Tip: Cylinder Air Dams

N941WR · #1 07-04-2012, 02:52 PM

The new baffle kits (You know you have the old baffle kit, if the drawings are hand drawn.) include air dams that get riveted in so as to deflect the air up and over the heads of #1 and #2 cylinders.

The only problem is that they are riveted in place and if you need to adjust them, and you will need to adjust them, you have a problem.

My suggestion is to replace the rivets on the ramps leading to the cylinder heads with flush rivets and platenuts. Then you can make a simple air dam that uses those three platenuts and when you need to adjust the air dams, you can remove them, trim them to size (or replace them, when you trim too much off), and screw them back in place. Remember, that the left and right air dams will be different because the platenuts will be in different places, if you put them where the rivets are supposed to go.

The other option is to forgo the air dams altogether and use foil tape, available at your local hardware store.

humptybump · #2 07-04-2012, 07:03 PM

Perhaps a niave question but I'm going to ask it anyway ...

"what is the purpose of the air dam ?"

Kyle Boatright · #3 07-04-2012, 07:09 PM

Quote:

Originally Posted by humptybump

Perhaps a niave question but I'm going to ask it anyway ...

"what is the purpose of the air dam ?"

To reduce the cooling air to the front cylinder(s) and deflect that air to the rear cylinder(s). Say your in-flight CHT's are 340F on #1, 350F on #2, and 380F on #3 and #4. The goal would be to install air dams of sufficent height on #1 and #2 to balance all 4 cylinders at (say) 360F.

N941WR · #4 07-04-2012, 07:18 PM

Quote:

Originally Posted by Kyle Boatright

To reduce the cooling air to the front cylinder(s) and deflect that air to the rear cylinder(s). Say your in-flight CHT's are 340F on #1, 350F on #2, and 380F on #3 and #4. The goal would be to install air dams of sufficent height on #1 and #2 to balance all 4 cylinders at (say) 360F.

Or in the winter to block more air to get the CHTs up by putting in taller blockers.

humptybump · #5 07-04-2012, 07:31 PM

Thanks Kyle.

I wanted to ask the question because I have done several searches lately for "low CHT" and found nothing. My CHTs have almost a 100F separation with the low one being around 260F in cruise and the high one at 355F.

I will be checking plugs, etc. this week but if I find nothing, I will plan to play a bit with air dams.

Kyle Boatright · #6 07-04-2012, 07:36 PM

Quote:

Originally Posted by humptybump

Thanks Kyle.

I wanted to ask the question because I have done several searches lately for "low CHT" and found nothing. My CHTs have almost a 100F separation with the low one being around 260F in cruise and the high one at 355F.

I will be checking plugs, etc. this week but if I find nothing, I will plan to play a bit with air dams.

You might swap around your CHT probes too. Occasionally you get a bad one. If Cylinder #3 (or whatever) is the high (or low) one and you move that probe to another cylinder and that one becomes the outlier, the probe may be the problem...

RV6_flyer · #7 07-05-2012, 03:05 AM

I had Superior investment cast cylinders and #2 was the coldest even with the temperature risers. Replaced cylinders with ECI cylinders after 2,200 hours and now #2 is a lot hotter. Removing the temperature riser and it is very close to the other three. #1 still has the temperature riser installed. This is with an O-320 CS.

Note: The ECI cylinders are the through hardened steel barrel just like the Superior was. The Superior through hardened steel cylinders still showed the cross-hatch hone patter and measured out new spec including the choke.

shuttle · #8 07-05-2012, 05:03 AM

Quote:

Originally Posted by N941WR

My suggestion is to replace the rivets on the ramps leading to the cylinder heads with flush rivets and platenuts.

Yep, good idea Bill. I did that with mine too. It is especially easy for the horizontal cold air induction engines (the ones that use the snorkel to take air from the No.2 cylinder front baffle ramp) as there is already a need for screws in that area to hold the air filter in place. Though I kept the original rivets and positioned the three screw holes between the rivets. I needed to matchdrill the rivet holes to the flange on the bottom of my air dam then oversize them enough to provide clearance for the rivets. Did likewise on the other side.

Steve

LettersFromFlyoverCountry · #9 07-05-2012, 06:32 AM

I just cut my down last week. Took about 1/2" off and it's pretty much evened out the temps.

I was going to pull the baffle off and go this route but Stein Bruch gave me a piece of stainless and said "put this behind it and cut it with a Dremel; it'll be faster."

I could probably cut more down more, but I want to see what winter brings -- assuming that winter ever comes to Minnesota again (it didn't last year).

LettersFromFlyoverCountry · #10 07-05-2012, 06:34 AM

Quote:

Originally Posted by humptybump

Thanks Kyle.

I wanted to ask the question because I have done several searches lately for "low CHT" and found nothing. My CHTs have almost a 100F separation with the low one being around 260F in cruise and the high one at 355F.

I will be checking plugs, etc. this week but if I find nothing, I will plan to play a bit with air dams.

Fuel injected?