Cylinder head plenums

[MarkW]

I have seen the typical plenums used like the James cowl and plenum but have not seen a discusion or pictures of the cylinder head only plenums like I saw on a new LSA using the new Lycoming 0-233. Very good looking setup as it doesn't cover the top of the engine, only the cylinder heads. I like the idea of covering the fuel spider and the one I saw looks like maintenance would be a lot easier along with removal.
Has anyone seen these on the I0-320 or 360.
Any ideas or comments?
I haven't even been able to Google a picture of one.

[RV8RIVETER]

They have been done. Paul Lipps did that on his Lancair, you can see pictures here. http://www.eaa.org/experimenter/arti...9-09_lipps.asp

I am in the process of doing mine that way. I have the cylinder wraps done, but still need to make the inlet guides and flow dividers as well as the outlet collector.

[Bubblehead]

I've thought about the same thing. Here are some pictures to get the creative juices flowing.

[DanH]

Originally Posted by MarkW

...a discusion or pictures of the cylinder head only plenums like I saw on a new LSA using the new Lycoming 0-233......
Any ideas or comments?

Most of the examples in the photos exhibit a typical design problem...they don't seal very well at the inlet. The whole point of using a plenum is sealing, i.e. not allowing any of the cool, high pressure inlet air (roughly a range of 6 to 26 inches H2O) to reach the lower cowl volume without passing in close proximity to a hot engine surface. Every bit of air which leaks through those crappy inlet seals is pure drag. Doesn't matter very much on a 100 knot airplane, but most of us would prefer a 200 knot airplane.

Now look at the photos of the fancy carbon "plenums" on the 233. Do they seal well, for example, around the pushrod tubes? Sheesh.

Also note they are one piece; no split between cylinders. Not good.

Yes, well fitted individual plenums with sealed intakes are possible.

A full plenum (or stock baffles) circulates relatively cool air around the spider and injector lines. Fuel pressure in them is quite low, and low pressure increases the possibility of boiling.

A full plenum also increases the deltaT between much of the engine case surface and cooling mass. Even the non-finned surfaces shed heat.

Notes about Paul's Lancair; those tiny inlets were possible only because the system was heavily exhaust augmented. That aside, take note of Paul's typical focus on fundamentals...the ducting wrapped around the entire circumference of both cylinder and cylinder head. He wanted cooling air in tight contact with the maximum hot surface area. His goal (and yours) is to raise air temperature as much as possible during the pass by the engine. It means you carry away more heat with less mass...the other reason he could use the tiny inlets.

[Grezdlitn]

I'm biased towards the full plenum as I have been running one on Grezdlitn for eight years now. I've only been compelled to remove it once, to check the plugs. The fuel injection spider and related lines don't require any maintenance
unless you are experiencing an issue.

If your going to build a plenum there are fewer steps required in building a full one as compared to two individual.

I'm with Dan on the air inlets! Strive to create a transition that utilizes 100% of the cooling air entering the inlets. I just helped with a project where we created some inlets very similar to the "Sam James" only out of fiberglass.

[LifeofReiley]

The split cylinder plenums have been tried by many, I don't know of any that were a real success.

[RV6_flyer]

Is anyone using one on a flying RV? How well does it work?

Unfortunately there have been a lot of aviation ideas that have been good ideas or that looked good but did not work well.

[LifeofReiley]

Mark Phillips worked through two different set-ups on his RV-6A "MOJO" you can read more here:

http://websites.expercraft.com/n51pw...ry&log_id=4996

He does nice work!!

[RV8RIVETER]

Originally Posted by LifeofReiley

The split cylinder plenums have been tried by many, I don't know of any that were a real success.

Paul Lipp's. The AR-6. Both of which cooled TOO much on the first attempts.

The devil is in the details. The cooling system is not just a type. Stock works for some, plenums for others, then the opposite for both by others. It should be looked at as an entire system. Answer questions like; where is the air coming from, how much, what speed, where does it need to go, how to get the most BTU's out of the cyl, how do you get it back into the free airstream?

[RV6_flyer]

Originally Posted by LifeofReiley

Mark Phillips worked through two different set-ups on his RV-6A "MOJO" you can read more here:

http://websites.expercraft.com/n51pw...ry&log_id=4996

He does nice work!!

But there is no flight data listed to know how well it worked.