Intercylinder Baffle Mod - Mixed Results

[David Paule]

Would rounded entry shapes help, or nozzle shapes at the exit? After all, there's air moving through there.

Dave

[MarkW]

Great work Michael and I am surprised I am beating Dan to this comment.
I know it is more work but having cowl pressures before and after would help determine what is happening to overall mass flow.

[BillL]

Originally Posted by MarkW

Great work Michael and I am surprised I am beating Dan to this comment.
I know it is more work but having cowl pressures before and after would help determine what is happening to overall mass flow.

Ya see - Dan has us trained!!

Nice work Michael, but as you know, higher pressure will force more air through remaining "leaks" like oil coolers, alternator and mag blast tubes. Do you have those and/or a plenum? Average rise = 10F, but drop was -27F. Balancing the airflows should reduce the rise to a drop and give extra speed too (lower mass flow).

It is good to be reminded (of the balance), though, as I was standing just yesterday looking at that area and wondering . . .

Looking forward to your progress, maybe round the edges of the risers as air won't just go straight down.

[Toobuilder]

I'm working with the asumption that most of the forward momentum of the incoming air (or is it better to say horizontal velocity?) is pretty low by the time it has made it past the front cylinders. I'm thinking most of the air in the upper cowl is essentially stagnant, but under ram pressure and looking for an easy way out. The rounded inlet I created by wrapping the pushrod tubes should be very inviting to air looking for an escape path. However, the shrouds do reduce volume quickly right down to fin height and remain that way for most of the circumference of the cylinder. Its this aspect that likely poses the most significant throttle to the system. With the heads retaining essentially the standard baffle configuration, the only other change is the fact that all other leaks were sealed - and that is always a good thing.

I believe that the cylinder wraps need more volume and yes, a better exit design.

Stay tuned!

[rfrost]

This topic is timely for me, as I am working on improving the cooling on my 9A. I am currently reworking my plenum and haven't started on inter-cylinder baffles yet, but am very interested in your results. In reading about the issue, I came across the link below which references five NACA reports on engine cooling and also discusses what the author considers the high points. I found it his summary informative and thought you might also be interested.

Rick

http://x-jets.com/a_cooling_efficiency.html

[Toobuilder]

Excellent!

Thanks for posting that info Rick... That has given me a few more pieces of the puzzle.

And if you do decide to stick with the stock intercylinder baffles, make sure you spend a pit of time tweaking them to seal better. A bit of bending, speed tape and RTV goes a long way towards plugging unwanted holes. Best to do this before the engine is hung.

[rfrost]

Michael, Good advice about doing the intercylinder baffles before the engine is hung, but a little too late ... I'm just finishing up Phase 1.

Rick

[crabandy]

i'm at the point of piddling some more with my baffling as well. I put new lycoming nitrided steel cylinders on just over 10 hours ago. Oil consumption seems to have stabilized and I seem to run about 20-30 degrees hotter than my previous chrome cylinders that the rings never seated on.
When I put the new cylinders on I also added some silicone baffle wraps A-La-DanH. I think at this point the higher temps have more to do with the baffle wrap than the newer cylinders.

The wrap between cylinders 1/3...


The wrap on the front of 1...


I wondered if the square edges of the baffle wrap to fins cause some turbulence inhibiting air from entering the fins as well as less volume (140* top side exposure per Rick's post).

I'm thinking about adding a radius like this 1 inch aluminum tube between the cylinders and wrap the silicone baffle material over the top to help the air flow, it also exposes more area on top of the cylinder. From Rick's post my fins are .5 inch deep so my radius should be larger than .5, perhaps .75.




I'm also thinking of adding a radius at the front of the front cylinders and the rear of the rear cylinders with the tubing cut in half. I'm curious about using automotive heater hose/radiator hose with the right diameter, easier to source and shape than the aluminum tubing.

[flyingriki]

Made all my cylinder wraps from metal since they are parallel and easy to curl the ends.
Made all the head wraps with two layers of Bid wetted put with JB Weld for epoxy. Good to 550 degrees, can be trimmed and painted. Used an old cylinder for mold, covered it with packing tape.
If you're interested I can send you some photos.

[BillL]

The rounded inlets for the cylinders don't have to be that strong, so I am considering using 1100 from the rack at the hardware store. It rolls around a 5/8" dwell just fine. Maybe even 1/2" with spring back.