Top VS bottom oil cooler

[Gripdana]

Looking for thoughts on the oil cooler top vs bottom mount. Sonex recommends the top mount for the Onex. I think bottom for everything else? I saw top mounted on the Turbo installed in the airplane and they recommend it in the FAQ section for the turbo. It seems to me to be easier (or less work) to do the top mount. Has anyone done it on other than Onex? What are the pros and cons?

[Bryan Cotton]

Dana,
Mike has done it. The thread is below:
viewtopic.php?f=7&t=606

[MichaelFarley56]

Hi Dana,

When I first started flying my Waiex, I had installed the bottom mounted cooler and flew it that way for around 70 hours. Last summer when I changed my engine compression, I removed the bottom mounted cooler and replaced with the Onex style, top mounted cooler and have flown behind that for the last 40 or so hours.

You are correct that the Onex recommends the top mounted and everything else is bottom mounted, but I know first hand that you can in fact install a top mounted cooler on a Sonex (or Waiex/Xenos). My airplane is set up this way, and I know several of the factory demonstrators are also set up with the top mounted cooler. If you decide to go this route, you either need to loop you oil cooler line or install a new oil pump that doesn't have the external ports. You'll also need to get the oil cooler mounting plate from Sonex.

After operating both systems, here are my pro's and con's for the top mounted cooler:

Pros:

- Easier oil changes. Plus, I know that all oil gets drained from the engine as compared to the bottom mounted cooler that would "trap" some dirty oil during changes.
- No external oil lines. Every time I changed the oil these lines would flex. I'm sure they'd last a long time but I didn't want to introduce a future failure point.
- Seems to work just as well as a bottom mounted cooler. My oil temps may have risen 2-5 degrees when I switched to the top mounted cooler, but I honestly think oil temps run around the same. This year on my Oshkosh trip, even though it got pretty warm I hardly ever saw any oil temp above 190-195. Most of the time it was cooler.
- This seems to be the recommended installation for the turbo! :mrgreen:

Cons:

- It's a tight fit between the cooler and the cowling. It does fit but you have to trim off a flange on the oil cooler so there's no contact. I also had to put a small depression in my oil cooler to clear the cowling hinge. I don't know if anyone has needed to modify their actual cowling but there's a possibility if you have big clearance issues.
- You lose one of the 1/4" NPT oil pressure ports. If you want both a digital and electric oil pressure gauge, you'll have to get a T fitting to thread into the case. I have this and it works just fine.
- You have to modify the engine baffling to incorporate the top mounted cooler. I think the new Onex engine baffling pieces will work but in any case, you have to make up the engine baffling so there's a pull of air through the cooler and out the back of the baffling.

Ultimately, it's your call. For the record I like my top mounted cooler and have no complaints with it!

Just my two cents on the matter. If you have any other questions please let me know.

[Gripdana]

Thank you both for the information. Very good info. I am going to install the Aerovee. I just don't know at what point I will go with the turbo. I have decided to set everything up for the turbo.