AMG 5.5L in detail (video)
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2006 E55, 2012 Jeep SRT, 2008 G37s 6MT (The Mrs.), 2005 Explorer
AMG 5.5L in detail (video)
Hope this isn't a repost.
http://www.worldcarfans.com/11108223...n-detail-video
http://www.worldcarfans.com/11108223...n-detail-video
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05 White Pano E55, Cadillac CTS-V
Cool video, only thing is they were acting like the cutting cylinders was some breakthrough but has been used for several years on other cars and American at that.
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'03 E55, Range Rover Sport Supercharged, Ducati 748R
i agree that others have been able to cut fuel/spark to certain cylinders but i don't think any of them also prevented cylinder charge by shutting down valve actuation. i could be wrong but if not, that's a pretty big innovation...
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05 White Pano E55, Cadillac CTS-V
I am unsure on the valves, that could very well be new, but unless I am thinking about it wrong, to me that is a bad thing having the valves stay closed. Think about it, if you turn your engine over with the plugs in it, it is much harder than with the plugs out of it. So what they are doing by keeping the valves closed is making those cylinders pressurize on the up stroke not once but twice (compression and exhaust stroke) in the 4 stroke cycle of the engine with nothing helping to propel it back down (the power stroke where air/fuel would be normally ignited to push it down). This is making the engine work harder to rotate when only 4 cylinders are firing, where if the valves were left open then it would obviously have less to overcome and be more efficient.
Now tell me where I am missing the boat here, but I don't see any other logical way of how keeping the valves closed on the dead cylinders is a good thing.
Now tell me where I am missing the boat here, but I don't see any other logical way of how keeping the valves closed on the dead cylinders is a good thing.
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'03 E55, Range Rover Sport Supercharged, Ducati 748R
first, with ALL the valves remaining closed (intake as well as exhaust) there is no compression stroke which is what makes it difficult to turn the motor over in your example. second, it seems to me that it's more efficient for the piston to operate in a relative vacuum rather than having to pull/push air through open valves.
i'm no engineer but that's my take on it...
i'm no engineer but that's my take on it...
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05 White Pano E55, Cadillac CTS-V
I am not sure if I am reading it wrong or you wrote it wrong but are you saying because all the valves are closed there isn't a compression stroke? That is exactly what a compression stroke is.
The only thing I can think of what you are trying to say is maybe because the intake valves are closed that no air was sucked in to then compress? But the pistons and valves continually moving with their normal function are going to have air in the cylinder, they just wont take in and release any different air once the valves are inoperative when the specified cylinders "turn off" and it becomes a "4 cylinder" temporarily. If you want to think of it that way, then the only way I can think of would be to have the valves go inoperative on the specified cylinders right as the exhaust stroke finishes pushing out the air, but now in this case you have the piston trying to go down fighting a vacuum since the intake valve isn't opened letting it go freely (think putting your finger on the end of a straw and trying to suck in) which once again would be causing a problem with efficiency since it is now just swapping fighting compressing air to fighting trying to pull a vacuum.
The only thing I can think of what you are trying to say is maybe because the intake valves are closed that no air was sucked in to then compress? But the pistons and valves continually moving with their normal function are going to have air in the cylinder, they just wont take in and release any different air once the valves are inoperative when the specified cylinders "turn off" and it becomes a "4 cylinder" temporarily. If you want to think of it that way, then the only way I can think of would be to have the valves go inoperative on the specified cylinders right as the exhaust stroke finishes pushing out the air, but now in this case you have the piston trying to go down fighting a vacuum since the intake valve isn't opened letting it go freely (think putting your finger on the end of a straw and trying to suck in) which once again would be causing a problem with efficiency since it is now just swapping fighting compressing air to fighting trying to pull a vacuum.
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'03 E55, Range Rover Sport Supercharged, Ducati 748R
your second paragraph is what i'm thinking and that's also why i said relative vacuum. i would think the valves would close with a static amount of air that would allow the most efficient free movement of the piston. even if you are right and the piston is fighting a vacuum on the down stroke, that same vacuum would also aid in the up stroke. seems that would still be more efficient than a compression stroke with no power stroke.
again, i'm outta my league and just speculating...
again, i'm outta my league and just speculating...
Last edited by chiromikey; Aug 23, 2011 at 03:03 AM.
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From: Jacksonville, FL
05 White Pano E55, Cadillac CTS-V
They should have explained that more in the video on how exactly it worked. I suppose the average person wont think of any of that or really care what is going on or how it works, they are just happy their V8 is getting 4 cylinder fuel mileage when not in the throttle. Then Mercedes is meeting the fuel efficiency requirements across their product line to make the governing evironmental fuel natzies happy so everyone is happy and no explanation for the masses is really needed.
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2018 E63s, 2004 E55 AMG
By keeping the valves closed on half the cylinders those cylinders basically act like an air spring. 4 cylinders fire, keeping the engine running and the other 4 just compress air and then expand. Think of a basketball bouncing, it bounces because the air inside compresses and then expands. If they didn't close the valves on the 4 shut down cylinders they would still need to suck in air as well as expel it, which consumes energy (pumping losses).
