FC thermoswitch for FD
Hey if you don't like the mod, don't do it. No need to jump all over the thread saying how it's worthless, esp. w/o any concrete data to support it.
It's a fact, however, that lower engine bay temps are better for the car overall... be it the engine, turbos, or even just the plastics, by stopping them from turning to glass
It's a fact, however, that lower engine bay temps are better for the car overall... be it the engine, turbos, or even just the plastics, by stopping them from turning to glass
Originally Posted by adam c
Even if you don't want to do this mod, you should be smart enough to realize that it could be beneficial for many people.
Oh and yes Adam, this is me agreeing w/ you
good find!!! i was just going to buy the miata switch. And to anyone who thinks this is a useless mod must not really care about their fd. If we can make our engines run cooler thats just that much better for everything under the hood especially the rats nest. So thanks again for the find.
Thread Starter
Joined: Jan 2002
Posts: 15,622
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From: Pensacola, FL
Originally Posted by jacobcartmill
dale we want you back in the FC section 
. I've been an FC guy for a LONG time - still am. But, I'm ready for new challenges with the FD . Heck, I pioneered a TON of stuff on the FC! Dale
Rotary Enthusiast
Joined: Aug 2002
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From: New York
Originally Posted by DaleClark
The plastic AST was a bad idea. Plastic/aluminum radiators are actually prety nice - very efficient, less prone to corrosion, and light weight. The sad thing is plastic end tanks CAN be replaced, but there aren't many places in the US that can do that kind of work.
Also, the FC had a clutch-driven fan as its main cooling method. The electric fan was a VERY small fan (about 8-10") in front of the radiator and condenser that only ran if the car got hot enough (kicked on by the thermoswitch) or if the AC was on to increase air flow through the AC condenser.
Considering the FC ran relatively cool, it's still odd that the FD ran so hot. They may have needed to run the car hotter to get fuel economy to where they wanted so it wouldn't have been hit with the gas guzzler tax. It may be another thing, like the precat, that Mazda *had* to do to be able to sell the FD in the US.
But, the good thing is we can find solutions around the things Mazda had to do. That's the goal with my car - to make it into the car that Mazda wanted to build.
Dale
Also, the FC had a clutch-driven fan as its main cooling method. The electric fan was a VERY small fan (about 8-10") in front of the radiator and condenser that only ran if the car got hot enough (kicked on by the thermoswitch) or if the AC was on to increase air flow through the AC condenser.
Considering the FC ran relatively cool, it's still odd that the FD ran so hot. They may have needed to run the car hotter to get fuel economy to where they wanted so it wouldn't have been hit with the gas guzzler tax. It may be another thing, like the precat, that Mazda *had* to do to be able to sell the FD in the US.
But, the good thing is we can find solutions around the things Mazda had to do. That's the goal with my car - to make it into the car that Mazda wanted to build.
Dale
JK of course. Good points you have there. They should have made mazdaspeed release everything you'd need! :P
And welcome to the REAL world. Ahem, i mean, a better one. FC's do rock though, FD is just prettier :P
That's a great find. Personally with a front mount and full beefed up single setup I have no cooling issues. And guess what I'm on the stock radiator (I think this is the only stock part in my engine bay) and use stock mazda coolant it's amazing. I do have the fan mod but rarely need to use it. I had been turning it on once the car reached ~83C but then it would go down to 81C which is a little colder than I want it when I'm boosting hard. Letting the thermostat do it's work and normal driving I've seen 89C the highest. When I get in thick traffic I turn on the fanmod and I won't see past 87C even if its for an hour.
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From: Dallas
I know exactly bupkis about FC's but still wonder how it took so long for somebody to figure out the stock FC switch is a drop in replacement!
I wonder if I kept my stock connector when I cut it off to fit the Miata thermoswitch...
I wonder if I kept my stock connector when I cut it off to fit the Miata thermoswitch...
I haven't taken extensive thermodynamics classes, but I know a guy who's researching cooling systems right now. He's said a few different times that a greater difference in temperatures will make the system more efficient, making it possible to use a smaller radiator (which will save weight and packaging). It's got something to do with the delta-T.
To increase the delta-T, you can either raise the coolant temperature going into the radiator, or lower the temperature of the air flowing over the radiator fins (by keeping the radiator in front of the engine, intercooler, air conditioning condenser, etc...). Either of these will result in a net increase in efficiency.
Mazda isn't the only manufacturer to run such a high coolant temperature. I've heard that modern VW's use very hot coolant temps, possibly near 250 F. They get away with it by increasing the cooling system pressure to raise the boiling point of the system.
-s-
To increase the delta-T, you can either raise the coolant temperature going into the radiator, or lower the temperature of the air flowing over the radiator fins (by keeping the radiator in front of the engine, intercooler, air conditioning condenser, etc...). Either of these will result in a net increase in efficiency.
