The Subaru SVX World Network   SVX Network Forums
Live Chat!
SVX or Subaru Links
Old Lockers
Photo Post
How-To Documents
Message Archive
SVX Shop Search
IRC users:

Go Back   The Subaru SVX World Network > SVX Main Forums > Technical Q & A

Reply
 
Thread Tools Display Modes
  #1  
Old 04-09-2003, 09:14 AM
sfsvx's Avatar
sfsvx sfsvx is offline
Yeah, it's a poodle - so what?
 
Join Date: Aug 2002
Location: Santa Fe, NM
Posts: 907
Stock vs. External Tranny Cooler

I understand that the efficiency of the stock cooler is higher because of the liquid-to-liquid interface. However, the temperature of the coolant in the radiator must be far higher than ambient air.

Given the higher coolant temperature (I'm guessing 150 - 180 degrees F) in the radiator, and the lower ambient air temp (Santa Fe seldom gets up to 100 deg F), is the actual cooling effect (as opposed to cooling efficiency) of an external cooler higher than the stock cooler?
__________________
Dick
**************
1999 Legacy GT 30th Anniversary Edition
2001 Outback Sport
Reply With Quote
  #2  
Old 04-09-2003, 11:30 AM
lee lee is offline
Registered User
 
Join Date: Mar 2002
Location: Indialantic, Florida
Posts: 2,940
what a good question. I have no idea and have to think for a while and would have to investigate heat echangers.

one thing to keep in mind is I "believe" (those who read the alignment thread know what my thoughts are worth - not much) that the ideal operating temp is somewhere around 150F. Just high enough to get the TC to lock up, but not so much as to markedly degrade the life expectancy of the ATF.
Reply With Quote
  #3  
Old 04-09-2003, 11:36 AM
svx_commuter's Avatar
svx_commuter svx_commuter is offline
Making tires round, Six now :)
 
Join Date: Feb 2001
Location: North Jersey
Posts: 3,433
I think the radiator and a 1/4 size (of orginal radiator) add should be in series, add on after the radiator.

A very large AFT (3/4 size) cooler is needed if the radiator is by passed.

I still do not know the answer to how hot the radiator fluid gets. If the fluid never goes over 180F the setting for the T-stat then the radiator should be included in teh cooling path with the add on.

The question is: How hot does the radiator coolant get after a repeated romping around on the gas pedal?
Reply With Quote
  #4  
Old 04-09-2003, 11:40 AM
svxistentialist's Avatar
svxistentialist svxistentialist is offline
Jersey Girl
Alcyone Gold Contributor
 
Join Date: Mar 2001
Location: Ireland
Posts: 8,270
Send a message via Skype™ to svxistentialist
Registered SVX
Re: Stock vs. External Tranny Cooler

Quote:
Originally posted by sfsvx
I understand that the efficiency of the stock cooler is higher because of the liquid-to-liquid interface. However, the temperature of the coolant in the radiator must be far higher than ambient air.

Given the higher coolant temperature (I'm guessing 150 - 180 degrees F) in the radiator, and the lower ambient air temp (Santa Fe seldom gets up to 100 deg F), is the actual cooling effect (as opposed to cooling efficiency) of an external cooler higher than the stock cooler?
That's a very good question Dick.

[This is what people generally say when they don't know the answer ]

The stock liquid/liquid cooler is more efficient as you say, which means it is better at taking away heat than a liquid/air model. If the coolant liquid was as cool as ambient air, it would be a no contest, stock would win over the additional cooler.

The stock cooler has one big advantage over the add-on model, it can heat up the tranny oil in the morning to the optimum viscosity, and maintain it within the desired range, usually.

I have the extra cooler on mine, and the high viscosity of the cold ATF causes clunky shifts in the mornings.

What the extra cooler does in warmer situations, heavy traffic and hillclimbs, it will keep the temp from going too high, i.e. prevents heat spikes beyond the normal range. This stops the ATF from breaking down and saves our trannies.

