5 Litre V8...... 33.6mpg average!

DAIR · 5 Dec 2011 at 13:12

Sorry if this is a repost (did do a search and couldnt find anything :eek:

)

The new SLK 55 AMG

http://www.autocar.co.uk/CarReviews/FirstDrives/Mercedes-Benz-SLK-55-AMG/260162/

No Turbo
No Supercharger

Pulsar_GTI · 5 Dec 2011 at 13:15

Not bad ... i use to get 30.3mpg in my old 5.7 v8 .. boring tho

Cosimo · 5 Dec 2011 at 13:37

That mpg is achieved by cylinder shut-off technology. Between 800–3600 rpm they can switch off four of the eight cylinders when driving in “controlled efficiency” mode. Very clever stuff.

BigDannyO · 5 Dec 2011 at 13:40

Excellent.

It's heartening to see that there are still manufacturers pushing the boundaries of technology on high performance engines without having to resort to smaller displacement+forced induction.

Freefaller · 5 Dec 2011 at 13:40

simulatorman said:
That mpg is achieved by cylinder shut-off technology. Between 800–3600 rpm they can switch off four of the eight cylinders when driving in “controlled efficiency” mode. Very clever stuff.

How interesting! Very clever stuff indeed! So much more interesting and clever than batteries!

PMKeates · 5 Dec 2011 at 13:41

What's also interesting is that Mercedes have had this technology for over 10 years.

Big Chris · 5 Dec 2011 at 13:50

They're not the only ones either are they? I'm sure I recall Clarkson mentioning something about it during a car review on Top Gear. Although maybe it was another manufacturer using a Merc engine?

Raymond Lin · 5 Dec 2011 at 13:54

But the car will sound like a 4 pot at idle and around town. That's half the fun!

33L · 5 Dec 2011 at 14:01

i beleive the chrysler C300 or whatever its called does this aswell.

Gav · 5 Dec 2011 at 14:09

33L said:
i beleive the chrysler C300 or whatever its called does this aswell.

It uses a lot of mercedes parts so its not surprising

Lashout_UK · 5 Dec 2011 at 14:13

Cadillac introduced cylinder deactivation in 1981, with the V8 8-6-4 L62.

Clarkey · 5 Dec 2011 at 14:15

Mitsubishi were doing this in 1992 with MIVEC-MD, on 4 pot engines too.

DAIR · 5 Dec 2011 at 14:16

Is there a reason why this isnt mainstream?

Disco Boy · 5 Dec 2011 at 14:17

Raymond Lin said:
But the car will sound like a 4 pot at idle and around town. That's half the fun!

Exactly... What's the point of buying a V8 and then getting the smoothness of a 4 cyl?

PMKeates · 5 Dec 2011 at 14:20

Lashout_UK said:
Cadillac introduced cylinder deactivation in 1981, with the V8 8-6-4 L62.

Yeah but it was crap

DRZ · 5 Dec 2011 at 14:24

Disco Boy said:
Exactly... What's the point of buying a V8 and then getting the smoothness of a 4 cyl?

You don't lose the smoothness really because of how it is done and because you still have the same engine balance. You don't suddenly lose the mass of the other cylinders!

This tech started in F1 IIRC, to stop the cars overheating on the line waiting for the start and during pit stops etc.

wez130 · 5 Dec 2011 at 14:37

33L said:
i beleive the chrysler C300 or whatever its called does this aswell.

Gav said:
It uses a lot of mercedes parts so its not surprising

Sure the 300C uses a hemi V8 engine

Cosimo · 5 Dec 2011 at 14:47

More on the engine:

http://www.egmcartech.com/2011/07/2...get-new-5-5l-v8-with-4-cylinder-fuel-economy/

Jonnycoupe · 5 Dec 2011 at 14:50

Freefaller said:
How interesting! Very clever stuff indeed! So much more interesting and clever than batteries!

Is it?

The balancer shaft system is the complicated and heavy side of adding it. Turning of 4 cylinder is pretty bread and butter. Honda also did VCM, Variable Cylinder Management.

You still have the extra friction of the cylinders so its not the same as just a 4 pot.

PMKeates · 5 Dec 2011 at 14:51

simulatorman said:
More on the engine:

http://www.egmcartech.com/2011/07/2...get-new-5-5l-v8-with-4-cylinder-fuel-economy/

Interesting point in that link:

MB said:
No less than 170 lb-ft of torque is still available in four-cylinder mode – enough power to ensure plenty of acceleration in most driving situations.

170 lb-ft is 230 Nm. In a car weighing 1610 Kg that's 143 Nm/ton. That is also known as 'pants' and will provide nothing like effortless acceleration except at low (sub 30 MPH) speeds. Unless you are driving the economy test cycle this engine will spend most of its acceleration time in 8 cylinder mode.

Peak power output in 4 cylinder mode is at most (there's not enough detail in the article) 117 HP, making for 72 HP/ton, if you can manage to rev it to 3600 RPM without clicking it in to 8 cylinder mode.