lml@lancaironline.net Mailing List Archive

Gary, One side note on the head temps. I made my plennum similar to yours.
My head temps run within 6 deg of each other usually 310-360 F depending on power and temps.

One thing that I did was to shine a light up through the bottom of engine with the hangar lights out and found and sealed EVERY gap in the baffeling except where cooling air needs to go with high temp RTV.
I also opened up the gap on the bottom of each cyl to 2.6" times the dept of the cooling fins as I read somewhere NASA had done some testing and determined that was the optimum opening. I also radiused the baffeling exits inder the cylingers rather than 90 deg bends on the exits. I understand that helps flow as well.

I have also come to the conclusion that there is airflow coming into the cowl through the nose gear slot and bottom exit cowl area. I see this when I get an oil leak. the oil runs down and then blows forward. Weird. Ayway, you may need a small 45 deg lip on the bottom of your cowl exit like I probably do.

One last thing of note, in my pictures you will see the exhaust wrap, that did make a difference on head temps and it also evened them up. My exhaust wraps around the engine like yours does and runs close under the cyinders. I wrapped those areas with 4 layers of exhaust wrap and 2 or 3 layres everywhere else and have had good results lowering engine compartment temps-unmeasured but it appears to be so. I tested the heat wrap on my heat gun. With 4 loose layres I could hold my hand on a heat gun nozzle on the high heat setting. That sold me on that stuff.

FWIW...
Randy Snarr
N694RS

--- On Sat, 3/7/09, Gary Edwards <gary21sn@hotmail.com> wrote:

From: Gary Edwards <gary21sn@hotmail.com>
Subject: [LML] Re: oil cooling
To: lml@lancaironline.net
Date: Saturday, March 7, 2009, 6:33 PM

It seems that most temp issues are with oil. Mine are not with oil, but with CHT's.

As you know (you have seen pictures), I have 2 smaller (6" round) oil coolers, one on each side (mounted to the engine mount) with naca ducts and short 4" to 6" long straight 2" inch scat duct to them. The scat duct is connected via glass enlargers. On the outlet side, there are glass reducers down to 4" scat duct, with the duct routed down to near the nose gear front cover on the firewall. It as close to the lower cowl outlet area that I could get.

The oil temps. are too low, especially in winter. It is difficult to get the temp to 180. In summer, the oil temp is about 190 to 200 climb and cruise. I tried (for winter) closing off one cooler with duct tape over the cowl inlet to raise the temp and it didn't make any difference. Tried it on both sides. I also removed the 4" outlet duct (reducers left on), to let the outlet flow directly into the rear cowl area, with no change noticed. In only one case, have I had a high oil temp; in Bend, Or., giving a friend a ride after a previous flight. Outside temp in the '70's. Never has happened again.

Now, if I could just get my CHT's down. I have to step climb with that issue when at gross weight.

Gary Edwards

LNC2 235/320

----- Original Message -----

From: randy snarr

To: lml@lancaironline.net

Sent: Friday, March 06, 2009 4:53 PM

Subject: [LML] oil cooling

All,
I am looking for suggestions on how to lower my oil temps. I am running an IO 320 on the original 235 frame. On warm days in a climb I have trouble keeping them below 220. I usually have to flatten out the climb to cool things down if they get up to 230 or so. Once in cruise it is not a problem and they will settle around 210. I would like to get them down to 190 if possible. The problem is on a 75 plus degree day when the airplane is already warm from flying and I need to go again. I am picking up outside air on a naca vent on the left side of the cowl. There is a 6" length scat tube (4"diameter) connecting the cowl inlet to a glass expansion section that is connected to the cooler.(see pics). It just dumps in the lower cowl area.
I am running a Stewart Warner oil cooler that many have had success with.

I have tried larger hoses to the cooler now using -8's and also removed the 90 deg fittings I used to have to improve flow.
I suspect my ducting and or connection to the cooler could be improved. I am looking for suggestions that could be done without cutting the cowl.

Thanks in advance!

Randy L.Snarr