EJ25 thermostat

[StanFoster]

I have a 165 degree thermostat in my SparrowHawk. Is this the temperature everyone else is running? Sure seems like it should have a 190 degree one it it. Anyway... I KNOW my thermostat is sticking open. The clues?

On warm up...the temp readout is around 180. After takeoff...it goes clear back to 130 on a 40 degree day. It stays there within a few degrees the whole flight. Then when I land and taxi...the temps start rising back up in the 180's.

I am going to put a new one in.....but would like to put a hotter one in while at it. Any thoughts pro or con for going to a 185-190 degree thermostat?

Stan

[automan1223]

180-185 best temp for making POWER. At least that is what every book on the subject has reported. If you can keep the engine at that is another story.

Jonathan

[Dean_Dolph]

Stan, it has been many, many years since this ole hot rodder did any serious playing with engines, high performance or otherwise. But Jonathan is right; the higher coolent temp is better for performance.

An internal engine is heat driven so the hotter the better. That is until it dies! And at least on ground bound vehicles, higher temps are better for the engine. The higher temp helps vaporize any moisture that trys to accumulate from combustion or cool down. This is the reason short trips that don't allow the engine to reach thermostat controlled temps are bad for an engine. I'm sure Jonathan has seen evidence of these problems.

Do you or anyone else monitor oil temp? That goes along with coolent temp. While there isn't a lot of danger from too cool of oil except for a viscosity that is too high for the flying temp; the oil temp should be running at least as high as the coolent. In googling to find out what others are experiencing; it seems that no one is concerned with temps in aviation Suburus up to and including 220 degrees F. I know we used to expect and accept 210 on the big V8s. The viscosity improver packages are so much better now than the old days that it is rare that high oil temps are a concern. I found during the googling that the aviation oils live at a Lycoming maximum of 245 degrees F. However, these oils are higher viscosity than what auto engines use.

[Aussie_Paul]

Unless AAI put the 165 thermostat in that is stracnge as every ej series Subaru I have seen uses a 176 degree thermostat.

A question if I may Stan. Do you or anyone else know if the car ecu with its AAI little black box add on, limits the engine rpm to 5500?

Thanks.

Aussie Paul.:)

[Chopper Reid]

As far as oil temps go, my experience is that temps are generally okay exept for turbo motors which without an oil cooler will boil the oil or very close too !

[Chopper Reid]

As far as radiator temps go, my 2.2 runs at 75 Celcius and while a hot engine might produce more power, it wont last anywhere near as a cool running motor so take your pick what you want !

[StanFoster]

Thanks guys.

Pual: I do not know it there are rpm limits at 5500.


My oil temperature runs around 190. However...that is with this cool running engine...so I am sure it will go up somewhat.


I will put in a 185 degree one and try that for awhile.

Stan

[PW_Plack]

Stan,

My uneducated opinion: Go with what the Subaru designers intended.

How could using a cooler thermostat help? You'll increase deposits, increase emissions, decrease power and fuel economy, and increase the temperature differential between various parts of the engine castings.

You won't gain any safety margin, because either thermostat will be wide open well before the boiling point in a pressurized cooling system.

[Harry_S.]

My opinion Stan...I'd go with the 185* Subaru stat, as well.

I meant 185* operating temp. I thought I had the SUB. part no. but can't find it. It is a 170* tstat. My water temp is usually betwixt 180 and 185.


Cheers :)

[automan1223]

Stan, quick question.

Do you mean to tell me after coughing up x bucks for the kit sparrowhawk does not have this printed info in the manual somewhere ? Depending on climate you are flying in ?

SPH did not include the tstat they wanted you to use ?

Jonathan

[StanFoster]

Jonathon:


Jim Logan personally called me today and was a big help...as he has been in the past. I really appreciated him calling me and told him so. While I am on the topic of "Jim".... The flack that poor guy has received over the years is totally unfounded. He is extremely educated on the ins and outs of these engines...and gyros. He is a most excellent pilot as I flew with him last year. My little gyro experiences wouldnt make a pimple on his butt. There....been wanting to say that for awhile....now back to the thermostat.....

