RV-9 floatplane high cylinder temps

[questair]

I have about 20 hours on the 180 HP RV-9 floatplane and have an issue with high cylinder temps. Rear cyls go to 440 on climb out. Fronts are fine. Have experimented with dams but no change. Changed to -41 carb which helped a bit, but not enough. Baffling is very good and it was always fine on wheels, but with slower speeds in all configurations on floats temps are a bit too high. OATs in Anchorage are generally cool, 70 or so. anyone have any ideas? Am thinking of louvers on each side of bottom cowl, maybe opening bottom a little more. I now have to level off and reduce the power to get temps down 75% level cruise and rears go to 415. Help.

[flyinga]

A neighbor has an RV-6A parallel valve O360 that had CHT problems. He copied the vents in the lower cowl of most Bonanzas; the "v" shaped ones not the straight ones found mostly on the turbo'd madels. Fixed the problem. It was a simple and elegant solution.

[turbo]

how about some nice pics of your float plane in alaska? how is the performance?

[ajay]

Louvers will probably work, but before you do check out Tim Olsen's suggestions;

http://www.myrv10.com/N104CD/mainten...022/index.html

even beads of RTV between cylinder heads can help

make sure your baffling is making a good seal, get a flashlight in under the cowling if you can, rub your hand around

[questair]

here is a picture: http://www.flickr.com/photos/bob_butcher/5989426778

The baffling is very tight. Have put a washer between rear baffling and rear cyl. have experimented with dams. No help. the -041 carb kit helped quite a bit but not enough. Since I did not have the issue on wheels in a hotter climate (Prescott, AZ), I believe the problem is simply the plane does not go as fast through the air on floats as on wheels. Avery has louvers that could be put on each side of the bottom tunnel that might help. has anyone had experience with them. I am even considering a small 3/4" lip on the exit end of the lower cowl. Perhaps a removable one. Plane does around 145 - 150 mph IAS on floats at 75% down low. It has a BA 72 " CS propeller. I put it on Baumman 2100 straight floats. It gets on the step right now and takes off remarkably quick. Empty weight is 1235#.

[LifeofReiley]

Originally Posted by questair

here is a picture: http://www.flickr.com/photos/bob_butcher/5989426778

The baffling is very tight. Have put a washer between rear baffling and rear cyl. have experimented with dams. No help. the -041 carb kit helped quite a bit but not enough. Since I did not have the issue on wheels in a hotter climate (Prescott, AZ), I believe the problem is simply the plane does not go as fast through the air on floats as on wheels. Avery has louvers that could be put on each side of the bottom tunnel that might help. has anyone had experience with them. I am even considering a small 3/4" lip on the exit end of the lower cowl. Perhaps a removable one. Plane does around 145 - 150 mph IAS on floats at 75% down low. It has a BA 72 " CS propeller. I put it on Baumman 2100 straight floats. It gets on the step right now and takes off remarkably quick. Empty weight is 1235#.

Is that picture taken in Moose Pass? I flew the Super Cub on floats there.

[snoop9erdog]

One suggestion is to increase the exhaust exit to gain an overall upper and lower plenum pressure differential. You may need to do some experimentation with aluminum tape to change the exit sizing/area to find a good temp average. We did this with the Adam A500 Carbon Composite Push Pull aircraft in Denver and this was a major factor to lowering cylinder and cowling temperature.

Correction...to avoid the confusion, I meant a change to the lower plenum exit area rather than a change to the actual exhaust piping area.

[Vlad]

Originally Posted by questair

I have about 20 hours on the 180 HP RV-9 floatplane and have an issue with high cylinder temps. Rear cyls go to 440 on climb out. Fronts are fine. Have experimented with dams but no change. Changed to -41 carb which helped a bit, but not enough. Baffling is very good and it was always fine on wheels, but with slower speeds in all configurations on floats temps are a bit too high. OATs in Anchorage are generally cool, 70 or so. anyone have any ideas? Am thinking of louvers on each side of bottom cowl, maybe opening bottom a little more. I now have to level off and reduce the power to get temps down 75% level cruise and rears go to 415. Help.

Tight plenum over cylinders maybe? Some ideas discussed here http://www.vansairforce.com/communit...lenum+pictures

[questair]

Originally Posted by snoop9erdog

One suggestion is to increase the exhaust exit to gain an overall upper and lower plenum pressure differential. You may need to do some experimentation with aluminum tape to change the exit sizing/area to find a good temp average. We did this with the Adam A500 Carbon Composite Push Pull aircraft in Denver and this was a major factor to lowering cylinder and cowling temperature.

Correction...to avoid the confusion, I meant a change to the lower plenum exit area rather than a change to the actual exhaust piping area.

Would you think that putting louvers on the bottom on each side of the tunnel would be effectively the same as opening up the opening on the bottom in the middle? I have even though of putting a NACA duct on the top of the cowling to get more air into the cyls with the thought that it is not a problem getting the air out at the speeds i travel, but getting enough in.

[questair]

Originally Posted by LifeofReiley

Is that picture taken in Moose Pass? I flew the Super Cub on floats there.

The picture, taken last June, is in the take-off channel at Lake Hood.