Ikarus

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I've said before that MB's high displacement engine strategy is not sustainable in times of tightening environmental regulations and rising gas prices. As other manufacturers have demonstrated, it doesn't take a +5L gas guzzler of an engine to produce a blazingly fast car. Here's evidence that MB is finally coming to the same conclusion.

Cruzer 8

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In the US they charge a gas guzzler tax on our SL550 --- EPA est 22 mph --- we get 28-29 on highway and since moving to AZ we even average 21 around town go figure
They could lower the compression and add a turbo but I think the overall performace and mpg would remain the same.
To me proper combustion chamber design, good ignition, and variable valve timing backed up by a transmission with the right gear ratio's with at least 7 or 8 gears that can maintain the engine rpm at the sweet spot and the addition of a free wheeling like overdrive that would require manual down shifting ---- might cause more brake pad replacment but would sure help in the medium speed range 35 to 55 mph and for those of us that drive in moutains and rolling hills this would raise our mpg

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SL 550 Mars Red

DansSlk

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I 50% agree with this, I totally agree that you can get equal amounts of power from smaller engines with forced induction or very high rev's and they can sound good while they produce that power, also they tend to be lighter and that has advantages in the handling and acceleration department.

BUT i also go along with Gene's statement, in my experience with cars the displacement has little effect anymore, my SLK for example has no trouble returning over 30MPG even with its mods and the relative age of the M113 engine when compared with the brand new units that have much more eco-friendly technology built into them and are able to return even better MPG figures, that 30MPG figure is something what would be acceptable in many new family eco-boxes and is a figure i very much enjoy pointing out when my car choice is questioned (much to the surprise of the wally asking the question).

Age and maintenance are such big factors, think of all the 2.0L beaters you see shooting about belching smoke, do they get as good a consumption figure as us? Do they hell as like but because they have a small capacity they get away with it and the poor chap with the 24L engine thats quite happy cruising along at idle using bugger all amounts of gas and with baby foxes coming out of the exhaust gets picked on.

Thats not fair.

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cousjcc

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I'm going to have to side 100% with Dan on this one. I've seen plenty of turbo'd cars that don't get anywhere NEAR the mpg you would think they could from a 1.8 or 2.0L four cylinder engine. The fact of the matter is, RPMs affect your fuel economy in a MAJOR way, and most of the turbo'd cars you see don't really get their full speed potential unless they're revving upwards of 4500 or 5000, some of them even higher like 6000rpm.

As an example, take whatever car you currently own and do a mpg test. Get on the highway and set it in its maximum gear (if it's an SLK with automatic tranny, just put it in "comfort" mode). Now drive a 100-200mile stretch of highway with cruise control on at 60mph. Take that same exact car, same stretch of highway, and instead set your cruise control at 75mph. The increased RPMs will result in decreased fuel economy. I realize that the increased wind resitance factors in but if you want to use that portion of the arguement, do the same thing in a manual but instead set the cruise control at 60mph BOTH times. The difference for this test would be to set your cruise at 60mph but in 5th gear the first time, followed by 6th gear the second time. That way there's no difference in wind resistance, the car is going the same speed, on the same stretch of road, with ONLY engine RPMs accounting for the decreased fuel economy in the lower gear.

High revving turbo'd cars may get marginally better mpg than some higher-displaced V6s and V8s, but by no means enough to spell the end for big displacement. There happense to be a certain chevrolet sports car that has upwards of 450+ bhp with a V8 engine that can still return 26mpg or more on the highway due to the fact that it can trot along practically at idle-level RPM's. You know which one I'm talking about .

I'm not dogging on turb'd vehicles mind you. Some of them are impressive when it comes to putting up numbers no doubt. I personally just prefer the feel of at least a V6 in my cars and probably won't ever go any smaller unless they stop making them all together. Torque can pull the corners of your mouth into a smile easier than just about anything.

Ikarus

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I'm sure the MB spokesperson quoted in the article wasn't referring to high-revving turbo engines of old, but the modern version mated with direct-injection. Those are the exact opposite of high-revving. If you've ever driven a car equipped with VW's 2.0 TFSI or BMW's twin-turbo 3.0, you'll have noticed that the maximum oomph (read torque) already comes on at around or below 2000 rpm. Check out this link here for more detailed info about the direct injection concept and why it helps fuel efficiency. As an interesting tidbit we also learn that MB once pioneered the technology with its 1955 300SL.

As an example, here's some key data for the 2009 Audi A5 2.0 TSFI: 208 hp, 258 lb-ft, 0-62 mph in 6.9s and this with a fuel efficiency of 36mpg (European standard combined cycle) and CO2 emissions of just 154g/km. Makes MB's current engine technology look a tad old-tech in my eyes.

cousjcc

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Like I said, I'm not dogging on turbos. I'm sure as the technology advances the fun factor will follow suit. However, 36mpg is not enough fuel economy for me to want to drive a car with close to 7 seconds 0-60. I'll take the SLK's 26-31 mpg highway (depending on driving conditions and habits, based on what people here have reported they got) coupled with its lower 16-18mpg but more fun 5.3sec 0-60 time any day. I'm all ears if you can point to a turbo that gets 35+ mpg highway but can return 0-60 times under 5.5 seconds, or any car for that matter.

Also, aren't direct injection and turbos two different things? I'm no mechanic and admittedly don't know much about engines, but it seems to me you could have direct injection on just about any properly built engine, turbo or no. So you could increase the fuel economy of larger displacement engines with direct injection no?

Edit: after reading that wikipedia article you pointed me to, it does seem to me that direct injection is entirely possible in a non turbo'd large displacement engine. So I am still failing to see the real argument for turbos. I am interested in the subject, so by all means I'm game to learn more if you can point me to any information that shows why turbos would be better than larger engines, direct injection aside since that appears to be something possible in either kind of engine.

Gabus

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MB have made a 1.8L twin turbo engine with 238hp/400nm that runs on 39 gpm in a S-class size car.... Diesotto.

http://tinyurl.com/6r7fo3
http://tinyurl.com/6kcbdk

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cousjcc

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Now THAT is an engine I could buy into. The car it's attached to in that link is absolutely disgusting to look at. However, if anyone can figure out a way to retro-fit that engine into my SLK (after the engine actually reaches consumer markets, that is) then I *might* be tempted to drive my first 4-cylinder engine in over 10 years.

Gabus

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I've heard that all R 172's except the 62(63) AMG will have diesotto's

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cousjcc

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If that's true, than in 6 or 7 years when it's time to get rid of my '09 and look toward a new car, then I'll probably be looking at R172's (as long as their body styling remains similar). Either that or retrofitting an R172 engine into my '09 . Only time will tell. They just did a face-lift so I don't expect the R172 for at least a couple years.

Ikarus

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Well, 6.9s for 0-62 in an A5 4 seater should translate to low 6 seconds for 0-60 in the SLK, and the 36mpg is already a combined city/highway figure and not just for highway cruising below the speed limit (which is what it takes to get the 350 near or above 30mpg). I hear you though, this A5 is not a car for you, but that wasn't really the point I was trying to make. It was just an example for the level of power efficiency that can be achieved with modern engine technology.

Yes they are different but complementary technologies. See for example here.

Ikarus

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Article about Ford's new GTDI engines (gasoline-turbocharged-direct-injection).