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PostPosted: October 4, 2017, 10:07 am 
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Joined: May 22, 2017, 7:36 am
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Whats up ma peeps,

Quick question, Mazda 12a Rotary, carb'd, simple wiring etc, thinking that with the known cooling issues of these motors, if I plumbed in a surplus heater core in the position that it normally is plumbed in, would that act as a heat exchanger and help with the cooling do you think?

I read this thread: viewtopic.php?f=27&t=3838&start=15 and there was talk of a 12v water pump plumbed in, i'm wondering where that might plumb into?

I really want to leave the current setup that I have for the radiator and water pump and I am focusing more on the heater hose/auxiliary line pictured here with a red line:

Image

My thought is, run the heater line, blue box is a heater core, green oval is a 12v water pump that continues after the engine is turned off.

Image

Any thoughts or ideas or concerns welcome.


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PostPosted: October 4, 2017, 10:28 am 
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Certain model Saturn SL's had the aux heater core pumps, as well as older Mercedes diesels.

Using the heater core for added cooling is a known trick if an electric fan happens to die and you start overheating when at idle.
Kinda funny having the heater on full blast in the middle of summer, windows down, in 90+ heat, but it works.

I'd say plumb it in, add a small pusher fan, and some vents/duct work to distribute the heat. :)

Most of the cooling on a rotary is actually done with the oil though, so you'd be better off getting a larger cooler.
The twin coolers from an RX8 or the huge one from a FC would work, and they have built in bypass thermostats.
I'd go for RX8 oil coolers due to the ease of packaging.

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PostPosted: October 4, 2017, 10:32 am 
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That one oil cooler you see in the picture will actually be two by the end of the day today, plumbed in series. Do you think that may be sufficient for oil cooling?


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PostPosted: October 4, 2017, 10:42 am 
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Probably sufficient, it looks about the same size as the RX-8 single cooler.

Just make sure you have a bypass thermostat plumbed in the line, to keep the oil at minimum temperature. ;)

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Walt
06 RX-8 Shinka
04 RX-8 GT
06 325xi
Some people never have anything except ideas. Go do it.
Emissions & fuel economy haven't exactly been areas of strength for past rotary power plants, but absolutely no one with a soul has ever cared.


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PostPosted: October 4, 2017, 10:49 am 
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A bypass thermostat? I am unaware of what that is. As it is right now, when the engine is running, oil is being pumped through the cooler(s) no matter what. Is a 'bypass thermostat' the same as 'bypassing a thermostat'?


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PostPosted: October 4, 2017, 10:53 am 
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It's a thermostat that opens at a set temperature, and lets the oil go to the coolers.
If the oil temperature is below the setpoint, it bypasses the coolers.

The factory RX7 and RX8 coolers had them built in.

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06 RX-8 Shinka
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Some people never have anything except ideas. Go do it.
Emissions & fuel economy haven't exactly been areas of strength for past rotary power plants, but absolutely no one with a soul has ever cared.


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PostPosted: October 4, 2017, 10:57 am 
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Nope, i don't have one of those, (i presumed that what it was). Should be okay without it then right?


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PostPosted: October 4, 2017, 11:41 am 
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Yeah, just have to wait a little longer for your oil temp to come up before winding her out. :)

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06 RX-8 Shinka
04 RX-8 GT
06 325xi
Some people never have anything except ideas. Go do it.
Emissions & fuel economy haven't exactly been areas of strength for past rotary power plants, but absolutely no one with a soul has ever cared.


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PostPosted: October 4, 2017, 11:44 am 
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Got it. Thanks.


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PostPosted: October 4, 2017, 12:36 pm 
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I vaguely remember a car one of my friends' parents had when I was young, which had a setting on the heater that said "desert". It vented the heater to a duct on the outside of the car, and thus cooled the engine without heating the cockpit. So in regards to the original question...
aidandebradney wrote:
...if I plumbed in a surplus heater core in the position that it normally is plumbed in, would that act as a heat exchanger and help with the cooling do you think?
...my answer is: Yup. I wish I remembered what car it was, I'm sure it was a domestic car from a major manufacturer, but it was half a century or so ago so it might have been a Studebaker or a Pontiac or similar historical relic.

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PostPosted: October 4, 2017, 2:34 pm 
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I had no problem cooling my 13B 6-port with the eBay Civic alum 2" radiator. I blocked off the heater lines on the engine. I did use the big OEM oil cooler. I could run 70MPH in 95+ temperatures and never had any cooling issues. The electric fan shut off with the ignition, so there was no post-run cooling.

Adding the heater core may help a small amount at the expense of added water hose/pump/ thermo switch etc. complication and the looks thereof.

You can plan for the addition, If you find you need it later on down the road, then install it.

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PostPosted: October 4, 2017, 7:40 pm 
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Well as it turns out, my surplus heater core at the back of the garage was considerably larger than I remember, about the size of a shoe box! So I opted to use my smaller oil cooler as a secondary micro coolant radiator. Mounted vertically at the side of the car, I can pop a little pusher motor behind it and have an opening in the side panel to vent it. May do nothing at all, i guess time will tell. Interestingly coolant hose fits 10an earls type fitting quite nicely.

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