180F T-Stat vs 195F T-Stat

[chuckerants]

Yesterday I had a chance to swap out the 195F with a Stant "Premium", T-Stat - Part #555256, vs Regular which is #13868. I ordered the part from RockAuto.com.

With the 195F, the T-Stat would open at around 200F or so and stay at 210F until getting heat-soaked and get as hot as 230F +. I could forget about using the AC as it would get scary hot.

I just got back from a 30 minute drive with the AC on full blast and on RECIRC. The drive was to the supermarket and back and I intentionally went the long way and even drove in boost.

The T-Stat opened at around 180F and got to 195F and stayed there pretty much for the entire time.

Along with the T-stat replacement, I also used an aluminum based high temp take to tape up the gap between the AC condenser and the front nose on top and below the car. I also used the tape to cover the gap between the fan shroud and the radiator.

If I had the time and more patience, I would have covered the gap on the sides of the AC condenser, radiator and the inside mouth of the car. I'm not sure how long the tape will hold, but if this works, I may try to find a more permanent solution.

I also bought a SPAL fan controller but I haven't installed that yet.

I'll have to take the Miata to work (stop and go) and see just how much this has improved the cooling system.

[socal pat]

Hey Chuck, I'm really interested in the new fan controller. In the meantime I would be surprised if the 15* difference head-start of the T-stat would make much difference. Once the t-stat is open it's open, and in your heat isn't likely to close therefore heatsoaking again. Now, your tape job along with the early-on fans should make a difference. Keep us posted though.

[chuckerants]

From reading the directions for the SPAL fan controller, if I use the SPAL temp sensor, it's already set at 160F and 200F. If I use my OEM temp sensor or even the Autometer sensor, I have to program it - which is very easy. I just have to re-read the directions a few more times and then post here asking for help about which wire goes to what. :)

I'll probably use the Autometer temp sensor as it's right out in the open for me to tap into.

As for the T-Stat, I would have thought that it would make no difference. However, as soon as I turn on the AC, with the 195F, the coolant temp would get pegged at 210F and slowly start creeping up.

FYI - the 195F T-Stat was one I got from Checkers or Napa, I can't remember. This time I made sure I got a Stant brand and a new Stant rad cap as well.

[chuckerants]

My initial thoughts were that in the end, there would be no difference between a 180F and a 195F T-stat once the car had a chance to get well within operating temps.

After driving the hour to work this morning, I believe I was wrong.

With the 195F, my coolant temp was well into 210F by the time the car was warmed up even cruising at freeway speeds. I could forget about using the AC as it would get to around 230F when in light to light or stop and go traffic.

With the 180F, my coolant temp did get to 210F, in city driving, but it cooled to 195F very quickly once I started moving again. Also, on the freeway, my temp was 195F just as I remembered my temps being the last time I had the 180F T-Stat.

The only thing different is that now I taped up the gaps on top and bottom of the AC condenser and the radiator.

It looks like when I install the SPAL fan controller to come on at 195F or even 200F instead of 207F (which is where the OEM ECU triggers the fans), I should be able to keep the coolant temps right where I need/want them to be.

Lastly, I am now able to use the AC without the coolant temp getting higher than 210F.

Bottom Line: The 180F T-Stat is better than a 195F for a FI Miata.

[Bo0osted]

Hey,

Great post. Could you provide a link to the t-stat u purchased? I looked for it on rockauto.com but couldn't find it.

Thanks!

[FormerDatsun510Man]

Chuck,

Your results jive with mine, except I am using the 160 deg F one. What happens is the coolant temps want to stabilize around 190-200 deg F when the car is moving steady state. As you noted, the temp the thermostat opens is not the temp that the coolant stabilizes at. It is quite a bit higher. However, I think that if my cooling system was better the temps would stabilize a little closer to 160 deg F, maybe 170-180ish. I think that shows that the cooling system ability right now on my car is limited to around 100 deg F over ambient (current outside temps in the 90s). When I turn the A/C on, it is fine as long as the car is moving along, however it will still overheat in city traffic... though it takes longer. My theory there is that with the A/C on, when the car is stopped, the heat of the engine and A/C is greater than the heat extraction of the cooling system. So at that point, regardless of the thermostat, the coolant temps will increase. The good news is since the starting coolant temp is lower with the lower temp thermostat, it takes longer for it to reach the overheat point (around 230ish). The bad news is... it still overheats.

What's next? I am taking off the flat metal plate that holds the fans on the back of the radiator, which is part of the BRP intercooler on my car. My theory is that the flat metal plate blocks at least a 1/3 of the cooling area of the radiator. Thus I could possibly gain a significant cooling ability, at least when the car is in motion. I will know soon enough since with the current thermostat, but I think it will drop below 190-200 deg F while cruising along. I also wonder if possibly it might cool better at a stop with the fans mounted directly to the radiator with those plastic mounting straps. I am going to try that. If the car still has problems with overheating with the A/C on while in traffic, I am going to try some stronger fans. If that still doesn't work :), the next step will be to swap in a TDR intercooler, which I know doesn't have these overheating problems.

