It's official - do NOT buy a Miata thermoswitch until you read this!
 

OK, I guinea pigged this one, and all worked out for the best :).

As you may recall, I posted a while back that I saw in a copy of RX-7 Magazine from Japan that they were using the '89-91 FC thermoswitch as an upgrade. This jogged my thinking...well, fast forward to today. I got the thermoswitch last week and installed it today.

Here's the deal -

- SAME operating specs as the Miata switch
- BUT, uses the stock FD plug - NO CUTTING OR HACKING. Unscrew old switch, screw this one in, plug it in, you're done.

It was about $50 from Ray Crowe at Malloy Mazda (1-888-544-3400). He didn't have it in stock, so it took a day or two for him to get it and ship it my way. But, I explained the deal with the switch to him, and he was VERY interested - I think if he gets an order or two, this will be a stocked item soon. Part number is PN41-18-840. It's for the '89-91 RX-7, non-turbo or turbo.

Dunno if you can see on the pics, but the FD switch has "108" on it, and the FC switch has "95" stamped on it. That's the switch-on temps - 95 deg. C and 108 deg. C. Fans come on sooner, car stays cooler, engine stays happier.

It was a little bit of work to install. I removed the crossover pipe and alternator, then had access. Unplugged the old switch (you have to hunt for the "button" to unlatch the connector - it was on the under side of mine), used a 17mm closed-end wrench to break it loose, then unscrewed it. Some water was lost, but it was just water in the top of the thermostat housing. Put a little oil on the O-ring on the new switch (came with the switch, and it was already on there) and screwed it in. Plugged everything back together, put the car back together, good to go. Pulling the alternator was the most time consuming part - it's a little tricky to get out of there.

Anyhow, this is a done deal - the Miata thermoswitch is now a "dead mod" :). Unless it's WAY the hell cheaper or something. I'd much rather have one that plugs right in just like stock!

Dale

I'm definately buying one.

Good info Dale. I have been waiting for the results on this one :) Did you check it to make sure the fans came on at 210?

Dale, a BIG THANK YOU goes out to you for testing this out. I'm sure this will be added permanently to the "3rd Gen Reliability Mods" as the way to go :bigthumb:

Yep, comes on at the right temp and everything - has the same operating properties as the Miata switch.

Dale

Great find Dale :D

this needs to be one of the links under FAQ for 3rd Gen & other useful links!

Dale...thank you so much for getting an FD! since you've gotten the FD you've done so much to help our community...thanks again! Keep it coming!

what again does the thermoswitch do again? does it just turns on the fans automatically at a lower temp?

The thermoswitch turns on the fan at a given temp. The FD thermoswitch turns on the fans at 108 deg. C, and the FC thermoswitch turns the fans on at 95 deg. C.

-Alex

Alot of people care :rolleyes:

If you havn't noticed our cars run pretty damn hot. The FC thermoswitch allows the fans to turn on sooner to help insure the car doesnt over heat. Especially people with front mounts, and heavily modded cars.

-Alex

Man dale your on a cooling mod roll. First you to the tb gauge mod/write up and now this, good stuff.

kinda sad you left second gens, but still glad to see ya making a scene the the community as a hole.

-Chris

:rlaugh:

Reliability is everything on an FD. Having the thermoswitch make the fans come on at 95ºC especially for people that live in hot sunny ass areas all the time. Or people that encounter heavy traffic going to or from work. Thats like saying, "Why get a bigger radiator? The stock one is fine." Again, maybe YOU haven't encountered close-overheating problems, temp. rising in heavy traffic on a hot day, etc. But MANY MANY MANY other people have noticed cooling differences and appreciate people like Dale in discovering more and more upcoming ideas, write-ups and information to help out the rest of the Rx7 community. Go do a search about the miata thermo-switch and see how many people love the earlier temp that the fans go on. You'll also find that many people question how to wire the miata thermo-switch due to the switch having two wires and not one. This FC thermo-switch makes things alot easier as to not stir up confusion during the swapping process and to also serve the same purpose as the miata thermoswitch. So before you go doing the whole "who cares?" thing, have some support for your statement so people don't just straight flame you for something like what you just did.

Mad props Dale. I was looking into the miata thermoswitch mod and now seeing this makes things alot easier with the wiring :). Annnd maybe the price?:confused:

Jeremy

Yes, Anyone with a Programmable Engine Management system, EMS...
Power FC, Haltech, Microtech, AEM, Etc... can change some settings in the programming of the EMS, to have the fans come on whenever you want.... so this is a Reliability mod for people with the Stock Computer (EMS).....

-DC

So is there any good reason not to grab one out of a junked FC? What are the chances of an old thermoswitch failing?

