Can you cool the coolant where its not getting cooled? (Long)

[Tarantula]

When I added a FMIC to my 95 Talon (RIP) I had issues with overheating. Now I have a 98 and I bolted the same exact mods and I have less issues. Horray!! Right. Well Summer is coming and I am doing a total remodel of the 98's engine. So I looked into the coolant system and how it works. The ones in red is what I want to focus on:
Water flow direction.
From lower radiator hose to thermostat housing. Thermostat housing to large water pipe. Water pipe to Water pump. Pump to inside block and head. With thermostat closed, water flows to heater core (lower 5/8" hose). than from heater core (Upper 5/8" hose) to small water pipe that wraps around the block, than back to Large water pipe.
With thermostat open, water flows to both heater core and upper radiator hose and into radiator where it gets cooled.
Upper radiator hose has a connection (3/8" hose to metal pipe). This flows behind turbo under large water pipe into oil cooler. Than oil cooler to large water pipe completely bypassing the radiator than into block. For the turbo, it flows from the block to turbo cartridge than to big water pipe; also completely bypassing the radiator. The Throttle body receives its water from the heater core inlet pipe from the thermostat housing and returns to the heater core outlet pipe that wraps around the block.

Now as I think this through, usually when you boost, the temps skyrocket. The turbo is heating the already hot water coming from the block and feeding it into the large water pipe, that is running cooled coolant from the radiator WTF therefore heating it back up. Also you have oil running through the turbo and this is some really hot oil. Well this oil is supposidly getting cooled but in actuality hot water from the head is being fed behind the 1000F degree turbine housing and is getting even hotter trying to cool the hot oil from the turbo and engine. And this too is being fed in to same water pipe that is getting the cooled radiator coolant that was warmed up a little from cooling the turbo. Not to mention that even the big water pipe runs behind the turbo getting its shared radiant heat from the turbine housing.
Makes me think "What was they thinking." Maybe its alright for stock but horsepower is heat energy. The more horspower we make our cars produce, the hotter its going to run. Now My question is this.

Can I take the water that the turbo heated and run it to a Transmission cooler (Like a small radiator)than run the now cooled coolant from the tranny cooler to the water pipe connection nipple. I chose the turbo's supply cause I figured that water has better heat transfer ability than oil, so the coolant from the turbo would most likely be hotter than the coolant from the oil cooler. I even thought about running a small fan on the tranny cooler to cool even more faster. I would place this cooler on the driver side hole in the bumper. For an even more extreme cooling, you can have a TRUE cooling system by running the turbos coolant on the SMIC side and the oil cooler water on the Drivers side. Than all of the water circulating is being cooled to some degree.
I got the idea from turning on the heat in the 95 to bring temps down. Since water is always running through the heater core. So turning on the heat is like running another radiator fan.
Please post thoughts comments and ideas. Thanks

 

[toybreaker]

I see your logic.

Audi engineered themselves into a corner in the 80's, and ran a supplemental cooler on some of their cars, but I *believe* it was on the t-stat loop.

In the 90's they went to an electric pump, that runs after shutdown, circulating coolant thru the sytem after a hard run...Tres' cool,...but the pumps are $$ and seem to be prone to leakage/failure. I have a few of these in stock, pm me if you want to play with one.

On the present generation cars they seem to have figured out it's all about the oil...

As for cooling the turbo, those wily engineers know a thing or two about thermodynamics. If you stay anywhere near the peak efficiency on the map, they won't self-destruct, even under prolonged abuse. What kills them is more the heatsoak following a heavy thermal cycle. The housings have several different thicknesses/cross sections, and they operate at VASTLY different temperatures. I trust the engineers to spec the proper materials for the housing/rotating assembly. It's up to me to put the heat into the system slowly, and equalize the housing temperatures somewhat by not boosting/cooling the system before shutdown. It's the sudden changes in temperature that stress things...

One very interesting anomoly has to do with the wastegate area.On internal wastegate systems, with the flapper closed, that area of the housing gets heated (mostly) by conduction. When the flapper opens, presto..hot gases..instant temp change...and boy does that metal change color/dimension in a hurry!!!It's amazing it doesn't freakin crack into a million pieces....The external wastegate systems are really cool to watch on a dyno...

I have had several conversations with the engineers at garret, and they assure me that the oil is the primary cooling factor in the turbo's center section. The oil is in direct contact with the bearings, and pulls an insane amount of heat out of the center section. For giggles, take an infrared pyrometer and shoot your turbo drain after a hard run, the results will suprise you!!!!

