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  #111  
Old 10-29-2018, 12:35 AM
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charosenz charosenz is offline
 
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Quote:
Originally Posted by rv7charlie View Post
To be sure we're on the same page, when you say bypass, do you mean from the water pump output back to somewhere on the block, without going through the radiator? If the answer is yes, is there any chance that when the pump starts working harder at higher rpm, more of the water is taking the path of less resistance, back through the block instead of through the rad?
Yes it is possible. But the bypass is 1/2" and the main radiator lines are is 1,25". I could easily pinch down the bypass to test the theory.

Last edited by charosenz : 10-29-2018 at 12:39 AM.
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  #112  
Old 10-29-2018, 12:42 AM
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charosenz charosenz is offline
 
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Last edited by charosenz : 10-29-2018 at 09:35 AM.
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  #113  
Old 10-29-2018, 09:34 AM
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  #114  
Old 11-07-2018, 03:53 PM
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charosenz charosenz is offline
 
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Default cooling gremlin

Well for those who may be following this thread I thought I would give an update. The gremlin still lives in my set up.!

Given that it appears as though the most likely culprit is trapped air, I have filled and refilled and burped this system 12 times. Each time pain staking making sure I do all I can to remove trapped air. burp it, run it with the cap off - everything. No changes.

I have ran with different thermostats and no thermostats. I have run with and without by pass hoses.

When I had a radiator with a top and bottom I reversed the hoses. Now I have a radiator that has the inlet and outlet horizontal.

Since the set up is running on a test stand with a just a radiator, it is no surprise it ends up overheating after hard runs. I think this is to be expected. It does fine at low loads and low rpm. But with the prop at full pitch and high RPM (over 20"MAP and over 3000 rpm) it overheats. This is to be expected. ( Anyone who has actual hands on experience running a water cooled engine on a test stand under load for extended time using a conventional radiator is encouraged to comment on this aspect.....)

The weird part, though, is that while the engine temp starts to creep up on heavy load.....the radiator outlet (2nd probe) starts to cool down.

In other words the engine temp probe, and the radiator outlet probe show temps that are close when - it is at low load. I.E. below 2500 rpm, and below 15" MAP. Once I start to push it the engine temp climbs and the radiator outlet probe temp starts to decline. The temperature difference I will call "Delta T". During low load the radiator outlet is 10*F lower. Above 3000 RPM and OVER 20" MAP the radiator outlet will drop as low as 155*F with the engine temp going over 200*F.


To me, it is as though there is a blockage of some kind in the system. Like an air pocket. But, if not an airpocket, then what?


1) Failing pump? Not likely

2) Pump pulley slipping? No indication of this.


3) FOD, (foreign object in the system? Who knows, would be crazy weird, but it would explain the systems.


Where to go???


I am going to try new tubes to evacuate any trapped air out of the two high spots on the block one more time.


If that does not work, I am going to install and incredibly small radiator, to see if I can keep the Delta T close even up to high temp. that would eliminate the current set up as the culprit.


I may put a thermostat back in but that really should not have anything to do with a high delta T...…


If you have any experience with running water cooled engines - especially on a test stand, I would really appreciate your thoughts....

This is certainly solvable, and in fact may be simply, but I am not there yet....

Thanks.

Charlie

Last edited by charosenz : 11-07-2018 at 03:57 PM.
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  #115  
Old 11-07-2018, 04:53 PM
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Do you have a diagram of your cooling setup?

From the video, it looks like a simple engine in/out, radiator in out. no overflow or bypasses. but I can't see everything from the video.

What are you using for cooling? (water, 50/50 glycol mix, Evans waterless?)

How's the radiator cap? Pressure rating? and can you check the pressure of the cooling system?

I've had weird issues when the radiator cap no longer seals properly. 1 symptom is the overflow tank will fill up and not siphon back when cooling down, but I also think the system doesn't pressurize and doesn't work quite right. If I have to remove the cap, I'll replace it with a new one.

How hot do you let it get before you shut it down?

Just a thought. (Subaru 3.0)
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  #116  
Old 11-07-2018, 06:08 PM
BillL BillL is offline
 
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It may be trapped air, but your cavitation comment may be more accurate. I would suggest you install a restrictor in the two bypasses you have there. Maybe a 1/4" hole in each. Then install the thermostat.


Here is why, the pump is likely located up high relative to the overall cooling pool, yielding low suction head. Then to aggravate the issue, the pump is sized for a particular back pressure, forcing flow through the head.

Part of the systems' restriction is the thermostat and part is the two coolers. The result of lowering the system restriction is 1. allowing vastly increased flow, that thereby increases pump inlet velocity and lowering NPSH, net positive suction head. This can create cavitation and . . 2. excessive bypass lowers the pressure, and therefore velocity across the head/block, which would aggravate the possibility for incipient boiling.

Overall, it is likely #1 is the major part of your issue as the power is not high enough to have the #2 issue.

After getting the flows right, then we can see if you need some vapor bleed lines. Bleed lines are not unusual for highly loaded engines and will collect gas and direct back to the top tank.

If you have the thermostat housing open, can you take and post a picture to see where the bypass is located?
Worth what you paid for it.
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Last edited by BillL : 11-07-2018 at 06:11 PM.
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  #117  
Old 11-07-2018, 06:43 PM
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rv6ejguy rv6ejguy is offline
 
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3000 rpm and 20 inches is pretty low hp, similar to going up a moderate hill in a car on the highway-perhaps around 40-50hp. I've run liquid cooled engines with props at these settings and nothing gets hot with some pretty small rads at 70F ambient temps.

