Reducing engine capacity at the flick of a switch?
Discussion
They have, although the ECU tends to manage the transition automatically rather than making the driver do it. It doesn't reduce the frictional losses though, so I wouldn't expect 40mpg from one. I suppose in theory you could have a clutch in the middle of the crank shaft so you could completely detach four cylinders from the running gear.
Blowfish said:
Why is it that no manufacturer has created an engine that could go from being a 500bhp V8 gas guzzling monster and shut down to a 120bhp V4 40mpg+ at the flick of a switch?
Um, on what basis are you making that statement?http://www.cnet.com.au/hot-new-mercedes-benz-slk-a...
Cnet said:
Mercedes-Benz's AMG division used to spend all its time figuring out how to get more speed out of standard Mercedes-Benz models. It hand-built 6.3-litre V8 engines and made an automatic transmission that shifted like a dual-clutch automated manual, but now AMG engineers have turned their attention towards efficiency.
The latest engines coming out of the workshop use high-pressure direct injection and now AMG is adding a new trick, cylinder deactivation, to its efficiency repertoire. The new SLK AMG will be the first car to feature the new cylinder deactivation technology. With it, the engine will cut fuel and spark to four of its eight cylinders when it is running under 3600rpm.
This feature will only take effect if the driver has put the car in C mode, which stands for Controlled Efficiency, according to Mercedes-Benz. The company assures us the transition from four- to eight-cylinder operation will be imperceptible.
The new engine, displacing 5.5 litres, produces 310kW of power and 540Nm of torque. That represents a 45kW increase over the previous AMG 5.5-litre engine. Mercedes-Benz never offered an SLK AMG featuring the newer 6.3-litre engine V8.
Cylinder deactivation is not new — we've tested it already in V8 Holden Commodores and Caprices, and it's also available in the Honda Accord. But in its announcement, Mercedes-Benz draws comparisons between its technology and that of Formula One race cars, lest we think that AMG has become mundane.
With cylinder deactivation, direct injection and a new idle-stop feature, which turns off the engine when the car is stopped in traffic, the SLK AMG is claimed to have 30 per cent better fuel economy than its predecessor. Although considering that fuel test cycles will probably run primarily when the V8 is chugging away on just four cylinders, the variation between the posted numbers and real-world driving should be substantial.
The new Mercedes-Benz SLK AMG will be unveiled at the 2011 Frankfurt Auto Show.
The latest engines coming out of the workshop use high-pressure direct injection and now AMG is adding a new trick, cylinder deactivation, to its efficiency repertoire. The new SLK AMG will be the first car to feature the new cylinder deactivation technology. With it, the engine will cut fuel and spark to four of its eight cylinders when it is running under 3600rpm.
This feature will only take effect if the driver has put the car in C mode, which stands for Controlled Efficiency, according to Mercedes-Benz. The company assures us the transition from four- to eight-cylinder operation will be imperceptible.
The new engine, displacing 5.5 litres, produces 310kW of power and 540Nm of torque. That represents a 45kW increase over the previous AMG 5.5-litre engine. Mercedes-Benz never offered an SLK AMG featuring the newer 6.3-litre engine V8.
Cylinder deactivation is not new — we've tested it already in V8 Holden Commodores and Caprices, and it's also available in the Honda Accord. But in its announcement, Mercedes-Benz draws comparisons between its technology and that of Formula One race cars, lest we think that AMG has become mundane.
With cylinder deactivation, direct injection and a new idle-stop feature, which turns off the engine when the car is stopped in traffic, the SLK AMG is claimed to have 30 per cent better fuel economy than its predecessor. Although considering that fuel test cycles will probably run primarily when the V8 is chugging away on just four cylinders, the variation between the posted numbers and real-world driving should be substantial.
The new Mercedes-Benz SLK AMG will be unveiled at the 2011 Frankfurt Auto Show.
Blowfish said:
Why is it that no manufacturer has created an engine that could go from being a 500bhp V8 gas guzzling monster and shut down to a 120bhp V4 40mpg+ at the flick of a switch?
This has already been patented too, for insurance reasons. Don't ask me to look up the patent number though!C
rhinochopig said:
My IL4 has FI and does 18mpg super unleaded if I drive like miss daisy - am I missing something 
Well, my IL4 has FI and does 40mpg super unleaded if I drive like miss daisy 
Although my engine is a petite 1.3 it does have 214 bhp, however if I atempt to use any of that wonderful boost I can watch the fuel gauge drop
AlexiusG55 said:
The first car with it was the hideously-unreliable Cadillac "V8-6-4" in 1981, which I think only lasted a year- and yes, that was at the same time they had the shoddy 5.7 diesel V-8 (a converted petrol engine).
yep the americans have been playing with it for a long time, i remember there was some silly prototype Cadillac eons ago with 16 cylinders that could turn most of them offrhinochopig said:
My IL4 has FI and does 18mpg super unleaded if I drive like miss daisy - am I missing something
Yes check your drive as it would appear you have a fuel leak (seriously). V12's do that mpg ad the M5 v10 does it so either a leak from your tank or fuel pipework or it's running fully on choke which will kill your engine.
