Quote:
Originally Posted by Wall$treet
So what is the downside cylinder shut down? Vettes seem to have been enjoying it for years successfully with gobs of HP, throttle response and great mileage?
|
Although Vettes have never used cylinder shutdown, Honda has used it for a number of years in their minivans, and to my knowledge there has been no downside at all - although if you are paying very close attention, you can feel the changeover, both ways.
Quote:
Originally Posted by Wall$treet
Problem is that I believe the two approaches to cutting mpg, being TT and cylinder deactivation really depend on what kind of driving you do. Atleast from my basic understanding.
|
That has certainly been correct up to now.
Quote:
Originally Posted by Wall$treet
Cylinder deactivation is not great for around the city driving benefit. The benefit is had mostly highway cruising when you do not go above 3k rpms.
However in the city, it is tough to really stay at 2500-3k and you would be above or below the range of "shutoff" so many times per second, not sure any savings would be had at all.
|
This has been the case, but in theory with a powerful and torquey engine, you can get away with more aggressive use of cylinder deactivation, utilizing it in city driving without pissing off the driver. You would of course limit this function to when the driver chose an economy setting.
We'll see, of course.
Quote:
Originally Posted by Wall$treet
Seems like TT is a more "usable" way of cutting mpg and still allowing normal driving behavior in addition to mpg savings in all types of driving.
|
That remains to be seen. Certainly you could wake up the engine instantly from the cylinder deactivation mode, while turbos won't be hurried the same way. In addition, turbos cost real dollars for every engine you build, including all the plumbing. Cylinder deactivation will cost as well, but not nearly as much.
Cadillac first did this in the late '70s or early '80s, as I recall, but it was not nearly as refined as what is already available now. (Plus they had definite problems with the system). As with the Porsche twin-clutch gearbox of that era, the control systems available just weren't up to the job. Nowadays, computer power gets the job done properly.
Bruce
PS - I am pretty impressed with this engine (on paper, of course), but I am particularly impressed with how light the damned thing is.
PPS - In theory, turning an eight into a four would tend to be less noticeable to the driver than turning a six into a three, so Mercedes may in fact be able to get away with more aggressive use of this technology than Honda could. Capiche?