Mazda Racing oil cooler, new $85. Anyone ever try these?

[bpu699]

Ok, here are pics of the oil cooler. Thoughts from the group appreciated, especially in comparison to a stock Mazda oil cooler....

Initial impressions:
1) Nicely packed (85$ shipped!)
2) Has some weight to it, nice TIG welds
3) They clearly pressure tested it for leaks. Has two stoppers with rubber seals, when opened pressurized gas escaped...

Did I mention dirt cheap?

Compared to a stock Mazda oil cooler, there is no thermostat to remove

The oil inlet/outlet base are HUGE. You could tap this for a 1 inch fitting if you wanted

Current fitting seems to be some type of 1/2 inch to 0.6inch straight fitting. Tried a 1/2 NPT plumbing would go in... My guess, its a 1/2 inch or 12mm regular fitting...

Now, you can easily tap the fitting to 3/4 inch, or weld on a 3/4 inch AN fitting... Tapping it would seem way easier, as long as you can make sure you can get all the shrapnel out...

The question I have, is how much oil can the core flow? Is this comparable to a mazda oil cooler?

[bpu699]

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[bpu699]

So, what do you all think?

I am leaning towards installing 3/4 NPT fittings, or may just drill and tap for 3/4 inch thread and use an aluminum washer...

Since I have no way to know the flow rate, the safest thing is to hook it up in parallel, that way flow rate is less of an issue (even if flow were ZERO, it wouldn't harm the motor... it just wouldn't cool any...)...

Its pretty neat that this is 1/10 the price of a name brand cooler...

Definitely worth more experimenting .

Actually I just had a bright idea . One could easily just place an AN fitting on either end, and get rid of the baffle. This would double the flow, as oil would only go through one end and out the other... HMMMM. May need to cut off the end caps

Bo

[Elombard]

Looks great I would go for it. Maybe cutting off the end plate is a good idea to tap the holes any way. Scary to worry about getting a piece in there.

[911pcar]

Like the best coolant radiators, engineers design enough flow resistance to maximize heat transfer. If the flow rate is too high, heat transfer is compromised. Imagine an oil cooler with passages as large as a garden hose (does that remind you of the trombone cooler?).

If you're worried one cooler is too restrictive, observe the pressure drop by monitoring and comparing the oil pressure drop betw. inlet and outlet.

For max. cooling, route the oil flow in series when two or more coolers are in the system. Oil flow will take the path of least resistance in a parallel flow set up.

Sherwood

[bpu699]

Originally Posted by 911pcar

Like the best coolant radiators, engineers design enough flow resistance to maximize heat transfer. If the flow rate is too high, heat transfer is compromised. Imagine an oil cooler with passages as large as a garden hose (does that remind you of the trombone cooler?).

If you're worried one cooler is too restrictive, observe the pressure drop by monitoring and comparing the oil pressure drop betw. inlet and outlet.

For max. cooling, route the oil flow in series when two or more coolers are in the system. Oil flow will take the path of least resistance in a parallel flow set up.

Sherwood

Heres what I am leaning towards, and tell me what you think about the logic:

Change the flow pattern. Right now, stock, flow goes in through the bottom 3 rows, and loops back and comes back through the top three rows

Compared to expensive coolers, that's a lot of resistance. If you look at a Setrab, the flow is much different. It feeds through the top, and goes through 72 short cooler fins to the bottom, and returns. 72 flow through fins definitely have less resistance than 6 long fins.

So, the plan was to change the flow to go through the cooler from left to right. So the oil would have 6 hollow fins to go through... that halves the resistance, and doubles flow. With that easy mod, you can easily hook up the cooler in series, if wanted.

Now, the amount of time the oil spend in the cooler is exactly the same... Lets say that the scavenge pump, hypothetically, pumps 5 gallons a minute. No matter what the route through the cooler, 5 gallons have to go in and 5 gallons have to come out, every minute. So if the oil goes left to right, it travels a shorter distance BUT it is going at 1/2 the speed, so net, its in the cooler for the same time. If you have the oil got through from the left, and circle around and come back on the left, it has to travel twice as fast to go twice the distance.

