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Three-valve heads

Three-valve heads

Three-valve heads

(OP)
Can anyone point me to modern automotive engines that have one intake valve and two exhaust valves?
 

- Steve

RE: Three-valve heads

(OP)
Me neither.  I saw an engine simulation model recently that was built like this, which got me wondering.  Maybe the model had a simplified intake system for some reason, but needed the full exhaust?

- Steve

RE: Three-valve heads

I owned a 1986 Honda Civic SI that had a 3-valve head. It was a 1.6L 4 banger, but I don't recall the exact engine designation.

RE: Three-valve heads

It might have been a not-fully-developed model as you suggest, but alternately I can absolutely visualize a boosted engine, probably a diesel, where the exhaust valves are independently actuated.  That is exhaust valves with individual ports, one plumbed to the turbo, and the other to the EGR circuit.  Then with control over valve actuation you can select whether you utilize the pulse energy for the turbine or to increase the EGR flow.  ~50% EGR flow is by no means out of the question for modern diesels.

PJGD

RE: Three-valve heads

The Civic engine (and every other 3-valve head that I've ever heard of) used two intake, one exhaust per cylinder.

RE: Three-valve heads

look at fords 6.8l v-10 3 valve dual overhead cam

RE: Three-valve heads

There was a 3 valve version of the Saturn 4cyl but it was two intake one exhaust. Two exhaust valves can run at a higher compression/expansion ratio for a given fuel octane rating because the exhaust valve temp. will be lower. You could achieve a single intake dual exhaust vavle configuration by simply eliminating the lobe needed to provide lift to one of the intake valves in a four valve head.-------Phil

RE: Three-valve heads

(OP)
I like PJGD's thinking.  Possibly something the OEM's (and independent consultants) are running in their test beds...

- Steve

RE: Three-valve heads

I believe that Borg-Warner are developing something along these lines with a concentric camshaft within a camshaft which allows one exhaust valve to be advanced or retarded relative to the other.  I think they call it VEMS(?).

PJGD

RE: Three-valve heads

(OP)
I've been told that Honda's "Wet Dream" engines: the CB250N and CB400N have this arrangement.  Sounds dubious.  I've been WWW-surfing, but cannot find any evidence.

- Steve

RE: Three-valve heads

There was a generation of Honda CB400/450 engines that had three-valve heads, but they were the conventional arrangement with two intake and one exhaust. The generation in question started in 1977 and continued through the mid-eighties.

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