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In my efforts to build a robust turbo miata, I have managed to overbuild my cooling system. I have a FM re-route with 180 degree thermostat, Megan Racing radiator, deleted water neck, and I have deleted the line that runs from the back of the head through to the water neck via the throttle body and oil cooler. I also have a FM thermostatic oil cooler.
I live in south central Kansas. We get cold winters and hot summers. Its a terrible climate.
Going into winter here, Im dealing with the typical "re-route with bypass" "my car wont come up to temp" issue.
I have tried the common recommendation to block off half the radiator. It was in the mid 30's the other day and my car managed to get into high 170's, but was not stable there.
FM's recommendation was to switch to a 195 degree thermostat. I imagine this would help some, but since the car struggles to get anywhere near 180, I doubt it would solve the whole issue.
The Plan Im Considering
Given The added cooling efficiencies the re-route and the oil cooler, im wondering if the stock radiator with the upgraded fans and proper ducting would be sufficient under the harsher conditions I would like the car to be able to endure (100+ degree track sessions).
The added bonus of this is packaging. I had to modify the mounting for my AC condenser, the mounts for the radiator and I still have rubbing issues with fan shroud rubbing the charge pipe elbow that goes to the throttle body.
Does anyone have experience running a stock radiator under with this kind of setup under similar conditions?
I could be wrong, but I'm pretty sure 180 is the temp its fully open, not when it starts to open. So a 195 would help in my mind, might not be stable at 195-200 but would atleast be 190ish instead of 170ish.
I'm sure I'll be corrected by someone if I'm wrong.
I think you've gone too far to optimizing it for hot track conditions to expect it to also be a good winter street car. Personally, I'd go back on some of the mods you've done, but the reroute is not the issue here. Remember, it's only a reroute of the Miata cooling loop, in FWD applications of the B6/BP what we call a reroute is the normal coolant flow path.
Start with going to a 195* thermostat, unless you have some other compelling reason to stick with 180. The only good reasons for that I know of are drift/drag car where you're not working the engine hard for long, or high altitude affecting the boiling point of water (so, not Kansas). A lower opening temperature thermostat doesn't change overall cooling capacity. It only gives you a bit more time before you overheat from steady cruising conditions, since you're starting from a lower temperature.
The stock oil cooler is not just a cooler, it also transfers heat from the coolant to the oil for faster oil warm up on cold starts. If you want a car that can handle both extreme heat and cold, you should put it back in place.
Stronger fans will not help you at the track, that will only help if you're overheating while stationary such as sitting in traffic or stopping immediately after sustained high throttle usage.
Lastly, most every diesel truck in the great white north has the quick fix for this.
At a certain point you're simply asking too much of a cooling system to be able to handle all conditions without any manual intervention. A piece of plastic slipped over half of your radiator in the colder months is far easier than swapping radiators twice a year.
I think you've gone too far to optimizing it for hot track conditions to expect it to also be a good winter street car. Personally, I'd go back on some of the mods you've done, but the reroute is not the issue here. Remember, it's only a reroute of the Miata cooling loop, in FWD applications of the B6/BP what we call a reroute is the normal coolant flow path.
Start with going to a 195* thermostat, unless you have some other compelling reason to stick with 180. The only good reasons for that I know of are drift/drag car where you're not working the engine hard for long, or high altitude affecting the boiling point of water (so, not Kansas). A lower opening temperature thermostat doesn't change overall cooling capacity. It only gives you a bit more time before you overheat from steady cruising conditions, since you're starting from a lower temperature.
The stock oil cooler is not just a cooler, it also transfers heat from the coolant to the oil for faster oil warm up on cold starts. If you want a car that can handle both extreme heat and cold, you should put it back in place.
Stronger fans will not help you at the track, that will only help if you're overheating while stationary such as sitting in traffic or stopping immediately after sustained high throttle usage.
Lastly, most every diesel truck in the great white north has the quick fix for this.
At a certain point you're simply asking too much of a cooling system to be able to handle all conditions without any manual intervention. A piece of plastic slipped over half of your radiator in the colder months is far easier than swapping radiators twice a year.
I should have paid more attention to what thermostat FM was shipping with their kits. That re-route block is suck a PIA to remove. The 195 definitely would suite my use case better, I'll probably switch it at some point, im just too lazy at the moment. As for the oil "warmer" I have a temp sensor im going to install at the pan. If it shows that Im having trouble getting the oil up to temp, I might re-install it. I just really like the simplification of not having extra water lines running. Would I route the output of that to the water pump inlet mixing manifold?
Over lunch today, I covered another 5-10% of the radiator, and at 39 degrees, it came up to 180 in a pretty reasonable time. After an extended drive and getting into boost, it has hanging around 200. This may just be the easy button solution. Its a small amount of fiddling I will just have to deal with.
Are you running a water cooled turbo? I noticed much more stable engine temps and faster warm ups using the FM reroute and 180 thermostat once I switched out to a water cooled turbo. I live in SC and it doesn't get too cold here so I don't have much to report so far in terms of over cooking. I will say that over the summer in high temps they were stable and maintained. I'm also running a triple pass radiator with a 14" SPAL fan so my cooling setup may be more over kill than yours is.
I drove in to work today, 26* out. It took longer to warm up on the highway, but coolant temps were stable at 190-195. Oil temps were at 210 on highway, 205 in town, measured at the sandwich plate. This is with a stock engine 2001 with a well ducted and sealed Koyorad 36mm radiator and 195* Superstat. No reroute, but I do have a bit more even cooling than earlier engines due to the revised '01+ head gasket. Point is, even with a big radiator and ducting beyond my needs, I'm still maintaining target temps.
Thermostats have a bit of bypass flow, more so for the oil cooler thermostats where completely blocking off a flow path is not an option. If the oil cooler is exposed to airflow, you're still removing extra heat from the engine. When I had an oil cooler installed on my car it was completely covered unless I was at a track day, regardless of the time of year.
11-01-2023, 11:12 AM
Overcooling with FM re-route
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