The 45 degree delta is something I've never seen in all my rad testing and this pretty well must be due to the water flow being low at high rpms which points to cavitation. My deltas are typically 10-20F across the rad inlet to outlet.

Maybe install a flow meter inline and see what's happening as rpms increase.

Bill's advice on the active bleed line is good. Those have proven to be highly beneficial on Subarus which can trap air easily due to their horizontal layout. I have a .125 ID hose going from the the top of my coolant crossover pipe joining the two banks to the top of my expansion tank.
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  #118  
Old 11-07-2018, 10:49 PM
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charosenz charosenz is offline
 
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Quote:
Originally Posted by jcaplins View Post
Do you have a diagram of your cooling setup?

From the video, it looks like a simple engine in/out, radiator in out. no overflow or bypasses. but I can't see everything from the video.

What are you using for cooling? (water, 50/50 glycol mix, Evans waterless?)

How's the radiator cap? Pressure rating? and can you check the pressure of the cooling system?

I've had weird issues when the radiator cap no longer seals properly. 1 symptom is the overflow tank will fill up and not siphon back when cooling down, but I also think the system doesn't pressurize and doesn't work quite right. If I have to remove the cap, I'll replace it with a new one.

How hot do you let it get before you shut it down?

Just a thought. (Subaru 3.0)

I am using Honda OEM coolant Type 2. It is a new cap. I shut it down when it gets over boiling. I know it is not working correctly.

Quote:
Originally Posted by BillL View Post
It may be trapped air, but your cavitation comment may be more accurate. I would suggest you install a restrictor in the two bypasses you have there. Maybe a 1/4" hole in each. Then install the thermostat.


Here is why, the pump is likely located up high relative to the overall cooling pool, yielding low suction head. Then to aggravate the issue, the pump is sized for a particular back pressure, forcing flow through the head.

Part of the systems' restriction is the thermostat and part is the two coolers. The result of lowering the system restriction is 1. allowing vastly increased flow, that thereby increases pump inlet velocity and lowering NPSH, net positive suction head. This can create cavitation and . . 2. excessive bypass lowers the pressure, and therefore velocity across the head/block, which would aggravate the possibility for incipient boiling.

Overall, it is likely #1 is the major part of your issue as the power is not high enough to have the #2 issue.

After getting the flows right, then we can see if you need some vapor bleed lines. Bleed lines are not unusual for highly loaded engines and will collect gas and direct back to the top tank.

If you have the thermostat housing open, can you take and post a picture to see where the bypass is located?
Worth what you paid for it.
Bill, makes perfect sense. Give I had some success today, I will definitely get the thermostat on for more testing. see my comment at the end on the relative success.....I do have an extra thermostat housing with both ports that return in to it I will take a picture tomorrow.


Quote:
Originally Posted by rv6ejguy View Post
3000 rpm and 20 inches is pretty low hp, similar to going up a moderate hill in a car on the highway-perhaps around 40-50hp. I've run liquid cooled engines with props at these settings and nothing gets hot with some pretty small rads at 70F ambient temps.

The 45 degree delta is something I've never seen in all my rad testing and this pretty well must be due to the water flow being low at high rpms which points to cavitation. My deltas are typically 10-20F across the rad inlet to outlet.

Maybe install a flow meter inline and see what's happening as rpms increase.

Bill's advice on the active bleed line is good. Those have proven to be highly beneficial on Subarus which can trap air easily due to their horizontal layout. I have a .125 ID hose going from the the top of my coolant crossover pipe joining the two banks to the top of my expansion tank.
Ross, and guys,

I did have some success today. I changed the way I was Bleeding the system. Hard to explain so I will share some pics of the set up. I have a tube exiting the high point of the block - where the OEM temp probe used to be. I added a filler cap in the block exit coolant hose and added an aftermarket overflow cap. I poured the high point tube in to the overflow bucket.

I no longer see the divergence of the delta T. But I ran out of daylight and was only able to do minor testing without the prop. But the Radiator exit temp stay relative to the coolant temp exiting the block. They were 16* to 22* apart, but the good news is they stayed relative to each other. The proof will be when I add the prop and do some load testing with it.

If it goes well I will add the thermostat back on and see if Bill's theory of flow works well for my set up. I hope it does!!!

Here is a pic of the overflow and bleed line set up.

http://www.halie.com/o76.jpg

(I wish I could get a real pic to show up and not just a link. I am using halie web hosting).

Here is a link to both radiator lines and the HOT temp and the COLD temp.

http://www.halie.com/o7y.jpg

I will get a pic of the inside of the thermostat housing (I have an extra one) to show where the bypass enters. It enters behind the thermostat and of course serves to warm up the block uniformly before the thermostat opens up.

I hate to be a bother, but I really appreciate all the help. I know this will get resolved,

Thanks!

Charlie

Last edited by charosenz : 11-08-2018 at 12:13 AM.
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  #119  
Old 11-08-2018, 08:29 AM
Tomcat RV4 Tomcat RV4 is offline
 
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Default Cooling

Dont know about cooling on eng stand, but I followed Ross from SDS info on
ducting too and from rad, never cooling problem, PROPER DUCTING MAKES ALL
DIFFERENCE IN THE WORLD ! Tom
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  #120  
Old 11-08-2018, 04:18 PM
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charosenz charosenz is offline
 
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Tomcat

Yes we're fortunate to have Ross' knowledge and expertise to draw from. He has been super helpful to me for years and the SDSEFI is an excellent product.

Do you have a alternative engine in your -4?

Charlie
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