Mazda isn't the only manufacturer to run such a high coolant temperature. I've heard that modern VW's use very hot coolant temps, possibly near 250 F. They get away with it by increasing the cooling system pressure to raise the boiling point of the system.
-s-
Originally Posted by scotty305
I haven't taken extensive thermodynamics classes, but I know a guy who's researching cooling systems right now. He's said a few different times that a greater difference in temperatures will make the system more efficient, making it possible to use a smaller radiator (which will save weight and packaging). It's got something to do with the delta-T.
To increase the delta-T, you can either raise the coolant temperature going into the radiator, or lower the temperature of the air flowing over the radiator fins (by keeping the radiator in front of the engine, intercooler, air conditioning condenser, etc...). Either of these will result in a net increase in efficiency.
Mazda isn't the only manufacturer to run such a high coolant temperature. I've heard that modern VW's use very hot coolant temps, possibly near 250 F. They get away with it by increasing the cooling system pressure to raise the boiling point of the system.
-s-
To increase the delta-T, you can either raise the coolant temperature going into the radiator, or lower the temperature of the air flowing over the radiator fins (by keeping the radiator in front of the engine, intercooler, air conditioning condenser, etc...). Either of these will result in a net increase in efficiency.
Mazda isn't the only manufacturer to run such a high coolant temperature. I've heard that modern VW's use very hot coolant temps, possibly near 250 F. They get away with it by increasing the cooling system pressure to raise the boiling point of the system.
-s-
.Anyway the higher the delta T the more heat will transfer keeping all else constant but you don't need to have the fans turn on at a high temp, you could size the system so that at max heat input you'll have the high delta T.
I believe Mazda had such a high temp fan switch in there to get the emissions and gas mileage requirements. Higher engine temps make the combustion process more efficient in any engine, it also helps reduce some emissions. There are down sides to high engine temps that we are already familair with.
Thread Starter
Joined: Jan 2002
Posts: 15,622
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From: Pensacola, FL
Originally Posted by sszablya
Thermoswitch = water temperature sensor/sender?
Does the FC sender's output resistance respond in an identical pattern to the stock sender?
E.G. what does it make the gauge do?
Does the FC sender's output resistance respond in an identical pattern to the stock sender?
E.G. what does it make the gauge do?
BTW, I ordered some things from Malloy Mazda today and talked to Ray Crowe. I mentioned that the FC thermoswitch worked great. He said he's stocking the switch now, has plenty in stock, and it's actually a little cheaper than the Miata thermoswitch!
Dale
Originally Posted by DamonB
I wonder if I kept my stock connector when I cut it off to fit the Miata thermoswitch...
Thread Starter
Joined: Jan 2002
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From: Pensacola, FL
Sounds like there's gonna be a run on fan switch pigtails...
If you can find an '89-91 FC with a bad engine harness, you can chop that connector off and re-splice it in. Not to mention you can use a LOT of the '89-91 FC connectors - I think the injector connectors are the same, etc.
Dale
If you can find an '89-91 FC with a bad engine harness, you can chop that connector off and re-splice it in. Not to mention you can use a LOT of the '89-91 FC connectors - I think the injector connectors are the same, etc.
Dale
A basic question...I understand w/ a PFC or other realtime programmable ECUs, you can just program the fans to come on at a different temperature. But IIRC, doesn't that require datalogging for the PFC (ie it's somewhat involved)? Because I'm kinda LD when it comes to changing values and programming using the PFC. Couldn't I just use the FC switch and be done w/ it? I don't see any compatability issues w/ the switch and the ECU - just that you don't NEED the switch if you have the ECU, yes?
Thread Starter
Joined: Jan 2002
Posts: 15,622
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From: Pensacola, FL
You need the PowerFC datalogit to change the fan settings in the PowerFC. This is a "hard" solution that's ECU independant.
If you have a PowerFC and datalogit, you don't really need the FC fan switch. But, I believe the ECU can only really control one of the fan relays - the thermoswitch is a main deal to control the relays.
Dale
If you have a PowerFC and datalogit, you don't really need the FC fan switch. But, I believe the ECU can only really control one of the fan relays - the thermoswitch is a main deal to control the relays.
Dale
Dale, so in short, the thermo switch is pretty much a good idea irrespective of what ECU you're running (unless you have a datalogit and changing the settings is as easy for you as switching channels w/ a TV remote lol)
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Joined: Dec 2001
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From: San Lorenzo, California
By default, the PFC turns the fans on LOW at 99C or 210F. You do need the datalogit to make changes from there. There is really no reason to perform the thermoswitch upgrade if you are running the PFC.
