Could anyone explain this to me?

ds20prefecture

mike65 wrote:

It was this or a propellerhead!

Mike.

This from the moderator of Astronomy?

AMurphy

CrowdedHouse wrote:

I think the old Bentley 'Blower' and Mercedes racing cars of the 1930's had 4 valves per cylinder

That may be correct, but it was about then generally.
However the only actual cutaway engine of the period I have seen with 4V/Cyl was of one of the engines (Don't know which engine exactly) located here

more on it here

also visited ZF, in the same town.

MTU and had a place about there also, one big happy family.

mike65

ds20prefecture wrote:

This from the moderator of Astronomy?

I'm only there to break the fights up!

Mike.

stratos

has anyone ever thought why are we using power sapping mechanical valves.
There must be a better way. electromagnetic valves under full electronic control. come on people think .

unkel

ds20prefecture, sound explanation!

AMurphy wrote:

btw, when (year) do ye think 4V per cyl was first deployed?.

Never mind 4V, wasn't 5V around as early as the 1920s?

kbannon wrote:

16 valves? jeez I have 24

Ye **** ye

I've been on 32 valves for well over 4 years now. The first memory I have of 32 valves was in Magnum's early 80s Ferrari 308

AMurphy

stratos wrote:

has anyone ever thought why are we using power sapping mechanical valves.
There must be a better way. electromagnetic valves under full electronic control. come on people think .

Even electromagnetic valves would require power to operate, "no freee lunch".
There have been rotary valves, disk valves, sleeve valves, gas spring valves and some other novel approaches... and no valves.

pedro ferio-vti

ds20prefecture wrote:

Twincam refers to a method whereby inlet and exhaust valves are operated by seperate camshafts. It is very common for 4 or 5 valve per cylinder engines to use two camshafts per cylinder bank, but it was also used on 2 valve per cylinder designs and there are 4 valve per cylinder engines with a single camshaft per cylinder bank (e.g. VW VR6)

There's pros and cons to each, I believe the principal advantage of a twin cam engine is more independant control over the timing of exhaust and inlet operations. The trade off is more mechanical complexity, more weight and a greater dependence on timing accuracy, where timing is the position of the valves relative to the combustion cycle.

Well said was going say something along the same lines myself!

ds20prefecture wrote:

Thanks - so the answer is "there are no valves in a rotary engine"!!

Yes. Also probably somewhat of an answer to this:

stratos wrote:

has anyone ever thought why are we using power sapping mechanical valves.
There must be a better way. electromagnetic valves under full electronic control. come on people think .

In that the Rotary engine was a revolutionary (excuse pun) when it came out in that it had very little moving parts, about 6-8 in total and NO valves! They were/are quite compact and lightweight too for their power outputs.

Cons to the Rotarys is that their energy efficiency is quite poor when compared to a 4 banger. When I say energy efficiency I mean how well it converts air and fuel to the pressure required to move your pistons up and down to get the car moving WITHOUT wasting the combustion process by giving off useless byproducts..... i.e. HEAT, which the rotary is really bad for.

All goes back to the basic theory/definition of Energy in that: Energy can never be destroyed, just converted into different forms. If our combustion process is being used to generate compression to drive the cylinders, it really is NOO good if its being wasted generating too much heat.... hope this makes sense!

Err, didn't mean to type this much. But the main reason car manufacturers are reluctant to use other types of engines other than over head multi valve designs is that they have them perfected so well at the moment with regards to fuel economy, cost to build, performance etc etc and to try to change that, whoever does it, will incur the most expense working the bugs out of a new type of engine over year, just like what happened to the Rotary which was mainly backed from Mazda with its Cosmos and RX- series of cars.

Hope this helps....... a bit

Capt'n Midnight

stratos wrote:

has anyone ever thought why are we using power sapping mechanical valves.
There must be a better way. electromagnetic valves under full electronic control. come on people think .

The electro magnets would cost more and probably be heavier than a timing belt. And then there is the tiny matter of completely trashing the engine if the onboard computer or any of the electrical connections or fuses fail.

[edit] found the rotary engines http://www.keveney.com/gnome.html 630K animated gif.

The Gnome was one of several rotary engines popular on fighter planes during World War I. In this type of engine, the crankshaft is mounted on the airplane, while the crankcase and cylinders rotate with the propeller. The Gnome was unique in that the intake valves were located within the pistons. :eek:

AMurphy

The Gnome, Was there not a series of books about someone titles "Biggles" who flew a Gnome.
I believe, that the gyroscopic effect of the rotating mass of the engine meant that when the pilot turned one way of the other, the plane also pitched up or down in response.
btw, have any of ye played with one of those gyrascopic wrist excersizers, wherby you can get a mass spinning about 20,000 rpm just from wriggling your wrist?.

RicardoSmith

lomb wrote:

never buy an 8v motor they sound like tractors and dont rev, 16v motors rev like sewing machines, and have more power.

Depends on the engine. The 1.8 mrkII golf GTI all had better low end torque then the 16v. Was nicer to drive since you didn't have to redline it to get the power. The 16v had more power at the top end only. So you had to stay in a narrow power band. To counter this they either use variable valve timing, or just use a larger capacity to start with.

camarobill

RicardoSmith wrote:

Depends on the engine. The 1.8 mrkII golf GTI all had better low end torque then the 16v. Was nicer to drive since you didn't have to redline it to get the power. The 16v had more power at the top end only. So you had to stay in a narrow power band. To counter this they either use variable valve timing, or just use a larger capacity to start with.

u know ur m2 plus the 8v give less trouble and most engine parts are cheaper,dont run down the 8v till u drive a m2 golf

ds20prefecture

stratos wrote:

has anyone ever thought why are we using power sapping mechanical valves.
There must be a better way. electromagnetic valves under full electronic control. come on people think .

I believe BMW have a Diesel engine equipped with electrically actuated valves. I might be just a prototype, though.

AMurphy

See; here

and
here


Which is interesting, given I drew up a sketch for one about 1970, and received an investors package, including video, for one in about 1985, from some Dubliner in the USA. Cannot remember the name, but I believe it was a 5cyl MB engine he had modified.

ds20prefecture

Classics Monthly reckons the Dolomite Sprint was the first mass-production 16V four cylinder engine.