Have you tried driving it like Schumacher if so what is the mpg?
The I6 3ltr BMW when driven like miss daisy does nearly 40mpg it is probably 50% larger than your engine
My wife's I4 turbo petrol Leon Cupra driving like miss daisy does mid 30's when driving at 9/10ths on the road I've yet to get lower than 25mpg from a tank.
EGR is similar I thought, part of the idea was to fill a petrol engine cylinder with something that wasn't 20% oxygen, which meant that you didn't need to inject as much fuel to keep the AFRs right.
Stratified fuel injection is similar too, with the plan to keep the fuel and air mix just in one section which would remain viable to burn, compared to if it were fully mixed and would be too lean.
I don't know if they'd fully address the problems though, you can "reduce" the capacity by the throttle, but the rotating mass still remains the same.
EGR means it doesn't have to be throttled as much, and it won't lose as much energy struggling for air through a partly closed throttle.
Stratified fuel injection is similar too, with the plan to keep the fuel and air mix just in one section which would remain viable to burn, compared to if it were fully mixed and would be too lean.
I don't know if they'd fully address the problems though, you can "reduce" the capacity by the throttle, but the rotating mass still remains the same.
EGR means it doesn't have to be throttled as much, and it won't lose as much energy struggling for air through a partly closed throttle.
SAAB built variable compression ratio engine in 2000.
Wiki said:
The Saab Variable Compression engine was a development project of Saab Automobile, for which it won an award both in 2000 and 2001.
In a normal internal combustion engine, because cylinder bore diameter, piston stroke length and combustion chamber volume are almost always constant, the compression ratio (CR) for a given engine is almost always constant.
One exception is the experimental Saab Variable Compression (SVC) engine, designed for the Saab 9-5. This engine uses a technique that dynamically alters the volume of the combustion chamber, thus changing the compression ratio.
To alter the combustion chamber volume, the SVC 'lowers' the cylinder head closer to the crankshaft. It does this by replacing the typical one-part engine block with a two-part block, with the crankshaft in the lower block and the cylinders in the upper portion. The two blocks are hinged together at one side. By pivoting the upper block around the hinge point, the volume of the combustion chamber can be modified. In practice, the SVC adjusts the upper block through a small range of motion, using a hydraulic actuator.
This design was originally patented by Gregory J. Larsen of Lakeland, FL USA. The SVC project was shelved by General Motors, when it took over Saab Automobile, due to cost.
In a normal internal combustion engine, because cylinder bore diameter, piston stroke length and combustion chamber volume are almost always constant, the compression ratio (CR) for a given engine is almost always constant.
One exception is the experimental Saab Variable Compression (SVC) engine, designed for the Saab 9-5. This engine uses a technique that dynamically alters the volume of the combustion chamber, thus changing the compression ratio.
To alter the combustion chamber volume, the SVC 'lowers' the cylinder head closer to the crankshaft. It does this by replacing the typical one-part engine block with a two-part block, with the crankshaft in the lower block and the cylinders in the upper portion. The two blocks are hinged together at one side. By pivoting the upper block around the hinge point, the volume of the combustion chamber can be modified. In practice, the SVC adjusts the upper block through a small range of motion, using a hydraulic actuator.
This design was originally patented by Gregory J. Larsen of Lakeland, FL USA. The SVC project was shelved by General Motors, when it took over Saab Automobile, due to cost.
Blowfish said:
Why is it that no manufacturer has created an engine that could go from being a 500bhp V8 gas guzzling monster and shut down to a 120bhp V4 40mpg+ at the flick of a switch?
My Hemi Jeep does this, or so the manual says. 'Displacement on demand' automatically switches from V8 to 4 cylinders - presumably as a V4, but it's all so seamless that you can't really tell if it's cruising on 4 or 8, or indeed working at all. It turns maybe 16mpg into perhaps 20 in the cruise, so hardly frugal. Of course unlike 'just' a regular V4 there are still 4 other cylinders and other big lumps of metal causing drag in the motor. But it is the most economical car in the stable with an average of 17mpg according to the computer. As to the 500bhp V8 gas guzzler, it's hard pressed to get over 10mpg, and it's a full-time V8 until something breaks Gassing Station | General Gassing | Top of Page | What's New | My Stuff