In colder climes, the extra cooler may be overkill. Remember, the ATF has to be above a certain temperature range [150ish I think??] before the lockup clutch will operate in 4. Oil being too viscous is also sure to affect fuel consumption.

Joe
__________________
Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty
Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea
Candy Purple Honda Blackbird Plum Dangerous
White X2 RVR Mitsubishi 1800GDI. Vantastic

40,000 miles Jersey Girl
Reply With Quote
  #5  
Old 04-09-2003, 06:34 PM
Earthworm's Avatar
Earthworm Earthworm is offline
Meow!
 
Join Date: Mar 2002
Location: Winnipeg, Manitoba
Posts: 11,957
Send a message via ICQ to Earthworm Send a message via AIM to Earthworm Send a message via MSN to Earthworm Send a message via Yahoo to Earthworm Send a message via Skype™ to Earthworm
Re: Re: Stock vs. External Tranny Cooler

Quote:
Originally posted by svxistentialist
In colder climes, the extra cooler may be overkill. Remember, the ATF has to be above a certain temperature range [150ish I think??] before the lockup clutch will operate in 4. Oil being too viscous is also sure to affect fuel consumption.
I can drive for 15 mins in 40 degree weather and only then would the TC finally lock up.
Reply With Quote
  #6  
Old 04-10-2003, 03:21 AM
svxistentialist's Avatar
svxistentialist svxistentialist is offline
Jersey Girl
Alcyone Gold Contributor
 
Join Date: Mar 2001
Location: Ireland
Posts: 8,270
Send a message via Skype™ to svxistentialist
Registered SVX
Re: Re: Re: Stock vs. External Tranny Cooler

Quote:
Originally posted by Earthworm
I can drive for 15 mins in 40 degree weather and only then would the TC finally lock up.
I can well believe this David. This will be costing you a little in the consumption stakes, and we all know the SVX is not exactly a paragon of virtue in this department.

A good fix is fit a valve that will deny oil to the extra cooler in cold winter weather, and work as it is supposed to using the stock one.

A cheaper solution, and just as effective, is to fit a piece of card or light aluminium across the front surface of the extra cooler, again, only in cold weather. Be aware if it is big and fitted in the usual place out front or in the sandwich position, you will also be denying cooling air to the rad and/or the aircon condenser. This would not be good or clever. If you hear the fans coming on a lot, working overtime, compromise and only block half the surface of the extra cooler.

The divert valve is the better solution. In either case, when the weather warms up, don't forget to open the valve or remove the card as the case may be.

Joe

PS Enjoy Reading!
__________________
Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty
Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea
Candy Purple Honda Blackbird Plum Dangerous
White X2 RVR Mitsubishi 1800GDI. Vantastic

40,000 miles Jersey Girl
Reply With Quote
  #7  
Old 04-10-2003, 03:29 AM
svxistentialist's Avatar
svxistentialist svxistentialist is offline
Jersey Girl
Alcyone Gold Contributor
 
Join Date: Mar 2001
Location: Ireland
Posts: 8,270
Send a message via Skype™ to svxistentialist
Registered SVX
Thumbs up

Quote:
Originally posted by svx_commuter
I think the radiator and a 1/4 size (of orginal radiator) add should be in series, add on after the radiator.

A very large AFT (3/4 size) cooler is needed if the radiator is by passed.

I still do not know the answer to how hot the radiator fluid gets. If the fluid never goes over 180F the setting for the T-stat then the radiator should be included in teh cooling path with the add on.

The question is: How hot does the radiator coolant get after a repeated romping around on the gas pedal?
I would not worry much on this score. The radiator for the coolant and the fans working it are very effective at keeping the temp even.

My dashboard temp gauge never goes beyond half way, in any hot weather, in heavy traffic, or when thrashing it speed-wise. Good cooling system IMO.

Harvey mentioned in a thread elsewhere that the tray beneath the rads acts in a way to duct extra air through for better cooling at high speeds. Don't know how this works, but I believe it. My temp needle never stirs for any kind of provocation.