-s-

Maybe we could start a Group Buy for it .... can we ??

thx ANDY

I am definitely getting one of these.....

However, I am perplexed as to why I have a 115 degree switch? Maybe because of the automatic tranny?

http://home.earthlink.net/~bajaman123/thermoswitch.jpg

You could get a switch out of an FC, but it might be a good idea to find a new O-ring for the switch to ensure a good seal. Dunno if Mazda sells that part, but I imagine if you go to an auto parts store with a selection of O-rings you could find one that would work.

That's interesting that you would have a 115 deg. C switch - I'll have to look into that one.

I'm still not 100% certain why Mazda tried to make the FD run SO hot. It may have been for fuel economy or something - a hotter engine gets better fuel economy. But, it really beats the hell out of all the other parts of the motor.

IMHO, if you can keep the temps reasonable, I believe that will promote longer engine life. Running over 100 deg. C may not be *bad*, but I think long-term it's not the healthiest for the engine.

I have other ideas on the fans as well - stay tuned. I've hopefully got some more good stuff on this one :).

Thanks for all the positive feedback!

Dale

Regardless, it is still SO cool that you found a lower temp switch that needs no mods and plugs right in....thanks Dale! :bigthumb:

I know I will be getting one.

Thanks Dale, for fixing another Mazda engineering flake...

I don't care how well everything works in stock form, the engineer's best route is to "Over-engineer" products. Make things MORE than capable of how they are when things are "Right". Twin towers that can hopefully withstand a hit by a 747 for example....

Plastic endtanks on something (Radiator) that holds coolant, plastic AST tanks, a HIGHER degree thermoswitch,...ugh. Gee, this new Rx7 will have more power, 2 turbo's, and probably make more heat...lets make things plastic and let the fans wait even LONGER to come on than the FC! BRILLIANT!

Hope the one guy who had these awesome idea's was fired. I know they wanted weight savings as a mindset, but come on...

Nonetheless, thanks for an awesome find. BTW- 95c is 205f for those of you (LIKE ME!) that have Water Temp gauges that read in Fahrenheit.

Yikes! 115 C is 239 F for God's sake! My poor car! :(

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

"However, I am perplexed as to why I have a 115 degree switch? Maybe because of the automatic tranny?"

This is a separate trans switch for autos, located where one of the plugs normally resides in the fill neck hsg. If coolant hits 240F, atx logic engages torque converter lock-up more often, to reduce heat from torque converter.

You still have 108C fan switch, behind t-stat. Replacing with FC-or-miata switch means, with ac off, fans come on 1st at 207F at med speed, vs 221F (ecu controlled) at slow speed then 226F at med speed. Note this may only change med speed trip to 221F for some.

Alternative is to run with parking lights on, or cabin fan at 3 or more, in hot traffic. This trips fans on slow at about 200-210F.

Aha! That explains things. Yeah, I just found the normal thermoswitch...my God but that is a bitch to get to, and I have the engine out and half apart! :eek:

Thanks for the info!
(Though I feel a little stupid.....) :o:

someone do it up.

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 :p:

OK, enough with the bickering - let's keep this on topic. The points were made.

Dale

Adam, not just that, but ONE person's experience is not even to be mentioned w/ respect to the experience of the masses. Even if HIS car is doing fine, that has no bearing whatsoever on what the vast majority of FD owners may go through. Ppl should stop making broad generalizations like "it's pointless" simply because it doesn't apply to them and only them.

Oh and yes Adam, this is me agreeing w/ you :p:

dale we want you back in the FC section :(

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.

Hehe :). 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

I guess we're real lucky to have ya Dale :)

Oh shutup, you mazda-huggin cotton headed ninny muggins...

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.

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?

Great investigative work, Dale. A perfect mod for those still running the stock or Pettit/M2 ecus. :bigthumb:

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...

Damon,

My thoughts exactly!!!!!!!!!

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-

Your talking Heat Transfer not Thermo:).

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.

The thermoswitch has nothing to do with the coolant gauge on the dash. There are 3 coolant sensors - one for the dash gauge that's full-range, one for the ECU that's full range, and the thermoswitch that's JUST for the fans. It's not a ranged switch - at a certain temperature, the switch closes and shorts to ground. Once the temperature drops a certain amount, the switch opens back up. That's why it's a thermo*switch* and not a thermo*sensor*.

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

I thought of that too. But then I remembered there was so little room and so little wire to work, I cut it off right at the connector. :(

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

Thanks a lot for the info, the miata thermo was in my rebuild list but im defiantly going to have to get one from the FC now.

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?

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

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)

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.

wow i have to order one now.... thanks!