant. Note that gear changes in this mode would inevitably entail momentary partial interruption of torque flow to the wheels.

The engines could be mounted horizontally, stacked one above the other in a single compact crankcase with a shared coolant and oil infrastructure. The second turbo stage would be a single shared twin-scroll unit.

Such a beast would surely sound very different from a naturally aspirated V8 but possibly very interesting. Fuel economy would be superb relative to total rated power.

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Interesting idea.

But something they could do over their 'summer vacation'

Make a V6 off the 6.2 V8.
4.7 liters 420hp. Perfect for the C-class AMG. [less weight, and didn't AMG just 'hot rod' the 7g-tronic]
No need to create an artificial difference to appease E & S-class buyers.

Create a flat plane crank version of the 6.2 for the E-class, 540hp [it would be more faithful to F1, than the V10 in the M5]
Then, make a V10 for the S-class. 650hp. Do what is necessary to get this engine coupled to the 7g-tronic.

The twin turbo V12 [S65AMG] still uses the 3 valve heads & 5 speed automatic.

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@ rgseidl,

I doubt fuel economy with a three-cylinder, working at low speeds and low power, yields improvements signifigant enough to make them comparable with hybrids.

The Honda Odyssey for 2008 features a new VCM engine capable of working with 3, 4,or 6 cylinders, available on the touring or ex-l version. Honda provides another V6 engine on the less expensive versions that is the exact same size but does not have VCM available.

Two engines of exactly the same size in the same vehicle from the same manufactuer: this is the perfect basis for comparison.

The improvement in mpg in the city for the VCM compared to the regular engine is 1 mpg, only one. It improves fuel-economy by just a 6.25%.

The system you mention should be more efficient though, so let's say it provides another extra mpg. Still, a difference of two mpg only improves mpg by 12.5%

Meanwhile, the Camry Hybrid provides a 57% increase in fuel-economy in the city (it rises from 21 to 33) vs. the regular version, while also providing more power.

The only place where your plan might make sense is on the highway. Still, the improvement in mpg between the VCM engine and regular engine on the Odyssey is just 8.6%

Unless the two-engine plan is really cheap, the cost-benefit analysis would probably be worse than for hybrids.

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@ Joseph -

valve deactivation is not the same as true cylinder deactivation. Honda's VCM system turns some of the cylinders into gas springs, but the pistons are still moving (generating friction against the liner and in the journal bearings). The coolant is still drawing heat from the compressed gas. The valves remain closed only because of lost motion springs, the friction losses at the cam are still there. Overall, you end up with just ~5% improvement.

With two engines, you can completely eliminate these remaining mechanical losses at low power levels. The trick is keeping a lid on weight and cost, because co-ordinating two power sources is always trickier than managing just one. Engine vibration and sound are also big issues.

For reference, the Mahle engine emits just 130gCO2/km in the NEDC cycle (~5L/100km or 47MPGus). Combine two of these as described above and you get a 300+ hp vehicle that sips fuel like a conventional one with 100hp under the hood.

As a first step, AMG could choose to uprate Mercedes' smallest V6 (a 3.0L) by adding two small single-scroll plus one shared twin scroll turbo.

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The comparison of the Honda Odyssey isn't the best.
Honda does not put the variable resonance intake manifold on the base engine. [At low engine speeds, when the resonance valve is closed, cylinder charging is boosted]

Also Honda launched the current generation Odyssey for the '05 model year.
Honda micromanaged the gear ratios of the 5 speed automatic.
The non cylinder shutoff models for '05 & '06 had 4th gear of about 25mph/1K, and 5th of about 35mph/1K
The cylinder shutoff models had 4th gear of about 23.7mph & 5th of 30.5.

So the cylinder shutoff system worked in the city AND highway driving.
The shorter gearing of 5th gear was reason enough to spend the money to get the EX-L or Touring models, just tip into the throttle [engine returns to 6 cylinder operation] and you can accelerate in top gear [where are regular Odyssey (LX & EX, no variable resonance intake manifold) has to downshift into 4th gear]

For '07 Honda redid its transmission. Honda did not differentiate 4th & 5th gears between engines. Overall the gearing was virtually unchanged. 4th-25mph, 5th-35mph.

Now for '08 Honda is returning to gear differentiation, but only for 5th gear. But 5th gear is too tall for just 3 cylinder operation [see '05 & '06] , that is why they have 4 cylinder operation now.
5th 32.15mph/1K vs. 35.

Honda just can't make up their mind.

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MikeW,

How do you know so much about a minivan? ;)

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By the way, MikeW,

What is "cylinder charging" ?

And rgseidl,

I know that the VCM system drags the other cylinders along when working in 3 or 4 cylinder mode. Note that I said, "The system you mention should be more efficient though"

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Why not? If you don't like something, you should know why.
For me, it was Honda's D5 (button for D3) 2 1 transmission selector.
5th gear is too tall, 3rd is too short, WTF Honda. [honda 'commands' that you leave it in D5, put your trust in grade logic. No, I will use my eyes/brain thank you]

'Inertial resonance supercharging' in Honda speak
Charge being air/fuel unit.
super-charging
turbo-charging

http://www.geocities.com/mikey9t6/car_uvwxyz_vris.htm
Honda only has one valve with controls the bifurcation of the intake manifold/plenum.

Honda didn't post the speed that the switching occurs, and the Ridgeline more/less had the same engine as the Odyssey, VTEC switching rpm-4600, Ridgeline-4400
See 'Dual Stage Induction Manifold'
http://www.hondanews.com/categories/822/releases/2430

and the Odyssey is so heavy, that it isn't that front heavy anymore. Only 55/45. It could use a low bias ratio (1.5:1) torque sensitive differential for more traction.

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Thanks for the geocities link, it's a good read.

MikeW, may I ask what you drive? I must be breaking several rules of web etiquette.

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I wonder if that intake system (that Jaguar uses) will be the way Ford gets 230hp from their 3.0 V6 in the '09 Escape.

I don't own a car, but I will drive any/everything.

You know, I haven't driven my brother's Jetta tdi DSG yet.
I drove his old Jetta tdi, and asked if I could see what the rev limiter was. So I put it into neutral, nailed the pedal, and it went to 5000.
Maybe he doesn't want me doing that again?

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