So either way, the oil is in the cooler for the same length of time.

Thoughts from the science minded folks on here?

Does anyone know the scavenge side pressures, or flow rate? That really determines what can be done. I know lots of folks are driving around with crushed oil lines, and clearly motors aren't blowing up left and right. Really makes me wonder what the flow rate is?

Out of curiosity... if your oil cooler line is completely crushed, and you don't realize it, what happens? Does the oil bypass the front cooler via the thermostat somehow? Of does the scavenge pump shortly fail?

More pics to come, plan to cut the ends off soon...

But for folks buying used mazda coolers, this seems like a solid alternative.

[Walt Fricke]

If the external oil thermostat is open (oil is hot), but there is an obstruction in one or both of the front cooler likes (as in one is crushed flat), then that is where the pressure relief inside the thermostat housing comes into play - it opens, and the oil heads straight for the tank.

I don't think many people run oil in one side of this type of cooler and out the other side. For most of our cars this complicates the plumbing. Porsche does not do that with the 964 oil coolers. Didn't do it with the RSR cooler, did it? Light airplane coolers are built out and back also - I used two of them in my GT4 car at one point. Fittings all just on one side.

The resistance in the system is just not something anyone has worried about beyond using large enough lines and fittings. Think of the extra trouble you are contemplating here - somehow opening up the part of the casting on the far side so you only need one exit fitting. The near side is probably easy - you can drill using the fitting hole which is vertical. The across and back design works fine in our cars.

If there is any benefit to in one side and out the other, I'd expect it to be that all the oil is at basically the same temperature - getting lower as it passes across, but still all as hot as it can be. More like a parallel setup. The out and back system is more like a series system, with the cooling efficiency getting progressively less as it turns around and starts back.

[bpu699]

Originally Posted by Walt Fricke

If the external oil thermostat is open (oil is hot), but there is an obstruction in one or both of the front cooler likes (as in one is crushed flat), then that is where the pressure relief inside the thermostat housing comes into play - it opens, and the oil heads straight for the tank.

I don't think many people run oil in one side of this type of cooler and out the other side. For most of our cars this complicates the plumbing. Porsche does not do that with the 964 oil coolers. Didn't do it with the RSR cooler, did it? Light airplane coolers are built out and back also - I used two of them in my GT4 car at one point. Fittings all just on one side.

The resistance in the system is just not something anyone has worried about beyond using large enough lines and fittings. Think of the extra trouble you are contemplating here - somehow opening up the part of the casting on the far side so you only need one exit fitting. The near side is probably easy - you can drill using the fitting hole which is vertical. The across and back design works fine in our cars.

If there is any benefit to in one side and out the other, I'd expect it to be that all the oil is at basically the same temperature - getting lower as it passes across, but still all as hot as it can be. More like a parallel setup. The out and back system is more like a series system, with the cooling efficiency getting progressively less as it turns around and starts back.

I hear you... and maybe the oil pressure relief valve cures any flow issues?

The mazda oil cooler has 6 oil fins. 3 go to the right, then oil turns around, and comes back through the three other fins...

The fins are 2 inches wide (50mm) and have a passage that's about 1-1.5 mm tall. So each passage has an area of 50-75mm... So, three of those gets you 150-255m flow area through the cooler. That's TINY!

A inch tube has an area - 490mm
A 3/4 inch tube has an area of 273mm (same as AN12)?
A 1/2 inch tube has an area of 113mm

Maybe I am over thinking it. Someone posted in a prior thread that if you have a restrictive cooler, you can blow out your scavenge pump?

The setrab coolers have a totally different orientation. Their fin are short, and run up and down. Plus, there are 72 of them (not 6). So the internal flow area is 12 times less restrictive...

If you change the flow of a mazda cooler to go felt to right (easy to do), you double the flow area as now the oil has 6 passages to flow through, not 3. So you now have a flow area internally of 300-500mm. Much less restrictive, no chance of damaging the scavenge pump.