Bill

[Serpico]

I look forward to your results Bill. I thought about that , but wouldn't the fans just be pulling air through the localized spots of the fans vs. pulling air through the entire radiator????

I guess we'll know soon enough.....


http://www.vidilife.com/video_play_954720_2_3rdsCobra_polycarbonate_fan_sh roud_delta_P_demo_.htm

[FormerDatsun510Man]

I was thinking the same thing as far as the fans. It might actually hurt low speed cooling while high speed cooling would improve.... which is the opposite of what I need. However, I think it is possible that the fan will pull more strongly with it being mounted right on the radiator. The metal plate holding the fans on the radiator is completely flat... it doesn't have any sort of radiused shaped like the stock fan shrouds. So I am thinking that the flat metal plate doesn't help the fans pulling air through the radiator much and might actually be hurting. I will know the definitive answer soon enough :).

Bill

[Serpico]

If all else fails , a group buy on the TDR intercooler kit sounds like the next step. Gary claims a 1psi drop through his core and I've measured about 2-2.5psi through my BRP.

Oh, and his allows more air through the radiator as well :)

More boost and AC at low speeds sounds like a win win situation to me!

[Serpico]

here's part two of the video if anyone's interested....

http://www.vidilife.com/video_play_954716_2_3rd_sCobra_polycarbonate_fan_s hroud_delta_P_demo.htm

[Tom @ Fast Forward]

Just be careful of the 160F stat in the cool of fall, winter and spring. Even out here in hot country when the temps were in the 70s, my engine ran too cold to get off the ECU warm up fuel cycle.

[chuckerants]

Hey,

Great post. Could you provide a link to the t-stat u purchased? I looked for it on rockauto.com but couldn't find it.

Thanks!

1999 MAZDA MIATA 1.8L 1839cc L4 FI
FRAM FV289 (FV-289) PCV Valve $ 1.96 $ 0.00 1 $ 1.96
STANT 27168 Thermostat Housing Gasket $ 0.55 $ 0.00 1 $ 0.55
STANT 45868 Thermostat $ 5.77 $ 0.00 1 $ 5.77

[Curiousgb]

Chuck,

Your results jive with mine, except I am using the 160 deg F one. What happens is the coolant temps want to stabilize around 190-200 deg F when the car is moving steady state. As you noted, the temp the thermostat opens is not the temp that the coolant stabilizes at. It is quite a bit higher. However, I think that if my cooling system was better the temps would stabilize a little closer to 160 deg F, maybe 170-180ish. I think that shows that the cooling system ability right now on my car is limited to around 100 deg F over ambient (current outside temps in the 90s). When I turn the A/C on, it is fine as long as the car is moving along, however it will still overheat in city traffic... though it takes longer. My theory there is that with the A/C on, when the car is stopped, the heat of the engine and A/C is greater than the heat extraction of the cooling system. So at that point, regardless of the thermostat, the coolant temps will increase. The good news is since the starting coolant temp is lower with the lower temp thermostat, it takes longer for it to reach the overheat point (around 230ish). The bad news is... it still overheats.

What's next? I am taking off the flat metal plate that holds the fans on the back of the radiator, which is part of the BRP intercooler on my car. My theory is that the flat metal plate blocks at least a 1/3 of the cooling area of the radiator. Thus I could possibly gain a significant cooling ability, at least when the car is in motion. I will know soon enough since with the current thermostat, but I think it will drop below 190-200 deg F while cruising along. I also wonder if possibly it might cool better at a stop with the fans mounted directly to the radiator with those plastic mounting straps. I am going to try that. If the car still has problems with overheating with the A/C on while in traffic, I am going to try some stronger fans. If that still doesn't work :), the next step will be to swap in a TDR intercooler, which I know doesn't have these overheating problems.

Bill

I hope you find the answer as I am having the same issues. I believe it to be caused by the highly restrictive IC from BRP. The TDR IC is 4' shorter than the BRP unit. I have seriously thought of cutting some of the cooling fins from the BRP IC but wanted to try all else first.

[Bo0osted]

Thanks! I ordered the parts from rockauto and came out to be $13. Can't wait to get it in.

1999 MAZDA MIATA 1.8L 1839cc L4 FI
FRAM FV289 (FV-289) PCV Valve $ 1.96 $ 0.00 1 $ 1.96
STANT 27168 Thermostat Housing Gasket $ 0.55 $ 0.00 1 $ 0.55
STANT 45868 Thermostat $ 5.77 $ 0.00 1 $ 5.77

[chuckerants]

Ok, after driving to/from work in typical commuter traffic, it still seems to be running cooler with the 180F T-stat.

When the temperature is less than 110F, the coolant temps are around 195F at cruising and around 200~205F when the ambient temps are 110F and above.

Coolant temps are still at 210F at stoplight to stoplight driving, but it definitely cools down MUCH faster.

Next stop, the SPAL fan controller - when I get the time.