Got me baffled

[Mike S]

I have a question for the VAF collective mind-----(AKA, VAF database).

My cyl head temps are a bit higher than I would like, and I am thinking of a possible fix by making a set of inter cylinder flow diverters.

Here is the area where I think a problem exists---



As can be seen, there is a large gap between the cyl bases, and the cyl fins.

I know that air, like water and electricity, is lazy and will take the path of least resistance, so I am thinking of blocking off the non finned area, and diverting the airflow in the finned area so it must go through, and not around, the fins.

My idea here is that in addition to the cyl fins getting better airflow, the fins on the head will also see increased air, and thus better cooling.

The next photo shows a paper pattern for the proposed baffle/diverter.



And here is a shot of the two areas for comparison.



Comments appreciated.

[TS Flightlines]

and is it a new engine??
Tom

[Mike S]

No, first runout/rebuilt.

I did not do the engine, came with a project, so I have no idea what should be there, if anything.

[DanH]

Mike,
Don't think you want to do that. As I recall the goals are either maximum turbulence at the open fins or all flow held between the fins. The NACA covered cylinder baffling pretty well in the 30's and 40's. Do some searches on the NASA reports server.

http://ntrs.nasa.gov/search.jsp?No=1...99985&as=false

FWIW, you may not need mods. Really seal all the baffle gaps first.

[RV7ator]

Ummm... I don't think that will help your CHTs.

There's something to be said for moving a volume of air around the cylinders as well as through the fins, and the bases get hot too. They are deserving of cooling air even though they don't have fins.

Also, what air does squeeze through the fins beneath your baffle will simply expand into the void between the cylinders after exiting beneath your baffle. Squeezing then expanding the air only adds resistance to flow as well as reducing the total volume. If the fins were completely jacketed around their circumference you may be on to something, and having typed this I believe someone did at one time attempt such a baffle system. Can't remember the outcome, but if it worked I should think the concept would have gone viral.

John Siebold

[Mike S]

Originally Posted by DanH

FWIW, you may not need mods. Really seal all the baffle gaps first.

I have gotten them sealed up pretty well, right now I am working on the casting flash between the fins in the area between the valves, and plugs. I am probably getting close to a 100% increase in open space by removing the flash.

Should help a bunch, this is one of the things I have found by searching for cooling issues.

[Mike S]

Here is a shot of the kind of baffles I am thinking of-----found these on a BD 4 builders site.

I think these are factory units???----A buddy described something just like these on his O 235 Pacer engine.

http://www.old.bd-4.org/images/build...050323-449.jpg

[DakotaHawk]

Mike, if you just passed 25 hours, you still have some "break-in" time for your cylinders. My re-honed cylinders ran about 400 - 425F for about the first 50 hours or maybe even a little longer. With 190 hours on my engine, the temps are finally starting to come down to about 375F when I run hard, and 350F when I back off in cruise.

Oil consumption is the best indication of break-in. When you can go 25 hours without adding a quart, you're just about there. I'm going about 20 hours before adding a quart now, so I guess I'm getting close.

[DanH]

Originally Posted by Mike S

Here is a shot of the kind of baffles I am thinking of

The inter-cylinder baffle on the left? Yes, that's an approach to routing flow between the fins.

Same concept, different approach....9oz plain weave glass saturated with Loctite 598 silicone. This shot is from the bottom; the wrap extends up to about the 280-80 degree point:

[Mike S]

Originally Posted by DanH

The inter-cylinder baffle on the left? Yes, that's an approach to routing flow between the fins.

Yes, the ones between the left cyls.

Originally Posted by DanH

Same concept, different approach....9oz plain weave glass saturated with Loctite 598 silicone. This shot is from the bottom; the wrap extends up to about the 280-80 degree point:

I saw that when I was searching cooling issues in past threads. Also, there are some shots of the same style of wet layup baffling from a Long Eze------but then it is updraft cooling.

What you have done is not going to be easy with the engine installed/baffled, which is why I am looking to an alternate method.

Going back to the original statement of air being lazy, I am just trying to re-direct the path of least resistance to somewhere the air flow will do the most good, and is most needed.

The cyl bases are cooled by the oil for the most part, consider a lot of designs using plenums dont even have any air over the crankcase or cyl bases.

Thanks for the input everybody, keep the ideas comming.