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Got me baffled

Mike S

Mike S

Senior Curmudgeon
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---:confused:

P2070024.jpg


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.

P2070023.jpg


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

P2070028.jpg


Comments appreciated.:)
 
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.
 
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
 
DanH said:
FWIW, you may not need mods. Really seal all the baffle gaps first.
Click to expand...

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, 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.
 
Mike S said:
Here is a shot of the kind of baffles I am thinking of
Click to expand...

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:

29mp0lc.jpg
 
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DanH said:
The inter-cylinder baffle on the left? Yes, that's an approach to routing flow between the fins.
Click to expand...

Yes, the ones between the left cyls.

DanH said:
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:

29mp0lc.jpg
Click to expand...

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.
 
Mike,

Just removing the flashing alone will drop the temps a lot. I saw about a 25 degree difference before and after. Another thing to consider is to make sure all you've sealed up everything. Some areas that cause issues on the RV-10 are around the prop gov, at the inboard area of the intake air ramps and around the upper engine mounts.

Most folks also wind up trimming or removing the air dams but that really should be saved for balancing the front vs. rear cylinders and not overall cooling.

Maybe I missed it, but I didn't see if this was an issue only during climbs. I saw in your pictures that one shot had very high temps - in the low-mid 400s but around 45 minutes into a flight at 4500 feet and another picture with reasonable temps but only 20 or so minutes into a flight.

If during climbout you might consider a little shallower climb - Try using 110 or even 120 kts unless geography dictates something more aggressive.

Bob
 
bcondrey said:
Mike,

Just removing the flashing alone will drop the temps a lot. I saw about a 25 degree difference before and after. Another thing to consider is to make sure all you've sealed up everything. Some areas that cause issues on the RV-10 are around the prop gov, at the inboard area of the intake air ramps and around the upper engine mounts.
Click to expand...

The upper mounts are sealed. The intake ramps are sealed, and the governor area is just a nightmare, but as good as I can get it.

I am really hoping for good results with the flashing exorcism.

bcondrey said:
Most folks also wind up trimming or removing the air dams but that really should be saved for balancing the front vs. rear cylinders and not overall cooling.
Click to expand...

Yep, took a quarter inch off the right side, but I want to make sure the rest of the system is optimal before I go to far with the air dams.

bcondrey said:
Maybe I missed it, but I didn't see if this was an issue only during climbs. I saw in your pictures that one shot had very high temps - in the low-mid 400s but around 45 minutes into a flight at 4500 feet and another picture with reasonable temps but only 20 or so minutes into a flight.

If during climbout you might consider a little shallower climb - Try using 110 or even 120 kts unless geography dictates something more aggressive.

Bob
Click to expand...

I have been using 120 MPH as a climb speed, got that from Mike Seager when I did the transition training. Things do cool off when I go to cruise-----but still for the air temps this time of year, I would expect lower.

Good eye picking up the info on the panel shots.

Thanks for the input,
 
Inter cylinder baffles

Here is another picture of that weird inter cylinder baffle you found on that BD site. There are two, an upper and lower which wrap around the cylinder fins

rightsidebaffe.jpg
 
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Do you have the gap under the ramps on the top cowl plugged so air can't pass under them?
 
N941WR said:
Do you have the gap under the ramps on the top cowl plugged so air can't pass under them?
Click to expand...

Yes, it is plugged----at least on the non governor side---on the side with the gov, it is a bit of a problem. I am going to fill the entire area with spray in foam, and carve out the area for the gov.

The outer end of both ramps is glassed into the top cowl.
 
Mike, something you might try.... don't pull it back to 25 squared. I know.... we were all taught that. Just pull back the prop to 2500, and leave the MP alone until level off. Then set the power you want. If it's still above 25", then pull it back if you want to run less than 75%. I have always run my c/s propller-equipped engines this way. If you think about it, it's the way we would run them if we had a fixed pitch prop on the front. I have never had any cooling problems. And climb rate is faster, which gets you to level off and cooler air much sooner.
Your fuel flow looks right for a normal IO-540.

Vic
 
vic syracuse said:
Mike, something you might try.... don't pull it back to 25 squared. I know.... we were all taught that. Just pull back the prop to 2500, and leave the MP alone until level off. Then set the power you want. If it's still above 25", then pull it back if you want to run less than 75%. I have always run my c/s propller-equipped engines this way. If you think about it, it's the way we would run them if we had a fixed pitch prop on the front. I have never had any cooling problems. And climb rate is faster, which gets you to level off and cooler air much sooner.
Your fuel flow looks right for a normal IO-540.

Vic
Click to expand...

Vic, thanks for the hint.

This is my first time with a plane that has the blue knob----so I am still figuring out the best methodology for its use. Also, first fuel injected engine.

One other factor, I have the ram air setup from Rod Bower, and that is giving me an inch +/- more MP when I open it up------usually still in climb out phase.

I am reducing the MP based on the ram air being open---hope that is the way to do it??
 
Mike, just don't reduce it in the climb. Leave it alone, and then set it for cruise at the power setting you want. Basically the Rod Bower system will give you some increase, but just set it to the number you want after level off. If you reduce it to 25" in the climb, you are just eliminating some of the available power, whether the ram air is open or not.

Vic
 
Mike S said:
I am reducing the MP based on the ram air being open---hope that is the way to do it??
Click to expand...

No. Think about it Mike....why open the filter bypass if you're going to reduce MP with the throttle? Better to throttle it with the filter....unless of course you like unnecessary engine wear.
 
DanH said:
No. Think about it Mike....why open the filter bypass if you're going to reduce MP with the throttle?
Click to expand...

Because the filtered air is taken from inside the hot side of the cowl----I use the filter on the ground, and then open the ram air valve in flight.

Perhaps I was less than clear in my prior post-----what I am trying to determine is when setting the power/prop at "25 squared" (as an example) should I set the MP and then open the ram air, thus gaining a bit more MP, or should I open the ram air first, and set the MP based on what I am gaining with the ram air??

Here is my setup, in case anybody is interested.

http://www.vansairforce.com/community/showthread.php?t=40855&highlight=cowl+mod&page=3
 
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