Turbo Temp/Lower pressure side heat - Optimization

[tps8903]

Hey Guys,

When Sonex was troubleshooting the turbo failures, one of the 4 reasons for failure was oil coke on the bearing. Step one in the test results was to remove the turbo blanket, which deceased the bearing block temperature.

It was determined that the first set of air cool mods didn't work enough so the liquid cooling add on was completed.

My question, at risk of having someone or the factory jump down my throat. Has there been any testing, or does anyone here have any experience with the liquid cooling AND the turbo blanket?

I only ask, because without the turbo blanket the ambient temp of the low pressure area, specifically next to the turbo gets HOT! Even with the stainless shield. I operate in Central Florida. My thought is I can dump cool air back there off the NACA, but then I am hurting the pressure diferential of my engine cooling (which works well). Or, I can blanket the turbo and force the heat out through yhe exhaust pipe.

There is no doubt I'll achieve the temperature goals with a quality blanket, I'm just not sure if I'll exceed the 250F bearing back temp.

I do have a sensor rigged for the bearing block. I'll likely test it myself if no one has real world data.

The reason I ask is that I've had 3 ignition failures in under 50 hours due to heat, I suspect off the turbo. So my goal is to cool it down back there without sacrificing engine cooling.

Thoughts?

[tps8903]

I'll take the lack of replies as no one has tried this yet.

As an update to my OP. I've installed a Turbo blanket and made sure exhaust wrap is seamless. I already had a probe attached to the thermostat for the liquid cooling to monitor the bearing block temperature (CHT#5). I installed another probe near the ignition coils to check ambient temperature (CHT#6).

I deleted the cabin heat to stop dumping useless air on the low pressure side. I already had the front hole on the cowling plugged (oil temps have never been a problem). I also deleted the cold air induction off the NACA and as a result the carb heat. Plane lost 3 lbs in the process. The cabin heat was obviously dumping wasted air. The cold air induction was sealed. But the nature of the design would allow excess air to travel backwards through the carb heat to prevent RAM air on the aerocarb. With a turbo I feel like cold air induction and carb heat are useless. I can pull 43inhg if I want to....

There are 4 paths to the low pressure side. Through the engine. Through 2 NACA vents and through the front cowling hole. So basically I'm starting with 1 restricted NACA vent for now, and will open others if needed. The restricted NACA vent is a blast tube for the coils for now. Trying to create a boundary layer of cold air between them and the turbo.

I also installed 4" vents above the turbo.

I bought a manometer to get an understanding of the pressure difference in the cowling, I'm going to route the tubes out the cabin NACA and in the cowl NACA with the blast tube and use duck tape to secure the 20" or so outside of the plane.

My exit area on the cowling is 51sqin. So it should be okay. But ultimately this is to find out if I need more. It's currently 12.5" wide. But if already considered stretching it to 18" or so.

I'm not sure if the 4" vents will draw air from the back of the cowling. I'm hoping they will. I need some airflow near the turbo. Any ideas on what I can do wo see if the is air being drawn through the top vents?

My goal in all of this is to maintain my good CHT and Oil temps (which I already have, while lowering the ambient temp behind the engine which is wreaking havoc on the ignitions. All while not cooking the turbo on shut down.

Let the experiments begin....

[Bryan Cotton]

Cool! This optimizing is equal parts fun and hassle.

[tps8903]

Cool! This optimizing is equal parts fun and hassle.

I also bought the Model B side vents. I'm going to do a test flight without them, with the manometer setup. Then install them and try again.

I was reading on here that the factory was concerned that having the bottom and side vents could rob each other of efficiency. I think worse case the side vents will add overall cooling, they may just be less efficient than they might be as a stand alone. We will find out for sure.

I'll post results here once I have data.

I'll have data on cooling the turbo with blanket on and liquid cooling installed.

Cowling ambient temps.

Pressure differential with lower exit and Model B exits

Pressure deiffential dumping various qualities of NACA air in to the low pressure side.

[pfhoeycfi]

I added deflectors to my B exits which solved my heat issues. I took manometer readings with and without and the PD from inlet to outlet Increased significantly with deflectors. Not quite the same issue but something to consider nevertheless.
Peter

[tps8903]

I added deflectors to my B exits which solved my heat issues. I took manometer readings with and without and the PD from inlet to outlet Increased significantly with deflectors. Not quite the same issue but something to consider nevertheless.
Peter

Excellent info Peter. Do you have the dimensions and or pictures etc of those deflectors?

Thanks

[pfhoeycfi]

I added deflectors to my B exits which solved my heat issues. I took manometer readings with and without and the PD from inlet to outlet Increased significantly with deflectors. Not quite the same issue but something to consider nevertheless.
Peter

Excellent info Peter. Do you have the dimensions and or pictures etc of those deflectors?

Thanks

The flange w the screws is 1/2 wide, the angle is 30, the height off the cowling is approx 3/4". I closed the ends.

[pfhoeycfi]

Pic

[tps8903]

Pic

Fantastic. I made a set today. I didn't close the ends. I made the 30° but made them a tiny bit longer so they are 7/8" up. I'm Mounting them inside home ever with epoxy etc.

[tps8903]

Well today I installed the Turbo blanket.

OAT was 91F as sea level. I flew at 2000' it was 87F at that altitude.

It performed as advertised. I don't know what the ambient temp of my cowling was before, but the paint would bubble in places. Today it was noticeably cooler.

During flight the ambient cowling temp at the center of the firewall next to the #2/#4 coil never went above 121F. I do have a single blast tube near the coils.

Shut down was a success as well. Max bearing block temp was 199F 5 minutes after shut down. Then trended down for the next 20 minutes. Ambient cowling maxed at
161F at 15 minutes.

Oil Temp in flight stabilized at 197F.

At 35" MAP #3 was my hottest at 370F. I don't know why it's running hotter than the rest at this point. At 30" MAP it's 365F.

My EGT #3 also appears to have failed. It read about 450F the entire flight. It was also reading different on shutdown. All the other ones read about 200F when it was heat soaking. #3 read 140F. So I suspect it's gone bad.

CHT Max continuous 35" MAP
#1 350
#2 335
#3 370
#4 335

Next step is to add the B vents with lip per suggestions.

Lessons learned so far.

Turbo blankets lower ambient cowling temp
Turbo blankets will not affect the shut down temps if liquid cooling is installed.