Aerovee Oil System
Posted: Mon Sep 16, 2013 3:20 pmHi everybody,
I recently purchased a Waiex equipped with the older AeroVee 2002. It has dual ignition, so is pretty much the same as the 2.1 except for the 20A alternator and a different crank.
The engine had only run for a few hours (and two flights) with the previous owner. During my inspection I noted excessive end play of the crank and a significant oil leak from the crankcase parting line. This cast doubt on the quality of the initial build, so I decided to have the engine rebuilt by an engine builder / machinist in the Minneapolis area.
After some lengthy discussions with the engine builder (who himself flies behind a VW in a 601), and a fellow Sonex owner who switched from an AeroVee to a Jab 3300, I decided that this was a good time to make some changes to the engine to hopefully make it lighter, a little more powerful, and more reliable - this will hopefully make me happier with it over the long term, in exchange for parting with a lot of money. ;)
Here is what I am having done:
- New crankshaft with 84mm stroke, chevy journals (to avoid case machining)
- New connecting rods
- New 94mm pistons
- New 94mm Nikasil cylinders
- Great plains prop hub and #1 bearing
- Compression ratio set to 8:1
The engine will be 2332cc when complete and should put out around 90 HP ... I shouldn't call it an AeroVee anymore. Timing is fixed with the AeroVee accessory case and will therefore remain at 28 deg before TDC. I will run it on AVGAS initially and plan to introduce MOGAS slowly, watching for detonation.
I will be adding a full flow oil filter to my engine, and this has caused me to spend some time thinking about the oil system. The AeroVee uses a dual relief case. With the oil cooler in the "stock" Sonex/Waiex location (below the sump), it seems like the full flow of oil is directed through the oil cooler at all times. This is less than ideal, since it will take the engine longer to warm up - though, the oil cooler is not getting much airflow while on the ground anyway. More important, however, is that the first oil pressure relief (at the hub end of the case), which bypasses the oil cooler when oil pressure across the top-mounted cooler is high (cold, thick oil), no longer has an oil temperature regulating function. Using a top mounted cooler would restore this function. I plan to fly in the Canadian winter, so this thermostatic function is important to me.
The other thing that I like about the top-mounted oil cooler is that it keeps the underside of the engine clear, making for easy oil changes. With a top-mounted oil cooler, I would close the lower inlet in the cowl as I think directing air over the sump would impede engine cooling - not improve it. Directing ram air into the lower part of the cowling reduces the pressure difference across the cylinders, heads, and top-mounted cooler. I'd be curious to see what the factory has to say, but I'm sure there is a reason that the Onex does not have this inlet. When running without an oil cooler, I can appreciate that airflow over the sump fins is important.
The potential for simplifying an eventual turbo installation makes me a big fan of the top-mounted oil cooler. Though, the turbo and my soon-to-be larger displacement may cause some cooling issues ... Finally, using a top-mounted cooler admits that the VW engineers knew what they were doing.
Unfortunately, my engine is in Minneapolis at the moment, and I am on the west coast. I am looking for some help finding some info:
1) I would like to know what size the "stock" oil pump is that ships from Sonex. I think this is just a measure of the diameter of a gear in the pump (21mm or 26mm or 30mm, etc.) - someone please correct me if I am mistaken.
2) I would appreciate it if someone would post some photos of the oil cooler bypass plate that bolts to the top of the case. I would like to see what it looks like from the underside to build an understanding of how oil flows through it (or is blocked by it).
3) I have seen oil filter mounts and oil pump covers with integrated pressure relief. Is there any merit to these? I'd like to avoid blowing a cooler or a filter and leaving a puddle on a taxiway after a run-up on a winter's day.
4) To those that have switched to a top-mounted oil cooler in a Sonex or Waiex - did you encounter any interference issues with the cowling?
5) I would like to hear about experiences with adjustable oil pressure relief valves. Where are these installed, at the oil pressure relief valve (oil cooler bypass - hub end) or at the oil pressure control valve (flywheel end)?
6) It seems to me that with the oil cooler bypass plate installed (for the "stock" Sonex/Waiex oil cooler installation), the oil pressure relief valve (oil cooler bypass - hub end) doesn't do much. Since this relief valve no longer bypasses the cooler, and the oil pressure control valve (flywheel end) is regulating oil pressure by directing flow to the sump, it looks to me like the system would function best if this relief was disabled. To disable it, it would need to be installed, but could be installed with a spring so stiff that it does not open. I'd appreciate it if an engine guru could chime in on this and correct me if I am mistaken.
This is a lot of info, with a lot of questions - Thanks in advance!
