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Has anyone switched from a bottom mount to top mount oil cooler in a Sonex. If so did you see any change in CHT or Oil Temp. I am based at close to 5000 feet and am considering a turbo upgrade and the top mount oil cooler is a requirement for the turbo upgrade.

Jerry

Mike is the guy who has done it. Probably ​others too.
viewtopic.php?f=7&t=1316&p=9295&hilit=Top+vs+bottom+oil+cooler#p9295

Edit:
Also the other Mike.
http://www.mykitlog.com/users/display_l ... 539&row=10

I've been very happy with the conversion. I've not had any issues with excessive oil temps in the summer. In the winter I need to blank off the entire oil cooler to get the oil to stay over 100 deg F. Makes screen cleaning easier, and has far fewer fittings and hoses to potentially fail or leak.

I’m 100% with Mike; the top mounted oil cooler is the way to go. The only issue I’ve heard from anyone is the potential for some cowling interference issues; otherwise, it works great!

For those who have made the change over; have you closed off the inlet previously used? Or reduced it in size?

Thanks,
Richard Stauffer

Thanks, I have ordered the parts. I was just worried about a possible increase in CHT due to another path of air out of the over engine pressure area.

I absolutely agree that this was a good change for my AeroVee. No more extra hose fitting, and now easy access for oil change. I did retain the baffle below the crank case and added a removable cover over the former Jeggs oil cooler location. This keeps airflow across the bottom of the crank case as well. Overall, cooling performance improved with the new set-up.

I did encounter a couple of problems during the conversion:

One of the oil cooler adaptor plate mounting holes on the engine case had a weak thread that required the addition of a Helicoil insert.

The other was a defective VW Oil cooler that made a big mess. It had a blow hole at a weld between the corrugated fin and the oil chamber. It gave out shortly after initial engine start. A new free replacement oil cooler took care of this problem and I am happy with its performance and the simplicity of the installation.

My suggestion though is to pressure test a new oil cooler with air before its installation to avoid any potential mess and consider reinforcing the threads of the mounting holes.

Jerry09w wrote:Thanks, I have ordered the parts. I was just worried about a possible increase in CHT due to another path of air out of the over engine pressure area.

By closing off the lower cooler cowling inlet, I'd imagine you may actually see an increase in cooling airflow over the cylinders due to a larger pressure difference between the top of the baffles and cowling exit.

By closing off the lower cooler cowling inlet, I'd imagine you may actually see an increase in cooling airflow over the cylinders due to a larger pressure difference between the top of the baffles and cowling exit.

This is exactly why I chose the top oil cooler. The hole to the bottom of the cowl made no sense to me.

Other people may have different results, but on my airplane I’ve flown it both with a cover plate over the oil cooler hole as well as leaving it open. I left the opening open when I had the turbo installed, figuring that the extra air flow through the cowling and turbo area wouldn’t hurt anything, but now that I’m flying normally aspirated, I installed my cover plate.

Honestly, in terms of oil temp, I really don’t notice much of a difference. I think Ryan is right that closing that opening off will increase the air pressure differential between upper and lower cowling areas which would help, but at the same time there is some natural oil cooling when leaving that opening there as you’ll have a lot of air flowing over the bottom of the engine case.

In reality, I don’t think it matters much. It seems that, once the AeroVee is broken in, there’s hardly ever an issue with oil cooling. I don’t hear of many cases where people are flying behind AeroVees and experience high oil temps; normally the challenge is to get the oil temp high enough, especially in the winter!