Anyway...my thermostat is labeled 165 degrees. This is a tad on the cool side..but not by 25 degrees as I thought. Jim explained that thats the temperature it starts to open. What Subaru recommends is just a little warmer ...at 170-172 degrees.

My problem has to be just a faulty thermostat that is opening way too soon.

Groen Brothers would gladly send me another one....but I am just going to take Jims advice and put a Subaru thermostat in it.

Stan

[automan1223]

Jim is a nice guy on the phone but that is not why he has taken heat from the group. Jim is perhaps one of the most skilled and talented CFI's and RAF 2000 pilot out there. The flack that got things going was 4 students that got killed of another cfi that was a die hard raf'r that had everyone taking notice. No offense to this other cfi but all raf pilots got their lumps.

Anyway I have not been able to get the subaru stock thermostat to give me the cooler, under 200 degree water temps I need without some drilling of holes in the valve. Did not matter what radiator, or setup I tried

I know they rate tstats a few different ways, start to open and fully open but I cannot remember what the sub stats out at in a pot of water. The only real way to tell what it is doing.

Remember stan you are flying in colder than a
witches,.. eh . .broomstick weather, its only natural that the thermostat may not be able to keep up with the hot dump and the cold shock of the radiators 30 something coolant.

Did Jim get his engine swap into the motorhome yet ?



Jonathan

[Canadian Rhino]

The Subaru engine cooling system is indeed different from any other out there. If you look real close you will see that the cold water is drawn in past the thermostat and on in to the INLET of the water pump.
It is not like other engines where the hot water goes OUT to the rad through the thermostat.
The first thing you are going to think is how could the thing open if it always has cold water going past it.
What Subaru did was to let the heater core curcuit return line hit the thermostat element square on. If you look close you can see where that line enters the up side of the thermostat.
The reason they use the 170 thermostat is because the engine will be at around 200 but loose some in the heater core.
A 195 thermostat would make the engine run at around 230 or so.
Stan in your case if you are not running a heater core and just the full flow bypass hose, it is likely being over flowed by the bypass and the thermostat is maybe being held open. You may try putting some restriction in that line, but not too much at a time as you cant block it off all together.
On a Subaru car if the heater core gets plugged the the engine will overheat because the return line cant offer enough heat to open the thermostat.
The plus side of this system is that there is always hot water mixing with the cold at the inlet which is where the thermostat is so as not to shock the engine with bursts of cold water like you see with so called normal systems.;)

[automan1223]

Good point but that would explain all my troubles if I in fact closed off the line to the heater core. However I have a u line connecting the core tubes and thus eliminate the core. My engine still runs hot even with all that flow,.....

without the 4 1/8" holes drilled in the center of the tstat plate.

Wonder why that is.

Jonathan

[StanFoster]

Rhino: That is some good information...thanks. I am going to have to "chew" on that awhile before I act. I do have a heater with the bypasses fully open. When it gets clear to me what you are saying...I will close those slowly down. My water temps go up to the 180's on warmup..and today they were clear down to 120 in flight. Again..I will reread your post about 10 times and maybe it will stick in my head.:D I will then try your suggestion and close down the bypasses slowly. Maybe my thermostat is fine after all.

If this works....I will post a big thank-you.

