Siezed low-time neglected turbocharger

[Rynoth]

Automotive "thermo time switches" are well proven for this. Car fans run when the car is off based on a temp set point. Very simple/proven solution.

I suppose my thought is one of simplicity... the current setup still requires pilot action during/after the flight to set the switch to "auto" so the thermostat can do its work. Having a timer that you quickly turn/set on shutdown could accomplish the same task and eliminate a bit of complexity (don't need the thermo-switch), as well as provide a known value for how much your battery will be discharged. I'm not saying that the current setup is bad by any means, I'm just looking for some info (how long does it take to cool down?) to tailor a potential alternate solution.

Another option, depending on how your master switch is setup, would be to wire the master such that the circuit to the thermo-switch is closed when the master switch is in the "off" position. This could eliminate some of the human factor from the operation of the pump. I used a DPDT ON-ON-ON style switch for master+alternator control and I believe this can be added to my switch.

[NWade]

Ryan -

The issue is that the "cooldown time" is going to vary based on your exact flight conditions, the way your particular FWF setup convects & radiates heat inside the cowling after shutdown, how long you were flying, what your max engine temps were, what the outside air temp & humidity are, what your density altitude is, etc.

Running the system based on temperature instead of a fixed time will ensure that the bearing is cooled until it is safe, regardless of the specifics of your flight or your post-flight environment.

Take care,

--Noel

[Brett]

Does it even need to cool down after?

I am going manually operate the system for a while.

[NWade]

Does it even need to cool down after? If running in general over 100f less then shutting down with no cooling the post temps obviously will rise but to a point over the critical temp the turbo have been slowly siezing at? I suppose I'll need to re read the graphs and look at my oil spec charts.

Brett - Yes, I suggest you go back and look at the Hornet's Nest updates. The temperature of the turbo bearing rises quite a bit after engine shutdown. IIRC from their spreadsheets and charts, 15-20 minutes after you shut the engine down the turbine bearing is 60-75 degrees hotter than it was at shutdown! Although the ultimate temps they recorded were below the theoretical breakdown temp of the oil, the strong assumption amongst several of us is that the oil coking and other seizing issues are being caused by the thin film of oil around the bearing soaking up all of this post-shutdown heat and then slowly cooking during this extended heating & cooling cycle. Since 100LL requires the use of a non-synthetic oil, the breakdown temp is going to be lower than modern full synthetics (*and* remember that this heat load is on top of the normal wear and tear the oil is undergoing from normal engine use).

Its worth nothing that Sonex specifically says that they added the electric pump after determining that convection alone was not enough to circulate the cooling fluid and provide adequate results. That strongly implies that yes, you need a system that is "active" after shutdown. If passive convection was enough to cool the bearing, they probably wouldn't have needed to add the pump.

Take care,

--Noel

[tljones42]

For those of you who have started working on the turbo water cooling, I started to construct the plenum for the radiator today and discovered the plans dimensions are too short for the radiator depicted in the Sonex photo (which I have). After using the radiator as a length template I later discovered that the 5/16 inch dimensions for the inlet and outlet cutouts are too small. If you haven't tackled this yet, save some time and use the radiator for a pattern for both length and inlet and outlet cutouts.

Tom Jones
Onex 0138

[kevinh]

For those of you who have started working on the turbo water cooling, I started to construct the plenum for the radiator today and discovered the plans dimensions are too short for the radiator depicted in the Sonex photo (which I have). After using the radiator as a length template I later discovered that the 5/16 inch dimensions for the inlet and outlet cutouts are too small. If you haven't tackled this yet, save some time and use the radiator for a pattern for both length and inlet and outlet cutouts.

Tom Jones
Onex 0138

Thanks will do. Starting on this soon.

[markschaible]

Hello SonexBuilders.net,

Our apologies for some confusion regarding AeroVee Turbo Cooling System’s radiator plenum. Our original specification and link to the radiator turned-out to be a different part than we intended to post (slightly longer radiator core). The longer radiator will still work as-intended and fit in your installation, but as several of you have found, the plenum drawing is too small for this radiator and you’ll have to cut the plenum to-fit.

We have now revised all downloadable documents to show the correct/recommended/most compact radiator with an updated vendor link in the shopping list. Current versions of all documents can be downloaded at: https://www.sonexaircraft.com/aeroveeturbo_update_030518/

[daleandee]

Don't mean to drag the thread off topic, and maybe this isn't that far off topic ...

On another forum there was some discussion of auto turbos being used on experimental aircraft and someone noted that there have been concerns with doing that if the aircraft was going to do aerobatics because auto turbos were not designed for the Gee forces that would be applied and that they could be damaged by them.

It was also suggested that +/- Gee forces might cause the turbo bearings to suffer intermittent periods where oil supply was insufficient. Being as how the oil system is pressurized that problem doesn't seem quite as realistic but testing data would clear any doubt.

I'm just curious if the turbo units being used have been tested for aerobatic use ... or is it just an assumption that they will work in that environment?

Thanks,

Dale Williams
N319WF @ 6J2
Myunn - "daughter of Cleanex"
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
Signature Finish 2200 Paint Job
171.9 hours / Status - Flying
Member # 109 - Florida Sonex Association
Latest video: https://www.youtube.com/watch?v=1VP7UYEqQ-g

[lutorm]

Well auto turbos do 1G+ in all different horizontal directions in race cars, so it's not like they don't see G-forces. But I agree, the rotation rates and rotor inertia might impose a higher load on the bearings than designed for if you do some high-rate maneuvering. That's an interesting question.

[Rynoth]

I would think that hitting a pothole at a decent speed would impart more forces on the turbo bearings than anything you could do in flight.