I played with a lot of oil only turbo's back in the day. Primarily on air cooled motors. It was simply a matter of correctly sizing the oil cooler, and controlling it thermostatically to deliver enough heat rejection for everything to live. What would kill things would be the heat soak at shutdown smoking the residual oil in the center section. An educated driver had very few real problems, but the boost it and go guys had endless trouble, and there was a very real learning curve.

This is why most oem installs use a water cooled center section, it will cut down on the heat absorbed by the center section/bearings at shutdown, reducing warranty claims. An interesting phenomenom occurrs in the turbo at hot shutdown as well, the local heat will move coolant thru the system, like a thermosiphon... from the hot turbo into the cooling system...so there is a limited amount of coolant already moving in the system without any external pumps. This *generally* keeps the center section temps reasonable enough that coking is minimized.

I've always felt that controlling oil temps is the key to a long and productive powerplant life. The piston crown temperatures is one of the key limiting factors to power output. As you say, more power=increased temperatures. The dsm engineers use piston sprayers to cool the underside of the pistons, and that goes a long way to keeping things reasonable under boost/high combustion chamber temps.

I run egt and oil temp gauges, and primarily watch the oil temp as an indication I'm having too much fun. I don't have near the mods most guys have, but, my commute home is 36 miles uphill, and most of that is dirt... . On a hot day, I can max out the oil temps, without getting vary scary egt's, (and the coolant gauge never budges off 1/2 scale, even with the oil approaching total thermal failure) Spraying oil on the undersides of the pistons works wonders at keeping the pistons cooler/dimensionally stable, but all that additional heat ends up in the oil...

I run the antifreeze/oil heat exchanger on my winter beater, and the external oil cooler on the summer car. The external cooler is way better at removing oil temp, and it doesn't dump it into the coolant, so the total temperature rejection is that much higher.

I *believe* egt is more about exhaust gas temp than actual engine load and that's mostly about the mix..( I don't actually know this , I'm just guessing) Increasing the volume, but not the temp of the egt's, will *probably* not effect the turbo housing temp on the same scale as the increased combustion chamber pressure/temps will increase oil and coolant temps...As long as the egt's don't get insane, the housing/center section will just plateau at a slightly higher temp.

My opinion, I'm probably wrong, I didn't pay much attention in school

I would say if you can keep the coolant temps reasonable, (think cool guy radiator...)
The radiator cap from a 300z tt is rated at 16#'s, and makes a nice upgrade (on a healthy cooling system, ymmv due to aging hoses etc...) and redline water wetter will cut down on nucleate boiling, (local hot spots boiling the coolant in the water jacket/head)
If you're still running the ac condensor, make sure the fins aren't all spranglified/full of cat hair, etc...It's a good idea to rinse the condensor from the backside anytime the radiator is out...A good set of aftermarket fans will take care of airflow requirements at lower roadspeeds/traffic lights and etc...

And make sure you're getting the airflow thru the radiator. Many fmic setups delete the airduct between the bumper cover and radiator support. This allows air to go anywhere except thru the radiator... no aiflow=no heat rejection. It's not that hard to reseal things with a little creativity and some thin plastic sheeting, secured with zip-ties.

I've wired my fans so I can turn them on manually, and I will run the engine at ~1500 rpm with the fans on for a little bit before allowing the car to idle down for shutoff. I think the turbo timers are a little hard on things. The alternator has a hard time producing radiator fan sized current at idle...and all my pos cars have rediculously low oil pressure at idle...so I prefer to stabilize things myself, it just takes a couple of extra minutes....Timers are good for the people who don't want to babysit their cars, but they do have their limitations.

Venting the hood will do good things for underhood temperatures, especially at shutdown.

Keep the egt's reasonable...(think dsmlink/aem/etc... and supporting fuel mods)

Run an adequately sized intercooler to keep the iat reasonable.

And run an appropriately sized thermostatically controlled oil cooler.

You'll get good service from just about any combination you can come up with. Oil temp really is the key, and as long as it's thermostatically controlled, It's unlikely that you'll have any substantial cooling system problems from adding power/heat, as oil removes most of the heat from the things we need to worry about.

A quality synthetic oil is a good investment if you're going to run high oil temp for extended periods.


Errrr...what was the question again...

I'm sure you could engineer some kind of additional cooling capacity into the cars cooling system, but I think that would only be neccessary under some really extreme circumstances...I would strongly suggest you run an oil temp gauge, and use that as a reference for how hot the important things are getting. The oil temp is a very good primary indicator of what's happening where the action is.

