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 Early K Series Heat Exchanger to Oil Cooler Modification 
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Post Early K Series Heat Exchanger to Oil Cooler Modification
I often wondered how useful the oil filter heat exchanger on the earlier K engines were. Since they were discontinued on later models.
But then I read this post on Probetalk:
mazda-head wrote:
"It heats the oil up faster by tying into the water temperature (good thing, no matter where you live from alaska to houston) and stabilizes the high temp to the water temp when demands are high. It's not thermostatically controlled, though and doesn't shed heat to the air directly."


http://forums.probetalk.com/showthread.php?t=1701316239

Then I realized that the placement of the coolant lines to the heat exchanger are routed from the block before the coolant reaches the radiator, then to the water pump neck where it gets circulated to the radiator. which means that it's circulating the coolant flow at it's hottest, not it's coolest.

The few benefits I can see from this are:
- Faster warmups which means less engine wear running cold during engine warmup/startup, lower cold emissions, etc.
- consistent (higher) oil temperature under light load and cold conditions.
- side-effect of stabalizing oil temperature during load

If the heat exchanger was designed to primarily cool oil flow, it would flow coolant after the fluid has passed through the radiator, but before entering the block. Which would be the fluid at it's coolest.

Which means you could make it be an "oil cooler" by rerouting the coolant intake line from the ATX coolant line on most KL series coolant intake neck where the thermostat is housed to either the heat exchanger directly OR for additional cooling, to the ATX oil cooler built into the radiator. ATX radiators will have the fittings already whereas you would need to tap out the fittings on an MTX radiator as I understand it.

Image

You would want the coolant intake line to run after the thermostat as to not flow cold water during warmup but before the block. Then the second line you would want to run in line wherever so it pulls fluid from the thermostat area, not the water pump area.

This modification would use all OEM parts and doesn't use any additional engine bay room which is nice. You would just be running a couple longer hoses.

But I am unsure exactly which line would be the best to use to ensure the coolant flow direction.

And no, I haven't done this myself. But I'm hoping for some constructive criticism.
If I do not like your criticism though, I reserve the right to be a jerk.


http://forums.probetalk.com/showthread.php?t=1701316239

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July 17 2014, 4:58 PM
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Post Re: Early K Series Heat Exchanger to Oil Cooler Modification
sticky!

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July 17 2014, 11:03 PM
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Post Re: Early K Series Heat Exchanger to Oil Cooler Modification
The reason these water / oil heat exchangers were eliminated was for cost not performance. The faster oil warm up and cooler oil at operating temperature were not great enough benefits (and most buyers wouldn't know) so Mazda was able to save a few $ per engine.

The oil heat exchanger is a cooler when the engine is at operating temperature. It has the benefit of not requiring an additional thermostat to protect against over cooling and actually helps during engine warm up.

I'm not sure I follow your proposed routing, but think it would be a fairly minor improvement to oil cooling. You suggest re-routing coolant not actual engine oil. Once the engine is warm the difference between coolant from the radiator and that flowing through the engine is not that great.
Routing some of the coolant through the transmission cooler means that only a small portion of the radiator is used for cooling that portion of flow. This might be a negative for overall engine cooling.

Routing engine oil through the transmission oil cooler portion of the radiator would be interesting, but off topic.

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July 18 2014, 12:58 PM
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Post Re: Early K Series Heat Exchanger to Oil Cooler Modification
Not sure if you knew this Kris but Yoda (Vaughn) is on the MX-3 on Facebook often. I suggest you post your idea/question there and direct it at him. I'm sure he would have a good 5 cents to add. Cheers :D

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July 18 2014, 3:15 PM
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Post Re: Early K Series Heat Exchanger to Oil Cooler Modification
There is on average a 10 degree temperature delta before/after the radiator. Our thermostats regulate at 180, which would lead me to believe that the radiator inlet temperature would be about 190 degrees.

This doesn't bypass the radiator. this would run a small amount of 180 degree fluid through a second pass on a small (ATX) radiator may further reduce the fluid temperature somewhat. It wouldn't affect the overall cooling capacity of the engine at all.
The difference of at least 10 degrees can be significant.

The pros of this method compared to air cooling:
Uses the engine's thermostat to stay regulated and avoid overcooling.
Uses the coolant's temperature to warm oil to operating temps quicker.
Water has a high thermal conductivity rating than air. something like 1BTU/ft/hr compared to .05 BTU/ft/hr.

Oil to air:
more affected by ambient temperature changes.
requires additional oil lines and increases the chances of oil leakage/loss. Personally I'd rather lose coolant.
would require an additional thermostat to help prevent overcooling.

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July 18 2014, 3:44 PM
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