Maybe none of this is an issues? Anyone know at what pressure the right rear fender pressure relief opens at? I see lots of posts and references in Google that there is a pressure bypass in the thermostat, but no mention of opening pressures... Obviously, any oil that bypasses the cooler isn't getting cooled...

If there are no issues damaging the scavenge pump, then this is all overthought...

But a mazda oil cooler has very low area internal flow, best as I can tell. Perhaps not an issue for a 911, but perhaps for a turbo?

Don't really know. Any thoughts appreciated.... Anyone know at what pressure in the cooler circuit the "bypass pressure valve" opens?

Out of curiosity, I would be willing to tinker, and place a pressure guage onto the mazda oil cooler to see what pressures get generated at its inlet... If its well below the blow off pressure for the valve, the clearly the flow is adequate. If its above the pressures of the blow off valve, then clearly the flow in the mazda cooler is lower than needed...

[bpu699]

https://books.google.com/books?id=rOKlQ0ZzL6cC&pg=PA190&lpg=PA190&dq=porsche+911+restrictive+oil+cooler&source=bl&ots=ICmlOLhqgi&sig=A-IpwdsHUFiyfICttJSNE-27_eI&hl=en&sa=X&ved=0ahUKEwit6InDv8bPAhVCLyYKHfImDzYQ6AEIRjAK#v=on epage&q=porsche%20911%20restrictive%20oil%20cooler&f=false

Bruce Anderson comments on Engine failures due to restrictive oil coolers...

[KTL]

For comparison sake, I used to run a Fluidyne "single pass" oil cooler on my racecar. It had AN-12 fitting on each end of the cooler (and AN-12 hose everywhere elsewhere in the car) and it did OK in terms of temperature. Ran around 220°F on hottest days. The engine was a wimpy 3.2 short stroke (SC-based engine) with the original SC oil pump



It only had a bit of separation behind it to aid in air flow thru the cooler. My point of mentioning that is because I think it's noteworthy the cooler was a bit compromised by not having good separation behind it to help the air flow thru it, yet the car did OK in terms of operating temperature.

Walt is correct that the oil line routing was a bit more cumbersome.
The outlet side of the cooler had the hose turn 90° up over the top of it, back to the hose in the right front wheel arch so it could get back to the thermostat.

In one of the Grady threads I was searching yesterday, I recall him mentioning he believed the bypass in the t-stat opens at 100 psi. That sounds a bit low based on the stiffness of spring inside the t-stat. Coincidentally I bought some of these springs a few weeks ago. Reason I bought some of them is because one member here indicated the spring relaxes over time and lets some oil bypass instead of going forward to the oil cooler. So that undesired bypass makes the engine run hotter. I figured for $7 each, that spring is cheap & not hard to replace during the next t-stat rehab I do.

[bpu699]

Now, that's an 11 row cooler, and single pass means the oil is flowing unidirectionally through the 11 rows...

The mazda is a 6 row, and oil goes both way (only 3 rows flow each way).

So the cooler you pictured, flows 4x more easily than a mazda due to 4x less internal resistance. (11 fins to 3 fins)...

I betcha on that cooler the choke point was the AN12 fitting... the cooler probably had little resistance...

The 930 pump probably flows a bunch more oil than a SC motor too, I suspect...


Will try to look inside the cooler this weekend to see how big the passages are in the "rows" in terms of height. 1mm? 2mm? 2.5??

If they are 2.5mm, then their flow area Is the same as the AN fitting, so not an issue...

Next, I try to figure out how many angels fit on top of a pin head .

You mention that the pressure relief valve might be 100 psi? That seems awefully high... Are oil radiators even rated that high for safety? I figured it might be 30-40 psa, because the return oil line drains to the oil tank, which is "open to ambient air."

The only way you would come close to generating 100psi, I would think, is if the oil line is completely crushed...

