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[HELP] Exhaust valve!

  1. Aug 25, 2006 #1
    Hi,
    I'm a newbie :frown:
    Now,I'm studying about general engineering!
    And I had difficulty finding materials of EXHAUST VALVE.
    Everyone,can you help me?
    Where and how I can get them?
     
  2. jcsd
  3. Aug 25, 2006 #2
    I've always found the Bosch mechanical engineering handbooks to be awesome, but I'm not sure how much they have on the materials used.
     
  4. Aug 25, 2006 #3
    A good book that I picked up a couple of years ago is Internal Combustion Engines & Air Pollution by Edward F. Obert. It's VERY indepth when it comes to the math and may be a little too much if your taking just a general engineering course. The book is written towards teaching an engineering major the fundamentals (and advanced processes) of an ICE.

    Although written in the late 50's (maybe 60's) the majority of the concepts still apply today.
     
  5. Aug 25, 2006 #4
    In that vein, Heywood is also quite a comprehensive text and has been updated sometime in the last 50 years. ;)
     
  6. Aug 29, 2006 #5

    brewnog

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    While Heywood's is an excellent reference, it doesn't discuss engine design, and you won't find anything about exhaust valve material in there.

    Anyway, you'd be looking at some high temperature steel for a normal exhaust valve.
     
  7. Oct 17, 2006 #6
    most valves both intake and exhaust are cast iron
    there are many types of cast iron
    the cast iron used for the valves is also heat treaded so they can take the heat
    hope this helps
     
  8. Oct 17, 2006 #7

    marcusl

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    I think exhaust valves are never cast iron. Because of the need for strength in the high temperature and corrosive exhaust gas environment, they are alloyed (cobalt steel, stainless, etc.) and sometimes the stems are chrome plated (or even a different steel altogether) for wear resistance. Only cylinder blocks and heads are cast.

    Look up 21/4N stainless and stellite
     
  9. Oct 21, 2006 #8
    Porsche and other auto manufacturers have experimented with sodium filled exhaust valves. The new Chevrolet Z06 has them i believe.
     
  10. Oct 21, 2006 #9

    moo

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    This is not a new idea, some older Ford and GMC truck engines had sodium filled valves. Always easy to spot because the stems are much thicker than normal. :wink:

    moo
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    Last edited: Oct 21, 2006
  11. Oct 21, 2006 #10
    Oh it's deffinately nothing new. Porsche was experimenting with it back in the 60's and the original idea came up long before that. It's just neat that it's made its way into mass production vehicles.
     
  12. Oct 21, 2006 #11
    Nickel and Nitrogen are also popular to alloy with.
     
  13. Oct 21, 2006 #12

    Danger

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    And some race motors use titanium, but it's not practical for street use (cost-effectively, I mean).
    I wonder how long it will be before they start using plastic. The good stuff, such as Torlon, is already being used for rods and pistons.
     
    Last edited: Oct 21, 2006
  14. Oct 21, 2006 #13

    moo

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    Actually seems a bit odd that sodium valves would be considered in hi-perf engines, as the idea is generally to keep the valve train light as possible. But stranger things have happened.

    Hey Danger - I dunno about plastic valves, the outer edge of exhaust valves stay pretty much red hot at high RPMs. I had heard about plastic rods, but wasn't aware of any used for pistons yet.

    But there's a lot of stuff I'm not aware of... :biggrin:

    moo
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  15. Oct 21, 2006 #14

    Danger

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    I'm not sure if the pistons are out of the experimental stage yet. As far as I can recall, they were plated with aluminum or such for flame resistance... at least on top. I would expect that if they ever do go to plastic valves, the same would apply. I should point out that I get sloppy with terms in cases like this. When I said 'plastic', that includes composites like Kevlar or carbon fibre materials. I suspect that carbon, with perhaps a vapour-deposition coat of something like nickel, would be suitable.
     
  16. Oct 21, 2006 #15

    moo

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    Another problem with plastic valves is prolly the thin stem. I know the rods are beefed up a lot compared to steel/aluminum, although still lighter of course. Not much room to add bulk to a valve stem without hindering air flow though.

    A little off topic here, but one experimental design I find particularly intriguing is solenoid operated valves, which eliminates the need for a camshaft and the hp needed to drive it. Not to mention the practically instant open/close action compared to the travel time lost on a cam.

    moo
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  17. Oct 21, 2006 #16

    That technology is really cool. I know pneumatic valvesprings have been used in F1 Indycar engines for a time too. The parts that i really find interesting is the fact that you could throttle the engine its self simply by "throttling" the intake and exhaust valves. The engine would also have excellent cylinder filling ability throughout the entire rev range. A constant "perfect cam" in a way. They could also shut down extra cylinders when the additional power isn't needed, helping fuel economy. A much better way than the old Displacement On Demand technology. The valves are actually held closed and the air that's trapped in the "dead" cylinder acts somewhat like a spring during the cycle and doesn't make the cylinder as much a dead load.

    After thinking about it for a second, I don't see why you couldn't just rid of an engine starter all together... open a couple of the valves just enough to let a little air in, squirt a little fuel, spark the chamber... boom.
     
  18. Oct 21, 2006 #17

    Danger

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    That has got to be the first time in my life that I've ever heard that suggestion, and it makes perfect sense (well, with injectors; it wouldn't work with a carb).
    Well, there's also the possibility that it wouldn't be too effective in my territory in winter. It takes more than that to get something turning over in -40 temperatures.
     
  19. Oct 21, 2006 #18

    moo

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    Well... first there's the nightmare of monitoring various positions the engine might have stopped at, and picking a piston in the proper range (we can't crank it backwards). And it's possible that occasionally none would be in that proper position.

    But without compression, it's more likely to just start a fire (or make a "poof" rather than a "boom" with enough force to turn the engine).

    moo
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  20. Oct 21, 2006 #19

    Danger

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    Actually, moo, there's no problem to determining the engine position; just take a reading from the distributor. And if it's any kind of a decent engine (ie: 8 or more cylinders; all else is crap), at least one of those pistons will be near the start of a power stroke.
     
  21. Oct 22, 2006 #20

    moo

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    Uh... read what exactly? Something would have to register tiny increments because it won't know where the engine stopped, and without movement there's no induced current.

    And then there's all those cars without distributors (especially a camless one!)... :biggrin:

    [EDIT] Btw - even with 8 cylinders, only every other stroke is compression, so odds aren't that low for none to be near the top of one. Although I guess with electronic valves ya could turn an exhaust stroke into compression if necessary, then just change all the others to stay in sync.

    But there's still the absence of compression, unless ya add something to move the piston. Like... oh, I dunno... maybe a starter? :smile:

    moo

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    Last edited: Oct 22, 2006
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