Actual Flying Rotax Installs

[CaseyCooper]

Hello all!

I’ve been out and about so I haven’t been on the forums. I’m very happy for you Kai! It’s a world of difference flying a Rotax in a Sonex compared to the other power plants! Your plane looks wonderful. Warp Drive definitely has spacers. They sell Sabre spacers. As far as your roughness, being that your plane was switched to efi might have something to do with it, but unlikely. Especially an Edge engine. They all run like a top. I would definitely check your plugs first, ensure proper gapping, maybe just throw in a new set for giggles and see if the problem goes away. New doesn’t always mean good! I’m very excited to see your progress and what kind of figures you’re seeing and maybe we can compare!

This last month I flew my Sonex to Airventure! It was a wonderful adventure. Interesting weather made things fun but there was no mechanical issues whatsoever with the plane. I managed to put on 36 hours of flight time and 3,500 miles under me on my trip

Next year Sonex is providing a Waiex for the One Week Wonder. They will be building it with a Rotax Is and they are currently working on a Sonex B with an Is in the shop. Some standardized equipment will be coming out for the Rotax installs as well

[Kai]

Good to hear from you!

Issue numero uno, even more worrysome than the slight airframe vibrations, is cooling.

During my Jab days I was constantly fighting high cht’s- nothing I did seemed to finally solve the cooling issue.

Now, with the Edge, I am still fighting them!

But now they are FAR too low. On a good hot quiet summer afternoon at 3500’ amsl I can see 75C oil temp. Coolant never rises above the high sixties. It’s going to look like the north pole in there when winter comes………

I have a split coolant radiator setup. Right and left hand cylinder bank flows are separately collected in small manifolds I made up and routed to their separate radiators- it should be possible to make this out in enclosed photo. Below the radiators the oil cooler (not shown in the photo) is sitting- it’s the biggest Rotax recommends: the EP has an oil jet cooling the underside of the piston crowns (piston cooling, insurance against detonation), so considerable heat from internal components is handled this way.

If I could find a smoothly operating three way flow valve with ø1” hose barb connections, a 50% reduction of the cooling capacity during flight would be possible- but as yet no such luck!

Perhaps in the US?

Thanks
Kai

[CaseyCooper]

Kai,
I experienced the same issues. I’m actually in the process of redoing my lower portion of my cowl to reduce and streamline my cooling system. I was expecting high temps since in the summer we operate up to 120f (48c) at max and I set it up too well. I’m running a stock 912 radiator and a aftermarket oil cooler in succession in my scoop. When flight testing in December, 65f (18c), I would see 130f (54c) cht and 100f (38c) oil. Which surprisingly a lot of people run those numbers all winter long here. Not saying you should! But people do. We always want around 200f (94c) right? So all I did for a temporary solution was put duct tape across my radiators to bring my temps up. During that time I bought a oil system thermostat that operates at 10% capacity until reaching 180f (82c), then it opens accordingly to maintain temps. I installed it and removed my tape and that in turn brought up my cht’s and they remain an equal temperature to each other in either summer or winter. As a plus, my warm up times went down to about 5 minutes total, when before I would sit for about 10-15 to warm up. I still need it warmer, we want to see 200f (94c) every once in a while to steam off the water and impurities in our oil. So my new cowling should help bring those temps a little higher, I’m also going to install adjustable louvers just to fine tune in flight with changes in atmosphere and terrain.
As a recommendation to you, so you don’t have to manipulate your mechanical integrity, I would do a pass of duct tape on each radiator and go fly it and add or remove tape until you see temps reaching where you’re happy. Then once you’ve reached your happy medium, bend some removable aluminum dams (like a c channel) that you can clip on your radiators just to block some airflow. We have to do that here with our oil coolers on some of the experimentals to bring the temps up in the winter. Then in the summer we remove them to allow the engines run a little cooler. It’s cheap, easy, and affective, without producing points of potential failure in the system. I do like your idea of a split system to help each bank. You could also consider installing a in-line thermostat in your coolant system. You can get a thermostat like mine in either 180f (82c) or 200f (94c) that will restrict the flow down then maintain temp. I would rather dam up my radiators but those are options I see. It would at least get things constant and in the meantime if you wanted to design some baffling to regulate your cooling system, you could still fly happily while improving your system

[CaseyCooper]