Bo

[Targalid]

Bo, since you have the cooler, why not try running a garden hose through it to see how much it flows. I am curious to hear the results of this experiment. You can look up the flow rate of the oil pump at RPM and then compare the outflow from a hose through the cooler into a bucket to get an idea of the volume it will pass in a given time. House water runs 60 to 100 psi (when fully on) and you can turn the flow up or down. The oil does not begin to flow through the thermostat to the aux cooler until 186F, at which point it is flowing at lower pressure than at startup. Point is, the water would be a good approximation. As for oil pressure, I can watch my pressure relief valve (the one on the engine) when the engine is cold. At not much over 3K RPM, with cold oil, the pressure relief valve trips at about 95 psi, dropping down to about 60 with valve open. It does this with every shift until oil temp gets warmer. Once warm, the oil never sees pressures much over 60 psi with my sedate driving style.

[bpu699]

Originally Posted by Targalid

Bo, since you have the cooler, why not try running a garden hose through it to see how much it flows. I am curious to hear the results of this experiment. You can look up the flow rate of the oil pump at RPM and then compare the outflow from a hose through the cooler into a bucket to get an idea of the volume it will pass in a given time. House water runs 60 to 100 psi (when fully on) and you can turn the flow up or down. The oil does not begin to flow through the thermostat to the aux cooler until 186F, at which point it is flowing at lower pressure than at startup. Point is, the water would be a good approximation. As for oil pressure, I can watch my pressure relief valve (the one on the engine) when the engine is cold. At not much over 3K RPM, with cold oil, the pressure relief valve trips at about 95 psi, dropping down to about 60 with valve open. It does this with every shift until oil temp gets warmer. Once warm, the oil never sees pressures much over 60 psi with my sedate driving style.

There are two pumps outlet, internal an scavenge. The internal pressure relief does what you mention. But there is apparently a third pressure relief in the rear passenger thermostat. That's the pressure relief I am curious about...

[911pcars]

Originally Posted by Targalid

Bo, since you have the cooler, why not try running a garden hose through it to see how much it flows. I am curious to hear the results of this experiment. You can look up the flow rate of the oil pump at RPM and then compare the outflow from a hose through the cooler into a bucket to get an idea of the volume it will pass in a given time. House water runs 60 to 100 psi (when fully on) and you can turn the flow up or down. The oil does not begin to flow through the thermostat to the aux cooler until 186F, at which point it is flowing at lower pressure than at startup. Point is, the water would be a good approximation. As for oil pressure, I can watch my pressure relief valve (the one on the engine) when the engine is cold. At not much over 3K RPM, with cold oil, the pressure relief valve trips at about 95 psi, dropping down to about 60 with valve open. It does this with every shift until oil temp gets warmer. Once warm, the oil never sees pressures much over 60 psi with my sedate driving style.

Might need to re-calc for viscosity difference betw. hot oil and water.

[Targalid]

I think both pressure relief valves have the same spring. I recall seeing they are the same part number. That was my point. So, the one in the external thermostat housing should be about 95 psi also.

[KTL]

High end oil coolers are rated much higher than 100 psi. A 60 row Earl's cooler I have is said to be tested for leaks at 175 psi and burst checked at 350 psi

https://www.holley.com/products/plumbing_an_fittings_and_hose/cooling_systems/oil_and_transmission_coolers/narrow/parts/26016ERL

Also worth noting that the pump I used showed no signs of being compromised by the cooler. The interior of the pump looked fantastic and the bores in the pump body to support the gerotor shafts were nice and tight.

http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/653744-sc-oil-pump.html

for whatever that's worth..............

The 930 pump flows a bunch more oil than the SC pump does. The 930 pump has a huge scavenge section by comparison. This pic shows various pumps and the one at the bottom is a 964 pump which is similar in dimensions to the 930 pump. You can see the left side of it (the scavenge side) is much longer than the other pumps. The longer the pump, the longer the are the rotors inside and the more it can pump.

From top of picture to bottom:

1. pre-'69 (aluminum)

2. '69-'76 (3 rib magnesium)

3. '76-'77 (4 rib magnesium 2.7L bypass mod)

missing in this sequence is the 78-83 SC 3.0L aluminum 4 rib pump

4. '83-'89 (aluminum 4 rib with built in strainer) Note that some of the 3.0L engines would have a so-called 3.2 Carrera pump since there were some SC engines produced with the later engine case with no removable sump plate)

5. 89-98 (964, 993 made of magnesium or aluminum depending on year)



Here's a picture of the real deal 930 pump



Targalid you should read this nice thread started about the pressure relief valves. It gives good insight as to where they are in the system and what their cracking pressures are

http://forums.pelicanparts.com/911-engine-rebuilding-forum/712724-ultimate-oil-pressure-relief-valve-thread.html

The external t-stat bypass is completely separate from the two internal engine oil pressure reliefs and the two oil paths are independent in terms of pressure. The external t-stat is fed by the scavenge side of the oil pump. The scavenge side of the pump does just that. It scavenges oil from the bottom of the engine case and returns it to the oil tank so it can be fed back into the engine. It just so happens that the t-stat and oil cooler are in that scavenge route. But that pressure within the scavenged oil route has no dependence on the oil pressure within the engine. Think about it and I believe you'll see what I mean. When the pump sucks oil out of the engine case, it immediately sends it to external hose/piping which takes the internal engine pressure relief valves out of the picture so to speak.

So in other words the internal engine oil pressure and scavenge route path oil pressure are completely independent, pressure-wise, despite being driven by the same component- the oil pump. The oil pump is sometimes referred to as a tandem oil pump and that's because it's two separate pumps in one body.

Also, your statement that oil does not flow through the t-stat and cooler until 186°F is not entirely correct. When cold, the t-stat is open on the side feeding the oil cooler and closed on the return side. So what that means is there is a "dead end" pile of oil coming out of the t-stat, thru the cooler and back to the t-stat. That pile of oil is seeing oil pressure from the scavenge side of the oil pump pushing oil back into the tank, even though the pump is being relieved by the somewhat low pressure free flow of oil going back into the tank. What's important here is the pressure against that dead end is greatest when the oil is cold and that's when the bypass in the t-stat is a very good thing to have.

My belief of the 100psi cracking pressure for the t-stat came from these threads

http://forums.pelicanparts.com/porsche-911-technical-forum/700478-large-leak-front-oil-cooler.html#post6947597

http://forums.pelicanparts.com/porsche-911-technical-forum/607698-oil-pressure-filter.html#post6013141

Here's a comment from pro engine builder Mike Bruns (used to be with JB Racing in Florida but not any longer, I believe, as it's no longer in his signature and he's not posted since late 2014) about the pressure in the scavenge circuit

http://forums.pelicanparts.com/911-engine-rebuilding-forum/695694-creating-crankcase-vacuum.html#post6936128

[bpu699]

Great post above...

So when one mentions 300PSI at cold start, and you look at the size of that turbo scavenge pump, it really makes you wonder how much oil actually goes through the oil coolers, and how much just gets diverted right away back to the engine...

I gotta tell you, I have had my oil tank open while my cold motor was idling, and it didn't look like oil was coming out of the filter at 100PSI or greater...

Many oil filters have a bypass feature, in case the filter gets clogged. I would think that opens well below 100 PSI. If we were running pressures that high on the scavenge side, especially once warmed up, I would be surprised...

But, I am learning more every day...

I wonder what the pressures are on the scavenge side warm?

If my car, on the track, can muster 4 bar (60psi or so) warm, then it has to be much less on the scavenge side. On the pressure side, you have, by design, no outflow. The oil HAS to squeak by bearings/bushings/piston squirters, etc...

On the scavenge side, it goes through a big brass 3/4 circuit, and 1-2 oil coolers...

Fascinating discussion.

Kevin, sounds like your oil pump looked great...

Bo

[bpu699]

Ok... Just got my AN12 fittings... The openings in these thing are way smaller than I thought they would be...

If they are that small, then the flow through the radiator is unlikely a point of restriction...

More to come