[alfa] Camshafts and valves (was 147 knock-off (Mazda 3))

[Alcon98340@xxxxxxx]

> Are you talking about the cam-less designs that use electronic controlled
> actuators to move the valves? I didn't know anyone had taken that into
> production yet. I remember reading about it a few years ago though, so it
> has been long enough for it to go into production use. At the time, if I
> remember the article, they first did it to see if they could, then they
> were going to try racing with it. I just wish I could remember who "they"
> was. It's been too long.

To my knowledge, BMW was the company working with electromagnetically 
controlled valves. Last I remember reading, they could only get them to work up to 
about 6,000 rpm. After that, they couldn't actuate quickly enough. I do not know 
if this was/is a techonology being pursued or developed by Porsche as well. 

>I was talking to a mechanic the other day at a machine shop, and he
>has a bit of experience with motor cycle engines. Some engines even
>have 8 (yes eight!) valves per cylinder. Also rotating heads where a disk
>with a hole in it rotates to the intake and exhaust position, but this is
>not
>very good because the port is only open for 1 degree for each rotation.

>I've also seen rotating spheres with slots cut in them that rotate in the
>heads.
>I have no idea how effect this is, but to me it makes sense as there is not
>up/down movement, just simple rotation. There is a US company than
>manufactures these heads (I think mostly for racing) but the website did
>show it fitted to a straight 6 Mercedes engine. Interesting, but I'm sure if
>it was worth while, Ferrari might have been using rotating valves for a few
>years now if it was :)

>I'll shutup before this gets too off-topic :)

>~Benjamin

I am only aware of one motorcycle that has an 8 valve cylinder head. There 
was a prototype head made for the older style air-cooled (may have been liquid 
cooled) Ducati v-twins that, to my knowledge, never became a widespread 
phenomenon. It was a non-factory project pursued by an enthusiast whose name escapes 
me. To correct myself, Honda also had an 8 valve head for their NR750 
motorcycle, which was put into limited production. There is a little more information 
at the end of the following paragraph. Here is a link that has a picture of a 
piston (oval, with two con rods), cylinder head, and a few others:
http://www.sportbikez.net/pictures/mod/nr750

I am aware of at least two projects to have used a rotating disk with slots. 
One of them is the company who modifies heads for usage in various cars as 
mentioned above (I seem to remember a straight 6 BMW engine instead of a 
Mercedes). To my recollection, this setup actually improved both power output and fuel 
economy. The other project was done by a gentleman in Australia, if memory 
serves correctly. He actually had a hybrid 2 stroke/4 stroke head of his own 
design. Don't ask me to explain how it worked. I can't currently find the web 
site, but he had an animation that showed it. If you really want the scoop about 
it, perhaps Kevin Cameron (of Cycle World fame, and a technical fiend) might 
have some knowledge. Almost nothing is too outlandish. After all, Honda created 
the NR750 (along with others of different displacement) which was an 
oval-pistoned V-4. This essentially gave it the advantages of a V-8 without 
technically breaking the rules of the sanctioning body. I won't even get into Felix 
Wanke's original concept for the rotary engine for everyone's sake. To make a 
comment in jest regarding Joe Elliot's query about whether the Japanese do 
anything original, I would say not much, they just tend to do it better. I guess it's 
my turn to be off topic. 

-Josh
'71 1750 Berlina
'72 2000 Berlina (Moxy)
'84 GTV6
'90 Honda VFR750
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided