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Todd M posted:

@Jimmy V.  @Jim Kelly

"Could you post a few pics of that ducting, Jim ? I'm curious about the configuration."

ditto

The project I bought has a Subaru engine, but no radiator yet.  It would be wonderful to not make a bunch of expensive mistakes.  Maybe the best thing to do is to buy the cooling essentials from SE?  Or at lease any shrouds and fabricated pieces?

Todd...perhaps start a new thread so we don't hijack this one and Ed Ericson and I may be able to provide a couple of tips for your cooling system. We both did homebrew Soob installs. 

@David Stroud IM Roadster D @Jimmy V. @Jim Kelly

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Yes and Jim Kelly knows lots about cooling too. 

 

Todd, what kind of room do you have under the front hood and under the car in the vicinity of the bumper brackets ? Pics would help. 

My rig was used on an older pan based Intermeccanica. One thing that worked very well for me was using 1.5" dia aluminum tubing to run the coolant for and aft for most of the distance. A buddy gave me some hang glider wing spars so I used that. Aluminum radiates a lot of heat so this assists the rad. On a hot day the tubes get quite warm so that tells me they are radiating heat passively as intended. The coolant ran from the engine up forward on the left side of the car and out of the rad and back to the stat on the right side of the car. You can reverse the coolant manifold and run both lines up the right side of the car but I found that my left and right design fit the rad openings better. I ran a dedicated small coolant line from the coolant manifold to the stat adapter per Tom Sheils' design. 

I used a Saab 9000 rad mounted almost horizontally ( up about 3-4 " at the front ) and it works very well but is probably much larger than needed. It has a fan controlled by a temp switch mounted on the inlet side not far from the rad. I built a rectangular air intake scoop at the front of the rad and reduced it in size over the years and finally it was about 2" x 12" which was still more than adequate even in heavy, hot Florida traffic. 

You'll need a bleeder at every high spot from the engine to the rad and back to the stat for initial coolant fill. I had one on the coolant manifold, one on each side of the rad hose going up and over the VW beam suspension and one more at the top of the heater. 

Here's a basic cooling diagram that worked for me. Many different systems will work. 

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Images (1)
  • Speedster cooling diagram with stat and Tom Shiels' adapter November 2014
Last edited by David Stroud IM Roadster D

I copied Stroud but used a Honda Civic radiator (like this) to fit neatly behind the existing grill of my MG TD replica. 1.5-inch aluminized steel exhaust pipe bent to my specs at a muffler shop with a sense of humor. I have the original "main" Legacy wagon fan on my rad. It fits perfect and it's wired into the stock Legacy harness and ECU cuz I'm cool like dat. Stainless steel shroud to put the air out the bottom of the car in front.

The general rule on radiator size for conversions is to use the largest one that will fit the platform.  The VW Vanagon guys state that you need twice the surface area of a stock Subi rad, merely because the new application doesn't have the efficiency of a stock Subi rad that sits directly in the front of the car at 90 degrees to incoming air.  It's tempting to  use a very thick radiator, but they lose their efficiency as they get thicker.  Aluminum construction, dual pass, as large as will fit, with the largest openings possible on the outlet side to reduce pressure.

Our applications are usually tucked away somewhere and hardly ever directly facing incoming air.  An effective fan shroud is critical, since it forces all the fan air through the rad.  Absent an effective shroud, air will seek the lower pressure direction of bypassing or going around the rad. 

Fan data is largely nonsense.  With the exception of Spal, fan makers perform their tests with no resistance on the output side.  That means that they place a fan in a large, empty room and test output as it blows into an empty space.  That's great for the company, but it's not how fans are used in the automotive context, when they blow through a radiator.  There is also lots of unproven assertions about pusher vs. puller fans, with conventional wisdom saying puller fans move more air, since they don't block the air entrance, like pusher fans do.  In extreme uses, some engine makers suggest you use both, puller and pusher on the same rad.

The most important elements of efficient cooling for Subi engines in a conversion application are radiator size and placement, access to cool air, and water movement through the system.  The down side is that those three parameters need expensive engineering data collection systems to collect the info, and engineers who can keep changing criteria to get needed results.  Since most of us don't have the engineering background or data collection systems, we need to just muddle through and not quit.

Bruce,

Hot rod guys have used everything from copper, aluminum, galvanized, stainless and exhaust pipe for radiator coolant lines, depending mostly on what they already had laying around for another use, then re-purposed.  Electrolysis with different metals doesn't seem to be a problem.

One of the upsides of metal coolant lines is heat radiation, as the metal bleeds off heat, thus reducing the demand on the radiator.  Some caveats: make sure the pipe/tubing is well supported to prevent cracking and not exposed to road hazards.  Most guys run it along side a frame rail or tuck it into a longitudinal to protect it from road hazards and/or debris.  As a safety factor, you may want to solder a bead on each end to help keep the hose from slipping off the tubing.

Jim Kelly posted:

Bruce,

Hot rod guys have used everything from copper, aluminum, galvanized, stainless and exhaust pipe for radiator coolant lines, depending mostly on what they already had laying around for another use, then re-purposed.  Electrolysis with different metals doesn't seem to be a problem.

One of the upsides of metal coolant lines is heat radiation, as the metal bleeds off heat, thus reducing the demand on the radiator.  Some caveats: make sure the pipe/tubing is well supported to prevent cracking and not exposed to road hazards.  Most guys run it along side a frame rail or tuck it into a longitudinal to protect it from road hazards and/or debris.  As a safety factor, you may want to solder a bead on each end to help keep the hose from slipping off the tubing.

JB Weld makes an easy bead on most any surface. 

aircooled posted:

Is there any reason that 1.5" copper tubing couldn't be used to plumb the radiator to the engine rather than run hose ?..................Bruce

There is a fairly strict "No-Yellow-Metal" rule in Subaruland. It is said that copper and brass do react somehow with the coolant and the heads to make 'em leak/blow head gaskets, which is the main issue with the Soob platform.

It may be superstition, but I tried to heed this as well as possible* in my build all the same, on the theory of why tempt fate?

Seems a good rule of thumb.

*Necessitated by my unique need to employ a properly British Smith's dual oil pressure/coolant temp gauge in the TD's dash, my car's cooling system has a single brass bit clamped in-line near the heater, where I take its temperature. So far, so good. 

As added info and to confirm the cautions of copper from Alan and Ed.  Two things can happen.  1) Copper will "anneal" and get brittle so use of it on anything that vibrates requires rubber dampers or something to absorb the vibration.  And, 2) copper will have a dielectric reaction to many other metals. This causes a rapid breakdown or corrosion like reaction to one or both of the different metals.  When a DIY guy tries plumbing, and sticks a copper fitting right into a piece of black pipe, give it about 6 months before the black pipe turns to mush!   

Thanks for the caveats...My thinking is to use copper front to rear uphill, both ways, Ha ha !  I see on my engine that it came with copper gaskets in some places and brass fittings as well.  Good point Ed ! Since these tubes would be insulated from physically touching the radiator or the engine by silicone hose connections and the coolant is a dielectric solution I'm hoping this would control any destructive electrolysis. Alan, I'm aware that copper doesn't like vibration and will crack but in this application where they would be pretty much insulated from vibration I hadn't thought cracking would be a concern.  Jim,  retention beads at the tube ends is a good idea. Possibly silver solder a solid copper wire around the tube ends ?

 The engines coolant inlet and outlet appear to be 1.5". Would 1.5" tubing/hose be sufficient or go larger due to more flow resistance because of the longer distance.  I realize that these questions may be elementary to some of you but now is the time to be asking so I hope you will indulge me...............Bruce

 

@David Stroud IM Roadster D - I am fairly sure that I had seen your drawing on another post, and I printed it and put it in my notebook of build info.  It makes a lot of sense and dispels some of the confusion.  But, here is a question.  And I have to put it in the 'stupid question' category, because I am guessing that as soon as I hear the answer I am going to regret showing my ignorance or lack of memory.

Why not use the air coming off the back of the radiator as the heater air, and delete the heater core and associated plumbing?  In most cars the radiator is in the engine compartment, and you don't want to be breathing that air, but it seems like the air going though the radiator in the front of the car is the same as any other air?

Bruce,

The quick and dirty answer is that your stock Subi water pump will likely produce sufficient flow with the 1.5" tubing you suggest.  The back story is interesting, to me, but long.  As an aside, my experience has shown that, for our platforms, a large volume of cool air to the rad is more important than water pump efficiency.

Car water pumps need to perform under widely varying conditions, with rpm's from 800-900, all the way to 6000 or so.  Most models have stamped, open vane impellers with lots of bypass, as there is a fairly substantial gap between the vane end and the housing.  Water pump makers don't like to publish data regarding flow, and, when they do, it's not worth much.  Example: Gates will state GPM for pump A at 6000 rpm.  Interesting, but we don't spend much time at 6000 rpm.  My queries were for GPM at 3100 rpm, my cruising rpm for freeway driving.  No info available.  Someone, somewhere has that data, but I could never find it.  Companies likely consider such info proprietary and keep it in-house.

Subaru corporation has also helped to muddy the water pump waters.  At various times in the recent past, one of the Subi gurus, like Cosworth or Crawford, produced a "revolutionary" and custom water pump design that eliminates the overheating concerns car guys experience with the old-fashioned stamped vane pump.  They merely reproduced an earlier version of the impeller that was cast, not stamped, and had a closer tolerance between the impeller end and the housing.  Of course, the "custom" application cost a lot more.  When forum members pointed out the similarity to an earlier Subi part, or asked for data to show increased efficiency, they were treated like ungrateful miscreants. 

Amateur engineers like us don't have expensive flow meters on the garage wall, or costly engineering tools or the experience to use them efficiently if we did have them.  All car guys can do is share their experience.  Not surprisingly, most of that shared experience is negative: I tried X and it didn't work.  Once in a great while, one of us succeeds. 

It's also useful to remember that Subaru designed engine parts for the Subi engine bay, which is in the front of the car where lots of cool air is easy to get.  No ducting is needed, and the rad is facing the incoming air directly.

In my Subi cooling research, I learned two important lessons: 1) Subaru engineers are very smart and very talented, and 2) if the accounting department can save a few cents on a specific part, they will lobby aggressively to do so, as those pennies saved multiplied by hundreds of parts times thousands of units means substantial savings to the stockholders.  We need to remember that all design changes don't equate to better performance.  Sometimes, an earlier model part functions better than its successor.

In addition, don't forget that the real restriction in your cooling system isn't an extra 16' of 1.5" smooth pipe, it's the restriction and back pressure of the rad itself.  New rad design is markedly different than the old copper/brass rads of the past.  Tubing size, spacing, and shape have all changed in the last decade or so.  Dual and even triple pass rads are common, but triple pass rads slow the flow so much that they can actually increase coolant temp, not lower it.  Friction loss from the small rad tubes is substantial.

Subi forums in particular, and automotive cooling sites in general, have lots of great info, but lots of nonsense also.  Sometimes the smartest guy on line is also a Richard Cranium, so he becomes the center of controversy, instead of the info he presents.

I look forward to your efforts and results, which I know you will share as you have in the past.

 

 

Last edited by Jim Kelly
Safety Jim posted:

Lane, I am going to guess that there were rubber connections at each end, or copper to brass usually works well.  Copper to some alloys or iron can be a real problem. I'll bet Stan has seen it in action more than a few times! 

Yes, the pipe is basically shoved into a rubber hose at each end, held fast  with hose clamps.  Kind of a cheesy way to do it, but that’s what they did.  I was more focused on the statement about heat causing brittleness over time.

Based on Stan's comment about the extra weight of copper over aluminum I'll have to rethink this and see if anyone around SoCal can bend some aluminum 1.5" tubing to my specs. That would be nice. However, modifying it in any way would require some welding and since I can't weld aluminum that could be a problem.

 Jim,  you right on regarding radiators. It used to be that multi rows of tubing in the core fins was good but not so now. They used to be copper core with .090" X .5" tubes. Each row staggered so that air flow weaved around and by each row. Testing showed that each row lost about 25% of it's cooling capability from the front row in the air flow to the rear row. By the time the last row got air it was only doing 25% of the job. They went to two rows and more square inches of radiator surface area and got better efficiency. Along the way they went to aluminum tubes and fins and got more. Then they went to .090" X 1.0" aluminum tubes and only one row of them and got even more. Initially the top and bottom tanks on these were epoxied onto the cores and problems were expierenced so now there are welded  and epoxied ones. The new epoxy does fine with heat now. My thoughts are getting an aluminum single 1.0" row core with the largest amount of square inch area possible.

