Turbo Subie Passes 250 Hours on the Hobbs

[Rotary10-RV]

Originally Posted by David-aviator

Thanks, Wade, what you suggest is very true.

A smooth plenum would probably make a world of difference as was well established as long ago as WWII. I think the diffuser angle is something like 12-14 degrees to and from the radiator to provide for no separated air flow.

The problem creating a plenum with this installation is the radiators are located quite close to the engine block, there isn't room for a plenum. The air coming through the radiator hits the engine and has to make a 90 degree turn to escape. The right radiator is about .75" from the block, the left a bit more. Air does find its way out of the compartment, but it is not a smooth flow.

David,
I have seen and worked on several Egg Soob conversions. The lack of exit space on the radiators is the biggest compromise Jan has made with respect to cooling. The testing that has been done in the past and more recently shows that the exit of the radiator can be even more important than the entry. Some people question the radiators on the side of the engine, or below. These locations will usually allow for better exits than the front cheek radiators. Egg has chosen to go with the cheek location for packageing reasons mostly. A better radiator location would help cooling a lot. IMO
Bill Jepson

[rv6ejguy]

I was doing an oil change and some checks on VZX this weekend. As I mentioned previously, the compression has been slowly falling for some time and oil consumption has risen to Lycoming levels lately. The latest compression tests have shown a reversal in the dropping trend and they are now starting to improve. I've been lacing the fuel with Marvel Mystery Oil for the last 20 hours or so in hopes of freeing up suspected stuck rings. The theory was that the 100LL was not agreeing with tight Subaru tolerances here.

The second item of note was that the NGK platinum spark plugs are not showing the high wear of the conventional plugs fitted earlier.

I changed the oil in the PSRU also. This looked nice and clear and did not have anything nasty (metallic) in it.

I also changed the IVO propeller brushes and did a good inspection of all hoses, engine mounts, exhaust etc.

The new scavenge pump is nice and dry which is really nice after the earlier one which leaked like a sieve.

I found a problem with the alternator belt idler. The bearing was loose again and upon further examination, it was evident that the bearing had spun in the pulley. I'll be boring the pulley to accept a larger bearing this time in hopes of making this part last longer this time around.

I hope to have it back together mid week and start piling on the hours again.

I need to get back to my RV10 doors soon.

[rv6ejguy]

I'm just completing the annual on VZX this weekend.

The Hobbs is now showing 297 hours and I did a dry and wet compression test plus pumped some high pressure air into the cylinders to listen for leaks. Bad news is that compression has dropped a bit more in most cylinders both dry and wet. There is a slight hiss out the breather pipe which is no surprise and a bit from the exhaust pipe as well. So it seems like the engine is just getting a bit tired and perhaps the 100LL is making valve seal less than great.

Oil consumption has seemingly stabilized (I hope) at around a quart every 6 hours or so. When new, it didn't need anything between 40 hour changes. I switched to Aeroshell about 20 hours ago in hopes that the sticky rings might get freed up. Appears not to have done anything so I'll switch back to Mobil 1 at this change.

I'm going to try running mogas instead of 100LL over the next year and monitor compression every 20 hours or so. Maybe if I get all the lead out of the system, something good will happen.

Some reports from NZ have indicated problems with compression loss due to exhaust valve erosion on Subes running 100LL at the 200-300 hour mark. Just wondering if anyone else has accumulated these sort of hours on a Sube running only 100LL and what problems if any they have had? Engines running mogas appear not to suffer these issues with one guy down under reporting 3800+ hours on an EJ22 without ever being opened up!

The PSRU oil is still coming out clean with no signs of distress. No problems with the turbo, exhaust system or the dreaded IVO propeller. Cooling is great and the NGK platinum plugs are holding up well.

I have to remove the left fuel tank to fix a persistent seep from the sending unit but other than that, things appear pretty routine with no big issues so far.

[GaryStofer]

Originally Posted by Rotary10-RV

David,
I have seen and worked on several Egg Soob conversions. The lack of exit space on the radiators is the biggest compromise Jan has made with respect to cooling. The testing that has been done in the past and more recently shows that the exit of the radiator can be even more important than the entry. Some people question the radiators on the side of the engine, or below. These locations will usually allow for better exits than the front cheek radiators. Egg has chosen to go with the cheek location for packageing reasons mostly. A better radiator location would help cooling a lot. IMO
Bill Jepson

The next biggest blunder that Egg did aside from the "no room for exit air" is that he took some standard Oil coolers and "grafted" on the 1" large H2o hoses to make them look like radiators. When you look inside those nicely welded on hose ports you see a 3/8" hole actually entering and exiting the cooler, not exactly what the coolant wants to see.... Then there is the debt of the cooler, about 2" too deep to be efficient.

[rv6ejguy]

I think many of the STI guys have now realized that there are far more efficient coolant radiators available and are fitting them.

Cheek mounted rad setups however are always going to be relatively high drag and inefficient compared to proper, duct mounted setups. Cheek mount is convenient to be bolt on out of the box with minimal hose runs and cowling modifications which is why Jan is using them.

[deej]

Hi Ross,
Why do you say "dreaded IVO propeller"? From previous posts I thought you liked the IVO...

-Dj

[rv6ejguy]

I was sarcastically referring to all the "experts" who told me how terrible the thing was going to be. It has worked flawlessly for me so far...

[deej]

Ah! Good to know. Thanks! My intent is to use an IVO on my Sportsman 2+2 with the Eggenfellner E6 (Arriving next month!!!).

Do you have any issues with the prop in really cold weather? I'm in Maine, and I think you are in Canada, and are likely to see below zero temps like we do here.

-Dj

[Geico266]

Originally Posted by rv6ejguy

Oil consumption has seemingly stabilized (I hope) at around a quart every 6 hours or so. When new, it didn't need anything between 40 hour changes. I switched to Aeroshell about 20 hours ago in hopes that the sticky rings might get freed up. Appears not to have done anything so I'll switch back to Mobil 1 at this change.

I'm going to try running mogas instead of 100LL over the next year and monitor compression every 20 hours or so. Maybe if I get all the lead out of the system, something good will happen.

Subies are not made for leaded fuel. Running synthetic oil with 100LL is not recommended as synthetics cannot disburse the lead. AeroShell 15w-50 is semi-synthetic so it cannot help in an "over leaded" situation. Try Phillips 20-50 for a few oil changes. Phillips is 100% dino oil with good lead disbursing qualities.

There is an additive called TCP that you can add to the fuel (and maybe oil) to help disbursement of lead deposits. We had to use in it Rotax 912's to "get the lead out". http://www.aircraftspruce.com/search/search.php

I'm not sure if TCP will help, but it is the only thing I can think of that scavenges lead.

[rv6ejguy]

I've been using Decalin lead scavenger for several years and internal inspection of the engine has showed no signs of lead deposits in the lower end, probably due to frequent oil changes. For the last 50 hours or so, have also been adding MMO to the fuel as many people swear by it to avoid lead problems.

I've just filled the tanks with Mogas and will be doing a test flight this afternoon. I'll stick with the Mogas for the next year and see what transpires.

We are on the learning curve here with what does and does not work. Experimental aviation at its best.