Andrew Doepner
Waiex W0014
I recently purchased a Waiex equipped with the older AeroVee 2002. It has dual ignition, so is pretty much the same as the 2.1 except for the 20A alternator and a different crank.
The engine had only run for a few hours (and two flights) with the previous owner. During my inspection I noted excessive end play of the crank and a significant oil leak from the crankcase parting line. This cast doubt on the quality of the initial build, so I decided to have the engine rebuilt by an engine builder / machinist in the Minneapolis area.
After some lengthy discussions with the engine builder (who himself flies behind a VW in a 601), and a fellow Sonex owner who switched from an AeroVee to a Jab 3300, I decided that this was a good time to make some changes to the engine to hopefully make it lighter, a little more powerful, and more reliable - this will hopefully make me happier with it over the long term, in exchange for parting with a lot of money. ;)
Here is what I am having done:
- New crankshaft with 84mm stroke, chevy journals (to avoid case machining)
- New connecting rods
- New 94mm pistons
- New 94mm Nikasil cylinders
- Great plains prop hub and #1 bearing
- Compression ratio set to 8:1
The engine will be 2332cc when complete and should put out around 90 HP ... I shouldn't call it an AeroVee anymore. Timing is fixed with the AeroVee accessory case and will therefore remain at 28 deg before TDC. I will run it on AVGAS initially and plan to introduce MOGAS slowly, watching for detonation.
I will be adding a full flow oil filter to my engine, and this has caused me to spend some time thinking about the oil system. The AeroVee uses a dual relief case. With the oil cooler in the "stock" Sonex/Waiex location (below the sump), it seems like the full flow of oil is directed through the oil cooler at all times. This is less than ideal, since it will take the engine longer to warm up - though, the oil cooler is not getting much airflow while on the ground anyway. More important, however, is that the first oil pressure relief (at the hub end of the case), which bypasses the oil cooler when oil pressure across the top-mounted cooler is high (cold, thick oil), no longer has an oil temperature regulating function. Using a top mounted cooler would restore this function. I plan to fly in the Canadian winter, so this thermostatic function is important to me.
The other thing that I like about the top-mounted oil cooler is that it keeps the underside of the engine clear, making for easy oil changes. With a top-mounted oil cooler, I would close the lower inlet in the cowl as I think directing air over the sump would impede engine cooling - not improve it. Directing ram air into the lower part of the cowling reduces the pressure difference across the cylinders, heads, and top-mounted cooler. I'd be curious to see what the factory has to say, but I'm sure there is a reason that the Onex does not have this inlet. When running without an oil cooler, I can appreciate that airflow over the sump fins is important.
The potential for simplifying an eventual turbo installation makes me a big fan of the top-mounted oil cooler. Though, the turbo and my soon-to-be larger displacement may cause some cooling issues ... Finally, using a top-mounted cooler admits that the VW engineers knew what they were doing.
Unfortunately, my engine is in Minneapolis at the moment, and I am on the west coast. I am looking for some help finding some info:
1) I would like to know what size the "stock" oil pump is that ships from Sonex. I think this is just a measure of the diameter of a gear in the pump (21mm or 26mm or 30mm, etc.) - someone please correct me if I am mistaken.
2) I would appreciate it if someone would post some photos of the oil cooler bypass plate that bolts to the top of the case. I would like to see what it looks like from the underside to build an understanding of how oil flows through it (or is blocked by it).
3) I have seen oil filter mounts and oil pump covers with integrated pressure relief. Is there any merit to these? I'd like to avoid blowing a cooler or a filter and leaving a puddle on a taxiway after a run-up on a winter's day.
4) To those that have switched to a top-mounted oil cooler in a Sonex or Waiex - did you encounter any interference issues with the cowling?
5) I would like to hear about experiences with adjustable oil pressure relief valves. Where are these installed, at the oil pressure relief valve (oil cooler bypass - hub end) or at the oil pressure control valve (flywheel end)?
6) It seems to me that with the oil cooler bypass plate installed (for the "stock" Sonex/Waiex oil cooler installation), the oil pressure relief valve (oil cooler bypass - hub end) doesn't do much. Since this relief valve no longer bypasses the cooler, and the oil pressure control valve (flywheel end) is regulating oil pressure by directing flow to the sump, it looks to me like the system would function best if this relief was disabled. To disable it, it would need to be installed, but could be installed with a spring so stiff that it does not open. I'd appreciate it if an engine guru could chime in on this and correct me if I am mistaken.
This is a lot of info, with a lot of questions - Thanks in advance!
Andrew Doepner
Waiex W0014