Quote:
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.
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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...