Is this new diagram for the book clear?
 

This is a really tough one to conceptualize. Let me know what you think...

http://forums.pelicanparts.com/uploa...e-engine26.gif

Please let me know your feedback...

-Wayne

Looks like the valves move farther than the pistons.

Kind of. Sometimes graphic data presentations cannot be scaled properly. In this case, pistons are actually travelling further than a few tenths of an inch. But if what you are trying to illustrate is the presence of valve-to-piston clearance, and even its cyclical timing pattern, then this graph helps to do that. It's just a little confusing potentially because it is not a graph that can help the viewer understand the actual distances involved. Or does it? Perhaps its scales are trustworthy for both valves and pistons.

O, and it's upside down.;)

Seems pretty clear to me ... but maybe a scale is needed on the right side for piston travel ... which is approx 6-7 tomes greater than valve lift!

And, it might make more sense for people with spatial orientation difficulties ... to have piston travel on the bottom, and visually at least twice as great as cam lift on the vertical axis ...

There is a similar graph in BA's book for cam timing.
Makes sense to me (even if it's somewhat out of scale), and helps one understand the concept of valve overlap.

Try putting a scale on the right for piston travel distance. Might help, but the one posted is fine with me at any rate.

Wayne,
Are you Japanese? You people love to explain technical concepts with graphs. :)

It might suffice to say (or add a caption to the chart) that the piston is closest to the valves during the overlap period (end of exhaust, beginning of intake) and piston is at TDC.

Sherwood Lee
http://members.rennlist.org/911pcars

Gee, correct me if I'm wrong...but if the synchronization is off? Yeah, valves CAN hit pistons? The illustration looked good to me...BTW, valves hitting pistons? Is that what is called an "interference" engine?

Wayne what you are showing is crystal clear to me.

Perhaps you should dredge up all the technical writting skills for this concept though. All the Porsche engineers could write is thecam timing procedure in the factory manuals..... not the easiest thing to grasp..

Your illustration clearly shows interference between the intake valve and piston......... not a good thing

I know your trying to open peoples eyes to the cam/piston relationship in the 911 engine.

beside the illustration you should mention the cams rotation in relation to the cranks...

then as a big tip to all the first timers........ let them know the dial gauge fluctuates wildly while timing the cams..... and that the reading is absloute.... positive or negative disregarded...... just look at the number when your done rotating the crank

Good comments, let me work on version 2 here...

-Wayne

Hey...maybe if we glue flint to the side of the valve....when it hits the piston it will create a spark!!
Far out...I just invented Flint Ignition!!
LOLOLOLOLOL
Bob

Bob, I think "we" need to go for a ride! :)

Piston should be on the bottom, valves on the top - that's how most people are used to thinking of it.

Might help to indicate compression stroke, exhaust stroke, etc too.

Finally, showing the crank and rod, valve and cam, in the appropriate positions might or might not add something - just a thought.

Sherwood, that's not correct! As the graph shows, at TDC, the valves may not be closest to the pistons. It's on the upward stroke that they are closest (of course, it depends upon the camshaft). That's the point I'm trying to make here - that the TDC point is *NOT* where you have to worry about interference!

-Wayne

It is an important art and science:

http://www.edwardtufte.com/448274615/tufte/

Highly recommended reading.

time the cams properly and you can look down the intake.. and rotate the crank and watch the valve follow the piston down. being able to describe the interaction between all these rotating parts is beyond me.....

Wayne I think you should just use points instead of clip art to illustrate the critical points

How's this?

http://forums.pelicanparts.com/uploa...e-engine27.gif

-Wayne

Nice! Now I don't have to stand on my head.

Say, Wayne.....it's almost September, the promised date of the B&W preview edition........we're waiting.

September has 30 days in it...

Odd, because I think of it backwards from how you guys think of it. When you're assembling the engine, the pistons are at the top, and the valves are at the bottom. If you stand next to the engine, and look down at it, the pistons are located above the valves...

-Wayne

Just wondering; if you flip the chart 180º, the components would be in their "normal" orientation - valves on top, piston on bottom. Most 4-stroke cycle charts are oriented in this way.

Sherwood