Joe
__________________
Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty
Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea
Candy Purple Honda Blackbird Plum Dangerous
White X2 RVR Mitsubishi 1800GDI. Vantastic

40,000 miles Jersey Girl
Reply With Quote
  #8  
Old 04-10-2003, 06:11 AM
Earthworm's Avatar
Earthworm Earthworm is offline
Meow!
 
Join Date: Mar 2002
Location: Winnipeg, Manitoba
Posts: 11,957
Send a message via ICQ to Earthworm Send a message via AIM to Earthworm Send a message via MSN to Earthworm Send a message via Yahoo to Earthworm Send a message via Skype™ to Earthworm
hehe, guess what...I don't have a separate cooler.
Reply With Quote
  #9  
Old 04-10-2003, 11:16 AM
kuoh kuoh is offline
Registered User
 
Join Date: Mar 2002
Location: Kansas City, MO
Posts: 1,200
Send a message via AIM to kuoh
FYI: The engine temp sensor does not give any indication of the tranny temp. There is simply too much heat mass and too little transfer area in the engine cooling system for the tranny fluid to significantly alter the thremal content. If you install a tranny temp sensor, you'll be able to see that the tranny temp can be significantly higher, in the area of 220+, and yet the engine temp needle will remain steady. The fans will just cycle more often and stay on longer to keep the cooling system at optimal temperature.

KuoH

Quote:
Originally posted by svxistentialist
My dashboard temp gauge never goes beyond half way, in any hot weather, in heavy traffic, or when thrashing it speed-wise. Good cooling system IMO.
Reply With Quote
  #10  
Old 04-11-2003, 03:32 AM
svxistentialist's Avatar
svxistentialist svxistentialist is offline
Jersey Girl
Alcyone Gold Contributor
 
Join Date: Mar 2001
Location: Ireland
Posts: 8,270
Send a message via Skype™ to svxistentialist
Registered SVX
Quote:
Originally posted by kuoh
FYI: The engine temp sensor does not give any indication of the tranny temp. There is simply too much heat mass and too little transfer area in the engine cooling system for the tranny fluid to significantly alter the thremal content. If you install a tranny temp sensor, you'll be able to see that the tranny temp can be significantly higher, in the area of 220+, and yet the engine temp needle will remain steady. The fans will just cycle more often and stay on longer to keep the cooling system at optimal temperature.

KuoH

Thanks Kuoh.

I didn't suggest the engine temp gauge relayed any indication of tranny temp. I was answering his query on whether the coolant temp went up when thrashing the car.

Must admit, if I was going to put in extra equipment, a tranny oil temp gauge is at the top of that list.

Joe
__________________
Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty
Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea
Candy Purple Honda Blackbird Plum Dangerous
White X2 RVR Mitsubishi 1800GDI. Vantastic

40,000 miles Jersey Girl
Reply With Quote
  #11  
Old 04-11-2003, 09:16 AM
kuoh kuoh is offline
Registered User
 
Join Date: Mar 2002
Location: Kansas City, MO
Posts: 1,200
Send a message via AIM to kuoh
Oops, sorry. I see where you were going with that now.

KuoH
Reply With Quote
  #12  
Old 04-11-2003, 03:12 PM
svxistentialist's Avatar
svxistentialist svxistentialist is offline
Jersey Girl
Alcyone Gold Contributor
 
Join Date: Mar 2001
Location: Ireland
Posts: 8,270
Send a message via Skype™ to svxistentialist
Registered SVX
Thumbs up

Quote:
Originally posted by kuoh
Oops, sorry. I see where you were going with that now.

KuoH
No probs man. Actually your point about the relevant sizes of the heat mass does answer why the lockup does not occur for 15 minutes, even without an extra cooler.

Touche.

Joe
__________________
Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty
Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea
Candy Purple Honda Blackbird Plum Dangerous
White X2 RVR Mitsubishi 1800GDI. Vantastic

40,000 miles Jersey Girl
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 08:30 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
© 2001-2015 SVX World Network
(208)-906-1122