Kai,
I read your last post and failed to see that you wrote you had an oil cooler, you could also do as I did! It greatly helped and it was not an expensive or difficult addition. It took about a half hour to install a oil thermostat. In using a oil thermostat it also helps keep your oil temps slightly higher than coolant temps. Which I would prefer

[Kai]

Herraripower,

Thank you for your c/f conversion! It takes the calculator out of my reading :-)

Testing with aluminium tape over the radiator grid is indeed an accepted method to get an idea og cooling efficiency. I have been doing so since these motors appeared on the market. But the coolers themselves are not the issue- the cowling is the culprit. Flow through the coolers during ground operations is insufficient- upstairs there must be a virtual storm in there. And I hate tape.

I had a Jab motor seize on me once because the oil thermostat failed and blocked flow; since then I have been a little reluctant to embrace them. But it would indeed solve my cold oil issue.

A thermostat on one of the coolant cirquits is acceptable as long as it does not block full flow through the heads, so an inline unit (even with an internal 10% bypass) is nogo for me. I would need a 3-way unit, sending either full flow coolant to the radiator, or through the full flow bypass back to the pump inlet (as is done on all car engines). As yet, I have not been able to find one. I know BMW made one a long time ago, but because of outlet positions it would be difficuilt to incorporate into my system.

You would not happen to know of another one, do you?

Thanks
Kai

[Paul Johnson]

Kai,

I have been researching something else but came across a Thermo-bob, I do not know if it is suitable for what you want but here is a link.

https://watt-man.com/new-shop/thermo-bo ... -fittings/

Regarde

Paul.

[aripilot]

With Laminova oil cooler you get engine temperatures to flying range fast.

Aripilot

[Kai]

With Laminova oil cooler you get engine temperatures to flying range fast.

Aripilot

Yep- no argument there!

However, you need to make absolutely sure that the cooling capacity of your radiator (which then has to cool everything; oil and coolant) is sufficient to handle the additional heat load. I have seen installations with an oil/coolant heat exchanger where an additional radiator was needed to handle it (!)

Thanks
Kai

[CaseyCooper]

Kai,
I personally do not know of any thermostats that would be suitable in the coolant system that you’re wanting to achieve, but I’m positive they exist!
Another option, and it may sound silly, but hear me out. The 912’s are water, air, and oil cooled by the principle that air helps keep cylinder head/coolant temps low, coolant helps keep oil temps low, and the dry sump oil can keeps the oil temps lower. So, with that being said, 912’s are not required to use oil coolers but people use them in applications where needed. So, you could take your oil cooler out of the equation completely and just remove it. Or just bypass it with a solid line from your can to your pump, and see what your temperatures do as a test. You may not even need an oil cooler. Your overall engine temps will come up and even out. During this time of year would be about your highest outside air temperatures the engine would see. Im 100% certain with temps your seeing that your engine wouldn’t overheat anyway. If it works, you wouldn’t have to do anything, you may even save a few pounds removing the cooler and extra oil it takes on.
Again, there’s a million ways to skin a cat. But I see that as another possible alternative.
I’ll keep an eye out though for something that may work for you. If not, at least you have some options!

[Kai]

Herrari,

No- not silly: just been there done that!

First option was just your suggestion: no oil cooler. The result was the oil temp almost went to the moon.

Second option was to install the cooling air side outlets. The result was now the ISS (MIR)

Third option was to install a Laminova oil/coolant heat exchanger. Results better, but the coolant still boiled- this time most likely because the cooling grids in my radiators just have 10% more cooling area than an original Rotax: they could not handle the added heat load.

./. Note (again): this motor has piston cooling. A lot of internal heat is added to the oil. A Laminova will dissipate this heat to the coolant.

Fourth option was to discard the Laminova and replace it with the biggest oil/air cooler Rotax suggests. WOW!! I still have to proceed fairly smartly on the ground before t/o, but once in the air the temps now drop like stones to the values described previously. This leads me to conclude that thermostats on both coolant and oil are a dire neccessity.

But now on a Rotax forum I read that actually there are no lower operational temp limits for the coolant!……. I don’t know what to believe. After all maybe this aircraft engine thing is not for me!

Thanks
Kai
(I can already hear the wailing siren of the vehicle with the nice man in a long white coat and a large hypodermic needle inside)