Engine Overlap
Tue, 30/03/2010 - 12:30
Kevin, I have just read you article on the 11 degree overlap in the new MTS engine, which was very interesting.
It does of course raise the question about can there be a technology made available that will allow different overlap angles depending on the rev range? I guess on the Ducati that would be heard if it is to be a desmo, which of course has valves opened and closed by cam shafts, so it would need some kind of ability to change to the lobe profiles or change to a different set of cams at a certain rev. How about not having valves opened and shut by cams at all but by some other means that are triggered by electronics? I would not be surprised if it already exists but as I don't keep up too much with engines that I can't actually get in there to take apart then I may have missed all the fineries.
Tue, 30/03/2010 - 22:05
#2
Honda call it VTEC :-D
Honda call it VTEC :-D
Thu, 01/04/2010 - 10:21
#3
Another interesting take on this is the new
Another interesting take on this is the new FIAT/Alfa range of 'Multiair' engines which effectively do away with the 'Throttle' as we know it.
It's worth having a look at this in more detail if you're really interested in where this technology is taking us. The gains in both Bhp and fuel economy are impressive.
Mon, 05/04/2010 - 21:41
#4
To come to automotive technologies: Honda use
To come to automotive technologies: Honda use it and some other Japanese car companies only in some models.
But if you look on the complete range of a manufacturer it's AFAIK BMW who is using in nearly every engine a system called VANOS (since about 15 years) to adjust the opening an closing times of the valves (today both on the intake and on the exhaust). But the curves of the camshafts are always the same.
Since approx. 8 years BMW use in some engines a system called VALVETRONIC. There the opening and closing of the valves can be reduced to zero because the valves can be completely disconnected from the camshaft. Because of that there's no throttle butterfly needed.
I think Audi is using a similar system but they claim more possibilities of adjusting the overlap. The BMW system is not able to modify the curves of the camshafts completely. It's only able to adjust the times more to "early" or "late" and to change the lift of the valves from zero to max (determined by the camshafts). But the loss of efficiency caused by the throttle butterfly will be away.
shuggiemac,
yes there can.
Ever heard of variable valve timing ?
Porsche use it, as do most of the japanese car makers, most noticably Honda.
Take a look here: http://auto.howstuffworks.com/question229.htm
In essence you can change the timing and/or the duration of valve lift.
Hope that helps.