clarkefarm
Active Member
Hi All
I recently took my FWF package with its new MPS supplied SOHC EJ25 engine to Flinders Island and reinstalled it in the scrub .http://img244.imageshack.us/img244/6249/killiecrankiehangardh9.jpg
The new engine did not have the additional Speedflow inlet which NSI had glued ? into the thermostat housing so I left my cabin heater unconnected and used the Subaru port (hose barb) for the heated throttle body of my NSI package. MPS have abandoned the heated throttle body and use the Subaru port for the cabin heater.
When refilling the coolant I came up about 3/4 of a litre short of the 7.5 litres that the system takes so should have been a bit more concerned but thought that maybe I had not fully drained the system for the trip down. There is a bleed button in the the thermostat which allows coolant/air to pass at a slow rate.
Ran the engine and it seemed fine but on the first flight had major overheating issues with one sensor showing 245? and the other 210? before spiking to 245? after I pulled the throttle. After landing coolant level had dropped so I thought that the problem might have been an incomplete fill. Refilled and ran hard on the ground until an indication of overheating. Tried the next day to take off and fly at low power settings with the same result. Blew about half a litre of coolant out of the reclaim bottle.
Called MPS; Gwen and then Craig, who on hearing of the disconnected heater, said that that was my problem.
Decided to remove the thermostat rather than modify the heater connections which I plan to reconnect when I add the extra port later after returning home.
Ran the engine and problem solved - running VERY cool on an 85? day. Flew around a bit and could not even manage 180? on full power take off and climb. Could just maintain 150? at a high power cruise - WOT and 4,800 RPM. As soon as I reduced power the temperature fell to 140? or less.
Next day flew back to the mainland over 100 NM of ocean with the engine running smoother and stronger than the NSI engine. Running WOT, 5,000 RPM and 150? coolant, 170? oil at a DA of 12,000'. Had a TAS of 160 kts (I never saw more than 155 with the NSI engine) although a 45 kt headwind stretched the 200 NM trip a bit.
Need to recalibrate my fuel flow indicator because the MPS system uses different injectors and lower fuel pressure (45 PSI v. 51 PSI on my gauges) so no accurate fuel flow numbers.
On thinking about what happened I have reached the following conclusion. The thermostat is working fine and opens at 180?. When it is closed the only way it can be opened is by the pump pulling hot coolant through the hose port (or ports) in the housing. In my case the amount of flow through the throttle body was insufficient to operate the thermostat before the coolant boiled and probably effectively cut this flow altogether.
On the NSI and MPS systems the pump has to pull heated coolant out of the top of the radiator neck, through the cabin heater and then into the thermostat housing. I wonder if the potential for heat loss across this "radiator" means that the engine operates at a higher temperature than intended by Subaru. Maybe there should be coolant from the hottest part of the engine directed straight to the thermostat.
The good news is that the NSI radiator is hugely capable of cooling the engine at maximum power settings in warm weather. There would definitely be scope for cowl flaps (to reduce cooling drag) if someone wanted to go this way. Who knows ? maybe a 170 Kt Subaru powered RV-9A is a possibility.
Rupert Clarke
Melbourne Australia
I recently took my FWF package with its new MPS supplied SOHC EJ25 engine to Flinders Island and reinstalled it in the scrub .http://img244.imageshack.us/img244/6249/killiecrankiehangardh9.jpg
The new engine did not have the additional Speedflow inlet which NSI had glued ? into the thermostat housing so I left my cabin heater unconnected and used the Subaru port (hose barb) for the heated throttle body of my NSI package. MPS have abandoned the heated throttle body and use the Subaru port for the cabin heater.
When refilling the coolant I came up about 3/4 of a litre short of the 7.5 litres that the system takes so should have been a bit more concerned but thought that maybe I had not fully drained the system for the trip down. There is a bleed button in the the thermostat which allows coolant/air to pass at a slow rate.
Ran the engine and it seemed fine but on the first flight had major overheating issues with one sensor showing 245? and the other 210? before spiking to 245? after I pulled the throttle. After landing coolant level had dropped so I thought that the problem might have been an incomplete fill. Refilled and ran hard on the ground until an indication of overheating. Tried the next day to take off and fly at low power settings with the same result. Blew about half a litre of coolant out of the reclaim bottle.
Called MPS; Gwen and then Craig, who on hearing of the disconnected heater, said that that was my problem.
Decided to remove the thermostat rather than modify the heater connections which I plan to reconnect when I add the extra port later after returning home.
Ran the engine and problem solved - running VERY cool on an 85? day. Flew around a bit and could not even manage 180? on full power take off and climb. Could just maintain 150? at a high power cruise - WOT and 4,800 RPM. As soon as I reduced power the temperature fell to 140? or less.
Next day flew back to the mainland over 100 NM of ocean with the engine running smoother and stronger than the NSI engine. Running WOT, 5,000 RPM and 150? coolant, 170? oil at a DA of 12,000'. Had a TAS of 160 kts (I never saw more than 155 with the NSI engine) although a 45 kt headwind stretched the 200 NM trip a bit.
Need to recalibrate my fuel flow indicator because the MPS system uses different injectors and lower fuel pressure (45 PSI v. 51 PSI on my gauges) so no accurate fuel flow numbers.
On thinking about what happened I have reached the following conclusion. The thermostat is working fine and opens at 180?. When it is closed the only way it can be opened is by the pump pulling hot coolant through the hose port (or ports) in the housing. In my case the amount of flow through the throttle body was insufficient to operate the thermostat before the coolant boiled and probably effectively cut this flow altogether.
On the NSI and MPS systems the pump has to pull heated coolant out of the top of the radiator neck, through the cabin heater and then into the thermostat housing. I wonder if the potential for heat loss across this "radiator" means that the engine operates at a higher temperature than intended by Subaru. Maybe there should be coolant from the hottest part of the engine directed straight to the thermostat.
The good news is that the NSI radiator is hugely capable of cooling the engine at maximum power settings in warm weather. There would definitely be scope for cowl flaps (to reduce cooling drag) if someone wanted to go this way. Who knows ? maybe a 170 Kt Subaru powered RV-9A is a possibility.
Rupert Clarke
Melbourne Australia
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