Ford has three valves per cylinder!

[XS650]

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Originally posted by Jimbo:
As far as I can tell, it is two intakes and one exhaust for greater intake area within the same bore. This slightly odd three-valve setup makes some sense because they wanted to keep with the cheaper single cam setup and four valves would probably not package well in a single cam head.

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It also makes sense because engines want more intake valve area than exhaust.

3 valve heads give most of the valve area gain of a 4 valve head. Assuming my trig and geometry was correct and my simplifying assumptions reasonable...

A 3 valve head potentially give about a 30% valve area advantage over a 2 valve head.

A 4 valve head potentially gives about a 37% gain over a 2 valve head.

 

[jtantare]

quote:

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Originally posted by XS650:
It also makes sense because engines want more intake valve area than exhaust.

3 valve heads give most of the valve area gain of a 4 valve head. Assuming my trig and geometry was correct and my simplifying assumptions reasonable...

A 3 valve head potentially give about a 30% valve area advantage over a 2 valve head.

A 4 valve head potentially gives about a 37% gain over a 2 valve head.

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Ah but you are forgetting one thing. Total valve area is irrelevant. Its all about circumference X lift. Air doesn't flow through the valve. It flows around the valve to get the combustion chamber.
I think the Coates valve has a lot of potential if they ever figure out their lubrications problems.
http://www.coatesengine.com/technology.html

 

[XS650]

quote:

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Originally posted by jtantare:
Ah but you are forgetting one thing. Total valve area is irrelevant. Its all about circumference X lift. Air doesn't flow through the valve. It flows around the valve to get the combustion chamber.

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You are correct, but the 3 valves still show the lions share of the improvement.

Assuming the same lift.

2 valves = 100% (total valve circumferance)
3 valves = 139%
4 valves = 165%

 

[jtantare]

quote:

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Originally posted by XS650:
You are correct, but the 3 valves still show the lions share of the improvement.

Assuming the same lift.

2 valves = 100% (total valve circumferance)
3 valves = 139%
4 valves = 165%

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These numbers sound much closer to real examples. But keep in mind there is a lot of variation in valve size between similar 2 valve and 4 valve designs. It depends on pent roof, quech area etc... Also 4 vavle heads usually have less lift than a 2 valve head. There are always exceptions to the rule.
What valve sizes are you using to come up with these number?
I would still take the 4 valve

 

[Palut]

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Originally posted by FowVay:
Palut, you may have experienced a poor example of this engine. The engine in my Accord performed incredibly well. It wasn't rated for high horsepower (in the 80 hp range I believe) but it seemed to be a perfect compliment to the higher torque output (120lb.ft to the best of my memory).

I do recall that it specified valve adjustments every 30,000 miles which were very simple with the threaded tappet design. Being a design of the 80's era the underhood looked like a bowl of spaghetti with a plethora of vacuum hoses connecting the carburetor to control solenoids.

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The engine in that car ('85 Accord LX sedan) has 86 hp at 5800 rpm, and 99 ft/lbs at 3500 rpm. By gutless, I was meaning that when that car is in 5th at freeway speeds, it has very little power. If you drop down to 4th and wind it up a bit, then its not bad.

Around town, it has a great amount of oomph for an engine that size, and is a lot of fun.

Of course, by the time I could drive, the car already had 180,000 miles on it. Its now at 238,000 and going strong!

 

[Shannow]

quote:

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Originally posted by jtantare:
I think the Coates valve has a lot of potential if they ever figure out their lubrications problems.
http://www.coatesengine.com/technology.html

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I like the simplicity of Arthur Bishop's system referred to at the bottom in patents.

When I was doing my thesis, I got to spend time at their test lab, watching the single cylinder test mule.

The rotation of the valve sort of "self stratified" the charge, flinging a fuel rich zone at the plug, with quite lean bulk mixtures.

BSFC was around 0.42

 

[brianl703]

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Originally posted by Eric Smith:
Alot of it may come down to the design the engine, intake/exhaust manifolds though.

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The 4-valve-per-cylinder Duratec V6 engines use a shutter assembly in the lower intake manifold to close off the intake passage to one of the valves in each cylinder at lower engine speeds, which improves torque. The intake passage, or runner, is longer for the valve which is not closed off. At higher engine speeds the shutter assembly opens up the shorter runner to the other intake valve, improving torque at higher speeds.

Ford calls this "intake manifold runner control". They said, at the time that it came out in 1995, that the Duratec engine makes 75% of peak torque at 1500RPM. I think the first application of IMRC was the 4.6L V8 in 1991, though.

I've driven my car with the IMRC disconnected. It makes a very noticeable difference. It feels like the engine lost 20HP.

 

[Jimbo]

As far as I can tell, it is two intakes and one exhaust for greater intake area within the same bore. This slightly odd three-valve setup makes some sense because they wanted to keep with the cheaper single cam setup and four valves would probably not package well in a single cam head.

Ford may use the word torque as much as they want in advertising, the trucks I have driven with that engine still feel gutless. GM and Dodge use a two valve pushrod setup with better results, and no blow-out spark plugs. Ford cant seem to decide if it wants to be complex and "high tech", like Toyota and Nissan, or simple like its "domestic" competition.