My logic tells me that this would give me  high water flow, low water resistance and maximum air flow over the fin surface. That's why I was asking about if, possibly, the 1.5" diameter copper (or aluminum) tubing would be big enough.  Automotive water pumps are unique unto their own. They are not precision, they are overlooked often until they start leaking,  have to handle a huge amount of shaft/pulley load, a wide range of RPMs and in extreme heat conditions internally and externally. Surprisingly, they do it pretty well!

I have some thermocouple test equipment which I will install later when this project gets to a point that I can get some readings. I don't even know what radiator I will use yet but I'm looking at Griffin's.....I guess the Madness has started. Again, thank you all for your input. It helps a lot !................Bruce

Bruce just use aluminized exhaust pipe; it works and muffler monkeys can bend and weld it water-tight and put flange beads on it for hoses as well. It won't rust because it's always full of coolant—not air. 

As for the water pump: I followed the knucklehead forum advice and replaced my engine's water pump with another just like it—cast impeller and not stamped. This was a PITA as the first one I ordered came with a stamped impeller and I had to send it back. The one I eventually used looked and felt much more substantial than the stamped one and it's worked flawlessly.

As for flow and pressure: best thing to do is route the lines with as little elevation change and as few bends as possible. Most of the "stress" the system will encounter is from pushing that stuff UP, not from pushing it father away.

 

 

Todd M posted:

 

...Why not use the air coming off the back of the radiator as the heater air, and delete the heater core and associated plumbing?...

 Well, at least two reasons come to my non-engineer's mind.

First, ducting air from the back of the radiator into another system would probably slow airflow through the radiator a lot. Up above, someone who actually knows what they're talking about said a radiator needs low air pressure on its downstream side, and forcing that air into a heating system would increase the pressure a lot, I'd guess.

Second, radiators have no warm water flowing through them when you first start the engine. That doesn't happen until the coolant warms up enough to open the thermostat. The colder it is outside, the longer it would take to start getting cabin heat. And, as the thermostat opened and closed once the engine reached normal operating temps, the cabin heat would fade off and on as well.

All of this notwithstanding, I'll bet British Leyland must have tried such a system on at least one of their cars.

 

 

Yep, you got it, Mitch.  What moves air is pressure differential, whether it's atmospheric wind or radiator fan air.  Ideally, you have high pressure in front or inlet side of the radiator, assisted by a shroud that forces all the air through the rad, and low pressure on the back or outlet side.  If you have a puller fan on the back of the rad, that's where the shroud is located, in order to, once again, force the air through the rad.  If there is no avenue for air to escape after it leaves the rad, it stalls, because you now have a high pressure situation on both the inlet and outlet sides of the rad.

In stock Subaru vehicles, a low pressure outlet is not much of a problem, since the engine compartment is open on the bottom, and selectively open through hood vents, creating a low pressure avenue for air travel.  The air that goes through the rad needs a place to escape, preferably a low pressure avenue that helps to pull the air through.  We need bigger rads and fans, since we don't have our rads perpendicular to cool, incoming air at the front of the car.

Last edited by Jim Kelly

There is a lot of bunk online about Suby head gaskets. I still don't understand why anyone would put a factory Subaru gasket back on an engine. It's basically setting yourself up to fail. It's an open deck engine with a crappy head gasket. It's most probably going to leak. I agree with Jim that the engineers are normally very smart. This one part causes a lot of problems so I guess the bean counters won that battle.

Open deck means there are no webs connecting the cylinder wall to the outer block. You have a freestanding cylinder that touches only the head gasket then head around the combustion chamber. It's going to move during the thousands of heat cycles throughout it's life. 

I did an EJ253 head gasket job last winter. It was steam-cleaning one cylinder for a while with coolant. The torquing procedure is complicated and must be followed precisely. I used FelPro gaskets and copper gasket spray. I did not have the heads or block machined. I merely cleaned the head and block. It hasn't leaked yet.

As far as tubing for coolant tubes, I'd use aluminum or steel. Leave the copper in your home, where it belongs.

 

Last edited by DannyP
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