Stan

[Aussie_Paul]

The Subaru engine cooling system is indeed different from any other out there. If you look real close you will see that the cold water is drawn in past the thermostat and on in to the INLET of the water pump.
It is not like other engines where the hot water goes OUT to the rad through the thermostat.
The first thing you are going to think is how could the thing open if it always has cold water going past it.
What Subaru did was to let the heater core curcuit return line hit the thermostat element square on. If you look close you can see where that line enters the up side of the thermostat.
The reason they use the 170 thermostat is because the engine will be at around 200 but loose some in the heater core.
A 195 thermostat would make the engine run at around 230 or so.
Stan in your case if you are not running a heater core and just the full flow bypass hose, it is likely being over flowed by the bypass and the thermostat is maybe being held open. You may try putting some restriction in that line, but not too much at a time as you cant block it off all together.
On a Subaru car if the heater core gets plugged the the engine will overheat because the return line cant offer enough heat to open the thermostat.
The plus side of this system is that there is always hot water mixing with the cold at the inlet which is where the thermostat is so as not to shock the engine with bursts of cold water like you see with so called normal systems.;)

Great post, I knew this about the Soobs, BUT not to the extent that having a bypass hose may cause problems.

Aussie Paul.:)

[STI]

Subaru Cooling System info

http://www.rs25.com/forums/showthread.php?t=40373

[StanFoster]

Thanks for the Subaru cooling info.

I went flying today....and first flew with the bypasses directing all the water through the heater and back to the thermostat. The temps still are normal on the ground...and then drop way back in flight.

So...I landed...and shut both valves off.....stopping all flow to the thermostat housing. I was expecting the temps to rise too high...but they never changed their ways at all.

It has to be a thermostat that is opening too early and staying open. I took Jim Logans advice and bought a regular Subaru thermostat...matching the number he sent me. I am going to install that tomorrow and do another flight test. I guess thats what these 40 hours are good for...to get the little bugs out.

I am over half way through my hours now and am loving this machine more every time I fly it.

Stan

[Canadian Rhino]

Stan, when you install the new one be sure to orientate it 90 degrees to the heater hose input. You want the hot water to hit the thermostat element square on and not hit the bracket that supports the element.;)

[StanFoster]

Phil: Ok...thanks for that as well. Man....I have a lot to learn...:eek:



Stan

[Harry_S.]

Stan;

I'm a little fuzzy on this but bear with me. If you already have the tstat installed, it's moot.

With the lower housing removed, with a mirrror you can look up into the block housing and see where the block opens up more to the inboard. In other words, the opening for the tstat is not straight up. The tstat is a bit offset, so I think the offset should go into the larger area.

Like I said...I'm a bit fuzzy on this...and it may not make a difference...but?!

Also, I don't know if the 2.5 has a difference in that area than the 2.2.


Cheers :)

[Dan_Reagan]

Stan

I had the same problem with cooling on my 2.2 on my AAI modified RAF. I took the thermostat out and set up a test by heating water to determine exactly when the thermostat opened. I don't remember exactly what the temp was supposed to be on the t'stat but it opened exactly where it was supposed to.

The temp guage would not move at all even though the t'stat was doing what it was supposed to do. My solution was to cover up 50% of the radiator in winter months and remove the cover in the summer. With the radiator partially covered the t'stat regulates great in the green. Not the ideal solution, but it works.

Dan Reagan

[StanFoster]

PROBLEM SOLVED...:D :) :D :) :D


I installed the Subaru brand thermostat which was much beefier. Anyway...now I have operating temps more like it. My heater hoses were now hot.....the temps read around 190...about 60 degrees warmer.


Stan

[Gyro Gerry]

Hi Stan. My EJ22 has a 172F Subaru thermostat and my water temp is 165 in flight. My oil temp is 225-230 in flight and I have an oil cooler. Before I put the oil cooler on, my oil temp was 30 degrees higher and was running about 255-260. I bought an after market cooler for about $100.00. Gerry

[Harry_S.]

I don't understand why AAI would not have a SUBARU tstat installed in that engine?:confused:

.

[StanFoster]

Gerry: I definately am putting on an oil cooler. Where did you hook the lines up to? There is a big plug in the crankcase that I suspect would be one place.


Thanks

Stan

[Chopper Reid]

Stan, if Subaru havent an oil cooler on their 2.5 powered vehicles, why would you need an oil cooler in a gyro where the amount of air flowing around the motor would be much greater??

