3 Valve Engine?

[Ross]

I've read about 3 valve engines, and I'm pretty confused, as usual. I understand with a 2V desig, there is one intake and one exhaust valve per cylinder. With a 4V design, like ours, there are two of each. How the heck does a 3V work?

[Agent M79]

From what I understand, it is 2 intake, 1 exhaust. The 2 intakes are individually a little smaller in diameter than the single exhaust valve.

[TripleTransAm]

I can understand the benefit of 2 smaller intake valves over a large one... you want some turbulence and swirl in the mixture as it enters the chamber for better and more controlled burn and less chance of detonation/knock. For the exhaust, you just want to move it out as fast as possible (within limits, of course). Notice I said mixture, since turbulent air before the injectors shouldn't really make a difference...

I saw the 3 valve head up close in 2001 when I was in the Chicago area on business. It was undergoing gasket design and testing, and the testers were very enthusiastic about this head, especially in dyno testing. At the same time, quality control is hopefully better nowadays at Ford... I also heard from another source that dyno testing at their facilities showed inconsistent power output.

[RCSignals]

Seems they put the 3 valve design heads into use in Australia first. (Beta testers?) It is now a "proven" design, and used in the 5.4 engines of the '04 F150s

[bigslim]

Mercedes went to this design a couple of years of ago. They have been getting more horsepower too.

[Mad4Macs]

Anyone remember these things?
http://www.flash.net/~lorint/lorin/
1 liter, 3 cylinders, 70 HP with turbo :rolleyes:

[RCSignals]

:lol: We are talking three valves not three cylinders ;)

But yes, those were very weird

[MapleLeafMerc]

As long as it means more horsepower, I'm on board.