I would be curious to hear from other people who run oil temp gauges as to their oil temps, and what,if any mods they did to bring them more inline with what they should be.
Mine scare me... over 250f into the cooler, without even trying hard on a hot day, just the usual tarmac/gravel rally home...and worst case has been 250f out of the cooler....( hot day, 60 mph tailwind...)Yikes!!!! My cars lead hard lives.. Thank god for synthetics!!!

Maybe someone will answer your original question...ooops...D )

And, yea,...I remember turning the heater on my old big block chevy on the way home from the strip on a 100* night....can you say...sweltering.....

 

[Tarantula]

Idid alot of things to this 98 that i did not do to tthe 95. I had serious trouble in the summer with the 95. For this one I don't have any problems with overheating, even with the AC running but I wrapped the turbine and o2 housings, and shielded the water pipe from radiant heat. I'm going to run a project that turns on the fans even over 50 mph via a VW thermo switch. But I want to do as much as possible to be prepared for the worst.
With regards to my Q, I don't want to change the way the turbo's cooling or oil cooler works. My main concern is the connections to the water pipe. I don't want any coolant that has not been cooled somehow entering the waterpipe. The coolant temp from the radiator is the temp I would like entering the block. Not preheated coolant from both the turbo and oil cooler. I feel that the temperature that goes into the turbo and oil cooler is fine. I don't have a problem with that. Its after the coolant leaves the turbo and oil cooler and wants to enter the system via the water pipe that gets me boiling

Now to those that run an external oil cooler, do you think that because by doing an external oil cooler and eliminating the oil/water exchanger the coolant run slightly cooler?

And do you think it might be worth cooling the coolant that exits the turbo or oil cooler before it enters the water pipe?

 

[sp00ln]

I've also had the same idea. I'm subscribing to see if anyone has attempted this.

Also, could you heat wrap your lower radiator hose so the cooler water is not exposed to the hotter elemets of the engine bay?

 

[Tarantula]

I've also had the same idea. I'm subscribing to see if anyone has attempted this.

Also, could you heat wrap your lower radiator hose so the cooler water is not exposed to the hotter elemets of the engine bay?

Well I wrapped my O2 housing, Turbine housing, Oil cooler coolant line, Evo Manifold and water pipe and for sure the engine bay runs cooler.
I ran a custom pipe setup with a VW thermo switch to turn my Rad fan on at 203 and shut off at 190. So far perfect. I have yet to see my temps go over 203. I'm going to try running the oil cooler line to a 24 row stacked oil cooler with a fan to see how this works. By running cold water through the stock oil cooler I'm going to see if temps will stay even cooler.
Today was a hot day. I ran the AC all day and temps never exceeded 199F. I'm sure my plan to cool the water that flows through the water/oil cooler will help. I'll post results.

 

[MrBoxx]

I'm interested in how this will work out. I've always thought about putting a small trans fluid cooler in-line between the oil filter housing and the turbo to cool the oil off even more before it hits the turbo. I never thought about installing a mini-radiator for the coolant lines though.

 

[sp00ln]

Well I wrapped my O2 housing, Turbine housing, Oil cooler coolant line, Evo Manifold and water pipe and for sure the engine bay runs cooler.
I ran a custom pipe setup with a VW thermo switch to turn my Rad fan on at 203 and shut off at 190. So far perfect. I have yet to see my temps go over 203. I'm going to try running the oil cooler line to a 24 row stacked oil cooler with a fan to see how this works. By running cold water through the stock oil cooler I'm going to see if temps will stay even cooler.
Today was a hot day. I ran the AC all day and temps never exceeded 199F. I'm sure my plan to cool the water that flows through the water/oil cooler will help. I'll post results.

Can you give me some details on the VW thermo switch? I'm interested in doing that.

I'm waiting for results

 

[Tarantula]

Can you give me some details on the VW thermo switch? I'm interested in doing that.

I'm waiting for results

Ok the Thermoswitch needed is Part # SW533 from Autozone. You will need
1-- 1/2" npt Brass Pipt T
1-- 1/2" npt Brass elbow
2-- 1/2" to 5/8" hose adapter
To install it you will need to drill and tap one of the holes of the Brass "T" The tap needed is M22 x 1.5. I found it at E-taps.com for $39 The Drill bit to use is 3/4" Try Ebay for these things. You can get them cheaper.
A pic of what I made (The project) can be found at the following link.http://www.dsmtalk.com/gallery/showphoto.php?photo=5456&cat=500&page=1
You take the setup and hook it into the heater hose that comes off the Thermostat housing. This is the coolant inlet for the heater core. The hose is 5/8" The Thermoswitch has 2 prongs. When it closes (200F) it will carry either current or ground across the two prongs. I chose ground to tap to the lo fan relay. This will turn on one fan. If you chose to use a custom fan than you can use 12V. Up to you.
Details of the project as well as useful info can be found here.http://www.dsmtalk.com/forums/showthread.php?t=137526&page=1&pp=25
I also, as a bonus, installed a LED in the car to let me know when the fan turns on and off.

 

[sp00ln]

Thanks for the info!

 

[Tarantula]

I'm interested in how this will work out. I've always thought about putting a small trans fluid cooler in-line between the oil filter housing and the turbo to cool the oil off even more before it hits the turbo. I never thought about installing a mini-radiator for the coolant lines though.

Ok. I've installed an oil temperature guage to see whats going on with the oil. After a couple of drives like I normally do, the oil temps rise to about 215-220F and pretty much stays there. The water temps rise to about 200 and cycles between 190-203F due to the fan controlling these temps (With my project). I have noticed that the oil temps are usually anywhere from 15-30 degrees higher than water temps. When my temps hit 217 (Climbing a very long steep hill with the AC running) the oil temps went up to 240F. I also found that the higher the load, the faster the oil temps rise. This concludes that oil temps do have something to do with water temps or at least it has influence. The higher the oil temps the higher the water temps gets and harder to cool down. Makes sense really. Than I wanted to see about how long it would take for the oil temps to lower to about the same temps as the water. I ran the car till the oil temps rose to about 220 (Normal driving) Pulled over and waited while the car was idling. The water temps dropped to 190 and cycled between 190-200F very easilyt and rapidly. On the other hand, It took a long time to get the oil temps to match from 220 to 190. So this concluded that running cool water through the oil exchanger like I planned would NOT work any better. Its just too small.WTF So I have decided that the best route is to get an air/oil cooler and mount a fan to it. This would directly cool more oil at a time as it passes through it and therefore the water temps are much more easily controlled.
Just wanted to update with my on going research.
When oil temps were below 220F, the water temps dropped quicker as the fan cycled.

 

[toybreaker]

Verifying your progress is a good thing.

Where are you measuring your oil temp? Is there a possibility you're checking inny temp to the anti-freeze oil heat exchanger? I would think the outty temp would follow the coolant temp down relatively quickly at an almost 1 for 1 ratio. It does on my car.

It is completely normal for the oil temps to be higher than the coolant temps. The oil is in direct contact with the hot, moving parts, and will see much higher temps from these parts, than the coolant sees from the water jacket.

External air/oil coolers are the final solution to most cooling system woes caused by increasing the heat load on the vehicles cooling system with high performance mods. The heat that they remove goes to the ambient air, not back into the cooling system to be removed by the radiator. In the real world, that heat just ...disappears...

Those wily engineers spec things out pretty well for stock power levels during the design/engineering phase. After we're done "improving" their designs for higher power levels, we have a higher heat load to remove from the cooling systems.

The coolant area of life recieves the most attention because it's hard to ignore the coolant gauge, and/or coolant boiling/leaving the system....

When in reality, it's the oil that's doing the job of keeping the moving parts cool, and alive.

A thermostically controlled oil to air heat exchanger will probably resolve any and all issues you are having. When you are picking the thermostat temperature rating, please do not choose one that will run the oil too cold. It has to be warm enough to keep moisture/condensation from forming in the oil, as well as circulate well thru all the small orifices in the motor...(think about the lifters)

Try and place the cooler to the side, so it doesn't block airflow into the radiator. Try and get the air to flow thru the core not around it. A duct from a 3000gtvr4 side mount intercooler (drivers side) is what I used, and it fit my 1g with minimal trimming. Try and recess the cooler, to prevent damage from a bumper shot.

The oil in modified motors lives a really hard life, and anything we can do to keep it from being re-refined (by excessive heat) inside the motor will provide real world benefits.

Good luck, and please keep us posted as to your progress. You're on the right track, and documenting your results will help others in the same situation.

 

[sp00ln]

Ok. I've installed an oil temperature guage to see whats going on with the oil. After a couple of drives like I normally do, the oil temps rise to about 215-220F and pretty much stays there. The water temps rise to about 200 and cycles between 190-203F due to the fan controlling these temps (With my project). I have noticed that the oil temps are usually anywhere from 15-30 degrees higher than water temps. When my temps hit 217 (Climbing a very long steep hill with the AC running) the oil temps went up to 240F. I also found that the higher the load, the faster the oil temps rise. This concludes that oil temps do have something to do with water temps or at least it has influence. The higher the oil temps the higher the water temps gets and harder to cool down. Makes sense really. Than I wanted to see about how long it would take for the oil temps to lower to about the same temps as the water. I ran the car till the oil temps rose to about 220 (Normal driving) Pulled over and waited while the car was idling. The water temps dropped to 190 and cycled between 190-200F very easilyt and rapidly. On the other hand, It took a long time to get the oil temps to match from 220 to 190. So this concluded that running cool water through the oil exchanger like I planned would NOT work any better. Its just too small.WTF So I have decided that the best route is to get an air/oil cooler and mount a fan to it. This would directly cool more oil at a time as it passes through it and therefore the water temps are much more easily controlled.
Just wanted to update with my on going research.
When oil temps were below 220F, the water temps dropped quicker as the fan cycled.

Well, I found an error in your logic ( I think ). Oil is thicker, correct? So it's going to take longer to cool down if it gets hot. But the opposite could be said as well, if it's cool, it will take longer to become warm/hot. Perhaps if your cooler water was there, it would prevent it from becoming that hot in the first place, and aid it during the cooling process. Just a thought....

 

[toybreaker]

The rate at which heat is removed by the coolant/oil sandwich coolers is a constantly changing equation. The greater the temp difference between the oil and coolant the more heat is transfered. The higher the engine rpm, the faster coolant and oil will traverse the cooler, which will also change the transfer rate. I'm sure there's a bunch of other factors, but those are what come to mind right off hand.

Transfer is the key word, the heat from the oil is transfered into the coolant. This increases the cooling system load significantly

You guy's are both right.

Tarantula's original thoughts were dead on, and are basically the same as your's are, spOOln.

Cooling the water before it gets to the turbo and water/oil heat exchanger will result in cooler oil out of the exchanger. But, it will be hard to control the extra cooling. Some days it will be too much, and cold oil doesn't flow/lubricate as well.

He's been running with an oil temp gauge lately, and has seen the correlation between coolant and oil temps for himself with the sandwich style coolers. I ran them on the first couple of my dsm's, but only use them on my winter car now.

I run the thermostatically controlled air/oil cooler in my mildly modded summer beater gsx . It allows the oil temperature to stabilize at a happy medium under almost all operating conditions. Which allows prolonged running at higher boost and throttle openings, sneaky: ) without letting the oil or coolant temps become too extreme.

I see tarantula lives near san diego. It gets fairly hot there, and inland just a bit it's a freakin desert. I ran across the anzo-borrego with a tail wind once, and it was HOT...

He's building a pretty fast, well thought out car, so I can see why he wants/needs reserve cooling capacity. I think he's on the right track with his idea to convert to an air/oil cooler, and I look forward to him posting his results.

 

[Defiant]

Transfer is the key word, the heat from the oil is transfered into the coolant. This increases the cooling system load significantly

Nah, I doubt it. Oil and water running temps in motors aren't that far apart in the first place, and the hotspot of the turbine spool is already intermingling their heats by having a watercooled hub. DSMs don't have Jaguar-like overheating issues to begin with. It's a pretty sound system as built.

 

[toybreaker]

I should probably qualify that statement with...."on cars with a large fmic, the sandwich coolers will add a significant amount of heat load relative to the limited capability of the now shrouded/obstructed cooling system radiator"....

Or some such....

The coolant/oil heat exchanger works well at moderating oil temps without an fmic.

It only shows it's limitations when you have an fmic, major mods and high ambient temps. By the time the air has passed thru the fmic, and the a/c condensor, the air has picked up a considerable amout of heat, and is less effective at removing heat from the cars cooling system. Add an extended period under throttle, like climbing I-70 here in colorado, or the grapevine on I-15 out there,...and the oil will begin to get hotter than that poor little sandwich cooler can deal with.

I've always felt that a lot less air actually passes thru all those cores, and any ducting to make the air pass thru all the cores pays large divedends.

Staggering the oil cooler off to the side, and ducting it's own air supply into it, will go a long way towards aleviating the air impasse at the front of the vehicle.

Defiant, it's funny you should mention jaguar and cooling system woes...got a 74 xke coming in this week for an overheating issue.... ...lucky me....