[Gyro Gerry]

Stan. The oil cooler that I Installed comes with an adapter that screws on where the oil filter goes and the filter is then screwed onto the adapter. It is a universal kit and comes with the oil lines which look like heater hoses. The lines are not the fancy braided chrome ones, but the kit is the right price for what you get. I flew with Bill Finnegan today and the oil temp was about 220 and the water temp was about 165 while we were using power settings of around 4900- 5000 rpms. Gerry

[StanFoster]

Gerry: Thanks. By the way....Bill Finnegan had first mentioned that you needed an oil cooler. Now....I do.:eek:


Thanks for the info....sounds like a nice kit to bolt on..and simple. Love your SparrowHawk....I was with you at Mentone 2004 when you were just deciding to get one. You were a catalyst for me to get my own.

Now I have a hot one.:D so this cooler will help.


See ya sometime. Stan

[Chopper Reid]

I don't understand why AAI would not have a SUBARU tstat installed in that engine?:confused:

.


The reason is pretty straight forward Harry, give AAI some credit for knowing why they provided an aftermarket tstat instead of the factory one.

Stan has changed his from one that had the temps right to one that now hasnt got the temps right.
Its just plain commonsense, you make the water hotter and it follows that you make the oil hotter. In a vehicle, the engine needs to run hotter to make all the pollution gear work, in a gyro, this is not needed so therefore AAI run the cooler temp to save having to put an oil cooler on !!

[Harry_S.]

The reason is pretty straight forward Harry, give AAI some credit for knowing why they provided an aftermarket tstat instead of the factory one.

Its just plain commonsense, you make the water hotter and it follows that you make the oil hotter. In a vehicle, the engine needs to run hotter to make all the pollution gear work, in a gyro, this is not needed so therefore AAI run the cooler temp to save having to put an oil cooler on !!


You came up with a good one there Brian, but...I don't buy it.

I have no knowledge of gyro's with Soob engines, having overheated oil problems.

I don't have any oil problem and my water temp runs 180-185.


Cheers
:)

[Gary_in_Orygun]

I need to do something about my water temp on a warm day. The picture shows the water temp getting pretty high after a climb to almost 2000ft (from near sea level). The temp at this altitude is 77, and I'm sure it was a lot warmer when I took off.

Randy Rogers mentioned he moved his radiator from the muffler side of the vertical engine supports to the outside, on the prop-side of the supports which improved his cooling. Although, he also recently lost a water pump, which may have contributed to his high temps before he moved his radiator.

Any opinions? I don't have an oil temp gauge/sensor, so who knows what this high water temp yielded in oil temps.

[KenSandyEggo]

Depending on your prop, it could flex enough to hit the radiator if you put it on the outside of the braces. I think someone experienced this.

An old repeat.....make sure your water temp gauge's ground wire is not clustered with any other grounds. This is a common source of erratic readings. Best is to run it alone to the battery ground or at least its own ground on the buss-bar. I had erratic readings and the gauge-maker gave me this hint. It cleared it up immediately.

[Gary_in_Orygun]

Ken, I do not have erratic temp reporting like you did. Mine is consistent and reflects what is going on.

What is a high-temperature for water coolant?

[Harry_S.]

You know what...this may be a problem for combustion engineers?!

I live here in Central Florida and with the carbed Soob, I have had no problems with my motor...until last week.:rolleyes:

For almost nine years now, I have semi safetied my carb heat control. Last week, the air temp was about 72*F, and I forget now what I did, digit wise, but the engine...coughed...and I instantly JO'd the throttle and it came back to life before I reached down to un-safety the carb heat control. Carb ice...I don't know...but I had enough altitude and open country that there was no problem at getting down safely.;)

As you know, carb ice can form at temps other than *cold* and 65-75* is prime to form carb ice with the right humidity. Be prepared for any happening.


Cheers :)